Our Duo Therm - gravity type - furnace does not seem to have any range of temperature settings. Furnace starts well enough, pilot stays on, but when the gas comes on even on the lowest setting it gets too hot after just a few minutes.
Turning the knob does not seem to change the amount of flame as far as I can see.
Any ideas?
Full Version: Duo Therm Furnace Settings
FiberglassRV > All About Our Unique Little Molded Fiberglass Trailers > Problem Solving -- Owners Helping Owners
Do you mean the trailer gets too hot, or the furnace?
in my 1300, i used the furnace to get the trailer warm, then generally left it on pilot till it got too cold, then repeated
in my 1300, i used the furnace to get the trailer warm, then generally left it on pilot till it got too cold, then repeated
QUOTE (Joe MacDonald @ Nov 5 2009, 06:22 AM) 
Do you mean the trailer gets too hot, or the furnace?
in my 1300, i used the furnace to get the trailer warm, then generally left it on pilot till it got too cold, then repeated
in my 1300, i used the furnace to get the trailer warm, then generally left it on pilot till it got too cold, then repeated
Yes the trailer gets too warm. I am trying to find a setting between "pilot" and "min"
You might try relocating your temperature sensing probe vertically higher in the trailer. Just a thought.
QUOTE (Chris McVeigh @ Nov 4 2009, 04:23 PM)
Our Duo Therm - gravity type - furnace does not seem to have any range of temperature settings. Furnace starts well enough, pilot stays on, but when the gas comes on even on the lowest setting it gets too hot after just a few minutes.
Turning the knob does not seem to change the amount of flame as far as I can see.
Any ideas?
Turning the knob does not seem to change the amount of flame as far as I can see.
Any ideas?
Funny you should ask this question because I was going to ask a very similar one!
I also have a Glen-Aire Duo-Therm gravity furnace -- mine was probably made in 1973. Anyway, like yours it has no thermostat and also has no proportional control -- it's either running full blast or it's just the pilot.
So my question is whether it is reasonable to replace the current control with a thermostatically governed one.
The current control says "General Controls" on the back.
Here are some pictures for mavens like Harry Young and others to look at and comment on:
Click to view attachment Click to view attachment Click to view attachment
BTW, I have carefully checked the firebox and made sure it is still airtight -- I don't want to be asphyxiated in my sleep with combustion products.
There's something wrong with the image insertion function -- I uploaded 4 pictures but one image refuses to display (all I get is the image referance number), and the last image is displaying in an entirely different part of my post than where I placed it. I finally gave up and deleted the image that wouldn't display.
When I try to edit the post it shows the placement is just what I specified, but when the post is displayed "for real" the image is displayed at the end of the post instead of with the other two.
Fiddlesticks!! Now the closeup image of the control isn't displaying properly!
Yet another try at showing the builder's plate:
Click to view attachment
Whaddya know, it worked!
When I try to edit the post it shows the placement is just what I specified, but when the post is displayed "for real" the image is displayed at the end of the post instead of with the other two.
Fiddlesticks!! Now the closeup image of the control isn't displaying properly!
Yet another try at showing the builder's plate:
Click to view attachment
Whaddya know, it worked!
Well now that I can see the model number of my furnace so easily, I Googled the following
"duo-therm" "65211-1"
and came up with the following link:
http://www.ntpdistribution.com/PDF/Via/41-...qkchart1of2.pdf
I downloaded the PDF file and I see that furnace 65211-1 uses gas control 41-0640 and has no wall thermostat, but furnace 65211-3 has a wall thermostat and uses gas control 41-0475.
In general, all of the furnaces listed on that page either use gas control 41-0640 and have no wall thermostat, or use 41-0475 and do have a wall thermostat.
Searching for
"41-0475" control
leads me to http://www.rvshop.com/Furnaces_c_1462-7-0.html where I see they have the control for a mere $214.29.
To that we need to add the price of a new thermocouple (this control uses a different one than the current control does) and a wall thermostat.
Several weeks ago in the "Hydro Flame for Trillium 1300" thread Harry Young mentioned Johnstone Supply, which is a chain of HVAC supply stores. Maybe their prices are better than RVShop's.
