Burying Linesets?

[keeney]

Due to various zoning regulations and the desire to locate the outdoor unit on my A/C away from the porch and deck, the only possible location is on the other side of the garage from the indoor coil (in basement). I intend to run the linesets under the garage floor slab and a short distance below grade on the exterior of the house through a 4" PVC pipe. This is the straightest and most direct route, and it still ends up being about 80 feet long.

Besides the issue of needing a shovel to access the lineset if it needs to be replaced, are there any other issues I should be concerned about?

The installation manual on the Carrier 38TRA mentions special considerations for linesets buried for more than 3' of their length, but does not elaborate on what they would be.

- Rick

[Noel Murdough]

Little things like....

condensing in the suction line during the off cycle from cool temperatures underground. Liquid doesn't pass through compressors very well, and.....

[beenthere]

You need to have a contractor get the blessing of Carrier.

Or you'll have no warranty, if the unit is still under warranty.

Do a search on this board, and you will find a thread where a guy has lost some thing like 3 compressors with his buried line set.

[keeney]

So how do I make it work? Add a trap on the suction side near the outdoor unit?

What is the minimum temperature the line needs to stay at? The manual talks about 55F as the minimum ambient - would that be a safe bet?

Would it be better to run the line 150' up and through the attic of the garage and then back down? That sounds like an upgrade in line size and a lot of expensive copper.

If the line needs to be re-routed, how do I tell my wife that it may be another week or so before we get air-conditioning (I have the lines in place, and the tech is scheduled to arrive tomorrow AM to do the brazing/evac/charge/startup)

- Rick

[cynic]

Just say honey you were right I shouldn't have done this :)

[beenthere]

It always best to do the research more than a day before the project is to be completed.

BUT, maybe if you post a request to Hvac r us 2, he will be able to answer all of your questions, since he is a carier rep.

He's one of the guys that comes out and voids warranties for bad installs.

Ok, he'll be able to tell all the info you want about weather carrier is ok with the line set done either way.

[plain spoken]

Line sets should be kept as short as possible for numerous reasons. Carrier does allow you to run up to 175' as long as you do it properly. They have a complete guide to tell you how to do this. Even at that you will loose some capacity and efficiency. Carrier does not allow you to bury more than 3' of lines, period! This 3' is to allow for a line set that comes out of a basement below grade and goes immediatly up to the out door unit.

Instead of all the extra cost and almost certain failures of the system, maybe you should really consider relocating the unit. No reason will be good enough when you discover the unit will not work properly and has premature failure due to your insistence on locating it in a bad space.

[keeney]

RE: It always best to do the research more than a day before the project is to be completed.

The house and A/C unit location was designed over 2 years ago...

I can go without A/C for a while, eat the cost of this mistake, and still be $100k ahead on the project in sweat-equity.

My plan now is to have the tech come out and look at it and get his opinion. If he doesn't seem to know or thinks it doesn't matter, that will be a warning flag not to proceed. If he pulls out an application note that says it will work but you need to add this valve/trap/heater/loop/length-above-ground/whatever, I will feel much more confident.

I can also reduce the amount of line that is below grade on the exterior of the house rather easily. The section under the garage is the big deal.

- Rick

[Shophound]

Oops...you've already done it. Hmmm...went from a hypothetical to a "oh crap!" :D

My childhood house had this same problem. Builder in '61 ran lineset under slab and to condensing unit in backyard. Lineset emerged from ground and tucked right into the unit, straight shot.

We blew three compressors on that rig. The tech that my parents used at the time was an old retired guy that did a/c out of an old Dodge station wagon. I think he was a low temp guy before he retired, because he slapped every bell and whistle imaginable on the new condenser once we decided to replace the one that kept blowing compressors.

He took the suction line where it emerged from the ground and ran it straight up into the air, bent it over to form a nice, high loop, added a suction line drier, then elbowed the remainder into the new condensing unit. He added a crankcase heater to the compressor, a TXV (non-bleed) to the evaporator, and a start capacitor to the compressor. He added hi head and low suction pressure cutouts and a delay on break tim delay. That condensing unit ran trouble free for over thirty years afterward.

Did you insulate the suction line, even though you ran it through the PVC underground?

EDIT: I type slow at times. You got more posts and one of your own as I was pondering and typing. The point of my post is look what trouble my parent's tech went through to make the thing run right. Why he didn't chase the lineset through the attic is anyone's guess, but that was the earlier days of central a/c. A learning curve.

[Edited by shophound on 07-20-2004 at 07:46 PM]

[smokin68]

Run the lineset above ground in the pvc or metal chase close to foundation....much easier to correct if problems occur.Can you run the lineset in a chase along the inside wall of your garage and punch through to outside?

[keeney]

Was that line under the slab insulated?

The suction line is nicely insulated and installed in a 4" PVC pipe that provides more insulation due to being plastic and having an air gap.

The best information I have found on the subject comes from a Trane manual I found on-line. After it says that it is not recommended to bury the lines, it goes on to say to slope the line 1" per 10' towrds the evaporator to keep any condensed refrigerant from flowing towards the compressor. It also recommends insulation and a hard casing to avoid damage. It also warns about contamination, but thats probably during brazing of joints down in a hole - not the case here.

Due to the length of the lines, it is already recomended to add a crankcase heater, liquid line dryer, and a hard-shut TXV or solenoid valve at the evaporator.

The Carrier manual mentions a 6" vertical rise is required for operation with up to 3' of buried suction line. After that, it says to consult the factory.

- Rick

[beenthere]

That Trane article is on their commercial equipment, it doesn't apply to you unless you have a Trane commercial unit.
Carrier doesn't care what Trane says.

Without prior aproval, Carrier can void your warranty, when you lose compressors.

Have your tech call the distributor, or Carrier direct, and find out from them if it is ok to run the lines the way you want, it will save you alot of head aches, in the next year.

[houstontx]

"Due to the length of the lines, it is already recomended to add a crankcase heater, liquid line dryer, and a hard-shut TXV or solenoid valve at the evaporator."

In addition to the above
suggest installing an accumulator at the condensing unit
and definitly an oil trap in suction at cond unit.

In my thinking
the slope of the lines toward evaporator is not needed
(hard-shut TXV and or solenoid and accumulator will
prevent any liquid from returning to compressor)
BUT
a slope toward the condensing unit for assistance
in oil return, with oil trap. (very important)

Have a Great day

[beenthere]

Read this before you hook up that unit.




hvac r us 2
** Site Supporter **

Registered: Apr 2004
Posts: 388
This is the most annoying thread I have read to date.

I am a Carrier rep, and let me tell you 80% of everything in this thread is nonsense!

First off I agree with Doc, regardless of how much equipment you buy as a dealer if you do it wrong we will point it out. Of course we would never hang a dealer out to a homeowner, but in private we would show the dealer where the mistakes have been made. Any good dealer would take our advice as they want the problem to be resolved/corrected.

This is NOT Carriers fault, they have already paid for several compressors. Your mad at Carrier? Why not go after and be mad at the installing contractor? They screwed up! And as I already stated, a good contractor would fix this problem if he knows he did it wrong.

What more can Carrier do? I mean really, they put it in the instructions, they instruct the dealers, they train them, and they have already spent thousands on giving you replacement compressors! What more do you want from Carrier? Again I ask you, why are you blaming Carrier? Your one of those people that will bash Carrier, when the only real problem is your installing contractor and you.

