That time of the year- AC symptoms!

[USAFpj]

Gents- As I'm deployed overseas, I sure could use some wisdom.

My heat pump is only 4 years old, but in Summer of 2018, the copper pipe leading from the handler to the condenser would freeze, and although the overall system would run, it would just not be cold air. I verified that this would happen after every run with the AC turned on.

We had a HVAC tech come out and he verified that there was a leak in the system. He offered to fill the system, but knew it was just a short term fix, and thought it would be best to have our installer fix it as it is under warranty through Ameristar (don't get me started).

We would temporarily run it in the Winter of 2018, but just enough to get it warm in the morning- all the while, collecting cash for the inevitable fix in Summer 2019.

Well, Summer's here, and the wife drops it down to 72 continuously, but we can't get the pipe to freeze?? She did say that it struggles at 72, though.

My thought is to drop it to 68, and run it for a day and see how it handles it? How do we not have any leak symptoms now, but did just a year ago?

Thanks for your thoughts, guys!

 

[RoyKing]

Freezing is usually a sign of too much Freon. The system is suppose to cut of the compressor when pressures drops enough for ice to form i.e. low pressure switch. Too much Freon won't let the pressure drop. So your unit was over filled and now leaked down some.

 

[USAFpj]

So is any testing or intervention needed? Is it worth it to have the installer come out and do a seasonal inspection, or just let it be? I have about a year left on the warranty of the parts, but labor is always on me.

I had always read that low Freon = freezing..

 

[techman]

Actually freezing is an indication of low freon. Lower pressure will result in the boiling point to be below 32 deg which means ice will start forming on the inside coil as well as on the large copper line (vapor line). If the freon charge was too high, it would result in a higher temp which would not cool as well. The service tech was most likely correct that you have a slow leak somewhere. Finding a slow leak can be a time consuming effort. Checking in obvious places followed by using a freon detector. It that does not work, putting a fluorescent dye in the freon allows the tech to use a UV light to hunt for the leak. I had a customer a few years ago that had a slow leak. Finally after I used dye, it still took a break of a week to allow enough of the leak to show up. Turned out to be in the outside unit where the lines in the coil passed through a steel support frame. Vibration caused a rub-through of the copper line. I suspect that there was a burr on the hole in the steel support that did the damage. Once found it was a 30 min fix. Still going fine today.

paul

 

[USAFpj]

Thank you, Paul. Why is the freezing not rearing it's ugly head? Has she just not worked the system hard enough?

 

[CADplans]

If you diagnose only using the frozen vapor line,,,
one possible cause could be lack of air flow across the evaporator coil,,

1) wrong fan speed
2) clogged filter
3) dirty evaporator coil
4) closed registers
5) on and on,,,,

 

[fitter1]

It also depends on ambient dew point to form ice on evaporator coil and suction line. Techman is correct on leak testing. If dye does not show up then freon charge must be reclaimed and introduce nitrogen to 300psig.with small freon tracer using sniffer and soap bubbles. Also last tech could of slightly over charged it and not enough freon has leaked out yet. Air flow must also be checked when leak is repaired.

 

[techman]

My experience on some systems is that they have a slow leak, perhaps from day one. If the leak rate is low enough, you could go a couple of years before it becomes an issue. Generally the boiling temp is 50 deg F. So you must lose enough refrigerant to get below 32 to start freezing. If you only leak a few ounces per year on a system with 5-7 lbs of refrigerant, it will be several years before you see problems. Most HVAC guys hate these slow leaks as they are hard to find. They get masked easily with a small charge top off (the famous "blow and go" fix). I have known of quite a few systems that would get 1-2 pounds every year or two.

As CADplans stated, dirty inside coil, clogged filter for fan issues can also cause freezing, so they would be the easy things to check first. But after that low charge is the most likely culprit. One hint is to look for a spot in the system for an oily area. As freon leaks it also carries a small quantity of oil with it. Sometimes you get lucky and see a film of oil on an inside or outside coil, or on a line fitting. That would be the first place to look for a problem. Another (but relatively rare) problem is a leaky schrader valve on the service ports. For a 4 year old unit, fixing the leak is the best solution. Do not be fooled into being sold a new system because of a fixable leak in the system.

paul

 

[Sigarms]

I kind of know HVAC systems. My experience has always been that you can't trouble shoot them over the internet:laughing:

There is a thing called a start up sheet or "commisioning report" that any decent HVAC company provides their customer. First thing is to look at that for a baseline...

Thing is, it's not what people want to hear, but after taking hundreds of phone calls from "service techs" in the field on issues, you find you need to put everything down in writing.

 

[Tractor Seabee]

Amen! It especially difficult when the owner does not know the proper nomenclature for the system parts. Like; is the frosting line the suction or the liquid line. Totally different diagnosis. 99 times out of a hundred a frosting coil or suction line indicates insufficient air flow across the coil for a myriad of reasons. We used to make many diagnosis using temperatures before we put the gauges on. These new AC units being installed today are a new breed of cat that us old timers are not familiar with. Most have a critical charge of refrigerant (Freon, is a DuPont brand name) and a few ounces either way makes a difference. I quit the trade 30 years ago so my experience is now worthless.

Ron