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Can a thermostat be added to a Harmon XXV?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by lizman, Aug 12, 2006.

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  1. lizman

    lizman New Member

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    I have a Harmon XXV and would like to control it with a setback thermostat. Is there a was to connect one up?

    It currently has a thermister that hangs out the back side of stove that senses room temp and adjusts according to settings on stove control panel.

    What I would like to accomplish is to have the stove bring up temp a couple of hours before we get up in AM, turn down when we leave for work, come up in temp 2 hours before we get home from work, and finally turn down after we go to bed.

    What I did last heating season was connect it to a timer which would turn on a couple hours before we get home from work then I turn the temp down manually when we go to bed. When I got up next morning I would turn it way down to basically turn it off so when the timer shut off power there wasn't a smoke problem, once the stove was out and the timer was off I would adjust the temp up so when the timer clicked on in the afternoon the stove would reignite and we come home to a pellet stove warmed home. We have central natural gas hot water system for primary heat.

    Thanks for any suggestions.

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  2. Shane

    Shane Minister of Fire

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    I don't sell that brand, but I'm fairly sure that a thermostat won't work with the Harman system.
  3. richg

    richg Minister of Fire

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    Lizman,

    I looked pretty far in to this, and the long and short of it is, "No", you can not hook up a thermostat to a Harman. This came from several discussions with Harman's tech support.
  4. Choppedliver

    Choppedliver New Member

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    YES you can run any low voltage T/stat on any harman pellet stove.
    this one is hard to explain but we will give it a shot,
    The thermister end has to be used along side the t/stat and the controls on you stove will still work along with the controls of the t/stat on the wall. The wiring needs to be ran in one series. 1.one wire from the stove go's to the thermister, 2.another wire go's from the stove to the wall t/stat 3. then the one wire left over from the thermister go's to the t/stat.
    It is one big loop.

    When the wall t/stat is off(open) the whole t/stat system (t/stat-thermister) is off(open), when the t/stat is on(closed) the system will run like it did before you hooked up the t/stat (stove turns up and down and on and off with the temp. setting on the stove's control board
    I leave the thermister probe right behind the stove like you have it now and also install the progammable t/sat behind the stove on the wall ,but I have had amny customers run the wireiing to another part of the room or house so it tell the temp. of the other part of the house

    You will not find this in you manual but it works well
  5. begreen

    begreen Mooderator Staff Member

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    I was wondering about breaking the thermistor circuit with the thermostat. So when the thermistor circuit is "open" or infinite resistance, the stove believes that there is no need for heat. Is that correct? Sounds pretty simple if that's the case.
  6. HarryBack

    HarryBack New Member

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    this seems fraught (sp?) with "issues" for folks who arent very technically adept. Stove Mode ignores the thermister loop anyways, so, im assuming you speak of Room Temp mode of operation. All the thermostat really is is an open/closed switch, opening and closing at a given selectable temp. When it is closed (calling for heat), the stove will still use the thermister, as explained earlier here, then the stove will utilize the given vaues set on the control panel for the thermister. So, my question is, why would you want to use a wall thermostat? You can extend the thermister wire up to 50' anyways. Seems meaningless, but Im sure theres a good reason. By the way, Harman doesnt reccommend this use. I dont think it would do anything adverse to the system, but I will say that if I ever were to go to work on a system with a complaint dealing with low heat or weird operation, the first thing Id do is tell the customer that its a non-approved installation, warrantee-wise, and stop chasing the ghosts at that point.
  7. lizman

    lizman New Member

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    Choppedliver,

    I checked the back of my Harman XXV and the thermister has a black and red wire connecting it to the stove with a couple of flat plug in terminals. Does it matter which wire I place the thermostat in the loop?


