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| how much does roof air affect MPG [message #104041] |
Sun, 24 October 2010 17:41  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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I know a lot of folks here don't feel it's worth doing anything radical for small improvements in mileage;
"8 to 10 depending on whether or not you tow"
But i have this ridiculous idea i want to toss out;
With a tankless water heater i would be left with an empty vented space. With a little re-engineering and maybe an exhaust blower, i could put house AC in the spot.
My 1965 Boles Aero Trailer came with a factory installed Westinghouse AC placed under the fridge and vented down- worked perfectly in a 24 foot trailer.
I would love to have a clean roof, lower clearance, and if there was a measurable decrease in drag that would be a plus.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] how much does roof air affect MPG [message #104044 is a reply to message #104041] |
Sun, 24 October 2010 17:59  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Dave,
They make a difference depending on speed and size and shape.
Lower the profile, less the drag.
Carrier low profile seems to be the best design.
Penguin is about the only choice now as Carrier quit production. W
still have few of them left.
To think that you do not need a roof unit is a wrong assumption.
e travelled all over the country and know it is something you need
when your parked.
On Sun, Oct 24, 2010 at 3:41 PM, dave silva
arrier<david.j.silva@uscg.mil> wrote:
>
>
> I know a lot of folks here don't feel it's worth doing anything radical for small improvements in mileage;
>
> Â "8 to 10 depending on whether or not you tow"
>
> But i have this ridiculous idea i want to toss out;
>
> With a tankless water heater i would be left with an empty vented space. Â With a little re-engineering and maybe an exhaust blower, i could put house AC in the spot.
>
> My 1965 Boles Aero Trailer came with a factory installed Westinghouse AC placed under the fridge and vented down- worked perfectly in a 24 foot trailer.
>
> I would love to have a clean roof, lower clearance, and if there was a measurable decrease in drag that would be a plus.
>
>
> --
> Dave & Ellen Silva
>
>
> Happy owners of a 1972 Flatnose Revcon
> Here by the generosity of the GMC community
> http://www.davesilva.com/revcon
>
>
> _______________________________________________
> GMCnet mailing list
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>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] how much does roof air affect MPG [message #104052 is a reply to message #104044] |
Sun, 24 October 2010 18:46 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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Jim,
I live in North Carolina. Not having AC would never cross my mind.
I'm thinking about putting the AC inside, under a cabinet and venting it out the water heater panel.
thanks
Dave
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: how much does roof air affect MPG [message #104082 is a reply to message #104041] |
Sun, 24 October 2010 21:31 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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The Carrier Low Profiles are quiet! I am the converted...
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: how much does roof air affect MPG [message #104086 is a reply to message #104041] |
Sun, 24 October 2010 22:57 |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
Karma: 0
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Hopefully Carrier (or someone else) will resume production of the Low Profile Air-V, it's really a great looking unit that works great!
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: how much does roof air affect MPG [message #104101 is a reply to message #104041] |
Mon, 25 October 2010 08:40 |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
Karma: 0
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| Dave wrote on Sun, 24 October 2010 17:41 |
I know a lot of folks here don't feel it's worth doing anything radical for small improvements in mileage;
"8 to 10 depending on whether or not you tow"
But i have this ridiculous idea i want to toss out;
With a tankless water heater i would be left with an empty vented space. With a little re-engineering and maybe an exhaust blower, i could put house AC in the spot.
My 1965 Boles Aero Trailer came with a factory installed Westinghouse AC placed under the fridge and vented down- worked perfectly in a 24 foot trailer.
I would love to have a clean roof, lower clearance, and if there was a measurable decrease in drag that would be a plus.
|
Years ago in another life I worked for Duo-Therm - I was there during the time our GMC's were built.
Duo-Therm designed a cabinet mounted central air conditioner - there were two of these units in every FMC motorhome that was built. Duo-Therm also designed a split system, with separate evaporator and condensor sections connected with copper tubing.
We initially thought that these central units would eventually replace the roof mount units, but as you can see, that has not happened. These units are no longer listed in their product line.
