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Old 05-24-2012, 09:28 PM   #1
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Pipe freezing


Hey guys... I have a major problem I was hoping someone could help out with.

I have a pretty old r22 central air unit with the compressor outside and the evaporator inside the attic.
It has always been a work horse. No problems. A few years ago it developed a small leak. Refrigerant lasts a few years.
This year it was low so I had my AC tech put it in.

Everything was running great for about 3 weeks. I am in NY so it isnt very hot out yet. mid 70s during the day and significantly cooler at night.

A few weeks after the R22 was added, the unit started freezing up. I didnt realize this and it froze solid and caused a small leak in the ceiling under the attic.

I had a buddy of mine with all equipment test the pressure and everything looked great. I cleaned out the compressor which was unbelievably dirty and it ran great for another 3 days or so and started freezing again. This time I caught it earlier and just turned off the unit.

I called the professional AC tech back and he came and looked at the pressure, condenser and evaporator coil.
He told me the pressure looks fine and it is not being caused by lack of refrigerant.

He said it could be happening because the weather is so much cooler at night. He had me lock the thermostat at 75 degrees and said if it holds it there for a few days without freezing, it is most likely fine and its the outside air temp causing the problme. If it freezes up it is the coil and since they dont make R22 coils anymore, I will need an entire new unit for $5,000 - $6,000. So now Im freaking out. I do not have the money for this right now.

Does any of this make sense? Wouldnt it be more likely that the coil was dirty and clogged than out right bad? And assuming the coil is bad, cant I just get an R22 coil for this unit either online or from a plumbing supply store? Would I really need an entire new unit and have to switch to 410?
that seems very extreme to me...

Any help would be hugely appreciated!!!!!!! Thanks a million in advance.

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Old 05-24-2012, 09:44 PM   #2
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Pipe freezing


You can still replace the coil with a new one made for 410a and change the metering device to an R-22 one. Just picked up an ADP coil this week and installed an R-22 orfice for an older system.

Your tech would have to remove all your refrigerant, replace the coil, pressure test, evacuate with a vacuum pump, and recharge for you. Will cost a few hundred bucks, but not 5K.

When you say the pressures were Ok, do you happen to know what they were? It is possible if you are slightly low on charge that your unit could freeze up when it's cooler at night and then work properly during the warmer part of the day. (providing it has cycled off, or been shut off to defrost the coil)

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Old 05-24-2012, 09:54 PM   #3
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Pipe freezing


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Originally Posted by HVACDave View Post
You can still replace the coil with a new one made for 410a and change the metering device to an R-22 one. Just picked up an ADP coil this week and installed an R-22 orfice for an older system.

Your tech would have to remove all your refrigerant, replace the coil, pressure test, evacuate with a vacuum pump, and recharge for you. Will cost a few hundred bucks, but not 5K.

When you say the pressures were Ok, do you happen to know what they were? It is possible if you are slightly low on charge that your unit could freeze up when it's cooler at night and then work properly during the warmer part of the day. (providing it has cycled off, or been shut off to defrost the coil)
Thanks a lot for the reply!!! I dont really know exactly what the pressure was. But 2 guys looked at it (One a DIYer with experience and the other a pro) and both said pressure was fine.

Is it realistic that I would need a new coil? I dont mind dumping some cash into it to get it to work. A few hundred would be a pleasure at this point
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Old 05-24-2012, 10:20 PM   #4
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Pipe freezing


Have him perform a nitrogen pressure test on the lineset and evaporator coil. He'll have to pump down the system, meaning trap all refrigerant in the compressor.

The goal is to isolate the leak. It could very well be the evaporator and most likely it is as that's where 99 of 100 leaks occur, but it also simply could be a shraeder valve, like on a bicycle tube, at the condenser.

As aforementioned, coils are (still) made to handle both R-22 and R410-A. it's the metering device (txv) that counts.
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Old 05-24-2012, 10:32 PM   #5
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Pipe freezing


There's about 3 things that could be leading to your problem as I see it from my laptop . You could be having some restriction in the metering device, you could be having some reduction of airflow through the coil, or you may still be undercharged.

Before you head out to change out a bunch of stuff, consider the following:

Do you change your filters on your indoor unit fairly religiously, or is there a chance that the coil may have gotten plugged up with dirt over the years, which is now causing airflow problems? (could also be the fan getting dirty as well) Might be worth just making sure that you don't just need a cleaning to restore the correct airflow.

How much do you trust the guys that have looked at your stuff, I know a lot of guys are experts when they stand to make a couple grand selling you a new system instead of a couple hundred fixing your old one. (Just asking)

Changing out the coil should correct all options, as you will be replacing the metering device, the coil will be clean, and the unit will be freshly charged. As in all things, if the job's done right you should have minimal problems.

That being said, if you change out the coil, and then something happens to old Bessy, now you're in for a whole new set up again, and the few hundred bucks will be out the window. That's the call you'll have to make.
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Old 05-25-2012, 03:39 AM   #6
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Pipe freezing


Pretty Old = End of Life.
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Old 05-29-2012, 06:03 AM   #7
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Pipe freezing


Thanks guys.

The air out of the registers seems fine. Also when turned on, there is almost exactly a 20 degree difference between the air going in through the filter and the air coming out of the registers.
Until it freezes up of course... then I get no air flow out of the registers until it melts.

Ive had it running for about 5 days now without problems. The first 2 days I did what my AC guy told me to do which was leave it on 75 to see what happens. It was only about 75 degrees out so the AC was mostly off. The last 3 days have been significantly hotter and the AC was running most of the day. I turned it down to 72 for 2 days and still havent had a problem (knock on wood).

So is it possible that outside air temp really was the issue here? This started happening a few weeks after he added refrigerant. Is it possible he added too much? Ive heard of that causing problems.

Thanks again!!!!
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Old 05-29-2012, 09:24 AM   #8
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Pipe freezing


From what you are saying it looks like the outside temperature could be the problem. But if you are leaking freon, changing the coil will only help if it is the coil that is leaking. It could also be the outside coil or the copper lines. Could also be ductwork issues. You need a competent tech to find out EXACTLY where it is leaking or if it is leaking.
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Old 05-29-2012, 10:10 AM   #9
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Pipe freezing


I don't think the outside temp caused the problem, I'll double check the inside air blow to make sure they are still strong. (assume you did not close any of the registers)
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Old 05-29-2012, 11:14 AM   #10
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Pipe freezing


did anybody check the round squirrel cage fins? if they are rounded off with dust/dirt the lack of catching air the coil will stat to ice to the condenser.ice travels from the evaporator out onto the suction line all the way out to the condenser....pressures will always be good on a restart with the house hot/warm.check that squirrel cage,is the return ducted to the back of the unit in the attic tight...sucking in hot attic are will add a unwanted load.if the unit has a good charge that insulated line out of the air handler should feel like a cold beer NOTE the outside temp effects the pressures within with a lower hi side and then a lower suction pressure as the night cools the day.


Last edited by biggles; 05-29-2012 at 11:16 AM.
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