Reply
 
Thread Tools Display Modes
Old 12-13-2013, 04:35 PM   #1
Junior Member
 
Join Date: Nov 2013
Location: Ohio
Posts: 7
Fuel Consumption

Folks I was wondering if anyone had any experience with using the coach generator for the AC while traveling instead of the engine AC compressor. Id heard that the efficiency loss using the AC compressor was worse than using the Generator for AC. Id started to do some calculations based upon some assumptions. Anyone with experience or inputs jump in on the discussion.

Assumptions:
@ 60mph w/Compressor OFF 9mpg fuel consumption is 6.7gph
@60mph w/Compressor ON 8mpg fuel consumption is 7.5gph
7.5 minus 6.7 = 0.8gph
Generator spec for fuel consumption @ full load is 0.7gph
Not a lot of difference between 0.7gph and 0.8gph
At estimated gas prices of $3.50/g *.1 = $.35/h of driving @ 60mpg

However if you use the 30% inefficiency rule for the Compressor, it implies that:
9mpg*30% = 2.7mpg loss implies 6.3mpg w/Compressor ON @ 60mph (fuel consumption is 9.5gph)
9.5 minus 6.7 = 2.1gph
Now the difference is significant 2.1gph vs 0.7gph
At estimated gas prices of $3.50/g *2.1gph = $7.35/h of driving @ 60mpg

I personally have never seen a 30% inefficiency using the compressor for AC. At most, Ive seen maybe a 1mpg loss. (11% inefficiency)

Equipment
2012 FR 2860 DS - Triton V10
Onan QG 4000

Any thoughts?

Thanks in advance.

Bob
__________________

__________________
65ac.cobra is offline   Reply With Quote
Old 12-13-2013, 05:20 PM   #2
2007 WildCat 32QBBS
 
05CrewDually's Avatar
 
Join Date: Jul 2011
Location: NJ
Posts: 1,762
The added oil and filter change interval on the generator would be enough for me to not do it.
__________________

__________________
*Current: 2005 Ford F350 Crew Cab Dually 6.0 diesel 4x4*
*Retired: 1987 F350 Crew Cab Dually 6.9 turbo diesel
2007 Forest River WildCat 32QBBS
05CrewDually is online now   Reply With Quote
Old 12-14-2013, 08:10 AM   #3
Senior Member
 
Join Date: Feb 2013
Location: iowa
Posts: 281
Not much difference imo but we often use both when it is hot. I see more of a mileage drop in high winds than i do with or without either ac on or off but i don't check my mpg often enough to give you hard numbers.
__________________
lbrunning is offline   Reply With Quote
Old 12-14-2013, 09:28 AM   #4
Senior Member
 
jonrjen's Avatar
 
Join Date: Sep 2013
Location: TEXAS
Posts: 766
On our past motorhomes which include Class A gas, Class C gas, and 3 different Class A diesel pushers I almost always ran with the generator running the a/c.

You can look at it in different ways, yes there is the cost of gas, oil, filters on the generator. But, the generator will also power not only the a/c but also the frig for receiving more bang for the buck if you looking at the equation from a wallet point of view.

Then there is also the point of view that not running the generator can end up costing more than running the generator. More generators will see the repair shop from lack of use then because of use. The cost of repairs from dried out gaskets and seals will far out weigh the cost of a few gallons of gas. Not to mention that the time the generator fails will be that one time that you choose to fire it up because you really need it and it won't start.

Another point of view is that after such a large investment in an RV if you can't afford the run the generator you may have chose to RV above your means.

You bought an RV to travel and be comfortable within your surroundings, so why not be comfortable.

FWIW: you do need to exercise all the components on the RV from time to time to keep them healthy, working and make you happy.
__________________
jonrjen is offline   Reply With Quote
Old 12-14-2013, 10:21 AM   #5
Senior Member
 
Join Date: Feb 2012
Posts: 956
Is it safe or even legal to run the generator while in motion? My question is based upon whether the generator electric fuel pump has an emergency cutoff as all chassis engine fuel pumps do to prevent continued pumping and fire hazard in an accident. I have not researched the circuitry to know.