RV manufacturers do not want to give up the cabinet space these use up, and they are much more difficult to install. Also, there are problems in getting the cool air distributed correctly, and the ducts have to be insulated. I checked out a small Champion motorhome that had all the cold air registers about 48 inches above the floor, and the AC was mounted at floor level. At eye level it was 85°, and at floor level it was below 60° and the AC was freezing over. No workee !
Based on my experience I would recommend leaving the roof AC up there - that is where it belongs. It is drawing in the warmest air in the coach, and the cold air coming out will find its way to all parts of the coach.
Someone mentioned Jim Anstetts coach, which has a roof mount AC reworked and mounted in the former generator compartment. I have seen this coach, and Jim said it works good for him. However, you should be aware that Jim has also added a lot of insulation to his unit - it is probably the best insulated GMC out there. And he was willing to give up a space in his coach that I would not - I want to keep the generator.
We have a Penguin heat pump on our coach, and based on how that works I would not recommend spending the extra money for the heat pump. It puts out plenty of heat, but it is much noisier than the furnace, and it is "drafty" in the coach. We run the heat pump only when we are out of the coach, and when we are there we turn on the furnace.
Summary: The AC belongs on the roof, and the heater belongs on the floor. Just my opinion, for what that is worth.
Erv Troyer Lagrange, IN
74 Sequoia
reo43@aol.com
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| Re: how much does roof air affect MPG [message #104104 is a reply to message #104086] |
Mon, 25 October 2010 08:57 |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
Karma: 0
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Senior Member |
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| GeorgeRud wrote on Sun, 24 October 2010 22:57 |
Hopefully Carrier (or someone else) will resume production of the Low Profile Air-V, it's really a great looking unit that works great!
|
I agree - the first time I saw the Carrier at an RV show I was impressed with the overall design and the innovations they had on it. However, as with several other major brand AC companies, the RV market is just not big enough for the price competition they have to put up with, so they just quit that market.
The Duo-Therm Penguin and the Coleman Polar Cub are still available - both are low-profile units.
Duo-Therm was one of the first low-profile units on the market, and someone was smart enough to get a patent for the design. Dometic (Duo-Therm's parent) filed suits against at least two other companies, and these were both forced to stop production on their low profile units. Since then the patent has expired, and the Coleman and Carrier brands were introduced as low profile designs.
Erv Troyer Lagrange, IN
74 Sequoia
reo43@aol.com
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| Re: [GMCnet] how much does roof air affect MPG [message #104105 is a reply to message #104101] |
Mon, 25 October 2010 09:22 |
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Good opinion. Valuable, too.
Some of the SOB mfgs tried doing the "basement" AC thing. From what I can
tell, it was a short-lived situation. The biggest reason was probably cost.
Too many roof systems produced and too few for under the coach.
Shucks, look at all these converted coaches for entertainers -- four or five
roof units sitting up there for maximized "zone" comfort. I've always
wondered if they had one, big generator or multiple smaller ones to handle
the house.
Byron Songer
1978 Royale by Coachmen
Louisville, KY
Personal - http://web.me.com/bnsonger
Eastern States - http://www.gmceast.com
Erv Troyer wrote:
> Summary: The AC belongs on the roof, and the heater belongs on the floor. Just
> my opinion, for what that is worth.
> --
> Erv Troyer Lagrange, IN
> 74 Sequoia
> 77 Birchaven (for sale)
> reo43@aol.com
_______________________________________________
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List Information and Subscription Options:
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--
Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
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| Re: [GMCnet] how much does roof air affect MPG [message #104109 is a reply to message #104105] |
Mon, 25 October 2010 09:51 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Byron,
The large custom coaches I have seen all used a single generator -- but I am sure there are exceptions.
A lot of them are also painted in dark colors -- lots of heat gain in the summer.
Dennis Sexton
73 GMC
Germantown, TN
USA
-----Original Message-----
From: Byron Songer <bsonger@songerconsulting.net>
To: gmclist@temp.gmcnet.org
Sent: Mon, Oct 25, 2010 9:22 am
Subject: Re: [GMCnet] how much does roof air affect MPG
snip..
hucks, look at all these converted coaches for entertainers -- four or five
oof units sitting up there for maximized "zone" comfort. I've always
ondered if they had one, big generator or multiple smaller ones to handle
he house.