What part of don't bury the line set dont you get? Seriously? Stop with the Trane this and that, there are factors you just refuse to acknowledge. Like the fact that it is a two speed unit? What do you think happens when you have low pumping capacity? Think about it...you have a system that has piping, indoor coil, metering device, all designed for the full capacity of the unit. When it runs on low stage it is already hard to control the Superheat without a buried line set where refrigerant can migrate. You keep complaining you didnt know about buried line sets, but you do now and yet you wont listen.

And you genuisses out there, do this, do that...your kidding me right? Add this, add that, put on an external accumulator...huh? In certain applications that may work.

Not sure, but did I mention the part about being a two speed unit? It already has an accumulator. Let's add another one to the suction line in a series...that should help oil return.

I assume like so many others you didnt notice the part in Tranes piping guidlines that said in BOLD letters " It is advisable to avoid running refrigerant lines underground" Wonder why they put that in there? In certian areas buried lines just dont work...like Ohio.

You got the correct advise in the begining of this thread, but refuse to take it. I predict you will carry on only hearing what you want to hear, you will loose more compressors, and blame Carrier for selling you a lemon.

You didnt buy a lemon, you created one.

Amazing, just amazing...people ask for help, you help them, then they dont listen anyhow.

Amazing...


__________________
If I can't fix it, it isn't broke!


06-28-2004 09:11 AM

[houstontx]

" I assume like so many others you didnt notice the part in Tranes piping guidlines that said in BOLD letters " It is advisable to avoid running refrigerant lines underground" Wonder why they put that in there? In certian areas buried lines just dont work...like Ohio. "

You might find yourself asking:

How does the AC know if the lines are underground vs. being run from
an elevated air handler along a lower plane to a raised condenser?

It can't !!!

Wonder what Ohio dirt has that other states dirt doesn't?

There ARE issues concerning electrolysis, oil return, access,
water table, drainage, etc.;

therefore it is not advisable to bury the refrigerant lines;

BUT a properly designed piping system can be installed on any plane.

Underground insulated refrigerant lines enclosed in water tight PVC
in an area not subject to water would be Better insulated and protected
from ambient elements than lines above ground.

NO ONE
will post a physical, scientific explanation why it can not be done.

As I have seen MANY installations with lines run underground that have
been in trouble free operation for over 20 years with NO problems;

I am waiting for substantial proof that I stand to be corrected.

Have a Great day

[beenthere]

Lines are buried in slabs, under slabs, and in alot of other (strange)set ups, but most are done with the guidence and ok from the manufacturer.

I've run 180' line sets, but with the manufacturers ok.
Get approval is what i have been telling this guy.
The tech coming out may have no idea whats going on, and just start this thing up, then the guy could lose his warranty.
And all he would he needs to do is make a phone call, or have the tech make it.

Without either a non bleed txv, or a LL selinoid valve, he will have liquid migration.

[karsthuntr]

Linesets in PVC and incased in concrete are not really "buried" are they? They will not have direct contact with the earth! You could make it work by putting a little heat in the PVC to keep ref. from condensing ie.. heat tape.

[beenthere]

Its not just the direct contact, its also the temp, and heat tape might work. Also, most under ground lines are also big oil traps, so some times you have to resize your line sets, and add x amount of oil.


Maybe i'm paranoid, but we call the manufacturer first, and give them a drawing of the line set runm and then make any changes, or what ever they said from there, and keep the warranty intack by doing this.

[keeney]

Some conclusions:

The general elevation profile of the lines will be similar if I route them in an alternative manner around the outside of the house (it will just look uglier), so I am not buying the issue of the buried line set being any worse of an oil trap than a conventional install in this case. The height difference between the indoor and outdoor coils is about 5 feet. That doesn't change regardless of how the lines are run. Both routings have no extra vertical sections (unless we intentionally add an inverted trap at the condensor).

Encased in a sealed PVC pipe, the lines are not subject to direct contact with the ground, so corrosion is not an issue, nor is external water condensation.

The only issue that makes sense for me to worry about that I have heard so far is that the lower temperature of being in the ground may cause the refrigerant to condense in the suction line and be drawn into the compressor in liquid vs. gas form.

Going by the instructions that the unit is rated to be operated in ambient temperatures down to 55 F, I would assume that this would be a safe lower limit for the suction line temp.

During the season when the unit will be in operation, I can't see the ground temp of something less than 12" deep going below 55 degrees. In fact, its probably subject to less temperature swing than a line hung bare on the outside of the house.

So, I can half convince myself that it will probably work fine.

On the other hand, if it voids the warranty and something fails (regardless of if its related to this issue), I am sure I will have wished I had done it the conventional way, even if it is much uglier.

So, tomorrow AM, I will call the distributor and ask them about the warranty. If they indicate it won't be covered in this situation, its off to the rental shop to get a diamond coring bit to put a new 3" hole through 12" of concrete foundation on the side of the house above grade (unless the tech happens to have such tool in his truck).

Thanks for the information.

- Rick

[dschwab9]

What about a liquid line solenoid and a pump-down cycle? If you pump all the refrigerant into the condensor/liquid line, it can't migrate to the suction line, right? Overkill for a residential system, but if thats what it takes....

[keeney]

Does that mean that at the end of the call for cooling the liquid-line valve closes, while a delay relay leaves the compressor on for a few seconds? How long of a delay? Sounds easy enough if the valve is already going to be there.

[dschwab9]

In a pump-down system, the thermostat controls the the solenoid and a pressure switch controls the compressor. Basically, at the end of the call, the solenoid closes, pumping all the refrigerant into the condensor. Once the suction pressure reaches, say, 5psi, the compressor shuts down.

On the next call, the solenoid valve opens, causing the suction pressure to rise, and the compressor restarts.

It's used on refrigeration units and some large commercial systems to stop liquid migration. Normally not on residential, but I don't see why you couldn't do it. Is this a straight cooling unit? You wouldn't be able to do pumpdown on a heat pump.

[keeney]

Its cool-only, so pump-down may be an option.

Does the LLS and pumpdown work on scroll compressors? Won't the pressure just equalize when the compressor shuts off?

[Irascible]

AFAIK know most or all new scrolls have check valves, so it shouldn't equalize through the compressor.

I'm dying to hear BT or somone else on this pump down idea. A non-bleed TXV or LLS sounds like a solution. But a pumpdown setup sounds really interesting. The only thing I wonder is with all extra refrigerant that you'll have to add to compensate for the lineset length, will the condenser have the necessary internal volume to pump down without a problem (on a hot day for example)?

[dschwab9]

You wouldn't have to pump it all into the condensor. Put the LLS right before the metering device, and you have the storage space of the liquid line also. All you'd be emptying would be the evaporator and the suction line, which isn't a lot of refrigerant.

An LLS right at the evaporator or a non-bleed TXV might be sufficient, but you still have some liquid in the evaporator when it closes. With pumpdown, there is definately no liquid in the low side of the system.

[mjstraw]

What more can Carrier do? I mean really, they put it in the instructions, they instruct the dealers, they train them,
...


For one thing, be consistent.

When I had a carrier condensor installed, the contract specified installation according to manufacturer's instructions and specifications. Install manual said a liquid line filter-drier must be installed. Contractor refused saying it wasn't necessary.

