TXV Questions

[skizot]

I am going to have the fixed orifice metering device on my system replaced with a TXV. I've been talking with a company about performing this task. I didn't ask them for step-by-step details on how they were going to install it, but I am looking to you guys for the right questions to ask about the install. They said that they would pump all of the refrigerant back to the condensing unit (I guess this is referred to as pumping the system down?) while they were installing the TXV. They also said they would be installing a liquid line filter drier. I've looked at the documentation for my unit, and the TXV should be able to be installed without any brazing, but I don't think that's the case for the filter drier.

a) Is pumping the system down the correct procedure for installing a TXV?

b) My condensing unit already has a filter drier on it. Is it OK for them to just leave it there and install the new one?

c) Does the new filter drier need to go inside right before the TXV, or outside?

d) Does the entire system need to be purged and evacuated? If so, this can't be done with the unit just pumped down, right?

e) If brazing is required for the new filter drier, does the entire system need to be purged with nitrogen, or just the section where they're installing the drier?

f) What questions should I be asking them?

[beenthere]

I am going to have the fixed orifice metering device on my system replaced with a TXV. I've been talking with a company about performing this task. I didn't ask them for step-by-step details on how they were going to install it, but I am looking to you guys for the right questions to ask about the install. They said that they would pump all of the refrigerant back to the condensing unit (I guess this is referred to as pumping the system down?) while they were installing the TXV. They also said they would be installing a liquid line filter drier. I've looked at the documentation for my unit, and the TXV should be able to be installed without any brazing, but I don't think that's the case for the filter drier.

a) Is pumping the system down the correct procedure for installing a TXV?

Yes

b) My condensing unit already has a filter drier on it. Is it OK for them to just leave it there and install the new one?

Not really

c) Does the new filter drier need to go inside right before the TXV, or outside?

At TXV is best

d) Does the entire system need to be purged and evacuated? If so, this can't be done with the unit just pumped down, right?

If factory filter drier is inside unit, and being removed it does

e) If brazing is required for the new filter drier, does the entire system need to be purged with nitrogen, or just the section where they're installing the drier?

Any area being brazed

f) What questions should I be asking them?

These. :D LOL

[bornriding]

Skizot...
Just one question??
Why are you going to pay someone to replace yur piston with a TXV????
I quarantee that you will NEVER make up the cost in energy saved...
( not unless the system lasts for more than 20 years ).
You would be much better off to use that money to :
1) blow additional insulation
2) Seal cracks & openings
3) Replace old windows

ETC......

Just mu thoughts,
Richard

[skizot]

Thanks, beenthere. Any other questions I should ask?


Skizot...
Just one question??
Why are you going to pay someone to replace yur piston with a TXV????
I quarantee that you will NEVER make up the cost in energy saved...
( not unless the system lasts for more than 20 years ).
You would be much better off to use that money to :
1) blow additional insulation
2) Seal cracks & openings
3) Replace old windows

ETC......

Just mu thoughts,
Richard

I've already blown the attic up to R-50 (R-60 in a couple of spots). I've also completed a massive air sealing project. I thought about replacing the windows, but they're not old, just bottom of the barrel, builder-grade windows (house is a little over 2 years old). The ROI for windows is way, way worse than the TXV.

[bornriding]

I've already blown the attic up to R-50 (R-60 in a couple of spots). I've also completed a massive air sealing project. I thought about replacing the windows, but they're not old, just bottom of the barrel, builder-grade windows (house is a little over 2 years old). The ROI for windows is way, way worse than the TXV.

I then ask again, why are you replacing the piston????
You will not 'see' a reduction in yur utility bill each month.

Richard

[Airmechanical]

I then ask again, why are you replacing the piston????
You will not 'see' a reduction in yur utility bill each month.

you will control humidity a little better with a TXV over a fixxed metering device

as you know seer will go up "slightly" as well



.

[gary_g]

I then ask again, why are you replacing the piston????
You will not 'see' a reduction in yur utility bill each month.

Richard

He 's having problems getting superheat and subcooling in spec.

Here's the story:
http://hvac-talk.com/vbb/showthread.php?t=360022

Take care.

[bornriding]

Skizot,
I apologize as i did not read the previous thread.( thanks Gary )
I would have the repair company pumped the system down & check size of piston. As others have stated, a larger piston will cause the symptoms that you are seeing.....low SH / high SC.
I'm not sure that I would go with TXV unless there is no other way...( this is due to many problems with todays manufactured TXV's ).

