Old Wall Heater Question


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Old 03-11-06, 06:24 PM
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Old Wall Heater Question

My house is 1953. I have an old "Commonwealth Force-Flo" natural gas heater, mounted in the wall. Model K-50 DWH, or, K-57 DWH. It's almost 6 feet tall. There's a motor in the bottom of it that forces out the heated air. The motor hasn't worked since I moved in two years ago. I just took off the juction box cover on the motor and saw that a wire splice had come undone, so I hooked it back together. The motor now works, but it doesn't shut off. The wiring in the junction box is as follows: hot wire from source (main breaker box) comes into box and is spliced to a wire that runs up somewhere into the upper portion of the heater. A wire from up in the heater then returns down into the junction box and is spliced to a wire that goes to the motor. The return wire from the motor comes back into the junction box and splices with the neutral wire that returns to the source (main breaker panel).

I'm wondering, is there some kind of thermostat(or something) up in the heater, that opens and closes, depending on the heat of the air, thus completing the electrical circuit when it wants the motor to run, forcing air out into the rooms of the house? If so, is my motor continuously running because, perhaps, the thermostat inside the heater is damaged, and will not break the circuit, letting the motor shut off until it is needed again?

I may be way off base, but I'm worried about the motor running ALL the time. That doesn't seem right. I need to do something to remedy that situation. Thanks in advance!!
 
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Old 03-11-06, 10:10 PM
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Are you able to remove the panel to get up where this fan control be at?

Sounds like it stuck closed, where the fan will run.

it maybe some type of disc type or something in the like that controls this.
 
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Old 03-12-06, 09:03 AM
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Jay,
Yup, it is a very little disc. One of the numbers on the back is "F-140." Could this be the temperature rating. Also on the back, it says, "Therm-O-Disc," maybe a brand name? There are no temperature setting controls or anything else on the disc. It is just a disc, with two electrical terminals on the back. This is a very old heater, I'm assuming. Do you think they still make something of this same shape and size that will work in my heater? If so, where might I find one? Thanks!
 
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Old 03-12-06, 09:08 AM
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repairs

It sounds like the bi-metal thermostat is stuck in the closed position. With power disconnected. The front cover of the furnace should just lift up then off away from the wall. Then you will see 2 eye shaped things with two wires that goes to them replace both of them. One is a high limit the other is the fan relay.
 
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Old 03-12-06, 09:47 AM
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Originally Posted by Willg54
Jay,
Yup, it is a very little disc. One of the numbers on the back is "F-140." Could this be the temperature rating. Also on the back, it says, "Therm-O-Disc," maybe a brand name? There are no temperature setting controls or anything else on the disc. It is just a disc, with two electrical terminals on the back. This is a very old heater, I'm assuming. Do you think they still make something of this same shape and size that will work in my heater? If so, where might I find one? Thanks!
F-140 = fan switch, closes at 140
L-170(?) or whatever temp = limit switch 170 is temp will open

After you have turned off power, you can continuity test the switch(with wires off switch) to determine if it is stuck in the closed position. We are assuming the wiring is correct and no "summer" switch has been added. Summer switch allows fan to be run without using heat
 
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Old 03-14-06, 08:50 AM
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The nearest heating supply store, according to the Yellow Pages, is in Denver, 50 miles from where I live. I might just go to a heating and air conditioning contractor here in town and ask them if they can get me the part I need. In the mean time, is there somewhere on line that I could find the part I need for my poor old gas heater? Thanks!
 
 

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