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Old 05-19-2015, 11:54 PM   #71
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1 kilowatt = 3400 BTU. 1 horsepower = 755 watts. 1 horsepower = .64 pounds per hour of gasoline and .34 pounds per hour of diesel. Therefore your dash AC at 8000 BTU = 2.35 KW = 3.11 HP = 1.99 pounds of petrol or 1.16 pounds diesel. All of this per hour lads. Don't sweat the cost, just don't sweat, enjoy, be cool dudes & dudettes.
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Old 05-20-2015, 09:33 AM   #72
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Double that for overhead of compressor and fans and then consider your comfort...

Turn on the ac and cut speed by a few mph so the reduced drag reduces hp requirement on engine to compensate for ac being on and enjoy the ride.

I cruise along with the trucks in slow lane in auto and less less stress not needing to constantly look for chp and am a lot more relaxed and get 20 to 24 mpg instead of the 18 when doing 70.

Just relax and enjoy the ride!
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Old 05-20-2015, 04:43 PM   #73
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AC use

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Originally Posted by dlaughlin View Post
Mr. Dezolen - Thank you for your most valuable insight. I NEVER thought about staying home. I will certainly do that from now on. I'm never going anywhere, ever again! Will you next teach me how to become a curmudgeon?

I just don't understand why some folks feel the need to be rude. "...stay home and save more."

The purpose of the question wasn't to be a cheapskate, although I am one. I am not worried about fuel consumption, per se.

I simply wanted to know how the dash A/C compressor is powered. If it truly takes 60 horsepower to power the A/C as some have stated, well, then of course a significant amount of power, thus fuel, is robbed from moving the coach forward. However, if it is 100 degrees outside, all A/Cs will need to be running.

Nowhere did I say that I would sacrifice my comfort to save a penny. IF comfort levels being equal, I will choose the more economical option of dash versus generator (whichever is better). But c'mon folks, I didn't set out to be lambasted by people that have utterly nothing of value to add to the thread.

For those of you that offered valuable opinions and insight, thank you! Your assistance was appreciated.

To the few curmudgeons like Mr. Dezolen...
No idea what the difference is running dash ac / generator to cool the coach down whether gas or DP. Enlighten me please.
I don't think I would make a very good politician as I call it as I see it.

You remind me of the numerous boaters I know that are afraid to take their beautiful cruisers out on the water because they might use some fuel. I see it at the marina all the time. They take the boat out of the slip and drive to the nearest beach which is just around the corner from the marina and drop anchor for the day. Never really go anywhere.
Seriously??
One of my best friends had a mint cruiser which went in with a full tank of fuel and winter stored with most of the same tank. He had perhaps 60 hours on it after 8 years. Unfortunately Cancer got the best of him before he ever really enjoyed the boat. He was always worried he might have had to spend a few bucks to actually use it.
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Old 05-20-2015, 05:15 PM   #74
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No idea what the difference is running dash ac / generator to cool the coach down whether gas or DP. Enlighten me please.
I don't think I would make a very good politician as I call it as I see it.

You remind me of the numerous boaters I know that are afraid to take their beautiful cruisers out on the water because they might use some fuel. I see it at the marina all the time. They take the boat out of the slip and drive to the nearest beach which is just around the corner from the marina and drop anchor for the day. Never really go anywhere.
Seriously??
One of my best friends had a mint cruiser which went in with a full tank of fuel and winter stored with most of the same tank. He had perhaps 60 hours on it after 8 years. Unfortunately Cancer got the best of him before he ever really enjoyed the boat. He was always worried he might have had to spend a few bucks to actually use it.
So, a young couple in their 30's with a couple of kids, excited about their 18 year old American Tradition (and trying to learn by asking good questions) remind you of a friend of yours that passed away from cancer and lightly used his mint cruiser for fear of fuel expense? He owned the boat for eight years and the OP might have owned the American Tradition a few weeks.

Really?
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Old 05-20-2015, 07:56 PM   #75
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Here is what I have found...

2 years ago I used the dash air a lot for minor needs. I didn't use the generator and house AC that much.

Last year I totally relied on the generator and house AC except in a few cases where the sun was pouring into the windshield and the dash AC provided direct cool air.

Now...no 2 years are exactly the same. Different roads, different winds, different hills and different driving patterns. That being said using strictly a MPG based on fuel put in the tank and miles driven. That means generator use other than while driving is also factored into this.

2013, 9001 miles, 5.96 MPG Total Cost $5620 Estimated generator use 100 hours.
2014, 7558 miles, 6.32 MPG Total Cost $4232 Estimated Generator use was 200 hours.

A couple points...

In 2013 the first 1000 miles or so was in cold weather, short runs and other high fuel burn events. If you those miles and full out then 2013 is closer to 6.2.

In 2014 we did a lot more boon docking with the generator. In one case we were broke down for 5 days in TX and ran the generator a significant amount of time . If you factor that in the 2014 MPG would have been a bit higher and closer to 6.5.

