1. Noavatar

    Mike C 2012-10-24 10:33

    Millivolt System trouble...

    Hi Jeff,

    I am an apartment owner "blessed" with many 2 wire millivolt heaters.
    I have one that is a particular PITA.
    It is an older floor unit. The crawl space is VERY tight with a dusty dirt floor. Compounding matters, I am claustrophobic!
    My handyman and I converted this unit to thermostat control from manual control rods about 2 years ago.
    Problem is:
    Voltage is low - maybe .3 to .4 Just borderline. Sometimes it works, sometimes not. It will usually fire up if you short the wires at the t-stat. Or, sometimes pounding on the floor above the heater will get the valve to operate.
    Last season, I suspected that the pilot was too high/hot. I turned it down and the voltage rose. All seemed OK.
    However, toward the end of the season it became balky again. I have yet to test, but I'm sure the voltage is too low again.
    It was incredibly hard for me to work on it last year. I disassembled the unit "in-place", while on my back in the dark and dirt, to access the pilot screw on the valve. Perhaps I didn't turn the pilot low enough.

    Q: The unit puts out steady constant low millivolts. Are there any t-stats on the market that are battery powered, that would sense the voltage supplied for safety and then trigger the valve with internally generated voltage (using the battery)?

    Thank you so much,

    1. jeff 2012-10-30 11:46

      I don't know of any (besides mechanical) thermostats that play well with millivolt systems. I've seen problems like you are describing caused by two things: The millivolt generator (some call it a 'thermopile') is a short brass tube that lives in the pilot flame and has wires coming from the end. It's what generates the small voltage that drives everything by using the heat of the pilot flame. I've had these get weak and not generate quite enough voltage/current to work the valve. A simple replacement (available at Home Depot) fixed it. Sorry yours is so hard to access. In the other case, the gas valve just got old and sticky. Banging on the heater would get it going, but was hardly practical. I found and bought online a replacement and it's still working fine. Since you have a low voltage reading, I would suspect it's the thermopile.
  2. Noavatar

    DaveB 2013-06-27 14:30

    Hello Jeff - your comments "Cooling Anticipator"

    "Just as the heat anticipator can artificially shorten the heating cycle to reduce overshoot, the cooling anticipator shortens the cooling off cycle in an attempt to prevent the temperature from rising above the set-point. __Cooling anticipators are less commonly used (or needed) than heat anticipators."

    __Is inaccurate - ALL T/stats have & require cooling anticipators. This is the mysterious resistor in the base of the thermostat. While less than rocket science and a fixed load (vs the variable heat anticipator) it is essential to proper operation. Unlike the heat anticipator that is in series w/ the heat control circuit (W) and only energized with a call for heat, the cooling anticipator is in a series paralle circuit with the cooling contacts and control load. When the cooling contacts are made, the electricity paths across the contacts the cooling anticipator is out of the circuit, once the call to cooling is satisfied, as long as the selector switch is set to cool, the electrical path goes thru the resistor to the cooling load... resistance = heat, this heat starts heating up the T/stat (hopefully is some proportion to the heat gain of the home). Again not the best science, but it does offset radical temp swings in the cooling mode.

    BTW — you can TEST the cooling anticipator by turning the T/stat to cool / 90 — you should read 3-6 V at the contactor. No voltage = no anticipator

  3. Noavatar

    wandyfisher 2013-07-31 11:58

    Hi Jeff,

    would be interested in the box to allow control of a millivolt heater with 24 volt thermostat


  4. Noavatar

    feliplay 2013-12-18 19:49

    I'm felipe, I have a question about how converted the 2-wire millivolt system to a standard 24vac system. Please i need your comments, because I have a system with Thermostat of Control4 and Chaffoteaux Boiler. Hoping your comments, Best regards.

  5. Noavatar

    Derketer 2015-04-08 03:34

    Glad you enjoyed it man! I can't wait to see you in game as I am lnvoig it. Me and a buddy login almost every night around 9-10PM CST to play for a few hours and have a blast. We both reolled Druids so we could get all the ports and buffs to help level our other characters like tanks that we plan to to play some day. If you see Diabeto in game say high, that's me the Halfling Druid, hehehehe. Hope to see ya in game soon!



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