Contacted Carrier tech support and they danced around the issue - said "should be OK if it's a new install" so contractor still refused to install one. I ended up hiring someone else after the fact to come in and install one.

[plain spoken]

You should not pump down a scroll. Carrier does not allow pump out on any of their equipment. The reason for not running the lines undergroud is possible oil trapping and liquid slug due to condensing the refrigerant during the off cycle. Straight cooling is not as critical as a heat pump but is still a problem.

To answer an earlier post as to how the lines know they are under ground and what Ohio dirt has to do with it; it knows it is under ground due to the cold temperature and Ohio is very cold in the winter so Ohio dirt would be worst than say south Texas dirt or Florida dirt. Yes, if you put it in PVC, insuslate it and keep it sealed you probably will not have a problem. However, it is difficult at best to completely seal the PVC. You also have to remember that the suction line will condensate and overtime water will build up in the PVC. When enough water builds up it will act as a heat sink to effect the refrigerant lines and cause the same problems.

While there are many different opinions and ideas, it is always better not to bury the lines. The possible problems greatly outway the benefits.

[dschwab9]

What happens if you pump down a scroll?

I know they don't like to run in a vacuum, but a pumpdown doesn't run it into a vacuum.

[plain spoken]

I recently was at a meeting where a Copeland engineer was one of the speakers. What they presented was that the scroll plate would be damaged by the heat due to lack of refrigerant flow to cool the scroll during pump down. Even this short period will cause damage that over time will destroy the scroll plate. Most new units do not have accumulators either, which means that the units may have a very difficult time pumping down since the coil may not be able to hold all the refrigerant. And yes you are correct, NEVER pump a compressor into a vacuum!

[dschwab9]

Does that mean you're not supposed to pump it down to, say, pull the piston or work on the lineset?

I find it hard to believe that it would damage the scroll. I've seen the run for weeks or months seriously undercharged and still work fine when recharged.

[houstontx]

"The only issue that makes sense for me to worry about that I have heard so far is that the lower temperature of being in the ground may cause the refrigerant to condense in the suction line and be drawn into the compressor in liquid vs. gas form."

To determine if this is an issue for your situation:

Since Freon 22 has a boiling point of < - 41.4'F >

If you live in an area where the ground temperature is
around minus -41.4'F then the condensation of the vapor
in the suction line WOULD be a consideration.

If your home is in this cold of a climate
the hard shut TXV, crankcase heater, and accumulator
would be needed. (wouldn't think you would need much AC)

If the enclosed piping is not dehydrated and
the PVC to copper area is not sealed,
condensation of moisture Would be an issue.

The piping must be installed properly.

Check with equipment manufacturer or a resident mechanical
engineer for recommended procedures.

Have a Great day

[plain spoken]

I think it would be best if you not pump it down to check pistons etc, and that is what the engineer told us they discouraged. But I would not think that would be to bad since it would only happen very seldom as opposed to possibly many times a day if set up for a pump down each time it cycled.

As to running low on charge. I guess it depends on how low and how long. Some equipment manufacturers put a discharge line thermostat on the compressors to shut them down if the discharge temp gets to high for this very reason. If the unit runs low on charge the discharge temp will go up and cause damage (actually the same goes for recips). Even though it may take back off and run, we can not be sure of how much damage was done that may shorten the life of the compressor or lower capacity.

[dschwab9]

Originally posted by houstontx

Since Freon 22 has a boiling point of < - 41.4'F >

If you live in an area where the ground temperature is
around minus -41.4'F then the condensation of the vapor
in the suction line WOULD be a consideration.

Boiling point of R22 is -41 at ATMOSPHERIC PRESSURE. Increase the pressure, and the boiling point increases. There is always liquid present in the system. With the system off, the saturation point of the refrigerant is going to be the same as the ambient temperature.

[Jax]

I have buried plenty of line sets in the fill of a house,, which is far different from in the ground. I haven’t done a slab in a long time tho.
But the one thing you said about running both lines in 4 inch PVC might not be wise. If there is any way water can get in, condense, or stand in the PVC, it will play hell with your super heat as it can transfer heat between the two lines. I have one where the contractor dumped the condensate into PVC and just let it drip out the other end.
Jax

[houstontx]

Forgot the pressure

This would change ground temperatures to
around/below 50 / 55 'F during the cooling season
for possible condensation of vapor refrigerant
during the off cycle of a normal F-22 system.

If your home is in this cold of a climate
the hard shut TXV, crankcase heater, and accumulator
would be needed, should install as a precaution regardless.

The piping must be installed properly.

Check with equipment manufacturer or a resident mechanical
engineer for recommended procedures.

Have a Great day



[Edited by houstontx on 07-21-2004 at 10:52 AM]

[dschwab9]

If the ambient temperature is 70 degrees and you have refrigerent sitting in a closed system, the pressure is going to be at the saturation point for 70 degrees. If it's 70, the refrigerant condenses at 70. If it's 80, it condenses at 80 (assuming the system is not running).

Condensing isn't the problem, it's already condensed. It's migration of the existing liquid that's the issue. You want it to stay in the condensor/liquid line. When it migrates to the low side of the system, you will have issues.

[keeney]

RE: "But the one thing you said about running both lines in 4 inch PVC might not be wise. If there is any way water can get in, condense, or stand in the PVC, it will play hell with your super heat as it can transfer heat between the two lines."

The suction line is individually insulated with a continuous foam rubber jacket. Even if the PVC was full of water, the two lines would be thermally isolated from each other. The PVC pipe itself is well sealed where the lines enter and leave. It is sloped to drain itself should it get water inside, and has a small drain hole at the low end.


During operation, the insulated suction line will tend to have a temperature based on the super-heat of the system, so during operation its not a factor.

Between cycles, the pressure will equalize, and the equilibrium temp will be the average temperature of the whole system. The buried part will probably be generally lower than the outdoor and indoor portions. This will tend to condense liquid into the suction side. It will stay there until the next start cycle, but hopefully draining by gravity into the lower portions of the system, which in this case is towards the evaporator.

So, adding a LLS valve would be one possible solution since it would keep the pressure lower on the suction side between cycles, hopefully well below the vapor pressure of the refrigerant at the ground temp so it stays in gas vs. liquid form. Not quite the same as a pump-down cycle, but better than letting the system equalize to a higher pressure.

Since the LLS is required for long-line applications with this unit by the manufacturer anyway, it sounds like the right answer to me.

- Rick

[hvac r us 2]

What State is this being done in?

[plain spoken]

I see a couple of problems with your installation theory. The insulation on the suction line is not water proof so it will not protect the line from the temperature of the water. The fact that it has a "drain" hole could be a problem if the water table raises and also could let moist air in to increase condensate. The term "hopefully" regarding the lines and state of the refrigerant is not good enough. You have been given good advice and reasons why this should not be done. You asked for advice and it was given, from people with lots of experience. If you choose not to accept, that is your choose. Again, Carrier says NO. So if you persist and do it anyway, just be aware you are on your own.

[Gunnery Sergeant Hartman]

I've seen buried linesets supposedly sealed on both ends, end up filled with water.
This played hell on the superheat and the system never performed.
RUUD's factory rep came out to look at the problem and ripped of the unit's tag and wrote WARRANTY VOID in permanent marker on the unit.

