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08-24-2014, 11:00 AM
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#1
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Senior Member
Join Date: Apr 2012
Location: South Carolina
Posts: 1,441
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Running Coach A/C vs. Cab A/C While Driving
There have been discussions about running the generator and coach A/C versus using the cab A/C. Although the need to cool the coach for passengers is an overriding reason to run the generator and coach A/C, some have mentioned the possibility of doing it to reduce the load on the chassis engine or to save gas.
We have a Sunseeker 3100 on a Ford E450 chassis with a V-10, and I checked the fuel flow with a ScanGauge II to see how much difference the A/C actually makes. Here’s what I found with the transmission in park and an outside temperature of about 90 degrees F:
Idle speed, A/C off: 0.55 gallon per hour
Idle speed, A/C on: 0.67 gallon per hour
2000 rpm, A/C off: 1.85 gallons per hour
2000 rpm, A/C on: 2.02 gallons per hour
2000 rpm was the best speed I could hold by reading the tachometer. It is about the rpm at 50 mph, and I usually drive faster than that, but it gives an idea of the A/C compressor load at normal speeds.
Since the additional gas used at 2000 rpm with the A/C running is only 0.17 gallons per hour compared to about 0.5 gallons per hour for the generator, it is definitely more economical to use the cab air only, if that will give you the cooling you need. As for the horsepower load on the engine, the additional 0.17 gallon per hour equates to only about 2.5 horsepower.
The cab A/C does add to the engine cooling load, but we have towed a 4000 pound car in 95 degrees up a grade more than 7% at 45 mph for more than 5 miles and the engine coolant temperature gauge never moved.
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08-24-2014, 07:23 PM
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#2
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Senior Member
Join Date: Jul 2014
Location: Lake Wylie
Posts: 502
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Thanks for all that info.
I'm a fan of dash air while traveling
I just can't get myself to put hours on my gen that aren't necessary.
I know they are meant to run and I'm not afraid to run it I just like the idea of saving it for when we need it.
__________________
I never saw a Hearse towing a Trailer
'71 Dads VW camper pop up Van
'78.....tents
'93 Coleman pop ups (I'm Dad)
'04 Fleetwood Jamboree 26q
'14 Sunseeker 2860DS
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08-24-2014, 07:32 PM
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#3
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Senior Member
Join Date: Feb 2013
Location: iowa
Posts: 285
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I like the dash air also when I am driving and the dw dogs have to have air so in hot weather I run both.
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08-24-2014, 08:56 PM
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#4
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Senior Member
Join Date: Apr 2012
Location: South Carolina
Posts: 1,441
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Ibrunning
The most important factor in this equation is keeping the lady happy.
__________________
RamblerGuy
2011 Sunseeker 3100
2016 Ford Edge Toad
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08-24-2014, 09:03 PM
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#5
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Camper Less Camping
Join Date: Apr 2012
Location: NW
Posts: 3,642
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Great analysis info, thanks for sharing
__________________
2013 Sabre 32RCTS-6 (sold)
Family of 4 whose always on the GEAUX!
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08-25-2014, 12:41 PM
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#6
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Senior Member
Join Date: Apr 2014
Location: Texas
Posts: 120
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I wonder in terms of tonnage, figuring it like your home's a/c system which is larger? The cab a/c or the unit on the roof, assuming you only have one unit up there?
We usually keep our generator running because of the other appliances we keep running, mainly the fridge. So we keep the coach air running, my concern is if the cab air will cool a 32 foot coach in Texas heat?
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08-25-2014, 06:08 PM
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#7
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Senior Member
Join Date: Apr 2012
Location: South Carolina
Posts: 1,441
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Quote:
Originally Posted by howzball
I wonder in terms of tonnage, figuring it like your home's a/c system which is larger? The cab a/c or the unit on the roof, assuming you only have one unit up there?
We usually keep our generator running because of the other appliances we keep running, mainly the fridge. So we keep the coach air running, my concern is if the cab air will cool a 32 foot coach in Texas heat?
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Sorry, but I don't know the tonnage of the cab A/C system.
During our first long trip we drove through west Texas in 104 degree heat. The two of us were okay up front, but when we stopped it was hot in the coach. It took several hours to cool it down once we were plugged in at the campground. In retrospect I should have run the generator and coach A/C for at least the last few hours on the road.
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08-25-2014, 07:47 PM
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#8
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Member
Join Date: Nov 2011
Posts: 86
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Sunseeker's Dometic fridges will run on propane if 120 volts is not available for heat. They default to 120. They use 12 volts to control the fridge.
Sent from my iPhone using Forest River Forums
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08-26-2014, 01:27 AM
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#9
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Member
Join Date: Apr 2014
Posts: 55
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We run ours non stop. The cab air helps the driver and that's it IMO. I can't stand the wind noise or buffeting with the windows open. We even leave it running when we stop for a sit down lunch or dinner at a restaurant. Nice and cool when we get in. We bought ours to travel in comfort.
Sent from my iPhone using Forest River Forums
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08-26-2014, 08:10 AM
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#10
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Senior Member
Join Date: Sep 2013
Location: VA
Posts: 291
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In most cases the cab AC can keep the driver and passanger cool. But on a hot sunny day, the rest of the coach is super warm. So I would have no choice but to run the genset and AC and deal with the hit. It was a lot better then having to deal with passangers behind me complaining about the temps.
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08-26-2014, 09:31 AM
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#11
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Senior Member
Join Date: Apr 2014
Location: Texas
Posts: 120
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I hear you, we travel in a pack and there's a reason they termed the phrase "happy campers". I would love nothing more than to not have to run the generator so much but it's not feasible.
We just got back from a 700+ mile trek to the Davis Mountains and I'm not certain the coach a/c shut off once on the entire journey. Once there it was fairly cool but it was nothing but hot between here and there.
August in Texas, who would a thought? Hehe
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08-30-2014, 08:01 PM
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#12
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Senior Member
Join Date: Jul 2013
Posts: 139
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Quote:
Originally Posted by RamblerGuy
Ibrunning
The most important factor in this equation is keeping the lady happy.
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AMEN!
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08-30-2014, 09:46 PM
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#13
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Senior Member
Join Date: Nov 2013
Posts: 289
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Living in the south it gets awfully hot just running the cab air. We resolved the problem by making a curtain that attached to the over cab bed by velcro and goes behind the seat to floor. Keeps the two of us very cool just on low. About an hour before we get to our destination I go back and start the generator to cool things down. The fridge runs off propane until we get to the campground.
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08-31-2014, 02:12 PM
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#14
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Senior Member
Join Date: Apr 2014
Location: Texas
Posts: 120
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Sure wished there was a way to fire the generator up from the drivers seat or at least the passengers seat.
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