[GMCnet] Restoration.Getting the most heat out of the furnace.

[Bob Dunahugh]

Our furnace's aren't the most efficient units. But I do want to get every BTU I can out of my heat discharge openings. And the 4 inch heat ducts that we have. I don't like the internal air turbulence that the outside wall creates. All the cracks in the walls. Plus the lack of any insulation. So I went off to Menards to come up with what is hoped will be more efficient. First is improving airflow. I have one run to the back that is 13 ft long. I had very little airflow. Then with all the heat lost along the way to the rear. i got some 4 inch rigid aluminum dryer duct. Then some 4 inch 90 degree elbows. This will get the smooth air flow I want. But the heat lost is a problem. Next thought is to cover the outside with the reflective bubble wrap. Held on with contact adhesive. Any other ideas out there? Bob Dunahugh78 Royale
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[Bruce Hislop]

Bob,
I wonder if the temperatures close to the furnace may be too high for the bubble wrap insulation.

We have the same issue, very little heat comes out the registers. Then the heat exchanger gets too hot and the hi-limit switch kicks out till it
cools. The furnace cycles many times before it gets the place warm. There were no obstructions through the hoses, just too much turbulence.

A couple years ago in the fall while shivering, I opened the front of our Suburban 30K BTU furnace and left the cupboard door open. Wow the heat that
came out was awesome. So much heat that the thermostat lags the temperature so I need to turn it down manually. I've left it like that since. The
blower has enough force to open the door, when then closes under gravity when the furnace shuts down.

I'd be interested to hear how you make out. I was thinking of making a duct from the front to back.




--
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

[Johnny Bridges via Gmclist]

Depending how hot the furnace outlet is, you might try 4 inch CPVC pipe in place of some of the tin dryer stuff. It won't lose nearly as much heat.
Also, some coaches had a booster fan in the long heat pipe run for the reasons you're finding. Whether thats a Good Thing or a Bad Thing is open to
discussion.

--johnny
--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[Todd Sullivan]

Bob,

You can purchase 4" flexible ducting which comes with insulation around it.
I bought one long chunk from Gensco and it was enough to do whole coach.
Any larger wholesale heating/ ac supplier can get it.

Sully
77 Royale
Seattle

On Sunday, April 24, 2016, Johnny Bridges via Gmclist <

[Bob Dunahugh]

I looked at the bubble wrap label yesterday. Good to 180 degrees F. I see two things here. If someone could go and turn their furnace on for 5 mins. And point an infrared temp sensor at the front cover. That would answer the question of how close the bubble wrap could be installed to the furnace. Or just keep the wrap about 3 ft away. But that heat loss could be saved. Can someone check that. My rubber furnace LP hose isn't made yet. Bob Dunahugh

[Pete Smith]

Google "stove pipe insulation" lots of choices.
You wouldn't need much to just cover few feet and then foiled bubble wrap for the rest.

Pete
--
Cary, NC

No Coach yet but decided it will be Definitely wet side bath, 77 or 78, 403, hopefully with good original Imron paint.

[Pete Smith]

And tiewraps would be easy cheap way to secure the bubble wrap.

[Hal StClair]

In all reality you aren't really 'loosing' heat from the non insulated ducts, all the heat loss is inside the conditioned space into the conditioned
space. You're just not feeling the heat from the registers but the heat is radiating into the living space. Also, if the return air is somehow
restricted you won't get the flow from the unit as noted by the improvement in air when leaving the cabinet door open. The original return air method
may have been compromised by a unaware PO, who knows.
Anyway, just some thoughts.
Hal
--
1977 Royale 101348,

1977 Royale 101586,

1974 Eagle Bus 45',w/slideout

[Bob Dunahugh]

Hal made the comment that the heat isn't lost. It's still in the coach. He's absolutely correct. I should have put it that the heat's just in a place that I don't want it in. My convertible Royale had a good clear cold air return. But the back was cool. and the front was hot. That has to be improver this time. Bob Dunahugh 78 Royale

[Wally Anderson]