Byron Songer
978 Royale by Coachmen
ouisville, KY
ersonal - http://web.me.com/bnsonger
astern States - http://www.gmceast.com
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: how much does roof air affect MPG [message #104112 is a reply to message #104041] |
Mon, 25 October 2010 09:57 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| hertfordnc wrote on Sun, 24 October 2010 18:41 |
I know a lot of folks here don't feel it's worth doing anything radical for small improvements in mileage;
"8 to 10 depending on whether or not you tow"
But i have this ridiculous idea i want to toss out;
With a tankless water heater i would be left with an empty vented space. With a little re-engineering and maybe an exhaust blower, i could put house AC in the spot.
My 1965 Boles Aero Trailer came with a factory installed Westinghouse AC placed under the fridge and vented down- worked perfectly in a 24 foot trailer.
I would love to have a clean roof, lower clearance, and if there was a measurable decrease in drag that would be a plus.
|
Dave,
I am strangely capable of answer this for a really different reason. My barn door is 9'6". I used to take both the AC unit and the rear Maxair vent cover off for the winter so I could move the coach into the warm barn to do winter projects (Yeah - I know that's cheating).
As I made a very significant point to never take the coach on the road when there was still and salt (fender solvent) present, but I did not reinstall the stuff on top until my spring work got rolling. That left most of a month with some decent trip lengths to tally fuel rates. I have been pathological about recording fuel use because my gauges were unreliable.
The result you care about:
There were two trips that were good for this data. It didn't matter enough for the data to show anything. The two fuel slips were about identical (actually the second was 0.05 MPG better - iirc). At this time, I still had the Coleman Mark ? on the coach.
What happened.
I was particularly surprised by the results when I ended up making the same run twice - a week apart - almost identical conditions (because a supplier lied to me) of about 200 miles (essentially DTW to Port Huron and back). Both times I fueled just before departure - even the same pump (the only pump at the station that is easy to get the coach next to).
I still keep these records and probably always will, both because I am paranoid (it serves me well) and for the tax records as the coach is my office most of the season. I have since traded off to a Carrier Low Profile and that just means I don't have to park under the willow tree and rig tackle twice a year.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: how much does roof air affect MPG [message #104132 is a reply to message #104112] |
Mon, 25 October 2010 11:54 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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Senior Member |
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| mcolie wrote on Mon, 25 October 2010 09:57 |
The result you care about:
There were two trips that were good for this data. It didn't matter enough for the data to show anything. The two fuel slips were about identical (actually the second was 0.05 MPG better - iirc). At this time, I still had the Coleman Mark ? on the coach.
|
So, bottom line, no measurable improvement in MPG.
Thanks
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] how much does roof air affect MPG [message #104193 is a reply to message #104133] |
Mon, 25 October 2010 17:18 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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| comcast wrote on Mon, 25 October 2010 12:03 |
But, they sure do look great without all that stuff!!
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You surely mean Greater...
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] how much does roof air affect MPG [message #104201 is a reply to message #104112] |
Mon, 25 October 2010 17:56 |
Jim Bounds
Messages: 842
Registered: January 2004
Karma: 0
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Senior Member |
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Driving my coach (Larry) home from Colorado I found there was no difference in
mileage with the generator off or on with 2 AC's running. This was with an Onan
Power drawer so as far as economy that way if you are underway, running the
generator does not detract from your mileage enough to make a difference.
Aerodynamically speaking, you would think cleaning off the roof would help but
would it make a difference is the question.
I tried a "basement" AC unit in my other coach (The Dumpster), the unit took up
the space of a generator in the pass. side. Venting the unit up took some more
space then turning the air flow 90 deg. to go forward really knocked down the
velocity of the air. By the time the air reached the driver area there was not
much pressure. Sometimes I even had an inversion where it actually reversed
cycle somehow and blew hot air at me. I would have to say the experiment told
me there was more at work that was aparent. I sold the coach "as is" telling
the new owner I was not liking the AC system.