[keeney]

Don't get me wrong, I am thankful for all the information. I was just hoping for more "this is what you need to do to make sure it works" kind of advice instead of the "that is crazy, it will never work, and you are an idiot to keep trying" type of sentiment.

In order to get to an understanding of what it would take to make it work, I am questioning "why" it is a bad idea. Not to argue that its probably not a bad idea, but to understand what makes it a "bad" idea so as to learn how to overcome the problem.

Yes, I understand that if the drain hole fails, it might be a problem! If the insulation stops insulating, it might be a problem! If the seal fails and lets rain water collect in the pipe, it might be a problem! If some kids fill the condenser with dirt, it might be a problem!

I am trying to balance these technical challenges against the ugliness of running the lines on the outside of the house or through the finished space of the garage. I am willing to spend a bit of effort and engineering to make my house look better. If I was going purely for the most functional, trouble-free house, it would be a steel pole-barn with pipes and wires coming out the most convenient locations and intruding into the living space wherever it would be most convenient to service them.

- Rick

[Irascible]

It seems to me that amidst all the "don't do its" you got your answer. Clearly the biggest problem with buried linesets is refrigerant migration to the buried portion of the lineset. Put a liquid line solenoid right before the evaporator or get a non-bleed TXV. I'd personally choose a condenser with an accumulator and then I'd make sure it had a crankcase heater. I might even put a crankcase heater on the accumulator. That way there'd be very little refrigerant in the evaporator or suction line. If what little was there did migrate and condense in the lines (or even if some leaked through and a lot condensed) the accumulator would be empty (from the heater) and would catch it and do its job. As long as you don't mind the potential of a voided warranty, I'd say go for it.

[R12rules]

Originally posted by houstontx
"Due to the length of the lines, it is already recomended to add a crankcase heater, liquid line dryer, and a hard-shut TXV or solenoid valve at the evaporator."

In addition to the above
suggest installing an accumulator at the condensing unit
and definitly an oil trap in suction at cond unit.

In my thinking
the slope of the lines toward evaporator is not needed
(hard-shut TXV and or solenoid and accumulator will
prevent any liquid from returning to compressor)
BUT
a slope toward the condensing unit for assistance
in oil return, with oil trap. (very important)

Have a Great day




This is the right way to do it. All I could add to this is to blow air down the PVC pipe which contains the lineset. Use a fan for this. This will prevent the sweating and cooling of the lines during operation.
Then when the season is over, shut down the fan.

If liquid slugging of the compressor is the big problem then adding the necessary components which will prevent such an occurance to take place would only make sence.

Unless your tech is above average, he may not think anything is wrong with what has been done.
Do NOT rely on him to "red flag" your project!

[dash]

Originally posted by hvac r us 2
What State is this being done in?

Original poster,profile says,MN,Minnesota?Kinda cold there,commonly ,almost exculsively,underground in Florida.

[hvac r us 2]

This is an interesting thread isnt it?

Chalked full of good advice, bad advice, facts and opinions.

The real challenge is learning to seperate fact from opinion.

Let me clear up a few things that I read...

First off somebody does publish a scientific explaination why buried line sets dont work, along with a 3 year case study. Does it really matter? The same information is in this thread. Besides, even if you post it or hand deliver it to them there will always be people that will argue the case regardless. There minds are already made up.

Along with everything else that was said about not pumping a Scroll into a vacuum another thing that can happen is arcing.

When there is no suction gas coming back to the Scroll, there is nothing keeping the plates from arcing against the orbit part of the compressor. This can cause internal arcing and ruin the windings.

Somebody made mention of a dealer that refused to install a liquid line drier. I still will never understand this type of thinking. Carrier puts in the instructions on R-22 units that it is recommended to install a liquid line drier. On puron units it is required and Carrier ships a drier with each unit. Again I ask how could you be upset with Carrier? They put it in the instructions, they give the dealer a drier...but the dealer refuses to put it in? Isnt that just a bad dealer? Shouldnt you be mad at them? Or possibly mad at yourself for choosing that dealer? I understand your frustration, but dont understand the logic. If I bought a new Chevy and took it to get the oil changed, I tell them to put oil in and they dont...when the engine blows is that Chevys fault?

I am getting way off track, sorry.

Okay, buried line sets. Listen, buried line sets are a problem, I think you know that...always has been, always will be.

I am not going to debate this topic. I think you know you should not do it, correct me if I am wrong but I think I hear you saying regardless of the good advice you recieved from people like Plain Spoken, Been There and others you are going to do this anyways right?

If this is the case tell me so and I will give you the info you are looking for on "how to", as long as you are not building this house in Ohio! :)

I guess this is a case of, if your going to do it anyhow, I might as well try to help you save this Carrier unit the best I can. :(


Good luck, hope you reconsider...let me know.

[Irascible]

Originally posted by hvac r us 2
I guess this is a case of, if your going to do it anyhow, I might as well try to help you save this Carrier unit the best I can.And that was my thought. In addition I'm of the opinion that so long as safety, code violations, etc. are not at stake then people should be allowed to do what they wish. I'll even help them do it so long as I don't think it'll come back to bite me in the rear. Yes, I know. That's a hard and sometimes risky thing to predict.

The three year study does matter in the sense that if you can point me to it, I'll read it. I love that kind of stuff.

The whole arcing thing was probably debated at length someplace. I should look it up. I understand that arcing can occur in a real vacuum. The gas is an insulator and without it electrons jump around much more freely. However, even 25 inches of mercury is nothing close to a real vacuum. I don't make a habit of it and haven't done one in a looong time, but I use to do pump down tests to check valves and they'd sometimes get to 25 inches with no problem and with no arcing.

And I don't understand the scroll/plate example. They're in contact so I don't understand how a potential difference (voltage) could ever build up between the two. I always assumed that the arcing spoken of was from an electrical component in the compressor to some grounded component nearby. Since I've never shorted a compressor, I don't have much experience with such things.

[houstontx]

Migration is not a problem with a hard-shut TXV and/or
a solenoid.

Most all blowers have a delayed Off which evaporates
residual liquid in the evaporator after shut down.

A normal operating system has evaporated ALL liquid
refrigerant through the evaporator to a point of
Superheating it up to the point in time of shut down.


Taking into consideration the above,
a hard-shut TXV, and accumulator,
in the unlikely event that some liquid existed
on the low side, after the delayed blower off,
the accumulator and crankcase heater would eliminate
any threat.

Since the boiling point of Vapor F-22 is -41'F
at atmosphereic it does NOT condense at 70 or 80 'F
unless it has additional pressure exerted on it.

If it did,
systems would be running very low discharge pressures.

If you have a Carrier, you may have warranty issues
if there is a future compressor problem.
( max 3 foot underground )

However;
there are Many, Many installations with underground lines.

Have a Great day

[mjstraw]

Originally posted by hvac r us 2 Somebody made mention of a dealer that refused to install a liquid line drier. I still will never understand this type of thinking. Carrier puts in the instructions on R-22 units that it is recommended to install a liquid line drier. On puron units it is required and Carrier ships a drier with each unit. Again I ask how could you be upset with Carrier? They put it in the instructions, they give the dealer a drier...but the dealer refuses to put it in? Isnt that just a bad dealer? Shouldnt you be mad at them? Or possibly mad at yourself for choosing that dealer? I understand your frustration, but dont understand the logic. If I bought a new Chevy and took it to get the oil changed, I tell them to put oil in and they dont...when the engine blows is that Chevys fault?

