Chattering GAs Valve


Old 01-13-01, 04:53 AM
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I live in a 35+ (if not 50+) yr old house. We moved in and the gas heater was not hooked up to the transformer. So I hooked it up and it worked for about a day. Then the gas valve began to make an aweful racket. It sounded as if the seal-a-noid (spelling???) wasnt fully activated, like it wasn't getting enough electricity to keep it open. It was so old that I figured it had just worn out and went and bought a new valve. Now $130 later I stillhave the same problem. I have spent hours down there, messing with the wires and what not, but I can't get the valve to stop chatterieng. Please help! The thermostat says, Milivolt: 12 V.D.C. @ .060 amps - 24 V.D.C. @ .060 amps. The valve is a White Rodgers Model 36C21U Type 206 with three posts for Pilot generator and thermostat hook up. The valve says, milivolt only, Use pilot generator E21 (which I used the one that was already there. It looked as if it had been recently replaced (last 10 years). The transformer was extremely HOT. I couldn't touch it! It said Type Q72A1K1, 115 volts 50-60 cycle, Secondary 25 volts, Output 40 V.A. Minneapolis Honeywell Reg. Co.. I don't know what all the acronyms mean, so if you could help me out I surely would appreciate it! Thanks Jefo

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Old 01-13-01, 05:41 AM
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Does the furnace have a wiring schemetic? Your transformer is AC and millivolt is DC, very incompatible. Has A/C been added to the system? Your control voltage wiring for heat should be millvolt dc according to your gas valve. Have you tested the thermopile output? It may be to low, or you may have a loose wire. Make sure you have sufficient flame on the themopile also. What is the millivolts for the valve? 250,500,or750.
Old 01-13-01, 08:09 AM
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The Mill volt gas valve (usally red in color) is powered by the generator that is in the pilot flame.
THE GAS VALVE DOES NOT GET HOOKED UP TO THAT 24volt TRANSFORMER.The generator should produce enough power if the pilot is clean.
There are two wires (or a 3/8 electric connector) that the generator uses to connect to the valve. This is the POWER to the valve.It is low voltage DC called MV(milla Volts). The other two wires go to the limit switch and thermostat. You could test the valve by jumping these out, the burner should come on.
Someone could have modified the system to use a 24 volt thermostat. If they did it would need a good isolation relay.Some of the cheap relays don't close MV circits very well.
Read the directions on that new valve,DON'T SEND 24VOLTS across the coil.It will damage the valve.

Good Luck
Mr Foster
HVAC Contractor
Old 01-13-01, 11:38 AM
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If you applied 24v to a millivolt gas valve you will need to replace the gas valve as it is now not safe to operate.
You may wish to consider calling a Hvac tech to correct your problem. Furnace could remain millivolt or be converted to 24v. Make sure you tell them what has happened.

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