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Old 06-22-2013, 09:24 AM   #15
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When we are on the road, our generator runs 95% of the time, and the dash air is used as needed. We have a four legged companion who rides in the passenger compartment and demands comfort so the rooftop AC is on most of the time. We typically have 2 or 3 computers, a crock pot and a bread maker running while we move also. Fuel mileage is what it is. Comfort and convenience always take precedent.

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Old 06-23-2013, 06:37 PM   #16
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An week ago I finally made my first trip of 450 miles where the AC was never needed. I got about .5 mpg extra over the same trip with AC running. Running the gen takes about .5 gal. per hr. with only 1 AC running. 2ACs will increase to about .75 gal. You can do the math but I will do whatever it takes to be comfortable.

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Old 06-24-2013, 05:57 AM   #17
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Originally Posted by mikell View Post
Dash AC 2 mpg give or take

Genny 1 gallon per hour at most

Do the math
I think your math is a little off there friend. According to a study the SAE did in conjunction with GM at one their test facilities, a full-size GM SUV with an 8.1 V8 engine saw an increase of 10% in fuel consumption, but only while the compressor was running. The fuel consumption was not affected when the compressor was off. Even with the A/C on full, the compressor is still easily able to outperform the rest (evaporator, fan, etc.) of the system. Typically the compressor runs about 60% or 70% of the time with the system set to max. cooling.

If an RV gets (as an example) 9 mpg and the A/C increases fuel consumption by 7% (70% of 10%) that would be an increase of 0.63 mpg.

To put that in perspective, at 60 mph and burning 9 mpg, that's 6.66666 gallons per hour, an increase of 7% would be 0.4666666 of a gallon per hour.

Considering how much larger capacity the dash A/C is than a rooftop unit, it seems the dash system is a better deal.
Ted 'n' Laurie, plus Jackson (aka Deputy Dog, the Parson Russell Terrier 'fur kid') and, Rylie (who crossed the Rainbow Bridge June 14, 2012).
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Old 06-24-2013, 06:11 AM   #18
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On ours (which gets, depending on conditions, 8-10mpg), I don't notice a difference dash AC on vs. off. I do notice the fuel the 10K diesel genny is using, and that amounts to about 1/2 mpg or maybe a little less.

Bottom line here, stay comfortable. It's just not that expensive, and the option?
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Old 06-25-2013, 06:35 AM   #19
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Shoud mention the testing was done under ideal conditions


I'm SAE Lifer

Retired Fuel Systems Advanced Product Development Engineer Delphi / GM

Been there done that

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Old 06-26-2013, 05:43 AM   #20
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Strange, mines like AHicks, can't see a difference running dash A/C or not. Ditto my Dads big A and everyone else I've asked.

You'd think people would notice a 25% drop in mileage, in my case that would be 125 miles less per tank.
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Old 06-26-2013, 06:28 AM   #21
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Wow yeah I don't see a 2mpg drop running dash A/C. I see a 2mpg drop running the dash A/C, generator and towing our Honda Fit.

This was not done under ideal conditions and I am not an SAE engineer. I am however virtualization engineer. Perhaps it's in my head...

All joking aside my rig is new and maybe the newer engines and compressors are more effiecient than older rigs. I honestly don't notice a difference with just the dash A/C running. The things that make the biggest dent in my mileage is wind, hills and towing the Honda Fit.
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Old 06-26-2013, 06:29 AM   #22
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The only danger I know of running the generator without a Gen-Turi exhaust extension is exhaust fumes coming up into the living space... Takes 2 hours for my generator to fire off the CO detector if I'm parked, slides in or out does not matter.

Rollling down the highway... Well. the exhaust fumes don't have a chance to come up into the living quarters because by the time they get that high the living quarters are not there any more. (How does that joke go, "The adrmial's fallen overboard he's half a mile behind" they are back with the Adrmial.

I run mine often when driving in hot weather and at least once a month no matter what the weather is, Usually when driving.
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Old 06-26-2013, 06:53 AM   #23
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I don't pay much attention to fuel consumption - with or without dash AC running or running the genny, I just want to be comfortable wherever I am. When I had DP A's I ran with roof AC's a lot in very hot wx. It seemed more practical than having to get rid of that humidity and heat everytime we stopped.

Now that I have a B+, I find my dash air is sooo much more powerful than that of my DP's, or it appears so at least, but of course there is a much smaller space to cool. My dash air keeps the entire coach cool and humidity down and it is always on internal circulation. (Don't want to bring hot humid outside air into coach.) I also use a 12v fan to push air all the way to the back while I am rolling (only have 25' unit now) and use the same fan with roof AC on for better circulation when engine not running. Works for us and I like to be comfortable.
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Old 06-26-2013, 11:32 AM   #24
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Originally Posted by Mr_D View Post
Why X3?

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