My point was that Carrier tech support didn't back up their printed instructions. They waffled, and my impression at the time was that they didn't want to offend the contractor.

So I was annoyed with both the contractor and with Carrier, but for different reasons.

What makes it even more interesting is that the installer was working time and materials - so he was turning down extra profit on the job. Go figure.

[hvac r us 2]

What makes it even more interesting is that the installer was working time and materials - so he was turning down extra profit on the job. Go figure.
[/B][/QUOTE]

Sometimes those are tough issues, even though a dealer is a Carrier dealer they are still an independant contractor. We can advise but really cant "make" them do anything.

Working T and M and still wouldnt do it? LOL Some people are just lazy you know? No cure for that!

[bja105]

Maybe, instead of finding a way to make a buried lineset work, we should find a way to make an exposed lineset look good. When we run linestes, wires, and drains up the side of a house to an attic air handler, we hide them in a fake downspout that matches the real ones. Perhaps you, your contractor, or someone on this board can come up with a similar solution for hiding your lineset in plain sight. That seems easier than re-inventing the wheel.

[plain spoken]

Originally posted by houstontx
Migration is not a problem with a hard-shut TXV and/or
a solenoid.

Most all blowers have a delayed Off which evaporates
residual liquid in the evaporator after shut down.

A normal operating system has evaporated ALL liquid
refrigerant through the evaporator to a point of
Superheating it up to the point in time of shut down.


Taking into consideration the above,
a hard-shut TXV, and accumulator,
in the unlikely event that some liquid existed
on the low side, after the delayed blower off,
the accumulator and crankcase heater would eliminate
any threat.

Since the boiling point of Vapor F-22 is -41'F
at atmosphereic it does NOT condense at 70 or 80 'F
unless it has additional pressure exerted on it.

If it did,
systems would be running very low discharge pressures.

If you have a Carrier, you may have warranty issues
if there is a future compressor problem.
( max 3 foot underground )

However;
there are Many, Many installations with underground lines.

Have a Great day



I really am tired of this thread and was trying to let it go, but...

The suction line that is full of the superheated vapor you just described is the problem. During the off cycle if it becomes cool enough it WILL condense into a liquid. The liquid slug on start up is the problem. While an accumulator will help, it will not stop all the liquid. This is a know and proven fact. Buried lines are much more susceptible to this. Case closed, I am done and out of here.

[beenthere]

[QUOTE]Originally posted by Irascible
AFAIK know most or all new scrolls have check valves, so it shouldn't equalize through the compressor.

I'm dying to hear BT or somone else on this pump down idea. A non-bleed TXV or LLS sounds like a solution. But a pumpdown setup sounds really interesting. The only thing I wonder is with all extra refrigerant that you'll have to add to compensate for the lineset length, will the condenser have the necessary internal volume to pump down without a problem (on a hot day for example)? [/QUOTE

I got split chillers with under ground lines, and pump down valves they work great. Of course the valve is in the mech room, and all lines are insulated. And every thing was known up front about the line set before the install.
Trane approved it.

[hvac r us 2]

[/B][/QUOTE]

I really am tired of this thread and was trying to let it go, but...

The suction line that is full of the superheated vapor you just described is the problem. During the off cycle if it becomes cool enough it WILL condense into a liquid. The liquid slug on start up is the problem. While an accumulator will help, it will not stop all the liquid. This is a know and proven fact. Buried lines are much more susceptible to this. Case closed, I am done and out of here. [/B][/QUOTE]


LOL I feel the same way! I keep getting sucked into this thread!

I read something that I just have to respond to, I start typing then finally tell myself "stop" and clear the fields!

I catch myself wanting to fire off all kinds of quotes and numbers that really look impressive...but the bottom line is as you stated...you will get liquid slugging!

So I sit back and try not to get involved in these debates as they will go on forever...but it still doesnt change the facts.

[Irascible]

Originally posted by plain spoken
The suction line that is full of the superheated vapor you just described is the problem. During the off cycle if it becomes cool enough it WILL condense into a liquid. While an accumulator will help, it will not stop all the liquid. This is a know and proven fact.First of all, I am NOT supporting the idea of buried linesets. Because it's my biz and my arse on the line, I won't take the risk.

However, when I see a statement I don't get I need clarity. Accumulators typically have enough volume to handle the entire refrigerant charge. But you're stating that it couldn't even handle the vapor charge of an evaporator and suction line. Yes, it will condense to liquid. But it's still a tiny fraction of the whole charge and the accumulator can typically handle the whole charge. Point me to this proof that an accumulator will not stop a fraction of the charge so that I may believe! :)

IF it can't, then as BT said the pump down is the way to go. Yeah, I know. He said he got approval too. But we can't have everything, now can we? :) Of course, someone said that shouldn't be done due to overheating of the plates. Given the relatively short amount of time the compressor would see low suction, I find that hard to believe as well. Need more proof! The scrolls are supposed to be tough SOBs. I've seen a couple here and there that lost charge, ran for a good long time that way and suffered no ill as a result.

[hvac r us 2]

Of course, someone said that shouldn't be done due to overheating of the plates. Given the relatively short amount of time the compressor would see low suction, I find that hard to believe as well. Need more proof! The scrolls are supposed to be tough SOBs. I've seen a couple here and there that lost charge, ran for a good long time that way and suffered no ill as a result. [/B][/QUOTE]

This thread is like a bad addiction, I just cant stop myself!

The proof you are looking for can be found in many differant publications including material published by Carrier and Copeland.

The real problem is "micron level" vacuums. At Micron levels you have removed all insulation around the motor (refrigerant acts as the insulator) and the motor becomes an emitter, the shell becomes a collector and the terminals can arc (inside and out)

This is why residential scrolls have a unique feature (Copeland only) which only allows the compressor to draw a compression ratio of greater than 11:1 thats when the floating seal drops you notice an equalization of pressures as it stops moving refrigerant.

So basically when your compression ratio hits this 11:1 you wont be able to go any lower, it's designed to prevent "micron level" vacuums.

Since a Scroll is close to 100% effecient it can pull down to those levels fast.

Same problem can happen in a reciprocating compressor, but hasnt been much of an issue because it takes a long time (if ever) to reach those levels.

Keep in mind not all Scrolls have the floating seal to protect them.

Okay this time I mean it...I am done with this thread! :)

[keeney]

My new plan based on the info so far is:

1. Significantly reduce the amount of lineset that is "below grade". Live with the ugliness of a lineset run along the front of the house in front of thousands of dollars worth of stone-work. Someday, the landscaping will maske most of this.

Then, based on the fact that its still a fairly long run and part of it still goes under one garage stall floor slab:

2 Add the LLS Valve. For now, just hard shut when compressor stops. Someday if required, I can add the controls to make it a pump-down setup.

3. The crank-case heater is an easy thing to add, so I will add that as well.

[Irascible]

Thank you hvac r us 2. I appreciate your breaking your vow of silence on my behalf. However, I had two questions and you answered a third one! As far as I know, no one was suggesting a pump donw that even approached a vacuum. Perhaps they draw a vacuum in other applications. But the pump down systems I've seen pump down to just above atmosphere.