If you apply those fudge factors it would be reasonable to say that in 2013 I got 6.2 MPG using dash AC when needed and in 2014 6.5 MPH with house AC and generator. That is a tad short of 5% increase.

One thing I noticed specifically with my coach was water and transmission temps. With the dash AC on it calls for more radiator fan action. At cruise water temp was around 180*-185*. With out the dash AC water temp was 200*-202*. Transmission temps were 2*-5* higher respectively. I think that helps contribute to the higher MPG.

Obviously I didn't have to rob HP by running the dash AC during bigger hills either.

In the end I got a bit more MPH, A better comfort level (for me, Sandee and our dogs), and better performance in hills. It also ensures the generator gets a lot of use which is good.

The only downside that I see is that while I saved a few dollars running the genny, you could incur an additional cost for an extra generator service. over the course of 2-3 years if you follow the service schedule closely.

Literally...YMMV
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Old 05-20-2015, 08:00 PM   #76
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Short answer, YES! Anything drawing power from an engine has a negative effect on fuel mileage.
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Old 05-20-2015, 08:09 PM   #77
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Short answer, YES! Anything drawing power from an engine has a negative effect on fuel mileage.
As does tire pressure, vehicle speed, headwinds/tailwinds, weight, hills/terrain, driver's habits, etc, etc, etc.
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Old 05-20-2015, 08:34 PM   #78
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No idea what the difference is running dash ac / generator to cool the coach down whether gas or DP. Enlighten me please.
I don't think I would make a very good politician as I call it as I see it.

You remind me of the numerous boaters I know that are afraid to take their beautiful cruisers out on the water because they might use some fuel. I see it at the marina all the time. They take the boat out of the slip and drive to the nearest beach which is just around the corner from the marina and drop anchor for the day. Never really go anywhere.
Seriously??
One of my best friends had a mint cruiser which went in with a full tank of fuel and winter stored with most of the same tank. He had perhaps 60 hours on it after 8 years. Unfortunately Cancer got the best of him before he ever really enjoyed the boat. He was always worried he might have had to spend a few bucks to actually use it.
As I showed above, about 3.11 HP but let's be liberal and say 4 HP, about 1/15 of the 60 suggested. It's not enough to consider in the overall operation of a coach. If you are spending ginormous sums of money on a rig and then worrying over 2 pounds per hour of fuel to stay cool you really need to give your head a shake, and have another cold beer by the river of your choice.
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Old 05-20-2015, 08:52 PM   #79
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Our cab AC doesn't use enough extra fuel to be noticeable with/without it. We do notice the drop when running the genny (7K Quiet Diesel) and roof AC's (both 13.5's). Not a lot, maybe 1/2 mile to the gallon, but no more. So not a lot different than many others are saying.

The bigger reason I wrote was regarding engine/radiator temps when running the cab AC. Our condenser, the part you would normally associate with being located near the radiator, is a stand alone unit with it's own electric fan - located about 35' forward of our radiator - ahead of the front axle. Not going to affect engine temps by much from that distance!
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Old 05-20-2015, 08:56 PM   #80
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As I showed above, about 3.11 HP but let's be liberal and say 4 HP, about 1/15 of the 60 suggested.
I don't recall anybody saying the AC compressor used 60 HP, however much has been said about the engine fan drawing that much power.
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Old 05-20-2015, 10:27 PM   #81
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I too was wondering how far of a drive you had planned. Would be interesting to hear back from you following your trip. If you are travelling in warmer areas I would think that the roof units would be far more efficient at cooling the large volume of air, especially when you have more than just two of you travelling.
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Old 05-21-2015, 05:52 AM   #82
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I too was wondering how far of a drive you had planned. Would be interesting to hear back from you following your trip. If you are travelling in warmer areas I would think that the roof units would be far more efficient at cooling the large volume of air, especially when you have more than just two of you travelling.

We're traveling from Northwest Arkansas to St. Louis. About 250 miles each way. It is supposed to be pleasant, in the mid-70s, so I'm sure the dash A/C will be more than effective. I will report back with my actual mileage though.
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Old 05-21-2015, 07:32 PM   #83
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Just purchased/picked up a new Berkshire 38RB in Texas - have driven around 1000 miles headed back to SW Florida - dash AC only - up to 10.7 mpg - speeds between 45 and 65 MPH on average - not forcing anything - very pleased with fuel consumption, and as others have stated - frankly don't care - just enjoy seeing this great country. Will see what happens when I get the TOAD setup and head out to New England and points beyond.


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Old 05-21-2015, 07:34 PM   #84
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Not enough to ever make me turn it off.
Generator is about .6 gal/hour. If it's too warm for the dash unit, the roof air is my ticket.
It just doesn't matter to me.
MH is point to point. Toad is 2/3 of my miles at good mileage.
Drive cool, my friend


BTW I never noticed a difference when running my dash ac in my 40' dp. But 10 mph would sure make a HUGE DENT in it.
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