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Old 02-24-2018, 09:31 AM   #1
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Generator Sizing

If I want to run 2 rooftop AC's and still be able to charge the batteries, what size generator am I going to need?

I am thinking around 4000 watts....
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Old 02-24-2018, 10:24 AM   #2
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Kinda depends on what they draw. You will always need more than what the stated running load requires.
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Old 02-24-2018, 12:37 PM   #3
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Quote:
Originally Posted by PNWorBUST72 View Post
If I want to run 2 rooftop AC's and still be able to charge the batteries, what size generator am I going to need?

I am thinking around 4000 watts....
Class As with 2 a/c run on 50amp shore power and(I think) a 13kw gen

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Old 02-24-2018, 12:52 PM   #4
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I had a 6kw Kubota in my last bus. It ran two 12.5k Btu roof airs just fine.

The roof airs that I ran needed about 1800 watts each while running and a little headroom for compressor startup. There are some newer high efficiency units that are closer to 1400watts.

As far as the battery charging, tell us what sort of charger you are running? Voltage and current?

What else will you be running from the generator?
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Old 02-25-2018, 10:15 AM   #5
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I am thinking 2 Dometic units at 1750W primarily while we drive. I am still not sure my OTR A/C will work, it blows cool so I am hopeful but just thinking long term.

Otherwise, we think we will be on shoe power primarily when using the AC's.
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Old 02-25-2018, 11:57 PM   #6
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Probably at least a 6kw unit. And stage the startups.

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Old 02-26-2018, 10:14 AM   #7
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Sounds funny but, could you install two smaller units, one for each leg? Each leg with a seperate breaker and just carrying 1 A/C.

I am really trying NOT to take up any under bus storage in my coach but I have 2-3 smaller areas that might fit the smaller genny's...

Remember I am converting an MCI Coach, not a schoolie.
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Old 02-26-2018, 11:02 AM   #8
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Quote:
Originally Posted by PNWorBUST72 View Post
Sounds funny but, could you install two smaller units, one for each leg? Each leg with a seperate breaker and just carrying 1 A/C.

I am really trying NOT to take up any under bus storage in my coach but I have 2-3 smaller areas that might fit the smaller genny's...

Remember I am converting an MCI Coach, not a schoolie.
The 6 kw that I installed was in an Eagle. Worked great. I don't think an 8kw would be outrageous but if ? I want to make the best choice, you should make a list of all of the loads that you will be running from your generator along with their power consumption (Watts) and total that up

That will give you a better idea of what size generator is needed.
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Old 02-26-2018, 11:17 AM   #9
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Well if I am mostly worried about being able to run the 2 A/C units, each at roughly 1700 watts, then two 2k generators would suffice no?

Now if I am boondocking, I would be close to my limits running both at the same time if I expect the generator to charge the 12v battery bank, which will be running my lights, outlets, small appliances.

Or I could run one AC and use the other charge the battery bank.

I want to use a separate quality 4 stage charger for the house batteries, and the 24v alt for the coach side. Keeping the battery banks separate...

Does that make sense?
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Old 02-26-2018, 11:45 AM   #10
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Quote:
Originally Posted by PNWorBUST72 View Post
Well if I am mostly worried about being able to run the 2 A/C units, each at roughly 1700 watts, then two 2k generators would suffice no?

Now if I am boondocking, I would be close to my limits running both at the same time if I expect the generator to charge the 12v battery bank, which will be running my lights, outlets, small appliances.

Or I could run one AC and use the other charge the battery bank.

I want to use a separate quality 4 stage charger for the house batteries, and the 24v alt for the coach side. Keeping the battery banks separate...

Does that make sense?
If the AC's are the ONLY load that you are going to be running then you could likely make it play. The Honda EU200i will run modern roof ac. Barely. It is actually rated at 1600 watts continuous, 2000watts surge.

I would suggest that you size the generator to not only run your AC's but also your house battery charger/converter, lights, tv, coffee maker etc.

I would also suggest that you have a modest amount of headroom.

My strong personal preference is for a diesel generator in a diesel powered rig. There are many benefits to diesel generators. The most obvious is that you don't have gasoline on board.

When I installed the Kubota generator in my Eagle I plumbed the fuel pickup into the main fuel tank with the pickup about 7/8 of the way down the tank. That way I could not run the bus out of fuel running the generator.

Regarding two generators and budget. If you don't want to spend$$$ on a diesel generator and are hot on the twin generator idea, take a look at the Champion 3100's. You can connect two of them in parallel. Then run one for light loads and fire the second one up when needed.

Just to throw a little chaos into the thread.... Have you considered Mini split AC's? They are much more efficient. More Btu's for less watts.
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