[hvac r us 2]

Originally posted by Irascible
I appreciate your breaking your vow of silence on my behalf.

LOL

Listen, I am a not trying to give anybody a hard time. I realize I am a little defensive when it comes to Carrier equipment, but that is only because I really believe in the product.

I just dont like it when people blame Carrier when the real problem is application/installation.

Maybe nobody was blaming Carrier and I jumped the gun a little...it happens. But I could see it coming...

Lots of things may or may not work. But anything that has not been tested is basically field testing.

I am not so sure I would want an experimental application in my dream house.

If you were only giving me the choice of a pump down set up or a buried line set...I would bury the line set.(did I just say that?)

I can not believe I am writing on this thread again, this time I REALLY mean it, I am done with this thread!

[dash]

Originally posted by hvac r us 2

Originally posted by Irascible
I appreciate your breaking your vow of silence on my behalf.

LOL

Listen, I am a not trying to give anybody a hard time. I realize I am a little defensive when it comes to Carrier equipment, but that is only because I really believe in the product.

I just dont like it when people blame Carrier when the real problem is application/installation.

Maybe nobody was blaming Carrier and I jumped the gun a little...it happens. But I could see it coming...

Lots of things may or may not work. But anything that has not been tested is basically field testing.

I am not so sure I would want an experimental application in my dream house.

If you were only giving me the choice of a pump down set up or a buried line set...I would bury the line set.(did I just say that?)

I can not believe I am writing on this thread again, this time I REALLY mean it, I am done with this thread!



We want you in Florida,if it's that easy ,to keep draging you back into problem jobs!Concessions should be a piece of cake!hehehehe

[plain spoken]

Originally posted by Irascible
Thank you hvac r us 2. I appreciate your breaking your vow of silence on my behalf. However, I had two questions and you answered a third one! As far as I know, no one was suggesting a pump donw that even approached a vacuum. Perhaps they draw a vacuum in other applications. But the pump down systems I've seen pump down to just above atmosphere.

You must be from Missouri. You have to be shown everything.:) Go to the source, check with Copeland. Again what I said came directly from a Copeland engineer. Carrier information I am sure of, it is in writing.

Now, like HVAC said: I AM DONE!

[smokin68]

Originally posted by keeney
My new plan based on the info so far is:

1. Significantly reduce the amount of lineset that is "below grade". Live with the ugliness of a lineset run along the front of the house in front of thousands of dollars worth of stone-work. Someday, the landscaping will maske most of this.

Then, based on the fact that its still a fairly long run and part of it still goes under one garage stall floor slab:

2 Add the LLS Valve. For now, just hard shut when compressor stops. Someday if required, I can add the controls to make it a pump-down setup.

3. The crank-case heater is an easy thing to add, so I will add that as well.



Did you think of a shallow trench for the pvc leaving only the top exposed to ambient. Easy to hide. You've probably got this covered,I'm just trying to help with asthetics.

[keeney]

RE "Did you think of a shallow trench for the pvc leaving only the top exposed to ambient. Easy to hide. You've probably got this covered,I'm just trying to help with asthetics."

That is close to what the plan is. The conduit with the lineset will be on the surface of the dirt, but substantially covered with mulch or landscape rock. Very close to abient temp.

[hvac r us 2]

Originally posted by keeney
My new plan based on the info so far is:

1. Significantly reduce the amount of lineset that is "below grade". Live with the ugliness of a lineset run along the front of the house in front of thousands of dollars worth of stone-work. Someday, the landscaping will maske most of this.

Then, based on the fact that its still a fairly long run and part of it still goes under one garage stall floor slab:

2 Add the LLS Valve. For now, just hard shut when compressor stops. Someday if required, I can add the controls to make it a pump-down setup.

3. The crank-case heater is an easy thing to add, so I will add that as well.

Add a hard start kit to aid in compressor starting ability. It's going to need it with the long line being applied.

[houstontx]

Keeney,

If you install a liquid solenoid at the evaporator, inspect for a time delay in the compressor contactor circuit. The solenoid should be in parallel with the contactor itself.

All scroll compressors may not necessarily have a functioning discharge spring check valve. If your pressures equalize, it may be necessary to install one.

A "delay on break" time delay could be installed on the compressor contactor circuit, set at a few seconds, for "partial" pump down, with a low pressure control in the compressor control circuit in the event of failure of the time delay.

PVC is widely used in pressurized water systems in sensitive areas with no
water leakage. The lines can be hermetically sealed and dehydrated so there is no moisture within the PVC for possible future condensation affecting line insulation.

The main opinions expressed against lines underground on this thread seemed to focus on the return of liquid to the compressor due to migration and or condensation of vapor in the suction line during the off cycle.

The liquid solenoid prevents migration.
The accumulator prevents migration of any existing liquid, if any, to compressor.
The crankcase heater vaporizes any liquid that gets past the solenoid and accumulator.

And

The possible condensation of the "superheated vapor" trapped in the suction line during off cycle with 55'F ground temperature would be LESS than a system operated with lines in ambient temperatures of less than 55'F. There are literally millions of air conditioning systems, computer rooms, process cooling, nightclubs, etc. that operate the systems with ambient temperatures in freezing and or near freezing ambient temperatures where the refrigerant lines are exposed to low temperatures, much lower than your max low of 55'F ground temperature.

There are MILLIONS of commercial refrigeration systems that operate year round in all ambient temperatures with line sets exposed to extremely low temperatures.

Every system in existence, especially fixed orfice systems, is subject to continuous liquid to the compressor when the air filters get dirty, the airflow is restricted (a homeowner closes off too many registers), dirty blower, blocked return air, wrong fan speed setting, bad blower motor, bad fan relay, bad blower motor capacitor, refrigerant overcharge, dirty evaporator, stuck compressor contactor, setting thermostat below 70'F, etc., etc., etc., etc.

Liquid to the compressor, though undesirable, is an everyday occurrence,
has been forever. In years past, most ALL compressors had factory installed crankcase heaters to help combat this and they were only discontinued,
on economy units, not because the liquid has disappeared, but as a cost saving ploy.

The handling of the common, often unavoidable, liquid is one of the main selling features of the scroll compressors

Some quotes from Copeland's web site:

Copeland Scroll - The Hottest Thing In Cooling Article Continued. . .

Copeland's unique patented scroll design enhances reliability by its superior ability to survive liquid problems; the scroll spirals separate when liquid refrigerant or foreign material is introduced.
(and)
· Axial and radial compliance allows the scroll members to separate in
the presence of liquid refrigerant, delivering unparalleled liquid handling capability.
(and)

"A second part of the problem may be that our
educational and training programs are out of date.
Twenty years ago liquid refrigerant slugging and liquid
floodback were very serious problems."
(and)

"Accumulators
Due to the Compliant Scroll’s inherent ability to
handle liquid refrigerant in flooded start and defrost
cycle operation conditions, accumulators may not be
required. On systems with extremely large refrigerant
charges or defrost schemes that allow prolonged un-controlled
liquid return to the compressor, an accumulator would be recommended."