    What I want is the stove to be controlled by the thermostat as far as temperature setting not just the on/off function. If the thermostat changes from 70 degrees to 62 will the stove respond accordingly or will the stove control setting determine the temperature setting? Does the thermister on the stove continuosly monitor room temp and the stove computer interpert the change in signal (resistance) to determine if more or less fuel is needed?
  8. HarryBack

    HarryBack New Member

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    Lizman-

    Maybe a foolish question......Why dont you simply use the temp control on the control board of the stove to regulate temperature?
  9. drizler

    drizler Minister of Fire

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    I don't know about Harmon but I had a hard time finding a microvolt setback thermostat to fit my Countryside. Finally after someone telling me which one to get I hooked it up just like you want, across the room in the middle of the house. Make sure you get a compatible model. When all was said and done it was oh so worth the hassle and I speak on the strength of 2 seasons heating almost exclusively with corn and pellets. Here is why you want a setback, and its a big reason.
    ALL THESE STOVES ARE SLOW HEATERS. I can set mine at 50K and its not going to heat the house up for nearly an hour and I don't even have a big house. Secondly DEM WIMMIN will always just reach for the boiler controls every time. I can't control that one because I work the night shift and they are up and either going or gone before I get home. By having the setback I can set the boiler at 45 and let the house temp drop to 55 at night and have the stove kick up to heat the house up an hour earlier than they get up. Just by judging how much I dump in there it makes a noticeable difference in how much I feed the beast. It is truly worth your efforts trust me. I don't much miss the lack of an auto start feature as idling at 10K it does a pretty good job of heating throughout the night. I think you will definitely find it worth the effort involved! Just make sure you buy a stat that "will work", in other words this is not the time to go Ebay shopping due to the difficulty in returning it.
  10. begreen

    begreen Mooderator Staff Member

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    We had a digital thermostat on the Quadrafire for 5 years. I put it on when I installed the stove and never regretted it. The stove came on 30 min. before I got up. It was sooooo nice coming down to a warm cozy stove. My son's daily ritual before heading to school was to stand in front of the stove for 5 minutes. He's already expressed concern about missing the stove next winter. At 11pm it would set back to a nice comfortable sleeping temperature. Ahhh. On weekends the schedule was delayed by an hour. Worked like a charm.

    The digital thermostat also was great when we had house sitters that were less familiar with the stove. One less control to fiddle with. All they had to do was feed the stove pellets.
  11. Choppedliver

    Choppedliver New Member

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    Wiring is a loop, stove and t/stats don't care which plug the red or white wires are hooked to.

    The new T/stat will only tell the stove to turn on or off and will not turn the stove up and down but when the t/stat is in the on (closed) mode the thermister will turn the stove up and down like it you have it set up know.
  12. lizman

    lizman New Member

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    HarryBack,

    The reason I wanted to use a thermostat was to bring up the temp before we get home from work and before we get up from bed each weekday. To use the temp control on the stove means someone physically has to turn it up - before we are home from work no one is home and early in the AM I really did not want to set the alarm to get up and turn up the stove then return to bed for an hour or two.

    Choppedlver,

    My concern with simply turning the stove off via the remote thermostat is: Will this process be similar to losing power or will stove gracefully stop feeding pellets with both fans still running until flame sensor tells everything to turn off. I did lose power once and the smoke did get into the house.
  13. HarryBack

    HarryBack New Member

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    In my neck of the woods, the coldest time is nighttime and early morning. If anything, we turn our P61 UP on thoise cold nights, since radiant heat does take abit to get from point A to point B. That way, I dont have to freeze in the am until the stove gets enough heat upstairs. I heat two floors with mine, there is roughly a 10 degree difference between the floors (colder upstairs).
  14. Choppedliver

    Choppedliver New Member

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    The T/stat would cut power to the thermister only making the stove think the thermister is unpluged, the stove will go in to a shut down mode that should take about an hour to shut off. it will not instantly shut out like when you loose power.

    side note when the stove is turned on to the "room temp" and your new T/stat is turned off(open) the stove will flash a one light on the control board telling you that the thermister is missing or bad. don't worry this will not hurt the stove
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