Coleman Mach 15 A/C & Generac NP50-G Genset

[JumboJet]

I installed a Coleman Mach 15 A/C as a second unit on my motor home. The rear A/C is wired to run from the 20 AMP breaker only from the generator (4800 Watts). The 30 AMP breaker connects to the transfer switch which then connects to the circuit breaker distribution box.

The A/C will start, begin to cool, cycle off, cycle on and trip the breaker.

The specification sheet shows 16.1 amp maximum draw during run with fan switch on high.

Question 1: Should the 30 AMP breaker on the Genset be switched off? Note: I unplugged the converter/charger before running the Genset.

Question 2: Would a Hard Start capacitor for the A/C eliminate tripping the breaker? Maybe?

Question 3: Do you think the 20 AMP breaker may be weak? Note: The Genset only has 37 hours on it.

I am considering wiring the rear A/C to be powered by both shore power and the Genset, but only running one A/C at any given time from the Genset. The front A/C is ducted and the rear A/C is free air. During a real warm day, it takes a while for the ducted A/C to cool down the sleeping area. I plan to cool down the sleeping area with the rear A/C and then switch to the ducted A/C at lights out.

Option 1:

[JumboJet]

dougrainer wrote:
It seems that your unit may be short cycling? How long does it wait before trying the 2nd compressor start?

Can you test the new AC on shore power? Doug

The temperature outside when I tested was 60F. I set the thermostat to the bottom, the compressor did not run very long and then would try to kick back on.

I tested the voltage from the generator at no load and it was 126 volts.

I tested the A/C from a 20 AMP household circuit and it ran fine.

Yesterday I ran the A/C from the generator when the outside temperature was 75F and the generator ran the A/C with no problem for 15 minutes and then I shut it down.

I ordered the components to build this:



If I am at a campground with 50 AMP service and I need to run both A/Cs, I will have the ability. I am going to run one hot to the 20 AMP outlet breaker and one hot to the 30 AMP RV outlet breaker. I could wire with just one hot and jump it across to both breakers, but I think I will use 10/3 with a ground instead of 8/3.

[dougrainer]

RV Gensets that are 5kw and larger will run 2 roof AC units with no problem. RV Gensets for YEARS have had a 30 and a 20 amp breaker with the 20 amp dedicated to the 2nd AC. So, your 20 amp breaker on the Genset is fine for running your new AC. The SPEC for your AC is a 20 amp breaker. It seems that your unit may be short cycling? How long does it wait before trying the 2nd compressor start? If less than 10 minutes, that may be your problem. If not, then YES, a Hard Start kit will definitely help you out. Coleman makes a Hard Start kit or you can purchase one locally. The NEW 15k will pull 14 amps at 95 degrees and the momentary surge amp on a 20 amp breaker will not cause the breaker to trip. If it does, the odds are the Genset Governor or running RPM's are not to spec. It is also possible you have a defective new AC unit(compressor) that does not release the load(equalizing) when shutting down. Can you test the new AC on shore power? Doug

[JumboJet]

naturist wrote:
I note that your wiring diagram is incomplete.

Here is my current plan:



Except for a few feet of wire, this is about an $85 project.

Transfer switch is: PowerMax PMTS-30 30 Amp Automatic Transfer Switch. Same as one already installed. I would jumper from the 30 AMP generator input connection on XFR switch one to the 30 AMP input on XFR switch two.

It did run and cycle several times on my house 20 AMP circuit connected with a 30 AMP 50' extension cord. No problems with breaker tripping.

[naturist]

The 20 amp breaker is too small, you need a 30 amp breaker there. The problem is not the 16 amp continuous draw, it is the 2-3 second surge when the compressor restarts. That surge is taking you well over 20 amps, if only for a couple seconds, which is why it initially runs, but then trips on the 2nd or third such surge. Those spec sheets say 16 amps when fan on high, and that is I'm sure accurate. But every motor draws 2-3 times their running power when first starting up. A hard-start capacitor might help, but the issue is the breaker, which might, after all be all that generator can handle on that circuit. Temporarily plug the AC into the 30 amp side, and I'll bet it will run all day without issue.

In addition, you need to make sure you NEVER allow the generator output to cross to the mains. That will cause immediate massive damage to the generator. And that is why you have a transfer switch.

If you hook the AC up to a 15 amp circuit, I doubt it will run even briefly, but will kick the breaker right away.

I note that your wiring diagram is incomplete.