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Old 03-20-2014, 05:40 PM   #15
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I ran a test for 40 miles of flat Hwy at 55 mph with AC on 7-8 mpg with AC off 9-10.5 mpg. You can do the math for yourself.
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Old 03-20-2014, 10:02 PM   #16
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Genset and house air, the only way to go IMHO
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Old 03-20-2014, 10:28 PM   #17
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On my dp with side radiator, that fan can consume up to 70hp. When you turn on the Dash AC it will run that fan much more then it would otherwise. Unfortunately I cannot tell when the hydraulic fan is running so I cannot gauge the duty cycle with and without AC on. I do believe that the gen and AC combo may break even or better tho!
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Old 03-20-2014, 10:54 PM   #18
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On a really hot day (85+) you'll need both to be comfortable.
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Old 03-21-2014, 07:05 AM   #19
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especially when driving into the sun!
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Old 04-07-2014, 09:03 PM   #20
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Quote:
Originally Posted by AKJohn View Post
He said the gasoline generator will use between 1 pint and 1 quart of fuel per hour and the house AC unit(s) will cool the MH more efficiently than the chassis AC. By running the generator it will improve the overall fuel economy of the MH. The additional benefit is putting more hours on the generator which for most MH owners does not get used enough.

Anybody tried the generator/house AC and have any definitive results?
When it's hot (say over 85 degrees) I run the genset and house a/c - usually just the front one. If it's cooler than that I run the chassis one. Just got back from a trip and had the genset crap out so ran the chassis a/c all the way home and the engine temp actually ran about 2 degrees cooler probably due to the electric fans run all the time when it is on, however when slowing down below 55mph the engine fan came on quite a bit.

I've run mine over 400 hours and my Onan Marquis gasoline genset burns right around 0.9 gallons per hour - I just figure 1 gph. Definitely not a pint to a quart unless it's maybe a 2000 watt unit.
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Old 04-08-2014, 06:05 AM   #21
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When I bought my MH the sales staff told me to run the house ac and gen.(I didn't believe them so Iran the dash air.) Five years later the dash air had a problem while on a trip so I ran the gen. and house ac. To my surprise I got and still am getting about one more mile per gallon on average and better AC in the MH.
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Old 04-08-2014, 06:58 AM   #22
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In theory, if the overall efficiency of the roof AC/genset combo is plus-or-minus within the same range as the overall efficiency of the dash AC/compressor system, then you'd end up at approximately the same fuel use either way, which is what bruceisla's rough calculation/empirical observation indicates (see the post above).

The dealer's comment sounds to me like one of those internet factoids, the validity of which unknowable due to an infinity of other factors. I'd think the right answer comes from, which seems to work the best and which do you like the best? Or, as Dylan said, "You don't need a weatherman to know which way the wind blows..."

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Old 04-08-2014, 08:46 AM   #23
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Although I don't think the load on the engine from running the dash A/C is significant on a MH, I always use the genny and the house A/C's when traveling in hot temps. I've been told that my 7500 watt Onan uses about 1/2 GPH. It's worth that to me. JMHO!
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Old 04-08-2014, 08:49 AM   #24
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Generator on, roof a/c and front fans on and we stay comfy.
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Old 04-08-2014, 09:26 AM   #25
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IMO, as others, I don't think the genset burns much more and if any than the engine does with the dash air on and about 1/2 to 1 gallon per hour. By comparison, running the dash air is like p.......into the wind and never hardly used it, even when it was working.
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Old 04-08-2014, 10:41 AM   #26
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I was talking a RV tech at the dealer the other day. He recommended running the MH generator and and house AC rather than the chassis AC while on the highway. The reasoning is that the chassis AC compressor will rob the engine of power. He said the gasoline generator will use between 1 pint and 1 quart of fuel per hour and the house AC unit(s) will cool the MH more efficiently than the chassis AC. By running the generator it will improve the overall fuel economy of the MH. The additional benefit is putting more hours on the generator which for most MH owners does not get used enough.

I agree that putting more hours on the generator is a good idea. I seldom use mine to power the MH and run it for about 40 minutes a month for maintenance only. I'm not so sure about improving the fuel economy by running the generator. I know it takes power to run the chassis AC compressor but I find it hard to believe it would make a significant difference in fuel consumption while driving on the highway. That 6.8L V10 is a pretty big compared to the AC compressor.

The issue of AC vs fuel economy was tested by the Mythbusters on cars. They got better fuel economy running the AC rather than driving with the windows down. But of course a MH is not a car.

Anybody tried the generator/house AC and have any definitive results?
Dont know where he gets that figure. Ours is 5000 watt and uses 1/2 gal. per hr.
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Old 04-08-2014, 10:20 PM   #27
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I don't have anything to add as far as which method provides better mileage but I do know that my coach stays cooler running the house AC. Biggest issue I have is when everyone (passengers) are sleeping and I get too cold while driving and have no way to turn the temp up. Anyone know of anyway to control the house AC's remotely?
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Old 04-15-2014, 06:18 PM   #28
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I asked my more experienced buddy the same question, he said that the house A/C doesn't cool down the driver area enough. Then i realized he has a Class C MH, so the drivers compartment is cut off quite a bit from the living area. If you ask me it's all about horse power, try turning off your engine A/C when you're going up a big hill and notice the power difference. Most newer A/C units are more efficient than older units, so driving on a level road isn't that big of a gas guzzler . Your generator will use the same amount of power whether you are going up a hill, down a hill, level...it doesn't matter. I use the hose A/C unless there is a lot of sun coming through the front window and I can't cool it down.
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