I've got a new idea, using a portable AC/Heat unit. I have a 12.5KBTU cool &
8500BTU heat unit-- takes 11 amps to run-- going to try taking the generator
apart, putting heat units outside. I would say -- don't try this at home in
that there is no warranty off stuff you rip apart like thins and also no
guaranty it will work so should you follow and try thins---- nope!
Heck, not even sure why I want to try all that and I see no way it will be cost
effective or efficient but hey-- I can so why not. If that doesn't proove I'm
as nuts as you guys are then well, I don't know what!
Saw a coach in our club some time back that the owner had torn apart his roof
ACs (2) and spread the parts all across inside the coach-- would not cool the
coach with 1 roof air but 2 would freeze you out. I thought he was nuts-- now I
am one!
Jim Bounds
-------------------------------
----- Original Message ----
From: Matt Colie <mcolie@chartermi.net>
To: gmclist@temp.gmcnet.org
Sent: Mon, October 25, 2010 10:57:40 AM
Subject: Re: [GMCnet] how much does roof air affect MPG
hertfordnc wrote on Sun, 24 October 2010 18:41
> I know a lot of folks here don't feel it's worth doing anything radical for
>small improvements in mileage;
>
> "8 to 10 depending on whether or not you tow"
>
> But i have this ridiculous idea i want to toss out;
>
> With a tankless water heater i would be left with an empty vented space. With
>a little re-engineering and maybe an exhaust blower, i could put house AC in the
>spot.
>
>
> My 1965 Boles Aero Trailer came with a factory installed Westinghouse AC placed
>under the fridge and vented down- worked perfectly in a 24 foot trailer.
>
>
> I would love to have a clean roof, lower clearance, and if there was a
>measurable decrease in drag that would be a plus.
Dave,
I am strangely capable of answer this for a really different reason. My barn
door is 9'6". I used to take both the AC unit and the rear Maxair vent cover
off for the winter so I could move the coach into the warm barn to do winter
projects (Yeah - I know that's cheating).
As I made a very significant point to never take the coach on the road when
there was still and salt (fender solvent) present, but I did not reinstall the
stuff on top until my spring work got rolling. That left most of a month with
some decent trip lengths to tally fuel rates. I have been pathological about
recording fuel use because my gauges were unreliable.
The result you care about:
There were two trips that were good for this data. It didn't matter enough for
the data to show anything. The two fuel slips were about identical (actually
the second was 0.05 MPG better - iirc). At this time, I still had the Coleman
Mark ? on the coach.
What happened.
I was particularly surprised by the results when I ended up making the same run
twice - a week apart - almost identical conditions (because a supplier lied to
me) of about 200 miles (essentially DTW to Port Huron and back). Both times I
fueled just before departure - even the same pump (the only pump at the station
that is easy to get the coach next to).
I still keep these records and probably always will, both because I am paranoid
(it serves me well) and for the tax records as the coach is my office most of
the season. I have since traded off to a Carrier Low Profile and that just
means I don't have to park under the willow tree and rig tackle twice a year.
Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan - DTW 3.2/4R
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: how much does roof air affect MPG [message #104202 is a reply to message #104041] |
Mon, 25 October 2010 18:06 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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The Air-V low profile is properly engineered so that the condenser fan always runs at high speed, regardless of the speed of the evap fan indoors. This is possible because they used two different motors for the fans (Imagine that!) instead of trying to run both with a dual shaft motor. With the indoor fan on low, and the outdoor fan running on high, the only speed it has, the unit is very quiet and puts out some nice cold air. Another bonus is that my 110V shore power cord doesn't get warm with this unit as it did with the old unit.
I am so happy I bought these units. An added bonus is that they will control a furnace too. I plan on connecting the furnace to the front unit. The wireless remote will do a nice job of controlling that.
These seem to use parts from ductless mini-split units. that compressor is really really quiet.
worth the $900 each IMHO.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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