Mahl floor furnace


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Old 01-17-10, 11:22 AM
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Mahl floor furnace

Hello, I have a 50+ year old floor furnace from Mahl Mfg. Co. (Model #50A). I just installed a new thermostat from Honeywell (model CT87K). It won't work. I called Honeywell hotline and they told me that I need 24-30 volts to work their thermostat. When I touch the furnace 2 wires together (from the wall), the furnace comes on fine. Honeywell said to call an electrician to fix the transformer. I have had this furnace for 20 years. Is the Honeywell guy right? Is there a transformer? I don't want to spend any money until I know this is true. Thank you.
 
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Old 01-17-10, 03:35 PM
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Some floor furnaces use a 24 VAC control system, others use a milivolt control system that generate electricity to operate the system directly from the heat of the pilot flame on a pilot generator.


See if there is a pilot generator that looks like that below in the pilot flame:

Amazon.com: Hayward CHXGEN1930 Comfortzone Pilot Generator for Millivolt Heater: Home Improvement
 
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Old 01-17-10, 05:41 PM
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Originally Posted by 123tonyb
Hello, I have a 50+ year old floor furnace from Mahl Mfg. Co. (Model #50A). I just installed a new thermostat from Honeywell (model CT87K). It won't work. I called Honeywell hotline and they told me that I need 24-30 volts to work their thermostat. When I touch the furnace 2 wires together (from the wall), the furnace comes on fine. Honeywell said to call an electrician to fix the transformer. I have had this furnace for 20 years. Is the Honeywell guy right? Is there a transformer? I don't want to spend any money until I know this is true. Thank you.
Where in california? Typically if you touch tstat wires together and you have a true millivolt, nonanticipated tstat then it is the tstat to blame. However, your meter is your best friend.
 
 

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