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Old 03-10-2019, 09:50 PM   #1
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Default Using GU to start AC

From what I read, a 2kW generator possibly doesn't have enough power to start a the roof AC... Would it be possible to start the AC using the GU (Underhood Generator) and then switch to the generator to run the AC? If I remember correctly, the inverter switch time is 10 millisecond.

The AC is a Dometic 641916C (15,000 BTU, 1800 W).

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Old 03-10-2019, 10:14 PM   #2
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Originally Posted by Yoshimura View Post
From what I read, a 2kW generator possibly doesn't have enough power to start a the roof AC... Would it be possible to start the AC using the GU (Underhood Generator) and then switch to the generator to run the AC? If I remember correctly, the inverter switch time is 10 millisecond.

The AC is a Dometic 641916C (15,000 BTU, 1800 W).
I once did an experiment with our Dometic 11.5K BTU unit and a high-end Outback inverter/charger switching over from shore power to inverter power while running the A/C. The inverter has a setting that determines how much delay there is between loss of shore power and start of inverter power. By default it is 6 cycles (100ms). On that setting, the A/C would stop during the changeover. When I changed it to zero, it worked fine.
(Yes, I realize that this doesn't answer your question. )
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Old 03-10-2019, 10:19 PM   #3
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A hybrid inverter could do it: https://www.magnum-dimensions.com/pr...ger-msh-series (but likely too expensive ............)
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Old 03-10-2019, 10:29 PM   #4
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Get a MicroAir Easy Start and install into the AC. It works wonders.

I have a 13500BTU Dometic AC on my travel trailer, and installed one. A 2200W Westinghouse inverter generator had no problems at all starting the AC compressor, even with the generator idling in ECO throttle mode.
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Old 03-10-2019, 11:29 PM   #5
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Originally Posted by FrayAdjacent View Post
Get a MicroAir Easy Start and install into the AC. It works wonders.
Agree. This is the cost-effective solution.
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Old 03-10-2019, 11:42 PM   #6
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Anyone install one of these on a R/T 210 Dometic A/C?
Do you have to remove the cover to access the wiring?
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Old 03-11-2019, 01:06 AM   #7
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Since I will need to run the AC on the generator only once (during a trackday next summer), I would prefer not to install a EasyStart.

So, does my initial idea would work? I start the AC using the GU/Battery then switch to the generator (by plugging the RV into the generator).
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Old 03-11-2019, 11:53 AM   #8
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There's a chance it could work but I think it would fail.

These inverter/chargers can function like a UPS. I think the problem will be the generator. Will it be able to respond to the heavy load fast enough? Also, some of those 2000W units are rated for only 1600W continuous and the charger part of the inverter will also start.

You could do a test inverter to grid transfer if you don't already own the generator. The grid would handle the instant heavy load better than a generator. If it fails on the inverter to grid transfer test then it is very unlikely it would work with a generator.

It would be hard on the inverter's internal transfer switch but the same type of transfer would happen when power is restored after an outage if the inverter functions as a UPS.
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Old 03-11-2019, 12:09 PM   #9
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Also be aware that the AC compressor is likely to cycle while the AC is running, and from what I have seen a hot compressor cycle can be even more likely to trip a breaker than a cold start, so probably would be hard on the genny also.


Ditto on the internal transfer switch as full load switching is hard on relay contacts, and the quality of the contacts in the inverter is probably not designed for full load switching.
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Old 03-11-2019, 03:20 PM   #10
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Quote:
Originally Posted by Deano View Post
Anyone install one of these on a R/T 210 Dometic A/C?
Do you have to remove the cover to access the wiring?
Yes, I've done it. You have to remove the unit from the roof to do it. Micro-Air will give you the schematic. The EasyStart does work reducing the starting current required making it less heart stopping when the Onan 2.8kw generator starts it. I know nothing about using a Honda 2000 to start the Roadtrek A/C.
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Old 03-17-2019, 10:28 PM   #11
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Quote:
Originally Posted by FrayAdjacent View Post
Get a MicroAir Easy Start and install into the AC. It works wonders.

I have a 13500BTU Dometic AC on my travel trailer, and installed one. A 2200W Westinghouse inverter generator had no problems at all starting the AC compressor, even with the generator idling in ECO throttle mode.

This!!!!!

Agree - I was able to start and run 13.5BTU ROOFTOP with my Honda EU2000.

Go search Youtube for microair - plenty of testimonyals!
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