| Feasibility of Running 2 ACs on 4kw Onan [message #298029] |
Fri, 25 March 2016 12:08  |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma:
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Senior Member |
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The previous owner of my coach lived in a much cooler climate than I do here in Texas, and I've been chasing down some heat related issues to get my coach ready for use this summer. High on the list is adding a second AC, to keep up with the 100+ degree days that are common here in DFW. If possible, I'd like to do this without upgrading the existing Onan 4kw unit. Looking at some of the newer ACs out there, it appears that I ~may~ be able to get away with replacing the one, original (13.5K btu, I believe) AC unit with 2, 13.5K Atwood Air Commanders. Per this brochure, it states the Atwood 13.5K unit can be run on one, 2000 watt generator:
http://www.askforatwood.com/images/air-conditioners-brochure.pdf
Other than what appears to be a heat-soak/vapor-lock issue with my current Onan in Temps over 95 degrees, (Also on my list to resolve before summer) it runs great. Per the previous owner and the genset's Hobbs meter, it appears to be a lower time unit. We don't do much dry camping, so the genny will only really be used while driving to keep the cabin cool, and the occasional night stopped somewhere while on route to a campsite, which would probably have the ACs set on low for the night anyway. Only other load I would be concerned about would be to run the fridge, which seems to pull around 100 watts. (Though it is about 3-4 times this at startup).
Per the Atwood Brochure, I'm looking at:
1270 Running Watts per AC (X2)
and say another 250 for the fridge and any other ancillaries...
That comes to 2800-3000 watts running, give or take, worst case. The Atwoods are supposed to be easier to start than some other ACs, but am unsure of how much overhead I would need to cover this. I would do my best to stagger starting both units, and try to manage them to prevent both compressors from cycling on at the same time...
Eventually, I do plan to upgrade the generator, but if I can get away with the 4K Onan for now, that's more gas money available to go places. FWIW, our fridge is a 110 volt Avanti home unit... Our rig does have a 2500 watt inverter, and 4, 6 volt Trojan 125s... So I think it would be possible to set up the fridge to only run off the inverter, when using both ACs on the genny if need be, and rely on the alternator to keep the fridge running and batteries up while traveling.
Thoughts?
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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