Another potential tech screw-up, what are the impacts?

[jpsmith1cm]

Ever see air bubbles come out of a water line?

How did they get there?

Refrigerant gas is heavier than air, yes, but since non-condensibles tend to enter the system through the low side, we'll start there.

So, a small volume of air enters the suction line through a leak and is entrained with the refrigerant vapor. Since it is all flowing through the piping, it is going to tend to be mixed together due to turbulence.

Vapor enters compressor and is pumped into the high side. Still turbulent and still mixed together.

As it follows through the condenser, the refrigerant vapor will condense and the air will not, but, I don't see them separating, but rather acting like the air bubbles that I mentioned earlier.

I, too, have an open mind and am willing to learn.

[lynn comstock]

Ever see air bubbles come out of a water line?

How did they get there? Faucet aerators draw air into a water stream using a venturi effect. Another is any condition where water pressure drops below atmosheric, then air pressure pushes air into the water lines......As it follows through the condenser, the refrigerant vapor will condense and the air will not, but, I don't see them separating, but rather acting like the air bubbles that I mentioned earlier. Air is above the water in a toilet tank and does not mix with flush water until the tank empties. If I have a blender, the mechanical energy of the blender will aerate the liquid contents of the blender until it stops. If the liquid in the blender is not very viscous, the entrained air will quickly separate out because of gravity.
I, too, have an open mind and am willing to learn.

Suggested Test: Next time you are scrapping a working system with a liquid line sight glass that is liquid filled during operation, introduce some air into the low side and watch the sight glass.

[SoFlaDave]

Basically all the air will rise/migrate to the next highest point after its introduced and just take up space there. Hence the high head pressure symptoms

[SonicExplorer]

I recommend you hiring an independant Licensed HVAC company to come out and do a thorough analysis of your system, have them check

The indoor wet bulb and dry bulb temp, relative humidity, indoor temperature, return air temp, supply temp, delta t, airflow, amp draw.

Outdoor temp, suction pressure, head pressure, check the subcooling and superheat, amp draw on the compressor and the condensing fan motor.

adjust charge as necessary.

by doing these checks it can be determined if there are non condensables in the system, if the system is charged properly and if the TXV is working properly.

I think you posted some numbers on pressures before and they seemed to be within range but without all of the proper checks being done we can't know for sure.

Sme compressors sound like crap but there is nothing wrong with them, there are some compressor that sound good but don't function properly, sound is subjective and uusually doesn't mean anything.

That's great information, if I end up hiring somebody I will make sure to explain I want all those things checked and then be provided with a sheet of the results so I can share them here.

I understand scrolls and 410a systems in general can make a lot of strange noises, and some identical systems can sound different one to the next. But in my case I know what I'm hearing is not what the system was originally doing. Used to be smooth start, very, very low consistent hum in only some areas of the house, lineset wasn't doing anything to raise an eyebrow. Now after the TXV change I have louder elongated starts, a louder thrumming noise (no longer a consistent hum) and the lineset is vibrating more. Maybe this is within the realm of normal but it darn sure isn't how the system was running before the TXV swap. Until very recently I was always running in heating mode, so it's doubtful the TXV itself has anything to do with this, rather it's probably something about the TXV-change-procedure that has somehow irritated the operation of the condensor unit. I'm guessing charge related and/or contamination as those seem to be the only two obvious options. Unless the compressor incurred some wear/damage during pump-down. Which is definitely possible although I'm not sure how THAT would ever be detected or proven.

[jpsmith1cm]

Air is above the water in a toilet tank and does not mix with flush water until the tank empties.

Totally inaccurate analogy.

You described the conditions in a recovery tanks, but not within a working system.

I've seen air bubbles in water when filled from faucets without aerators.

[chamberlain]

I wonted to say hi to R,S.E.S brouther , alot of times we help by experiance and the person on the job has to take it from ther, good job.

[udarrell]

I finally ran some searches on the subject of non condensables.

This was the method we were taught to check for & remove non condensibles:
Removed Link To Competing Website

IMHO; Who is partially right &/or partially wrong within this discussion forum is of little applicable value to any of us!

A most used, effective way to detect & eliminate the problem is what counts!

[lynn comstock]

I finally ran some searches on the subject of non condensables.

This was the method we were taught to check for & remove non condensibles:
Removed Link To Competing Website

Good 10 minute way to check. I agree.

For removal of non condensables and saving the refrigerant, the procedure that I suggested in Post 79 checks and allows separation of non condensibles as they remain above the liquid seal that you leave in the recovery tank.

[HeyBob]

Gentlemen,

As usefull as that information can be, it is a direct link to a Penton competitor that we are not allowed to link to.

I had to edit the two previous posts. If you want to pass links via e-mail or PM that is acceptable.

Your future cooperation is greatly appreciated.

