A/C Compressor shuts off after few minutes on heat cycle

[JeffandErin]

1984 Carver AC. Salon AC is a Marine Systems Air Model CM16H
Symptom: When started on heat cycle, the unit will operate for 3 to 5 minutes. Then the compressor will shut off. About 30 seconds later, there will be an extreme spike in amperage draw and the main 100 Amp AC breaker will trip. The water pump breaker does not trip nor does the salon AC breaker. Just the main 100 Amp breaker

The Fwd and after AC units operate with no issues - its just the salon unit.

Yes, I have strong water flow out all 3 of the outflows (2 on port, one on starboard). I have opened and cleaned the pump strainer several times.

I have removed the return air vent and cleaned the filter. I tried testing by run the AC unit on heat mode with the return air cover removed and it did not change anything

When the compressor shuts down, it is not warm to the touch (I thought it might be overheating)

My marina mechanic spent a very short time troubleshooting (its haulout time where I live and he is very busy). He told me that he tested the Freon and said it was fine.

If I run the system on Cooling - I have no issues at all. Its only on the heat mode.

My marina mechanic suspects that it is the reversing valve. I had no idea what that was - so I did a bit of Google research. It seems to me that if the reversing valve were sticking - I would get no heat at all. That is not the case. When I run it on heat mode, I get heated air blowing into the salon. It runs that way for about 5 minutes and then the compressor shuts off. The air handler/blower fan continues to operate and move air. About 30 seconds later, there is a spike in amperage draw and the main 100 amp breaker trips.

I shut off the salon ac unit, reset the 100 amp breaker, and i can turn the ac unit right back on in heat mode.

Any help would be appreciated

[km1125]

I wonder if you have an issue with high pressures. The reversing valve might be causing a restriction in the line and causing the high pressure on the output side of the compressor, tripping the high pressure switch, which shuts down the compressor. Once pressure drops, the compressor comes online, but it's pushing against an already compressed system which causes it to stall and would trip a breaker. Not sure why your main is tripping instead of the breaker dedicated to the unit though, as that should be the one to trip.

You might try going through a series of switching from heat mode to cool mode to cycle the reversing valve. Perhaps you can get it to work more consistently and fully open in the "heat" position.

Also, is the fan running on high? If not, that could contribute to the high pressures too (not CAUSE it, just help make the issue worse).

[JeffandErin]

Thank you KM for your reply.

I have tried cycling between heat and cold several times during my various troubleshooting sessions. It does not seem to have changed anything.

Im going to try one more time and do what others have suggested - bang on the reversing valve.

If nothing changes though, I will probably just replace the entire unit. Im ASSUMING that the Freon is the old R22 and that I would be unable to recharge the lines after discharging them to replace the reversing valve

[g36]

If it comes to it and you open up the system for repair you can use a r22 replacement gas. There are a few out there, you can google options. I have been using 407c for the last year and a half in one my r22 systems due to a leak that developed. I wasnt going to purchase new then and if it fails in the future so be it. I'm just saying you don't necessarily have to junk it because it's r22 if you want to gain more life out of it. Want something new or more efficient that's a different story of course.

[bud37]

Source of the post Im going to try one more time and do what others have suggested - bang on the reversing valve.

Worth a try...they can be stuck.....I believe there are a few videos around about this very thing.

[tomschauer]

A couple things to think about here.
I have been in the HVAC/R business for over 30 years. I have replaced hundreds of compressors, TXV's, pumps, coils etc. But I can only think of two reversing valves in all these years, and they were because of contamination in the system. They are pretty simple and fool proof, either they switch, or don't. If they don't its usually just the coil. If when you switch from cool to heat or vice versa, if you hear a swishing sound, the reversing valve is working.
When the unit switches from cool to heat, there is a check valve and a secondary metering device in play. Depending on the unit, the heating metering device may be a TXV, or just an orifice. Both will have a screen in front of them to collect any debris in the system.
If, as you say, the unit will run normally for hours in the a/c mode, something is most likely wrong on the metering side of the heat mode. (this is assuming you have adequate airflow over the coil)
If you want to take the time to find the refrigerant diagram and post it, i would be glad to show you where to take temp readings to find the problem.
If you are able to braze copper, have nitrogen to purge while brazing, have a vacuum pump, r-22 and a charging cylinder or scale to properly recharge the system etc. You can fix this. If not, don't throw good money away. If it's not don properly, it won't last long.
Also, the compressor, as mentioned by others, should not trip the main (100 amp?) breaker. It should trip the 20- or 30-amp breaker to the unit. So you will want to replace that breaker no matter what.

[JeffandErin]

Tom - Sir, thank you very much for your detailed response.

You describe switching from cool to heat (and vice versa). I have been doing that. However, your description leads me to believe that I should be doing so (by adjusting the thermostat dial) with the unit running - in order to hear the reversing valve switching. I have not been doing that. I have been shutting the unit down, then adjusting the thermostat dial, then restarting the system.

The compressor makes quite a bit of noise - Im unsure that I would hear the reversing valve switch?

As I am unskilled to perform any of the tasks you describe, it appears that my options are limited to replacing the entire unit

[JeffandErin]

UPDATE
Based upon what Tom offered (above), I went back to the boat this morning. I pulled off the dinette seat to expose the salon AC unit. Pictures attached

I started the AC on cool, let it run for a couple of minutes and then slowly turned the thermostat to heat. Once the thermostat clicked, I continued to move the thermostat slowly to heat. Then, I heard a click from the AC unit and a slight whoosh. Sounds like a whoosh of air but I assume that this was a pressure change.

Then I continue to turn the thermostat to the hottest position and let it run for a minute or two.

The air was warm, not hot

I then reversed the process and slowly turned the thermostat back to the cool position. When the thermostat clicked, I heard a click from the AC unit and a very significant whoosh when going from heat to cool.

I repeated this process 6 times - going back and forth between cool and heat. Each time I would hear the click and the whoosh of pressure change. When going from cool to heat, the whoosh was very faint, but when going from heat to cool it was very significant.

I was unable to identify the reversing valve location (see pics) but I doubt that I would have had room to do any tapping had I found it

So, if no one has any other suggestions, I guess I am resigned to replacing the entire unit.

[km1125]

Wow, that thing is really packed in there. A new unit will be smaller, even though it will have the same capacity. I'm surprised there's enough airflow around that to get through the evaporator/condensor.

I had the same boat, but it didn't come from the factory with HVAC. I started to add it, but I started in the aft cabin. The salon would have been my next project.

[tomschauer]

Jeff, it sounds like you had it running for a fair amount of time without tripping the breaker.
When the system is in the heating mode, the air flow over the indoor coil is critical to keep the head pressure and amperage in check.
That unit is in there really tight! Try running in the heat mode with it exposed as in your pics. Also, it you can actually look at the coil, clean it.
If it runs for an extended period, you have found that air flow is your problem. And if that is the case, you will have the same issue with a new unit.