Richard

[skizot]

Skizot,
I apologize as i did not read the previous thread.( thanks Gary )
I would have the repair company pumped the system down & check size of piston. As others have stated, a larger piston will cause the symptoms that you are seeing.....low SH / high SC.
I'm not sure that I would go with TXV unless there is no other way...( this is due to many problems with todays manufactured TXV's ).

Richard

No worries. I have done a lot of reading on here about the advantages of a TXV, and I figured since they are going to perform similar work to get the piston out to check its size, why not install a TXV (since I'll already be paying for most of the labor).

The manufacturers data I have for my unit lists a Lennox 26K35 TXV. Have you come across any problems with that particular model (or brand) of TXV?

Thanks.

[skizot]

beenthere,


b) My condensing unit already has a filter drier on it. Is it OK for them to just leave it there and install the new one?

You said not really. What problems would it cause to leave the internal filter drier alone, and install a new one? With the system pumped down, the internal one won't be exposed to the atmosphere.

[beenthere]

LLFD are restrictions in the line set.
Having 2 is just more restriction. And later, can make it harder to diagnose problems.

It is unfortunately a common thing to have 2 LLFDs on a line set, because many do not remove the factory one.

[skizot]

LLFD are restrictions in the line set.
Having 2 is just more restriction. And later, can make it harder to diagnose problems.

It is unfortunately a common thing to have 2 LLFDs on a line set, because many do not remove the factory one.

I wondered about the restriction aspect of it. Is removing the factory one very difficult, or should I be asking them to just replace that one (maybe the factory installed drier is harder to find) instead of installing a new one? I spoke with them about this, and they were just going to leave the factory one there and install a new one between the condenser coil and evaporator.

[beenthere]

Best removed.

Difficult? No. Takes a little time though.

[skizot]

This is going to require a complete evac. of the system though, since the factory drier is behind the LL/SL valves, right?

[beenthere]

This is going to require a complete evac. of the system though, since the factory drier is behind the LL/SL valves, right?
Yep.

[skizot]

OK, so the price for the total install doubled when I asked about removing the factory filter drier. Sounds like they don't want to mess with removing it. So my next question is, if the system already has a factory filter drier on it, and it's not going to be exposed to the atmosphere, then is a new filter drier really necessary? The unit is a little over 2 years old.

[beenthere]

Text book.

If you open the system, install filter drier.

Your call.

[gary_g]

Would a second filter drier really be that bad of an idea?

[beenthere]

Would a second filter drier really be that bad of an idea?
Yes.

[skizot]

Text book.

If you open the system, install filter drier.

Your call.

Since the part of the system that's going to be open is not the part where the internal filter drier is at, I'm not seeing how the "new" filter drier placed before the TXV is going to catch any more moisture/debris than the factory installed filter drier - which is also before the TXV on the liquid line. The part that's opened will have nitrogen run through it during brazing, and then a deep vacuum pulled before the refrigerant that's been pumped down into the condensing unit is released. Please don't take my statement as arguing, as I'm just a H.O. trying to get a grasp on all of this, and I'm just thinking that this isn't quite a text book situation. Aren't most filter driers that are on systems are after the LL/SL valves, so they would definitely be exposed to the atmosphere and need to be replaced if the lineset was opened (or a new one be installed on systems that don't have a drier at all)?. But what about in this case, where the factory filter drier is before those valves, and will be closed off after the system is pumped down?

[beenthere]

Lots of factory FDs are in the outdoor unit.

Think of it this way.

With the service you have had so far.
How confident are you that the company doing this work, is going to do everything as well as they say?

As I said before, there are alot of systems with 2 FDs in teh line. Because someone didn't remove the factory one.

And they have caused problems.

Its your luck, so its your call.

[skizot]

Lots of factory FDs are in the outdoor unit.

Think of it this way.

With the service you have had so far.
How confident are you that the company doing this work, is going to do everything as well as they say?

As I said before, there are alot of systems with 2 FDs in teh line. Because someone didn't remove the factory one.

And they have caused problems.

Its your luck, so its your call.

Yes, and my luck is bad. :LOL: By the way, this is a different company.

However, my question still stands. How is this new filter drier placed down the way going to do a better job than the factory installed drier, which isn't being exposed to the atmosphere?

[beenthere]

You mean the one from the factory that you think and hope it wasn't exposed to the atmosphere when it was originally installed. As in, if the installing company didn't pull a good vacuum.
If they didn't flow nitrogen while they brazed the lines.
And if they actually purged there guage sets before checking or adding gas on all those service calls.

