ACE 30.2 AC problem

[RFerguson]

Hi, My name is Bob Ferguson and I’m new to the forum. I have a new to me 15/16 ACE 30.2 which I picked up in early March just in time to bring home and park. I’ve had more time to learn and trouble shoot some of the systems than I expected. I’ve been following the forum for several months and found the knowledge here invaluable for working on my unit.

It’s been cool here in central NC so I have only had a couple opportunities to run the AC which worked well in early April but I’ve run into a problem with it during the heat of the last couple days. I’m running the unit off a 15 amp shore power circuit through a Hughes 30 amp surge protector. The AC starts ok and is showing good temperature drop pulling about 14 amps total at the surge protector but several time during the day appeared to cycle the compressor before reaching thermostat set point and attempt to restart relatively quickly ( I didn’t get a good cycle time reading but under 2 minutes) resulting in an amperage surge and power cutoff at the surge protector.

After experiencing this several times on Sunday, I hooked the system up Monday without the surge protector and the unit ran all day with no problems and (to my surprise) actually kept the RV reasonably cool in 85F weather.

I know little about AC units but understand that the compressor has to bleed off pressure before restating and that if it doesn’t it can cause a power spike.

Is it correct that trying to start with the compressor under pressure will cause a power spike? What would cause AC to cycle off before reaching set point? What controls the compressor start delay? Can this be something flakey with the thermostat or is something failing in the AC?
The AC is a Colman 15K with the original thermostat.

[Beau388]

Everything is operating normally. The A/C compressor will draw about 20 to 30 amps when starting but only for about 1/4 of a second. On a 15 amp circuit current draw will usually drop the supplied voltage enough to trip a EMS. Since all the conventional circuit breakers can handle this current surge, they will not trip as they do not monitor voltage like an EMS does. A low voltage A/C start tends to overheat the A/C compressor and can cause motor failure. AirExcel (Coleman) recommend that all 15,000 BTU A/Cs only be operated on 20 amp or greater A/C circuits or on generators of 3,000 or greater wattage.

[16ACE27]

15 Amp circuit - that's your problem. The 15K BTU AC will easily draw 16 to 17 amps by itself when up to pressure in the heat. Add anything else on in the coach (lights, fridge, converter, etc) and you are pulling too much for a 15 amp supply.

[Travelin' Texans]

You can use the AC without the EMS, but wouldn't recommend doing so. The EMS is doing it's job to prevent damage to your electronics from low amperage.
Your problem is not the rv, but the lack of power at the source. To add a 30 or 50 amp plug is probably cheaper than replacing the RV ac.

[cavie]

RFurgason, your A/C is on a 20 amp breaker or is supposed to be. Your A/C has a built in time delay. The analog t-stats that come in most RV's are a long way from being accurate. Nothing wrong with your A/C. Do a search on replacing with a Honeywell digital. You tube is your friend.

FYI AC = alternating current Electric. A/C = air conditioning. That way we are all on the same page.

The term Voltage Spike is used to describe a high voltage spike usually happens during a storm or a catastrophic accident with the power company. Not caused by anything having to do with your RV. The EMS may be doing it's job shutting down power due to high or low voltage. It to has a built in time delay.

[RFerguson]

Thanks all for the input. When it warms up again I’ll run the A/C on the generator to see if I can duplicate the issue and take a look at replacing the thermostat. Appreciate the help.

[RFerguson]

Well, I replaced the thermostat today and started the A/C on generator power and got basically the same results. The A/C starts fine, runs for 4-5 minutes. Then you can hear the load drop on the generator and about a minute later load back up enough to shut the generator down. It was doing the same thing last week on 15 amp shore power through a surge protector and shutting the surge protector off on high amps (or low voltage). It appears the compressor is cutting out and back on while still pressurized. Is that enough to overload the power circuit? Thoughts on that or other causes? Thanks

[Beau388]

Originally Posted by RFerguson

Well, I replaced the thermostat today and started the A/C on generator power and got basically the same results. The A/C starts fine, runs for 4-5 minutes. Then you can hear the load drop on the generator and about a minute later load back up enough to shut the generator down. It was doing the same thing last week on 15 amp shore power through a surge protector and shutting the surge protector off on high amps (or low voltage). It appears the compressor is cutting out and back on while still pressurized. Is that enough to overload the power circuit? Thoughts on that or other causes? Thanks

Typical time for the A/C compressor to cycle off is 4 to 5 minutes. This is usually a time delay built into the electrical system. If the A/C tries to cycle too soon, the compressor will lock and draw 46 amps stalling the 4000 watt Onan (which can only produce 33 amps at full load). The only reasons for the A/C to short cycle are blocked condenser (high pressure cutoff), faulty evaporator temperature sensor or a bad time delay switch on the compressor.