Understanding Coach/RV Performance by CAT

[Chet18013]

We run the generator to keep the WHOLE coach cool while going down the road. Our generator is a 7.5KW Onan and it uses a little less than .5 gph. It has no trouble running both roof AC units.  Running the dash air increases the load on the engine and fuel mileage will go down. To what extent, I'm not sure. But I consider it to be a stand off. The benefits are the entire coach is cool, and you have more power to pull the hills when the dash AC is not in operation.

As far as wear on the genset, these diesel gensets are designed for continuous duty and it is actually better for them to be run. Ours now has 2468 hours on it  and all I ever have done to it was replace the electric fuel pump at about 800 hours (premature failure and the coach, a Beaver Marquis now has 131,000 miles). I fully expect to double the hours on it before considering an overhaul. I do change the oil and filter every 100-110 hours--without fail.

Chet18013

 

[BernieD]

Jeff & Smoky

We too run both of our A/Cs off our generator (7.5kw Onan) just like Chet. At 1/2 gallon per hour for the genset, that is less than .1 gallons per mile on the highway. I would expect your dash air to use more than that, but no I don't have any documentation on that. You also gain by reducing all the heat buildup in your engine compartment from the dash air. Ever see those signs "10 mile grade ahead, turn off A/Cs to prevent engine overheating"?

 

[Jeff]

Jeff & Smoky

You also gain by reducing all the heat buildup in your engine compartment from the dash air. Ever see those signs "10 mile grade ahead, turn off A/Cs to prevent engine overheating"?

Bernie:

You mean like westbound I-90 climbing out of the Columbia River gorge in WA. 8)

 

[Jim Godward]

Jeff,

That is why we go to Portland first on our trips west and come back on I-90.? ?

Not really, but it makes a good story!!? ?VBG  It seems to just work out that way as the schedule for seeing grand kids worked best that way the last couple of times!

 

[BernieD]

You mean like westbound I-90 climbing out of the Columbia River gorge in WA. 8)

I don't remember the signage on I-90, but I-10 climbing out of Indio/Palm Springs comes to mind.

 

[Smoky]

Like Gasser, it is very hard for me to believe that running two roof conditioners and the genset uses less fuel than the dash air.  Would make an interesting experiment.

 

[blueblood]

Like Gasser, it is very hard for me to believe that running two roof conditioners and the genset uses less fuel than the dash air.? Would make an interesting experiment.

I did the calculation six years ago using an ISB 275, ONAN 7500QD and whatever ac's were in my Discovery. It was cheaper to run genset. I'm on road and the data is probably on my desktop so can't look for it and don't know if my present ac's and an ISL 400 would show similar results. It was no real surprise to me. My memory is foggy on it right now but I believe the engine ac uses about 35HP. The engine ac is in rear most and hottest part of coach and coolant must be pumped to front (40+ft) and return plus it has a fan at dash to operate as well. In any case, I saw it as an opportunity to keep my genset in excellent working condition by providing a high level of exercise something which is hard to do in "normal" course of mh living while keeping the entire mh comfortable for my dogs <vbG>

 

[Chet18013]

I think you've got it right, Leo

Chet18013