(NOTE: No voided warranty due to liquid )

http://www.copeland-corp.com/cp_ac/cp_ac_0_1_a.htm

( At the extensive Copeland site, the only references to "underground" pertains to low temperature commercial refrigeration systems and has nothing to do with liquid refrigerant compressor damage)

A system with a positive shut off of refrigerant, accumulator, and crankcase heater, no matter where the lines were located would be LESS susceptible to liquid at the compressor than one of millions of fixed orfice systems installed in "normal" situations.

Actually, the efficiency of an underground system would be slightly
higher than one that had refrigerant lines in a hot attic or exposed to the sun.

For a manufacturer using a scroll compressor to void a warranty because of the possibility of liquid condensation due to the ground temperature in areas with 55'F and above ground temperatures and NOT restrict system use in low ambients or low thermostat settings is ludicrous; especially if it is installed properly with the addition of positive liquid shut off, accumulator, and crankcase heater.

There are also a few MILLION heat pump systems in operation that
have their line sets exposed to Very Cold temperatures.

Unless there is some secret unpublished data somewhere, even the smartest of compressors can not tell the difference between operating as a heat pump in 15'F ambient around the refrigerant lines, a computer room AC system operating at 35'F ambient, a crowded restaurant or nightclub with a large internal people load operating in 34'F ambient vs. an air conditioner with the lines underground at 55'F, as far as liquid condensation in the suction line is concerned;
except during the Off cycle, where the "heat pump", the computer room system, and the nightclub would have liquid condensing in the suction line and the underground system would have very little if Any.

A "partial" pump down i.e.. (35/40 psig) would widen any Remote possibility of condensation and be well within the dictates of acceptable scroll/recip compressor service.

"Did you think of a shallow trench for the pvc leaving only the top exposed to ambient. Easy to hide. You've probably got this covered,I'm just trying to help with asthetics." (Smokin68)

Have a Great day

[hvac r us 2]

Seriously, I am trying to let this thread go but just can't...

Although most of the information on this thread really looks impressive with quotes and numbers, it doesnt hold any merit. Not a whole lot of facts stated here...just opinions.

Copeland Scroll may be more tolerant to a liquid slug since it does not have suction valves, but will still fail if pumping a liquid.

Does the term "liquid dilution" mean anything to anybody?

A Scroll has bearings in it right? Bearings need oil right? Liquid refrigerant is a great solvent right?

Okay here's a pop quiz...What happens to a compressor when the bearings have no oil?

Tic
Toc
Tic
Toc

BUZZZ...times up!

Can you say bad compressor?

Seriously though, no reason to even be technical here right? This is elementary stuff.

Millions of refrigeration units run in extreme temps and with buried lines? I agree, but there is a little bit of a differance isnt there?

I mean, I cant remember the last time I saw a residential split with a liquid reciever and a pump down mode.

There are differant components involved right? Like a liquid reciever?

Even if you add an accumulator, depending on line size (liquid) and total lenght still may not do the job. It would have to be sized to handle 70% of the total refrigerant charge...any line set approaching 100ft you would probably be SOL.

Comparing a heat pump running in cold temps in the heating mode to an a/c unit running in the cooling mode is two differant things isnt it?

I mean think about it, a heat pump only uses about a third of the refrigerant in the heating mode and stores the rest in the accumulator. An a/c unit uses 100% of the refrigerant and stores none. A heat pump compressor has a higher compression ratio. This is not by accident but by design.

Point being can we compare apples to apples here?

I cant believe people try to justify what is known to be a problem.

Still always falls back to the same conclusion.

Now for the million dollar question...

Name the number one reason compressors fail?

"lack of oil"

Is that your final answer?

Should be, cause it's correct!

I really didnt intend on debating this subject or show any disrespect to anybody, just wanted to provide the correct advice.


Can't we all just get along? LOL I am guessing that is probably a no, since I am of the opinion that if you put three people in a room at least one person will disagree.

But isnt that what makes this country great? :)

[beenthere]

Originally posted by hvac r us 2
Seriously,
Can't we all just get along? LOL I am guessing that is probably a no, since I am of the opinion that if you put three people in a room at least one person will disagree.

:)







I have to disagree with that.

[houstontx]

********************************************
** "Although most of the information on this thread really
** looks impressive with quotes and numbers, it doesnt hold
** any merit. Not a whole lot of facts stated here...just
** opinions."
*********************************************

Reminds me of a Classic Example of Pavlov's Theory of Bureaucracy

http://elsmar.com/ubb/Forum5/HTML/000088.html


*********************************************
** "Copeland Scroll may be more tolerant to a liquid slug
** since it does not have suction valves, but will still
** fail if pumping a liquid."
********************************

True


Yes, this is elementary stuff

The original Focus of THIS thread got onto the condensing of
liquid in the suction line during the off cycle as the main problem
with underground line installations.

I suggest those interested,
back up about 3 feet and start over.

Assuming an 1 1/8 OD inch suction line

The internal volume of which is .539976 cu ft / 100 ft length

The volume of superheated refrigerant 22 @ 55# absolute
is 1.0702 cu ft per pound
( "partial" pump down by low pressure control set at 40 psig, NOT in a vacuum)

IF the ground temperature is low enough to condense all of
the vapor in the suction line, the result is .504556 pounds liquid.

Assuming 21 x 36 - 4 row 3/8 OD tube evaporator coil
is approximately .173611 cu ft with return manifold allowance
this is approximately .162223 pounds liquid

If we increase the suction line length to 150 ft
the corresponding liquid would be .786834 pounds

Along with the evaporator contents we have .949057 pounds liquid
An amount approximately equal to Less than One pound

This is the TOTAL Possible amount of liquid
that would be in the specified part of the low side at any given moment
(Liquid line solenoid and discharge check valve)
and it is SPREAD OUT OVER the 150 Ft length of the suction line;
this is NOT a slugging or flooding condition.

The condensed liquid would be further prohibited from
entering the compressor by the "Empty" accumulator
where upon startup it would be evaporated by the
added heat from the circulating superheated vapor
and the low pressure suction of the compressor.

One WOULD see an accumulator and "partial" pump down mode
on a "properly installed" underground line system.


************************************************** ****
** "There are differant components involved right? Like a
** liquid reciever?"
************************************************** **********

NO,
a receiver in a low ambient protected enclosure,
without a liquid line solenoid in the liquid line
would AGGRAVATE liquid migration.


************************************************** *****
** "Even if you add an accumulator, depending on line size
** (liquid) and total lenght still may not do the job. It
** would have to be sized to handle 70% of the total
** refrigerant charge...any line set approaching 100ft you
** would probably be SOL."
************************************************** **********


See the Total Refrigerant Charge that would be on the
low side above. The accumulator would only have to
handle around ONE pound of refrigerant.
(Note: Liquid line solenoid)


************************************************** ******
** "Comparing a heat pump running in cold temps in the
** heating mode to an a/c unit running in the cooling mode
** is two differant things isnt it?"
************************************************


NO,
at 65 ambient and 65 indoor, it is the SAME
whether in heating or cooling mode.


************************************************** ********
** "I mean think about it, a heat pump only uses about a
** third of the refrigerant in the heating mode and stores
** the rest in the accumulator. An a/c unit uses 100% of
** the refrigerant and stores none. A heat pump compressor
** has a higher compression ratio. This is not by accident
** but by design."
************************************************** *********



Assuming a typical split heat pump with fixed metering devices.