As for AC during travel since there are only two of us I made a curtain to enclose the cab area on extremely hot days if the chassis AC can't keep up. It rarely is needed though.
__________________
ATVer is offline   Reply With Quote
Old 12-14-2013, 12:39 PM   #6
Love My Sunseeker
 
DXSMac's Avatar
 
Join Date: Dec 2007
Location: Pacific Northwest
Posts: 788
Quote:
Originally Posted by ATVer View Post
Is it safe or even legal to run the generator while in motion?
I did it, accidentally. I stopped at a rest stop, used the generator to power my computer and check my email. My generator is so quiet, I forgot it was on, started up the engine, and drove 70 miles before I realized it was still on! I didn't notice any difference in mileage. I track mileage on a spreadsheet on every gas fill.

Also, on other RV boards, one RV couple said they run their generator, put a roast in a crock pot, put the crock pot in the sink, and when they get to their destination, VOILA, a meal! That's outrageous to me.

I think you might have to turn it off if you are on a ferry or going through an extremely long tunnel like the Eisenhower Tunnel through Colorado, well, I know you have to have your propane off for those situations. Maybe your generator, too!
__________________
JJ only, my cat went to Rainbow Bridge July 2015

I love my Sunseeker, when I'm on a trip I don't wanna go home!!!"

Total days camping each year: AS MUCH AS POSSIBLE!
DXSMac is offline   Reply With Quote
Old 12-14-2013, 03:29 PM   #7
Senior Member
 
jonrjen's Avatar
 
Join Date: Sep 2013
Location: TEXAS
Posts: 766
Fully legal to run with the generator running. One thing to check out however is at what level of the fuel tank the generator will no longer be supplied fuel. On our Jayco Class C if you allowed the gas tank to run lower than 1/4 full the fuel feed to the generator would no longer run due to the point at which the fuel line was plumbed into the gas tank.
This is standard on most motor homes so that if the generator was left to run it would not be allowed to fully drain the fuel tank and stand the motorhome in place with an empty tank.
__________________
jonrjen is offline   Reply With Quote
Old 12-14-2013, 06:50 PM   #8
Senior Member
 
Join Date: Dec 2011
Location: Collinsville, IL
Posts: 830
Quote:
Originally Posted by jonrjen View Post
Fully legal to run with the generator running. One thing to check out however is at what level of the fuel tank the generator will no longer be supplied fuel. On our Jayco Class C if you allowed the gas tank to run lower than 1/4 full the fuel feed to the generator would no longer run due to the point at which the fuel line was plumbed into the gas tank. This is standard on most motor homes so that if the generator was left to run it would not be allowed to fully drain the fuel tank and stand the motorhome in place with an empty tank.
Same on Sunseeker. Generator fuel pickup is about 1/4 of the way up in the tank.
__________________
2012 Forest River Sunseeker 2300 Chevy
RvBill3 is offline   Reply With Quote
Old 12-15-2013, 12:03 PM   #9
Senior Member
 
Join Date: Oct 2012
Location: Cobbs Creek, VA
Posts: 201
I use the generator/roof a/c primarily for the jonrjen reason; the generator needs to be run under load to stay healthy; particularly with e enhanced fuels. But for convenience, mostly use the motor driven unit. There is probably a quart of fuel that lies dormant in the generator fuel hose and carburetor that, unlike the fuel in the tank, never gets refreshed unless you run the generator. Plus short runs (to microwave a hotdog on the run for example) doesn't give the generator a chance to warm up and drive the voitiles from the oil.
__________________
Geri is offline   Reply With Quote
Old 12-21-2013, 10:07 AM   #10
Senior Member
 
Join Date: Nov 2013
Location: Okeechobee, FL
Posts: 175
I ran the generator many times on my Class A - sure, will consume more fuel. Just downsized to a 2600 Sunseeker and modified the front overhang bunk curtain to run all the way down to the floor. Now, when I used the vehicle air conditioner, it only has to cool up to the back of the front seats. Gets so cold (Florida), I have to cycle it on and off.
__________________

__________________
Bob & Sue Rowan
Okeechobee, FL
2012 Coachmen Mirada 29DS (SOLD)
2015 Keystone Bullet Travel Trailer
2016 F-150 Lariat with Auto Trailer Backup
Dog = Morki (Yorkie-Maltese) - Zoe
Malabarbob is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Virginia Campgrounds

Reviews provided by




ForestRiverForums.com is not in any way associated with Forest River, Inc. or its associated RV manufacturing divisions.


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 02:18 PM.