what size external generator needed to run roof a/c - RV-Dreams Community Forum

vanamaniac · RV-Dreams Community Member

what size external generator needed to run roof a/c

Lucky Mike · RV-Dreams Family Member

to run the A/C with nothing else in line needs 2500 watts or better..........The 800 watt you just bought might hold a small dorm fridge up but will not handle a micro wave or anything that really needs more than 5 amps

Sushidog · RV-Dreams Family Member

How many BTU is your roof AC? I have a 1,200 watt - 1,500 watt surge Triron genny that will run my 5,000 BTU (window unit type) AC in my Aliner. Rooftop ACs vary from 8,000 BTU to 15,000 BTUs. However my little genny will not run my Dometic microwave. smarttrucks.1freecart.com/i/87019/triron-small-portable-1500-watt-surge-generator-4-stroke-model-rt-1800.htm For that you need the equiv. of a EU2000 Honda (1,600 watt) generator.

Altitude also impacts the size genny you need. If you stay a lot in the mountains you will need a little larger unit than someone who uses theirs primarily at sea level. Generally speaking, 3,000 watts+ is needed for a 13,500 BTU AC (reliably at altitude). 2 - EU2000's will be needed (with a parallel connecting cable) for a 15k BTU unit. There are a lot of variables though, as some ACs require more start-up amps than others.

Remember just because a generator can do it, doesn't mean it should do it for long periods. Just because your car can go 100 MPH wide open doesn't mean it's a good idea to run it 100 MPH driving to work every day. IMHO

Chip

Terry and Jo · RV-Dreams Family Member

To add a bit to Chip's comments, although not directly related to running the a/c, if you will be running a gasoline generator at higher altitudes than when at home, carry some extra spark plugs and tools to change plugs in the generator. As one goes higher in altitude, the oxygen level reduces and the fuel mix gets richer in fuel. That leads to fouling of the plug and the need to change plugs if the generator is used quite a bit. I learned this lesson the hard way and had to start driving to different towns to find the right plugs and tools to change the plug. My situation required a socket, an extension, and a flex-joint to make it where I didn't have to dismantle the case to get to the plug.

Oh, and when we went shopping for all that stuff, we had to go to three different stores in two different towns to find what we needed. Small towns don't give one a lot of options for finding parts and tools.

Terry

-- Edited by Terry and Jo on Monday 25th of November 2013 08:42:12 AM

Lucky Mike · RV-Dreams Family Member

Something else you may want to think about......

you stated you wanted to put the small generator you bought from habor freight in the compartment on your class B...

do not run this generator in that compartment , it is not designed to cool or ventilate in a closed area. it will create a very hazardous environment ........greater chance of fire.....asphyxiation...or electrocution. (portable generators require an earth ground that is in the instructions that none of us do!)

also 800 watts will not handle a 20 amp circuit so it will not run the converter onboard without causing damage over time. (a short time) it will create " brown outs" Low voltage cycles and surges

if you do a couple of experiments with it you will see what I'm explaining ..

take your coffee maker and plug it into the generator, fill the coffee maker with water and turn it on or use a blow dryer set on high

......at 800 watts that generator will either go into a heavy load or stall out

......if you put a voltage meter and look at the output it will show 80 or 90 volts in its down sweep and 120 to 150 in its recovery as it tries to stabilize itself.

..This all in itself will damage components burn wiring and traces on circuit boards and damage all the GFI curcuits in the coach. and if you get lucky it will just blow out the generator (this will cut coach repair costs in the long run)

Note: all these observations have personally been experienced by myself firsthand , and 2 coaches were injured in the making of this!!

-- Edited by Lucky Mike on Monday 25th of November 2013 09:20:27 AM

-- Edited by Lucky Mike on Monday 25th of November 2013 09:22:21 AM

HabDaddy · RV-Dreams Family Member

I went thru this problem last summer. I had to decide to purchase one larger unit to run the A/C, etc or get two smaller ones. None of the 2000 watt generators will run the A/C by themsleves (these are your typical low noise Honda, Yamaha, etc).

I researched this for quite some time and decided to go with two 2000 watt generators withe package that links them together to form one large generator. I went with Champion since they are 1/2 the cost of a Honda/Yamaha yet are just as quiet. I decided to do this for two reasons:

1. Weight - a 3500 watt generator is typically at least 150lbs. I did not want to keep pulling that out of my truck at each stop. Last thing I need is to kill my back while camping.
2. Backup - in case one generator decided to call it quits, I do have a backup. No, I would not be able to run the A/C but it would run everything else. It might be a bit warm without the A/C but at least I would not have to cancel the trip due to lack of power.