Carry on!

Bob

[SonicExplorer]

Gentlemen,

As usefull as that information can be, it is a direct link to a Penton competitor that we are not allowed to link to.

I had to edit the two previous posts. If you want to pass links via e-mail or PM that is acceptable.

Your future cooperation is greatly appreciated.

Carry on!

Bob

Are they allowed to paste the text from the link, or at least relevent portions of it? I would have really liked to have read it and to try and learn something.

[lynn comstock]

Totally inaccurate analogy. I disagree.
You described the conditions in a recovery tanks, but not within a working system. Think about it some more. In a working condenser a stable equalibrium is created that has a liquid layer sealing the bottom portion of the condenser just as liquid lies at the bottom of the recovery tank.
I've seen air bubbles in water when filled from faucets without aerators.

Me too. But there is always a reason. It is not a "normal" condition

[Admin]

Are they allowed to paste the text from the link, or at least relevent portions of it? I would have really liked to have read it and to try and learn something.

Sorry, but that is not allowed.

Admin*

[jpsmith1cm]

Me too. But there is always a reason. It is not a "normal" condition

Then why do the bubbles uniforally fill a sightglass?

Wouldn't the less dense vapor rise to the top and more dense liquid settle to he bottom?

The answer is turbulent flow and that is also the reason I think that the non condensibles follow the refrigerant.

Any other explanation for my measuring 50 degrees of subcooling and still having a flashing sightglass????

Yes, that is an actual measurement from an actual system that I worked on with non condensibles in it.

[lynn comstock]

Then why do the bubbles uniforally fill a sightglass? These bubbles (with subcooled liquid are refrigerant vapor bubbles and not non condensables.)
The answer is turbulent flow which creates pockets of low pressure where refrigerant vaporizes creating the bubbles that you see. and that is also the reason I think that the non condensibles follow the refrigerant. But you see this even in systems that have zero non condensables. Thus the bubbles are not non condensables.

Any other explanation for my measuring 50 degrees of subcooling and still having a flashing sightglass????

Yes, that is an actual measurement from an actual system that I worked on with non condensibles in it.

Was the subcooling pressure and temperature actually measured at the sight glass? If not, yes, there can be other reasons such as a restricted drier upstream of the sight glass.

[jpsmith1cm]

Measured close enough the the SG to not be anything else.

My thoughts were directed at poking holes in the logic that density and density alone, is responsible for the location of a gas in a system.

Now, a static vessel. Absolutely, yes. Running system, not buying it.

[lynn comstock]

Now, a static vessel. Absolutely, yes. Running system, not buying it.

I understand your desire to get the real truth here.

I'll try again with the analogy of a water tower.

• Water in the sump.
• A mist of water, water vapor and air above the sump.
• Water pumps lose their prime if air bubbles are pulled into the pump suction.
• The water moved by the pump may contain dissolved air but not any significant pockets or bubbles of air or the pump will lose its prime.

Is that any better?

[SonicExplorer]

New Carrier split 3 ton 410a/TXV heat pump is making rather loud, intermittent hissing/swhooshing noise in the small line where it enters the AHU. Happens in cooling mode only. Often occurs at start of a cooling cycle, but can also occur sometimes during the cycle. Typically lasts aywhere from 10-60 seconds and then goes away. I also checked the outdoor condensor and no odd sounds in the lines out there, only at the AHU.

What's the best guess as to potential causes? The research I've done seems to indicate it could be vapor making the hissing noise (when apparently there should be no vapor in the line at that point, instead should be just liquid?) which might mean the unit is slightly undercharged ??

Thoughts ??

Sonic

[lynn comstock]

...What's the best guess as to potential causes? The research I've done seems to indicate it could be vapor making the hissing noise (when apparently there should be no vapor in the line at that point, instead should be just liquid?) which might mean the unit is slightly undercharged ??

Good guess.

Number two guess is that friction loss in the liquid line or temperature gain or liquid lift (causing a pressure drop) is causing or contributing to the condition. Sorting it out is a job for a pro.

[SonicExplorer]

Good guess.

Number two guess is that friction loss in the liquid line or temperature gain or liquid lift (causing a pressure drop) is causing or contributing to the condition. Sorting it out is a job for a pro.

Right, definitely for the pros to sort out. Problem is, I have the 3 Stooges for an installing company, that's why I'm trying to get my thoughts together for when they come out to check the charge in the near future.

Just out of curioisty, how little undercharged could a system be to cause something like this? Are we talking as little as a few ounces, or a rather a considerable amount more?

[trouble time]

There is a piston type metering divice on most carrier heat pumps, the hissing sound that you hear is this pistion re-positioning its self for the cooling cycle. Most heat pumps default to the heating mode, in the off cycle.
The reversing valve can also make a hissing sound as it cycles.