Furnace choice

boybach

boybach

Well-known member
Dec 9, 2020
1,033
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Found an new, uninstalled furnace for sale - an Atwood 8531-IV DCLP. Very compact unit and 30,000 BTU. Measures 7-3/8" High x 16-1/2" Wide x 18" Long.

Ignition furnace operates on 12 VDC (7.6 amp) and LP Gas.
7.6 Amp Draw, Electric Ignition Cut. Front Door and Thermostat is not included.

Suitable unit for the GMC?

Thanks in advance for any insights

Larry
--
Larry - Victoria BC -

1977 Palm Beach VIN TZE167V101295 - 40,000 miles, PO said everything working but forgot the word NOT. New wiper blades, New SS exhaust system,
operational Onan genset, R134A A/C, New fuel lines
 
The Atwood furnace requires you to cut a hole in the outside of the coach for the exterior access door. Not the end of the world, but not really my
cup of tea. it does allow for easy service if needed.

suburban has SF and NT furnaces, the SF series are smaller in height, and a little wider, and also use a little more 12v amps. They can be
installed by removing the couch(you have to do that to remove your sol aire anyway), and you can either mount them up at an angle to the wall and
still have to drill a new hole for the intake, or many of us bought 600 degree flexible silicone hose from mcmaster-carr to use on the exhaust to
utilize existing vents holes in coach, and was able to mount the sf flat to the floor. The NT series I do believe is taller and slightly skinnier
then the SF series and can be installed through the cabinet door?

no matter what furnace you use, you will have to do some air plenum modifications.

http://lqqkatjon.blogspot.com/2021/05/sf-30-furnace.html

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jon - I'm on the west coast and some years it does get very cold but I think 30,000BTU (like the old sol-aire) should be OK for my purposes.

I know the Atwood CAN be installed from outside, but if I get it I'll try to do it from the inside first. Apparently it can even be installed
vertically.

I just had a look at your blog Jon, great detailed write up and pics - will be a big help in removing the sol-aire. It also gave me a good overview of
the working area and what mods will have to be done - appreciate it, many thanks for doing a great step-by-step of the job.

cheers

Larry
--
Larry - Victoria BC -

1977 Palm Beach VIN TZE167V101295 - 40,000 miles, PO said everything working but forgot the word NOT. New wiper blades, New SS exhaust system,
operational Onan genset, R134A A/C, New fuel lines
 
Went ahead and bought the Atwood and installing it from the inside. Had to extend the exhaust but a 1-1/2" O.D. pipe slipped in snug to the Atwood's
1-1/2" I.D. exhaust.

Raised the furnace on blocks to line up with the existing exhaust port and welded up an angled flange to deal with the coach curvature. Salvaged
several plenum fittings from the old sol-aire in order to match the 2" and 3-1/2" hoses in the coach. Propane hookup had to be moved to left front
corner from right back corner and electrical hookup from left back corner to right front. PIA but not impossible.

testing tomorrow with any luck

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
I did the exact same changeout. Only problem I had was with the ground wire for the furnace. I suggest running a ground wire back to the coach fuse block, where the battery negative terminal is located. Do not depend on the coach frame for your ground.

>
>
> Went ahead and bought the Atwood and installing it from the inside. Had to extend the exhaust but a 1-1/2" O.D. pipe slipped in snug to the Atwood's
> 1-1/2" I.D. exhaust.
>
> Raised the furnace on blocks to line up with the existing exhaust port and welded up an angled flange to deal with the coach curvature. Salvaged
> several plenum fittings from the old sol-aire in order to match the 2" and 3-1/2" hoses in the coach. Propane hookup had to be moved to left front
> corner from right back corner and electrical hookup from left back corner to right front. PIA but not impossible.
>
> testing tomorrow with any luck
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
We got it running today and boy does it ever kick out the jams.
I say WE because my trusty mate Jayson did most of the work, he's coming back tomorrow to install the ducting. He made several sheet metal
contraptions to fit the furnace from the inside to ensure the combustion chamber air intake and blower air were never the twain to meet.
I'm lucky to know him, he's one of my fishing buddies and an HVAC pro. He volunteered to do the install - I think all my fishing buddies feel sorry
for the old man (me) so I get lots of help. :)

As far as the ground goes, I'm not sure where he grounded the case but he did install a green wire onto the case. I'll see where it leads tomorrow
when I get back out to the coach.
The coolest thing is we were able to utilize the old stock Sol-Aire exterior grill vents (only one actually, other is sealed off) so from the outside
everything looks bog-standard.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
> I did the exact same changeout. Only problem I had was with the ground wire for the furnace. I suggest running a ground wire back to the coach
> fuse block, where the battery negative terminal is located. Do not depend on the coach frame for your ground:

Well good advice alright!

Today the furnace quit after running for barely 2 mins and I got a 3 flash error code on the control board led. My HVAC buddy was long gone and I had
to do some thinking! Your post about the ground wire got me going in the right direction for sure!

We mounted the furnace on the old sol-aire mount but added a pair of 2x4's, raising it up about 3" so we could use the sol aire exhaust port.
Anyway, my buddy ran the ground wire to the case of the furnace. When it quit I ran one of my old test leads (crocodile clip both ends) from the case
ground connection to the frame of the coach and ran through the ignition cycle again. It started and I ran it for about 10 mins without a hiccup -
before it was quitting at around 2 mins.

So my solution was to move the green ground wire to the frame. Fixed!

Larry

--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Jon,

Next time you are using your coach in cold weather, try taking the front cover off the Suburban furnace and leave the cabinet door open. You will be
amazed at the volume of hot air the furnace can deliver when the blower does not have to work against the restrictions of the ducting and vents.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
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Applied GMC
Get your shine on at www.cruzingear.co

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