Furnace ducting

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
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Ontario Canada
Our furnace in our 77 Palm Beach has been replace by a PO with a Suburban 35K BTU unit. There are two 4" (I'm thinking) duct tubes going forward to
outlets under the front sofa. And also two 4" ducts going to outlets under the cabinets to the rear. There is also a 2" tube heading behind the oven
and on around the back to the bath module.

The furnace starts and fan runs, but not much air comes out the furnace grills. I can hear the over-temp switch kick in and shut down the burner
while the fan continues. It will cycle the burner On/Off while running until it eventually warms up.

I've check the duct work for obstructions and found them completely open and clean. Obviously there is alot of resistance to air movement through the
existing flexible duct work.

If I open the furnace access door and remove the front cover of the furnace, the volume of hot air will put you out of the coach before the thermostat
can react. So the furnace is working great. We've just left the front cover off since and open the door when we need heat. However leaving the
access door open is a nuisance and one of these days I'm going to trip on it and break it with my clumsy feet. Also we now have grand-kids so they may
join us in the not too distance future.

So I was thinking about getting rid of the hose ducts and installing a custom metal duct from the front to the back along the floor and inside the
cabinets and the sofa. I'd leave the front cover off the furnace and make a duct from there down into my duct work and block off the tube openings.
I'm thinking this would have less resistance to air movement and keep little hands safe from the furnace.

Has anyone done this? Experiences? recommendations?

Thanks all

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 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
 
My new Suburban works with three ducted outlets plus the 2 inch, but wouldn't with only two outlest and one blocked.. which I unblocked. My problem
was the airflow switch.. there wan't enough air moving through the thing. The overtemp hasn't opened yet.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Try operating the furnace with all of its covers in place with the cabinet
door which exposes the furnace open. It could be that there is not enough
make up air entering the furnace. If it works better or properly with the
cabinet open you need to add more make up air ventilation to the furnace
enclosure. Do you have the installation manual for the furnace? Super
helpful. If you dont have one i will try to find the electrinic copy of
mine for my suburban. There are very specific ventilation guidelines for my
suburban and problems that you mention were listed as a possible result of
a poor make up air circuit

Sully
77 eleganza 2
Seattle
On Thu, Mar 9, 2017 at 3:40 PM Johnny Bridges via Gmclist <

> My new Suburban works with three ducted outlets plus the 2 inch, but
> wouldn't with only two outlest and one blocked.. which I unblocked. My
> problem
> was the airflow switch.. there wan't enough air moving through the thing.
> The overtemp hasn't opened yet.
>
> --johnny
> --
> 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me
> in hell" - ol Andy, paraphrased
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Sully,
I've run it with the service cover closed and the door open, still not much air movement through the ducts. The entire side of the cabinet is open
from the sofa to the floor. There is about a 2" gap along the underside of the sofa cushion. I've operated it with the sofa raised, still not much
air.

John, I don't know if there is a booster fan to the bath left in mine. I can't see it from the side looking over the furnace towards the back of the
range. I've never heard it either. In any case that would not affect the floor level registers.

I'm thinking the air turbulence is preventing smooth airflow to the registers.

I've got the same issue with the fireplace in my house. There are two squirrel cage fans blowing air though the back of the fire place and out the top
front just below the mantel. The fans are clean, take then out and run them, they will cause a hurricane. But they blow just enough to perceive some
heated air is there. I used a bore scope camera and there is no obstructions there.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 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
 
I've not seen that furnace, but I would check to see if there was a knock out that should have been removed during installation for ducting.
--
Galen Briggs
New Virginia, Iowa
1978 Palm Beach
 
Bruce check put my photo set of a furnace installation I did to a 74 for some clues to help you your problem I did have some problem with it getting
too hot and the limit switch kicking out. I used the bottom cut ouy of the furnace and needed to add another duct to the system to increase air
flow. I suspevt I could also add another duct (i think ) to improve circulation to the driver area. I also found the rear duct folded up in the rear
to add to poor air flow.

Good luck.
--
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
 
Just sitting here waiting for our flight home to the Great White North. When we are back, I'll try to post some pictures on the photo site of what I
have and what I'm thinking of doing.
I talked to one of my Heating contractor clients and thought it would greatly improve the air flow. Just need to figure out how to get duct work
inside the cabinets without destroying them.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 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
 
If you have the four ducts or two ducts and the bottom cutout of your furnace open that is enough air flow for proper operation. I had the same
problem with my Suburban furnace, it would cycle on and off many times before finally heating the coach. Turned out to be the thermostat. The
thermostat needed to be set to to stay on longer for each cycle. I have the original Solair thermostat that worked with the Solair furnace but needed
to be adjusted in order to function with my new Suburban furnace.
--
1977 Palm Beach
TZE167V100274
 
Here is my furnace installation. Its a Palm Beach so the doors are louvered, so return air should not be a problem.
http://www.gmcmhphotos.com/photos/misc/p62439-furnace.html

I would run a duct forward and back from here behind the cabinets and the sofa. I would put a 90 degree rounded corner from the front of the furnace
down to the ductwork and close off the existing side openings for the hose ducts.

Normally there are covers on these two duct openings. I removed the hoses since they just took up valuable storage space.
http://www.gmcmhphotos.com/photos/misc/p62440-furnace.html

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 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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