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Millivolt thermostat ?

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by DBCOOPER, Feb 3, 2013.

  1. DBCOOPER

    DBCOOPER Feeling the Heat

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    I have seen several people tell people that they need a millivolt thermostat. A millivolt thermostat works with a standing pilot gas valve system. Several thermocoulpes in series generate a voltage while sitting in a pilot flame. It works like the thermocoulpe in some stoves work to prove a fire is established. They usually make .75 volts. So a milivolt thermostat is designed for millivolts not 24 volts ac like my quad uses in its control circuit. I have never seen a pellet stove with a standing pilot light. Are there any stoves that the manual specificly requires a millivolt thermostat?

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  2. imacman

    imacman Guest

    This is right from the Englander manual for my stove:
    "An external thermostat..........can be used on our Pellet/Corn/Multi-fuel units as long as it is a low-voltage that works with millivolt systems."

    Most stoves that I've seen or heard about use a millivolt stat.
  3. DexterDay

    DexterDay Guest

    A lot do say millivolt systems. But Quad States a 12 volt AC stat.

    I see what your saying DB... Makes sense. Although, it is printed in many manuals that way.
  4. jtakeman

    jtakeman Minister of Fire

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    Most of these control boards made by ACE use micro processors(Enviro-Breckwell-Kozi-ect.). Pretty sure they are using 5V which might be to low for a 24V stat. But I do see some of the stats rated for pellet stoves also work on millivolt and 24V systems.
  5. tjnamtiw

    tjnamtiw Minister of Fire

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    IMHO, I think that they are really saying that you only need a thermostat that can 'handle' millivolts, meaning the contacts (of what ever kind) are capable of handling only low voltage and resultant current. Yes, Quad says 12 volt stat. Did you ever have luck finding such an animal? :)
  6. jtakeman

    jtakeman Minister of Fire

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    Not sure its because of the lower voltage, probably more like the resistence is too high within the stat?
  7. ekarlis

    ekarlis Member

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    I was told by a distributor that Honeywell stop making millivolt stats & all the new stats are digital 24 volts. All the control boards that I have seen have a transformer that generates 24 volts for the stat. The stat is merely a switch
    & the power comes from the board & it is not millivolts. The last millivolt system I installed was in 1970's. The current
    furances have been using hot surface ignition w/24volt system. This has been a confusing issue w/ millivolt systems,
    but as far I am concerned millivolt systems are long gone & dead for stat use. Hope this helps
  8. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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  9. silverfox103

    silverfox103 Feeling the Heat

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    My Harman PP38 (1997), made does require a minivolt thermostat. Digital thermostats will not work, that I know. It's a very inexpensive thermostat, I think they have them at HD for around $12.

    Tom C.
  10. ekarlis

    ekarlis Member

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    Called Honeywell & spoke to a tech. He said that the 750 millivolt stats are compatable to a 750 volt system.
    They are derated 24volt stats. Also he said that they can not afford to have a separate assembly line for
    750 millivolt stats
  11. Thaddius Wenderoth

    Thaddius Wenderoth Feeling the Heat

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    The thermostat I use is an internet connected stat from Hunter Fan. It states it will work with both systems. Heres the link and what it says about it.


    http://www.hunterfan.com/Innovations/Universal-Internet-Thermostat/

    The Hunter Universal Internet Thermostat works with most HVAC (Heating, Ventilating and Air Conditioning) system you have—conventional, heat pump, radiant, you name it:
    • Electric air conditioning
    • Up to 2 Stage Heat/2 stage Cool systems
    • Single and two stage heat pumps with auxiliary heat
    • Gas, electric and oil furnaces
    • Gas and oil fired boilers
    • 2 and 3 wire hot water/radiator systems
    • 24 Volt and Millivolt systems
    • AC or battery power NOT FOR USE with 110/220 volt electric baseboard heat
  12. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    Let's keep things in the correct scale here, a 750 millivolt stat should never be used on a 750 volt system even if such a system exists. The stat would be toast on first call for heat.

    Funny about that derated part, since I'm finding a higher price tag on the millivolt ones than the 12 volt and 24 volt versions.

    The voltage rating is for the "maximum" voltage that should go though the switch when it closes or what the anticipator's heater can handle.

    There are even stats that can be used on all three normal none electric heating system control voltages.

    In the case of pellet stoves one can determine the lowest voltage rating that will work by using a volt meter and measuring the voltage across the terminals since the controller is providing the power for the circuit.
  13. ekarlis

    ekarlis Member

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    Smokey:
    From a HVAC prospective, a 750 millivolt generator works with 750 millivolt stat. This is a 750 millivolt system&
    it has been used for years on furances. Please explain to me why a millivolt generator will not work with millivolt
    stat? This what I call a system. Not being sarcastic, just do not understand what you mean.
  14. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    You used both 750 millivolts and 750 volts in the same sentence that is a 3 orders of magnitude difference.
    tjnamtiw likes this.
  15. ekarlis

    ekarlis Member

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    Smokey:
    Apologies. You are right, 750 millivolt will not work on a 750 volt system. Where do you find a 750 volt system?
  16. Thaddius Wenderoth

    Thaddius Wenderoth Feeling the Heat

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    Electric public transportation vehicles use 750V. So your nearest subway or tram. :cool:
  17. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    No need for an apology at all.

    I just didn't want someone months from now scratching their heads or making assumptions. We have enough of that on here already. Usually it is of the my stove is so clean you can eat off of the inside of it variety.
    tjnamtiw likes this.

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