HVAC Intermitten Issues - Brain Teaser

Factual Questions
1

Hey everyone and HVAC Experts,

I have been looking up possible issues with my home HVAC, which has my father stumped who worked HVAC 20+ years, but I find issues close but not exactly what I have.

So I have a brand new unit installed for my home last July. It was working like a champ, and then one day it just stopped blowing cold air. I saw that the copper pipe was not getting cold or the one supposed to get warm wasn’t getting warm.

Then I had another buddy come out to take a look and was told that it was a possible bad TXV, and had too much Freon in the system, due to the gauges going haywire. So he let out some Freon, then the copper pipe started to freeze over. So my dad got a new TXV and brought it down to have it installed, and discovered my buddy took too much Freon out of the system, and that he was probably using the wrong kind of gauges. (Only thought as to why his gauges were reading so high).

Anyways… he got the Freon just right and it started to blow cool air again. No need for the TXV. Right on, good to go. He kept the gauges on for several hours to see any change and there was a slight drop in pressure/coil temp, but not enough to warrant a leak. So he added Freon back in and got it to where after a while it was stable, again, and even colder than ever. Awesome. Ok now we run to the store with everything working. When we get back the compressor just shut off. The A/C never reached our target temp which was 72 it only got down to 78 and the compressor was shut off. So it never turned off then on. It just stopped working while it was trying to cool the house. And when we shut off the system it never even tried to turn on again.

We let the fan/blower just go over night since it was kind of cool last night and let the natural air circulate through the house. But then this morning, after a power cycle, everything was working just fine. Got down to target temp of 77 and auto shut off. I will see if it is working when I get home.

I know a lot of information and probably just fluff, but want to include everything to let you know everything I know. I am researching compressors, capacitors, and hard start kits. I eliminate hard start kit since it starts, it just randomly stops working. I doubt it is the compressor, since the compressor will work. And it doesn’t seem to be the capacitor, since it will start. But I don’t know that is why I am asking all of you guys.
:confused:

2

I’m going to open the replies by punting.

I’m not a homeowner, and am not responsible for the AC unit that cools my apartment, but I’d be inclined to ask myself “How long is the warranty on this thing?”

A unit that’s mounted in the window I wouldn’t expect much, but if it’s one of those units that sits on a slab in the back yard, I might think you should have a few years of protection.

3

If the unit runs for too long and it’s especially humid in the house the evap coils (the ones in the furnace) can freeze over. When this happens it won’t blow cold air anymore and depending on other things, may shut off the outside unit. Setting the t-stat to “fan only” and/or just giving it time will allow the ice to melt and it’ll start working again.
That would be my first guess. All the monkeying around may have contributed to the problem or not done anything at all.

If it’s not working when you get home, see if there’s an access panel in the plenum (the sheet metal above the furnace where the AC lines go in) that you can pop off and look at the coils. If they’re iced over, you’ve found part of the problem. The next part is figuring out why. Could be low on freon, could be too much humidity, could just be that it’s been running for too long at a time. But at least you’ll have part of the answer.

4

You may have a combined start/run cap, and possibly the run segment is failing. Start/run caps have three terminals on top, or it’s possible that the unit has separate start and run caps.

Caps are cheap enough to probably be worth the gamble.

Otherwise, I hope the thing has more than a one-year warranty.

As for icing, that usually shows up in the form of reduced air flow, rather than a compressor shutdown, but a new system may have protections that I’m not familiar with.

5

My dad did say that the house was very humid. So that is the most common answer I have heard so far. And the fan only is what we set it at last night. I hope it is all good when I get home. Thank you for all your guys’ insight.

6

First of all, I don’t mean to sound snarky. BUT,

7

continued from above. (Why one can’t edit after 5 minutes I don’t understand. Evidently I hit the “post” button inadvertently.)

You have too many people trying to work on this unit. Why didn’t you call the person that installed it in the first place?

The “wrong gauges” thing makes me wonder if the first guy was assuming that R-22 was in the unit but it was 410A instead.

Contrary to what was said by another poster, high humidity will not freeze up a coil. Other problems, including but not limited to a low charge CAN. And the compressor “running for too long a time” will not cause it to just shut off.

It’s possible that it’s going out on an internal overload due to being too hot, or the motor current too high or both or possibly some other reason. Maybe the thermostat is defective and is satisfied at the wrong temperature.

There is just not enough to go on to hazard a guess here. You really should call your installer and hope that all the monkeying with it has not voided your warranty.

8

I agree too many hands.

My experience is commercial rather than residential.

I would also doubt icing over. If the evap is icing over the compressor will keep running, unless here is a low pressure switch, then the compressor will cycle.

my SWAG would be faulty wiring or faulty stat.

Now the problem you may have with all the hands on the unit. You may have a mixture of different gasses.

Go over all the name plates. Find out which refrigerant gas the compressor should be using.

Then find out which gas your dad added. Look at all the paper work that the contractors left and see which gas they added to the unit. Make sure that they are all the same.

If gasses have been mixed the charge needs to be evacuated ( it is illegal to just “let some out”). Depending on which gasses were used you may now have some problems with the oil.

You may now be screwed, If I was the installer you guarantee is history with others working on the system and adding gasses.