Sure wish I could find a picture of the 41-0475 control to see if it would fit without too much effort. I'm getting pretty adept at yanking that furnace out and putting it back in....
"duo-therm" "65211-1"
and came up with the following link:
http://www.ntpdistribution.com/PDF/Via/41-...qkchart1of2.pdf
I downloaded the PDF file and I see that furnace 65211-1 uses gas control 41-0640 and has no wall thermostat, but furnace 65211-3 has a wall thermostat and uses gas control 41-0475.
In general, all of the furnaces listed on that page either use gas control 41-0640 and have no wall thermostat, or use 41-0475 and do have a wall thermostat.
Searching for
"41-0475" control
leads me to http://www.rvshop.com/Furnaces_c_1462-7-0.html where I see they have the control for a mere $214.29.
To that we need to add the price of a new thermocouple (this control uses a different one than the current control does) and a wall thermostat.
Several weeks ago in the "Hydro Flame for Trillium 1300" thread Harry Young mentioned Johnstone Supply, which is a chain of HVAC supply stores. Maybe their prices are better than RVShop's.
Sure wish I could find a picture of the 41-0475 control to see if it would fit without too much effort. I'm getting pretty adept at yanking that furnace out and putting it back in....
The controls I am looking at now are
Honeywell VS820A1336 $125
http://www.pexsupply.com/Honeywell-VS820A1...-NPT-13864000-p
Robertshaw 700-501 $130
http://www.pexsupply.com/Robertshaw-700-50...s-Valve-100-000
Robertshaw 705-501 $58
This one adds thermostatic control to the existing control instead of replacing it entirely.
http://www.southsidecontrol.com/acatalog/P...5_501_1759.html
Remember, each of these controls still requires a wall thermostat (about $25) and a millivolt thermopile (about $35).
The question is whether it is worth sinking $200 into this old furnace or buy something new. What I really like about the old furnace is that it is dead quiet and consumes no battery power.
Honeywell VS820A1336 $125
http://www.pexsupply.com/Honeywell-VS820A1...-NPT-13864000-p
Robertshaw 700-501 $130
http://www.pexsupply.com/Robertshaw-700-50...s-Valve-100-000
Robertshaw 705-501 $58
This one adds thermostatic control to the existing control instead of replacing it entirely.
http://www.southsidecontrol.com/acatalog/P...5_501_1759.html
Remember, each of these controls still requires a wall thermostat (about $25) and a millivolt thermopile (about $35).
The question is whether it is worth sinking $200 into this old furnace or buy something new. What I really like about the old furnace is that it is dead quiet and consumes no battery power.
Duo Therm 65810-2
Click to view attachment Click to view attachment
Looking at some old manuals I found that some models had a regulator adjustment screw under the temp control knob - no such luck with mine. Maybe the problem lies with the thermometer not telling the gas to switch off when it gets hot enough. Had a temp of 75 at floor level inside the trailer the other day and the heat was still pouring out.
Does anyone else have better luck with their gravity type furnace.
I must admit we have had the trailer in the family for over 30 years and we have never been able to just let the furnace run.
Click to view attachment Click to view attachment
Looking at some old manuals I found that some models had a regulator adjustment screw under the temp control knob - no such luck with mine. Maybe the problem lies with the thermometer not telling the gas to switch off when it gets hot enough. Had a temp of 75 at floor level inside the trailer the other day and the heat was still pouring out.
Does anyone else have better luck with their gravity type furnace.
I must admit we have had the trailer in the family for over 30 years and we have never been able to just let the furnace run.
Chris,
I'm thinking from your last post that you do have the operating instructions for your furnace. But if not, I have a copy of them in front of me and could perhaps answer a question. What I have is "Duo-Therm Owners Operation Instructions for Direct Vent Heaters" [Form No. 19-424-7]
It looks like even the model(s) with no thermostat do have temperature control via the black dial shown in your photo.
Raya
I'm thinking from your last post that you do have the operating instructions for your furnace. But if not, I have a copy of them in front of me and could perhaps answer a question. What I have is "Duo-Therm Owners Operation Instructions for Direct Vent Heaters" [Form No. 19-424-7]
It looks like even the model(s) with no thermostat do have temperature control via the black dial shown in your photo.
Raya
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