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MCraw 07-27-2019 02:08 PM

3 Roof A/Cs Problems
I have a 2006 CC Magna with 3 roof heat pumps. We were loading up for a trip and I was running the mid unit only and noticed it starting cycling. It would run for some time and shut off for 3 seconds then turn back on,

We got to our destination which was 100 degrees and started running all 3 units on 50amp shore power. They seemed fine. I monitored the Total Coach System to make sure I wasnít overloading the electrical. I had 24 amps on leg 1 and 36 amps on leg 2. I thought I was ok as I was not over 50amps on either leg

The next morning, as it heated up outside, I ran all three again on shore power but the mid and rear units started cycling and the rear was blowing warm air. I called Just Answer and got a hold of Randall who is an RVIA Certified Tech who teaches RV Systems at a college near Weed, CA. He told me I could not run all three units on shore power. That shore power was limited to 6000watts or 50amps total for both legs. As a home builder, I always thought 50amp 220v was 50 amps on leg 1 at 110v and 50amps on leg 2 at 110v. Randall says that is not the case with an RV. I deferred to his expertise. He said I had to run the generator with all three units running at the same time. He had me check the voltage at each unitís breaker in the bathroom to make sure there wasnít some kind of voltage drop. He thought I might have overheated the compressors and permanently damaged to units. After testing mid and rear unit while running the front unit they seemed fine. We ran the front and rear all day and they were fine until about 10pm the rear unit started putting out hot air again.

This morning I am running the front and mid unit and the mid started cycling a few minutes ago. I am not sure what to do at this point. I live in the SF Bay Area and there are no good repair facilities that I know of.

Any suggestions would help

DJ55 07-27-2019 04:41 PM

I'm surprised at what the tech said, because you are correct that 50 amps in a RV gives you 50 amps on each of two legs. See here for a quick article covering this by a RV electrician expert.

Since your ACs do work properly at times, I wonder if the cycling is perhaps being caused by coil freezing. See here for an article describing how to diagnose that problem. Although I've never heard that coil freezing would end up with your unit blowing warm air (unless perhaps you have your thermostats to run the fans all of the time rather than on/off in auto mode).

Good luck with figuring this out!

smlranger 07-27-2019 04:55 PM

We had a 2007 Allure 42' with three 15KBTU heat pumps. We never had an issue running all three on shore power. I disagree with your RV expert.

The mid coach unit was always finicky. At times, it would short cycle. My tech support guy suggested I replace the temp sensor in the hallway nearest the middle AC. That helped.

Are you running the units on High cool? If you run them on low cool, they don't circulate as well and are prone to freezing up. Also, have you cleaned both the condenser and evaporator coils recently? You will be amazed how nasty they can get over time and if dirty, they can really impact the units ability to cool.

twinboat 07-27-2019 05:04 PM

Tech is wrong. 50 amp 240 volt is 12,000 watts. 50 amps@120 volts per leg.

If what he said was true, you would have tripped the breakers out on the pole.

The ACs compressors shouldn't short cycle, most have delays in the compressor circuit to prevent starting up against high head pressure ( locked rotor ).

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