bugs53
Jacksonville, Fl
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I just finished an article by Bill Hazell (Lazy Days Mag) who has stated it is more economical (GAS MILAGE) to run your generator and roof air,while traveling, than to run your dash air.
He did not explain completely, so I am asking the forum for more info.
Keeping the math simple, Onan 7KW runs approximatley 1 gallon of fuel per hour. Driving 50 miles per hour would mean approx. 50 miles per gallon.
Let us say,
A Motor Home, using dash, air getting 8 miles per gallon, driven 50 miles uses 6.25 gallons of gas.
If by turning off dash air you could increase 1 mile per gallon, that now means you are using 5.55 gal per 50 miles. If there would be an increas in gas milage to 10 mpg then you seemingly use 5 gallons of gas for every 50 miles.
It appears on the surface that you have to get an extra 2 mpg to make it work, even considering normal wear and tear on Genny. What am I missing here?
How about some help here. 
bugs53
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Economical Handyman
S. California
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Interesting information ! Not to make fun of your info.
But if it is HOT, fuel is the last thing I consider.
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Admiral
Lodi, Ohio
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Yes, EH comfort is foremost and I've had both on in 100 degree weather with passengers in the back.
As far as economy though, it's my opinion since your coach engine is already running, adding a little more resistance with the AC compressor wouldn't make as much difference as running a 10-20 hp engine in addition to it.
While we're on the subject, how far back in your coach is it still comfortable with just your dash air on in, say, 90 degree humid weather?
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djevans
Tennessee
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Some good thinking going on here, but in the summer, we start the generator, both AC units and turn on the dash air as well. So we're probably not a good example.
But I will say this, I don't necessarily subscribe to the "writers" theory. Two diesel engines running or one diesel with an additional load.
Hmmm... I'm thinking there's some faulty computing going on. It might on some units with smaller gas generators and lighter AC units, BUT, our generator kicks in and goes to the highest speed if even one air conditioner comes on line.
Don . . . near 36.171N 086.784W, TN near here
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rvten
Crossville,TN
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When doing the mountains and hills. Not using the engine air. Takes a little load off the engine.
Tom & Bonnie
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trnfla
Tampa
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Also, the article points out that running the generator is a good way to excerise the generator like everyone is suppose to do monthly...
He also stated that this only applies to gas and diesel not LP generators.
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bingoldsby
Oregon State Parks - somewhere
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My opinion is that when it's hot enough to use the dash air, that's the time it shouldn't be used at all - for the protection of the engine and transmission. My dash air condenser covered up the entire opening of the engine's radiator - which also contains the cooling sections for the transmission and engine oils. Turning on the air conditioner and dragging up hills on a hot day seemed like a terrible thing to do to the engine and transmission by dumping more heat into it all.
Because I was having some engine heat problems (even after having the radiator recored), I decided to remove the dash air condenser completely. I now HAVE to use the generator and roof air when it's hot. It works great and I stay really comfortable.
I have no other reason to run the generator but in that situation, so it's good exercise while doing something productive and important. And the engine is much, much happier for opening up the front of the engine radiator completely.
Gas?? I don't know. Can't change any of it anyway.
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chiefcramer
USA Somewhere
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I think the figure of 1 gallon per hour to run the generator at full load is too high. Try checking the numbers at 1/2 gallon per hour which should be closer to actual usage.
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djevans
Tennessee
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chiefcramer . . .
Well ours is a Quiet Diesel and runs closer to 3/4 gallon of diesel per hour at the higher RPM. (moderate load) Some do run a bit more. With no load it's closer to .4 per hour. But even one AC unit on kicks the generator in to high speed.
I think he might have rounded up for "example" sake. I think if you cut his 1 to .75 he's still short.
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Jim83Itasca
La Quinta Calif
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chiefcramer wrote:I think the figure of 1 gallon per hour to run the generator at full load is too high. Try checking the numbers at 1/2 gallon per hour which should be closer to actual usage.
Chief, My Onan 6500 running with both airs on consumes 1 GPH (measured) and with the PD9245 cranking also.....
Jim
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