You have no way to know what condition the current one is in.
Including, that it could be restricting already. And causing some of your troubles.

If its removed, it eliminates another possible service charge, and additional cost to remove it later.

You can pay to have it done right the first time. Or pay more to have it done later.

[skizot]

Good points. I will have it removed. Speaking of "what ifs" though, they could damage some other component in the condensing unit while doing the brazing required to "patch" the place where the factory drier was installed. :-p However, I get your point. I just don't understand why it doubled the price of the install. Seems to me like the company I'm talking to just doesn't want to do that part of it. Maybe I'll call around some more.

[lentz]

Call someone else and get their opinion and price. Beenthere is right, pull the old one out and install a new one. I usually install one-one size larger.

Good Luck

[beenthere]

It will take them twice as long.

So the price will be more.

[Shophound]

Good points. I will have it removed. Speaking of "what ifs" though, they could damage some other component in the condensing unit while doing the brazing required to "patch" the place where the factory drier was installed. :-p However, I get your point. I just don't understand why it doubled the price of the install. Seems to me like the company I'm talking to just doesn't want to do that part of it. Maybe I'll call around some more.

It is because the refrigerant must be recovered and then restored. That takes time, and recovery equipment ain't cheap. Additionally, your prior quote did not include removing and straight piping where the factory liquid line drier was. That's more time flowing nitrogen and more time using the torch. And possibly longer vacuum pump run time, since more of the system was opened up and exposed to moisture.

Bottom line: any time a system is opened to atmosphere, it can and does absorb moisture and non-condensibles. This would include your lineset even if you left the condenser and factory drier isolated and did not change it.

[skizot]

Yeah, I don't mind spending some extra money to have things done correctly. Do things right the first time, eh? :) I really had to twist the guy's arm to get him off the "leaving the factory drier in place is fine" kick. He told me that he's been doing this for 37 years and that that's just not something you have to be concerned with. He said the extra drier wouldn't have any effect on the pressures.

With them evacuating the entire system, I can have them weigh the charge to see how far off it is from the factory (the factory charge sheet says it comes charged for 15' of lineset, and I'm almost exactly at that).

[beenthere]

I've been doing this for XX years. Is one of the worst things someone can say.
Means he doesn't know how many systems he's left the old filter drier in.
That the customer called someone else in to fix it right. And he never found out about the problem.

[skizot]

I've been doing this for XX years. Is one of the worst things someone can say.
Means he doesn't know how many systems he's left the old filter drier in.
That the customer called someone else in to fix it right. And he never found out about the problem.

Yeah, unfortunately this company seems to be the most competent out of the last 3 I've dealt with. The other two I called today wanted to charge me for a service call just to give me a quote on installing a TXV. Seems kind of backwards to me. If you want my business, and you feel that you've got to come and check out the system beforehand, then that's the price of doing business in my opinion. You don't charge someone just for a quote.

I've about given up with the HVAC companies in my town. There are about 12 of them, and not a single one is a member of the ACCA. The closest company that is, is about 35 miles away. And the thing is, while this town is by no means large, it's not the smallest either (about 120,000).

[beenthere]

Thas a decent sized area.

[john_ertw]

skizot, this doesn't really answer your questions, but is a comment from someone looking in from outside the box:

Is your system cooling your house?

If so, why not save the money you plan to spend. If your system fails early, replace the whole system with the one you really want and make sure everything is setup properly right from day one. I fear that your system has been adjusted so many times that it will never be setup as per a textbook or you will spend enough money to make a new system look attractive.

Now if your system isn't cooling your home, give this a shot by all means.

[Shophound]

skizot, this doesn't really answer your questions, but is a comment from someone looking in from outside the box:

Is your system cooling your house?

If so, why not save the money you plan to spend. If your system fails early, replace the whole system with the one you really want and make sure everything is setup properly right from day one. I fear that your system has been adjusted so many times that it will never be setup as per a textbook or you will spend enough money to make a new system look attractive.

Now if your system isn't cooling your home, give this a shot by all means.

IIRC, his system cools his house, but at marginal performance. It is also not very old. He's looking for a boost in performance and perhaps efficiency.

If a customer understands the value of a TXV and is willing to pay for it, by all means accommodate the person. The end result, done correctly, is an evaporator that performs better and a compressor that lives a longer, happier life. Hmm...maybe that translates over to the customer as well? :)