Where during the Off Cycle in extreme cold conditions
Most ALL of the system refrigerant migrates to the outside coil
and on to the accumulator, necessitating the large accumulator;
It Gets Fairly FULL and the compressor does not have appreciable,
if ANY, slugging or flooding.


The heat pump compressor pumps the same volume
and the same % of refrigerant at comparable operating
temperatures.
The % of the total refrigerant in the system that is
circulated is only influenced by the change in specific
volume changes as the evaporator temperature lowers.



************************************************** **********
** "Point being can we compare apples to apples here? "
************************************************** *******


Comparing suction line condensation to suction line condensation.


************************************************** *******
** "I cant believe people try to justify what is known to be a problem."
************************************************** ********


See Pavlov's Theory of Bureaucracy

http://elsmar.com/ubb/Forum5/HTML/000088.html


************************************************** ********
** "Still always falls back to the same conclusion.
** Now for the million dollar question...
** Name the number one reason compressors fail?
** "lack of oil"
** Is that your final answer?
** Should be, cause it's correct!"
************************************************** ********


True, some manufacturer's say
1. Miswiring single phase compressors
2. Oil pump out due to floodback and/or liquid migration
3. Overheating
4. Mis-application of compressor
5. Incorrect or bad electrical parts
6. Gauges and/or meters that are out of calibration
7. Inexperienced/uneducated technicians -
sloppy installation and maintenance

However, this is NOT an issue here,
a very small percentage of installations have underground lines,
therefore the major cause of lack of oil is NOT due to underground lines.
The industry overall lack of oil is due to piping
incorrectly installed to facilitate proper oil RETURN
and flooding caused by a myriad of other causes.

In summary:
As stated by others, the heat pump accumulator prevents
liquid to the compressor while having to accomodate up to
70% of the total charge, a standard AC system with a liquid line solenoid
would only subject the added NORMALLY EMPTY accuulator to approximately
ONE POUND of condensed refrigerant.
( The amount of condensed Vapor ISOLATED on the low side at shut down )

If my memory serves me right.
Many years ago there were some stories going around
about a couple of notable systems that were Devastated by Underground Lines.

The Complete System Devastation was caused by
refrigerant leaks in the suction lines which were
subject to mud and water. The systems had no/non-functioning low pressure controls
and sucked the entire systems full of contaminates,
rendering them Total Scrap.

Therefore is Not Advisable to install lines underground
UNLESS it is done properly.

Since there are few "contractors" who actually follow all
instructions and recommended procedures, it is probably
good business practice to forbid underground lines.



************************************************** *********
** "I really didnt intend on debating this subject or show any disrespect to anybody, just wanted to provide the correct advice."
**********************


Same here


************************************************** *****
*** Can't we all just get along? LOL I am guessing that is probably a no, since I am of the opinion that if you put three people in a room at least one person will disagree.

But isnt that what makes this country great? :)
*************************



Have a Great day



[Edited by houstontx on 07-28-2004 at 12:31 PM]

[plain spoken]

I am not going to do it.....I am not going to do it...... I am not going to do it.........Bye

[beenthere]

Originally posted by plain spoken
I am not going to do it.....I am not going to do it...... I am not going to do it.........Bye


Your unSpoken words carry wisedom!

[james mo]

I saved myself $1,000, but created 20 years of cooling problems and repairs---My time is so valuable, I cannot even start to figure what 20 years worth of headaches would come to.

[hvac r us 2]

Originally posted by plain spoken
I am not going to do it.....I am not going to do it...... I am not going to do it.........Bye


:)

[dash]

Originally posted by hvac r us 2

Originally posted by plain spoken
I am not going to do it.....I am not going to do it...... I am not going to do it.........Bye


:)


Oh come ,one of you,just one more time!

[dash]

Originally posted by hvac r us 2

Originally posted by plain spoken
I am not going to do it.....I am not going to do it...... I am not going to do it.........Bye


:)


Oh come on now ,one of you two,just one more time!

[duane]

Originally posted by Irascible
AFAIK know most or all new scrolls have check valves, so it shouldn't equalize through the compressor.

I'm dying to hear BT or somone else on this pump down idea. A non-bleed TXV or LLS sounds like a solution. But a pumpdown setup sounds really interesting. The only thing I wonder is with all extra refrigerant that you'll have to add to compensate for the lineset length, will the condenser have the necessary internal volume to pump down without a problem (on a hot day for example)?

There's a Copeland 8 ton scroll compressor in the chiller I installed 5/04 in a customer's office building. The TEV promptly failed in July,so system pumped itself down before I got there(a closed TEV acts just like a closed LLS valve). Compressor was still running because insufficient room in condensor caused persistent 20 psi, which isn't low enough to trip the 15 psi low pres cutout switch. Was surprised to see that pressure was equal in both high and low side gauges. Two pressures on this beast equalize, but I don't quite understand how. Any clue?

[mark beiser]

Originally posted by hvac r us 2
I mean, I cant remember the last time I saw a residential split with a liquid reciever and a pump down mode.

I can show you 7 of them on one house in Westover Hills, Texas. :P

Rich people, mansion, 7 systems they never want to see or hear, 175 to 250 foot linesets, 125 feet of each lineset runs underground. All 7 units use a pumpdown cycle and have rather large liquid recievers added to them. 5 of them have have been running since 1979, 2 of them since 1988. The systems are VERY interesting to charge, lol.

Ok, so thats a rare exeption, and an engineer and a Lennox rep were involved with the designs, or so I was told. ;)

[beenthere]

A pump down system is easy to install.
You'll need a reciever to hold the extra charge, and someone that knows what he's doing to size it properly, and wire it up, and set the pressure control.
Even if its a Scroll you will want a start kit on it.

The MANUFACTURES rep, will still be able to void warranty if they did not give approval before you install the pump down system.

We consult the Manufacturer first before we install long line sets (140', 180') or under ground lines. We don't risk losing warranties.

Get approval FIRST!

[beenthere]

Originally posted by duane

Originally posted by Irascible
AFAIK know most or all new scrolls have check valves, so it shouldn't equalize through the compressor.



There's a Copeland 8 ton scroll compressor in the chiller I installed 5/04 in a customer's office building. The TEV promptly failed in July,so system pumped itself down before I got there(a closed TEV acts just like a closed LLS valve). Compressor was still running because insufficient room in condensor caused persistent 20 psi, which isn't low enough to trip the 15 psi low pres cutout switch. Was surprised to see that pressure was equal in both high and low side gauges. Two pressures on this beast equalize, but I don't quite understand how. Any clue?


There should have been a reciever before the TXV, and the LLSV. So the system could work right, so the txv shutting down completely would have had the same effect as the SV, but if it left some gas go through it might have been enough to keep the comp running with out enough gas coming back to cool the comp, and destroyed the scroll that way, and then equalized through the txv. Or the overheated warped scroll.

[cem-bsee]

ground temp of 55F in MN? get real -- maybe if one puts the lineset down 7ft!
I can put water thru cable insulation in 24hours, so why does anyone think that foam will keep out water away from the refrig line?

BTW, how deep is the incoming water pipe? In Marion IN in 1983, pipes which were not down 36 inches were frozen.

[djsreps]

Put 40' of line set in the ground and switch over to heat mode and that is where the bulk of the heat goes before it can reach the evap coil.