BobDunahugh wrote on Sun, 24 April 2016 09:43

Our Suburban furnace has a 160F limit switch so the outlet shouldn't get much more than that. Some had a 180F limit.
--
Wally Anderson
1975 Glenbrook
Megasquirt 455 port injection science project
Omaha Nebraska
Bob Stone hydroBOOOOST
Greater Midwest Classics
GMCES
http://wallyandsue.blogspot.com/

[Ken Burton]

Bubble wrap is highly flammable. I would not use it anywhere near a furnace. Even if you do not catch it on fire, you might melt it. Use a foam
product like Microfoil (nofp.com) instead. You could also use aviation air duct (orange silicon) stuff but it will not have the insulation qualitys
that you are looking for.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Bob Dunahugh]

WOW Wally. Didn't think of the temp for the high limit switch. Thanks. Good point. And since that switch is in an area of the highest heat inside the furnace. So the temps coming out of the furnace duct ports has to be in the 120 degree range at most. Well within the limits of the foil bubble wrap. As to a fire hazard. I just heated a piece of sheet metal to 230 degrees. The bubble wrap just melted very slowly. Then I put a piece to the flame of my Ox/Act torch. That did make it burn. But the flame was in no way aggressive from the wrap. So that debunks the fire hazard issue of the wrap starting a fire. As to adding to a fire. In the big scheme of thing. What doesn't burn in there? I've certanly experianced that first hand. Bob Dunahugh78 Royale

Hal made the comment that the heat isn't lost. It's still in the coach. He's absolutely correct. I should have put it that the heat's just in a place that I don't want it in. My convertible Royale had a good clear cold air return. But the back was cool. and the front was hot. That has to be improver this time. Bob Dunahugh 78 Royale

I looked at the bubble wrap label yesterday. Good to 180 degrees F. I see two things here. If someone could go and turn their furnace on for 5 mins. And point an infrared temp sensor at the front cover. That would answer the question of how close the bubble wrap could be installed to the furnace. Or just keep the wrap about 3 ft away. But that heat loss could be saved. Can someone check that. My rubber furnace LP hose isn't made yet. Bob Dunahugh

[John Wright]

Bob,
The placement of the thermostat is very important! If you have it in the back where almost all are located with any doors closed such as the bath door open then the back will be cold and the front will be warm. I would suggest having it midway in the coach. We are discussing moving the unit to a more central location than in the back. We use electric heaters unless it is really cold (snow & ice) outside. We typically see the cold weather when going to Tucson in late Nov or early Dec. It would be nice if you had an album put together on the resurrection of your coach. By all means put it on the GMC Photo site.

JR

[Gary Kosier]

Bob,

Put a heat strip in the rear air conditioner. When plugged in, you'll be
warm and you probably will not even need the furnace.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "Bob Dunahugh" <yenk...@hotmail.com>
Sent: Tuesday, April 26, 2016 2:04 PM
To: <gmc...@list.gmcnet.org>
Subject: Re: [GMCnet] Restoration.Getting the most heat out of the furnace.

[Bob Dunahugh]

JR. I've been thinking the same thing of moving it. The drive in bath will have a curtain. No door. And now we'll both be sleeping over the rear tires. So at least we'll be closer to the middle. I've wired the thermostat so I can move it to the middle if the wrap doesn't work well. As for an album. On paper, and online. Billy Massey has helped a lot by posting photo's. But that's another project. Right now I hope the light at the end of the tunnel. Isn't a freight train coming at me. It's been a long 5 and a half months now. And for some people to do this. It's years. Getting close now. Bob Dunahugh






WOW Wally. Didn't think of the temp for the high limit switch. Thanks. Good point. And since that switch is in an area of the highest heat inside the furnace. So the temps coming out of the furnace duct ports has to be in the 120 degree range at most. Well within the limits of the foil bubble wrap. As to a fire hazard. I just heated a piece of sheet metal to 230 degrees. The bubble wrap just melted very slowly. Then I put a piece to the flame of my Ox/Act torch. That did make it burn. But the flame was in no way aggressive from the wrap. So that debunks the fire hazard issue of the wrap starting a fire. As to adding to a fire. In the big scheme of thing. What doesn't burn in there? I've certainly experienced that first hand. Bob Dunahugh78 Royale