A/C Problem need a second opinion

[ehnco]

My central A/C for the last 3 seasons has not, in my opinion cooled my house adequately. It's a single floor rancher with crawlspace/attic, very well insulated. On a 90-95 degree day it would struggle to cool my house to 80-82, running all the time. I called a tech out last season who said it was drastically overcharged and recovered a bit of freon from the system. Unit still was not up to par and would only cool the house to 80-82 on a 90 degree day. I call again...this tech says it's undercharged, so he adds freon. The end of last summer here was relatively cool so it worked fine until the end of the season. This season it worked great until we had a few days of record high temps......hottest day of the year the A/C won't cool. I go out, open the cover to the compressor/condensor unit to find the start capacitor bad as well as the lead wire burned to a crisp. I replaced both and the A/C runs fine for about 4 hours and then the compressor shuts off. (Condensor fan was still running). It was 102 that day and I figured the thermal limiter shut the compressor off and went in turned off the A/C inside at the thermostat. I waited an hour and turned it back on. Compressor starts and cools the house for 2 weeks. Next extremely hot day, same deal. I am familiar with automotive A/C (ASE certified tech) but am not familiar with home units. I call for service. The guy discovers the high side pressure EXTREMELY high. I figure it's an expansion valve. The guy tells me the evaporator (A) coil refridgerant line is clogged (not the fins clogged with dust or debris - he specifically said refridgerant line) and that it should be replaced at a cost of $800. I have never heard of a refridgerant line in an automotive system clogging with the exception of the old GM DA 6 compressors with teflon piston rings which used to come apart. Is this even possible or is this guy trying to rip me off ? It shows all the symptoms of a bad expansion valve. Then a salesman from his company calls me the next day trying to convince me to replace the entire HVAC system and that they can't even find an A-coil for my unit (more BS I believe as they are common, right?). The unit outside is a Trane, inside unit is a Williamson oil burner/evap. combo. Just need a second opinion before I call the service manager back requesting that he send a tech out to replace the expansion valve.....even the tech as he was leaving said it's a possiblility it's only the expansion valve....I'd do it myself, but I got out of the automotive field years ago and sold my vacuum pump, gauges, etc.....

[ehnco]

I opened the cover for the A-coil and the high side line is almost touching (1/4 inch) from the capillary tube sensing bulb (which was uninsulated, and attached with a metal clamp).....on automotive systems that use TX expansion valves, the capillary tube was well insulated with foam and no where near the high side line. Hopefully I have solved the problem. It's 3 AM here and supposed to be 96 tomorrow with high humidity....we shall see. :confused:

[danski0224]

If you have a TXV valve, maybe you need to find a tech that checks the operation of the unit with a superheat chart and not "gauge pressures".

If the sensing bulb was attached to the liquid line, that is not good. If it is attached to the suction line, but inside the plenum and not insulated, then it is installed properly. The bulb can also be outside the plenum, but it needs to be insulated.

What has changed since three seasons ago? New system?

If the outside stuff was changed, and the work was sloppy or if the old compressor lunched, the indoor metering device could have junk in it.

[mattison]

They do and can get internal restrictions. It's actually pretty common. I'm not sure about cars today but when I did automotive back in the 80's a common problem was the orifice tube getting clogged. It's about the same thing.

But on to your problem. For that kind of money I believe I'de get a 2nd opinion. Another thing is. What is the age of your a/c system. If it's near the end of its life cycle "say 15years" and it does end up needing a coil I would pass on it and get a whole new system. High head pressure does not automatically mean a restriction. we would need to know low and high pressure. On a restriction as he's describing you would have low suction and high head. Definitly call an authorized Trane dealer to look at it.

[ehnco]

The sensing bulb is attached to the suction line, however the liquid line was in contact with the bulb as well. It seems the liquid line is much cooler (very warm, not so hot that it burns your hand as usual) to the touch today and liquid line is super cold. We are having record heat today and so far it's 78 in the house (very comfortable). Usually by now the unit would have shut down and it would be 85-90 in here on a day like today (98 degrees, 100 percent humidity). I will keep an eye on it...it's supposed to be hotter here tomorrow...I am also installing an attic fan...it's easily 140-150 up there on days like today. The unit is 11 years old. If I have any more issues with it, I am considering having it replaced next season.

[Jay11J]

The TXV buld should only be touching the suction line only. Also should be wrapped so that way the build is only sensing the suction line.

[ehnco]

The TXV buld should only be touching the suction line only. Also should be wrapped so that way the build is only sensing the suction line.

In my experience as an auto a/c tech(I left the field years ago), that's what I thought. It was 100 degrees today and the compressor did not shut down, although it still not quite as cool as it should be in here. Too cold at night, and most of the day until about 3 PM then it gets warmer in there (82 on a 100 degree day). When I was an auto tech and they were phasing out R-12, you had to have a license to purchase the remaining stock of R-12. Is this also the case with R-22 ? (needing a license to purchase?).

[mattison]

Ever since EPA mandating you've had to be licensed to get R-22.

Try removing the top of the condenser with the power off and hosing the coil out really good from the inside out.

[james curry]

your sensing bulb should be on the outlet of your evaporator , thats how it maintains constant super heat , anywhere else is not acceptable as it could pickup different temps and make the expansionvalve hunt. I guess youve had work in past that required opening the system , if it was not evacuated right and long enough their could still be air in the system , which will cause high head pressure. if it cuts out again , i would have it reclaimed and evacuated. some o f these service people only learn on the job and never really learn the science about the system ,air seeps in cracks that is very hard to get out . it needs to be evacuated for atleast an hr or more. i would try that because if you can save your self from buying a new unit that would be nice right? watch the service man and you will see him evacuate and charge in no time, when he should really be there for a while. i hope this helps! and make sure that sensing bulb is at the outlet of the evap