Duo Therm electric furnace won't shut off

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Duo Therm electric furnace won't shut off

Postby Hardrock » Mon Sep 24, 2007 11:35 am

Vintage Duo-Therm electric furnace in mobile home will not shut off. Thermostat 'clicks', but unit keeps running and producing heat. How can I determine what is wrong and are parts available? This unit is probably original to the mobile home made in 70's. model #305001-2
Thank you in advance for any suggestions.
Steve
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Postby Mark » Mon Sep 24, 2007 1:45 pm

You probably have a bad relay or sequencer (in case they used sequencers back then). Right now our info on Duo Therm is very limited. Someday we'll come across a set of manuals and be of much more help to people. If anyone has any Due Therm manuals, please contact us!

Meanwhile I'm not sure how to match-up your part. Posting or e-mailing us a pic of your relays might help.

Mark

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RE: Duo Therm electric furnace won't shut off

Postby Hardrock » Mon Sep 24, 2007 8:18 pm

Hi Mark,
There appears to be a couple of sequencers: White Rodgers 24A15-5. The ends of the wires going to the bottom sequencer are corroded and a little fried and it appears some of the wires are not original.
Is it possible to replace this sequencer with a universal type? The specs are: spst, 1 switch, on 35, off 30 and normally open.
One additional question: I think I blew a fuse while switching to fan mode while trying to diagnose. The fuse is a 'fustat 4.5A type S'. The problem is that when I look into the fuse socket I see the numeral 5 and also a 3-1/2 and am not sure what fuse to use to replace. I have not been able to find a 4.5, but a 5.0A can be ordered.
Thanks for the suggestion about the sequencer.
SteveImage
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RE: Duo Therm electric furnace won't shut off

Postby hvac1000 » Mon Sep 24, 2007 9:38 pm

Replace the fuse with like same OR look on the wiring diagram to see exactly what fuse it takes.

The sequencers you have are the old style White Rodgers and they can be converted to the new style stack type. The White Rodgers sequencers are very expensive but they do hold up well.

Mark has sequencers in stock but it might be best to talk to Robert when he gets back on the possible conversion to a different type sequencer and the part numbers you will need.

He will need all the information off the old sequencer..
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RE: Duo Therm electric furnace won't shut off

Postby Hardrock » Tue Sep 25, 2007 12:32 pm

HVAC 1000, I have been unable to find a 4.5Amp dual element type S fuse - Will a 5.0Amp thread in? What additional information off of the old sequencer will he need that I did not provide in my post? When will Robert be back?
Thank you for your help,
Steve
Hardrock
 

RE: Duo Therm electric furnace won't shut off

Postby hvac1000 » Tue Sep 25, 2007 6:14 pm

As long as the screw base is the same a 5 will work. It is within or close to the 10% rule. Watch the base of that fuse. There are two types on is Edison and the other is a smaller version designed not to allow over fuseing.

The sequencers are a question I will leave for Robert. He has more experience changing these over. I did one last year for a friend but it was one of those I had to be there to do it things. The wiring is not that tuff it is just knowing where they all go.
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Postby Hardrock » Tue Sep 25, 2007 6:53 pm

After much searching, I found the 4.5Amp fustat plug fuse from an on-line source.
Some sequencers list the time on or off as a range, i.e.: 1-90 seconds. Are these actually adjustable? Is this what makes them "universal"?
Hardrock
 

Postby hvac1000 » Tue Sep 25, 2007 11:22 pm

They are not adjustable
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