Community Forums

MrMark52 · 08-12-2022, 11:27 AM

Quote:

Originally Posted by DFord

OP says the compressor runs for about 5 minutes before it gets noisy and trips the breaker. That's what led me to think it was liquid finding it's way back to the compressor.

(I've had many double shaft replacement motors that had equal length extra long shafts that had to be cut to length on the job.)

Those rotary compressors are cantankerous to say the least. IF liquid were to make it thru the accumulator and get to the “reed”, it would probably shatter the reed and render the compressor useless.

In the end, sadly, I bet he’s going to find he’s got a bad compressor. I can still see where it could be an electrical issue although I really don’t know what the OP considers as a “thump” vs. what I consider a thump.

On both our MoHo as well as our previous MoHo’s rooftop units, we hear a thump when the compressors kick on or off (MoHo roofs are big acoustical amplifiers). I have heard it in window units and other MoHo’s as well. Some quieter than others.
Monitoring the unit current is the only way to know for sure what’s going on at the time the compressor quits, or, follow the troubleshooting chart in the Service Manual - https://manuals.heartlandowners.org/...ice_Manual.pdf - Particularly Section 2.3 sub 2 (although I wouldn’t let the temp probe being properly installed be the only clue as to what’s wrong).

And I agree, some replacement dual shaft motors do have equal length shafts. But looking at the service manual for the unit, the old motor was CCWLE so likely the OP installed the new motor the same way which insured the correct rotation of the evap blower wheel and condenser fan.

Justin Alias · 08-14-2022, 03:25 PM

Thank you both MrMark52 and DFord for your responses, troubleshooting recommendations and providing some good overall insight.

In the end, I decided not to waste any more time or money on an old unit. I went ahead and purchased and installed a new one. It was easier, and took less time, to uninstall/remove the old Carrier roof unit and install the new Advent Air unit than it was messing with installing the new motor. Best of all is I finally got a break from the heat. I believe I made the right decision.

The new unit is an Advent Air 13.5K BTU (ACM135). The reason I purchased this particular one is because it is a direct replacement for the Carrier setup; which includes the Carrier adapter wiring kit (ACCARKIT) and start capacitor. Because of this, I was able to reuse the existing ceiling distribution box and incorporated ducting. It also meant that I could still use the remote thermostat; which also controls the furnace.

I also opted to purchase the Advent Air heat strip (ACMHD). This way I can take advantage of electric heat when connected and save on LP. Unfortunately, though, I will have to change the Carrier ceiling distribution box to an Advent Air in order to use it. A different project for a different time.

DFord · 08-14-2022, 04:14 PM

Thanks for reporting the final outcome to your problem.

I'd heard Carrier stopped making RV air conditioners. The rats could have stayed out of the business altogether and no one would have noticed.

Glad to hear there's a replacement available so you don't have a mess trying to find a way to of controlling it. If I still had an RV with a Carrier a/c, I'd save the information you provided for future reference. Swapping the units themselves out is no problem but the controls can be.

Start capacitors are great to have and allow more rapid start of the compressor and fewer circuit trips but they are something else to go wrong. I think the benefits outweigh the liabilities.

Good luck with finish work.

MrMark52 · 08-14-2022, 07:38 PM

All A/C compressors use PSC type motors so must have some means of starting - be it a start relay or start cap or both start relay and cap, or PTC type of start system.

We had a unit with built in strip heat in our previous coach. But the fan was noisy, as was the lp furnace.
We found a portable desk heater to work just as well.

Not sure what your fuel costs are - but am surprised your costs for lp are more expensive than for electricity.