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2441TH + pellet stove + transformer

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  • 2441TH + pellet stove + transformer

    Hello all—

    I’ve read through many of the “wiring” and “two-wire conversion” topics, and don’t quite see my particular issue (I know, I’m “that guy”).

    I’m installing an Insteon 2441TH to my Harman Advance pellet stove. Harman and their forums have descriptions on how to hook up a smart TStat. The basic idea is to “break” the connection with the onboard room-sensing thermostat (on the pellet stove) thereby tricking the stove into a false error mode. When heat is called for from the Smart Tstat at the R&W terminals, this completes the connection and the pellet stove will be satisfied and fire up.

    One little addition is I’m powering the Insteon with a 24v transformer plugged into the wall.

    SO... The Insteon is successfully powered when I hook up the transformer to the 24Com and 24R connections. The pellet stove wires are supposed to be connected to the R (24R??) and W connections (so I have two wires going into the 24R???).

    This combo almost works: stove starts with the appropriate error mode, sits idle. When heat is called for from the Insteon, the error mode goes away and the stove fires up. Great, BUT— the stove won’t go back into error mode when I tell the Insteon “no heat.”

    So I can turn the stove ON remotely, but can’t turn it back off again. That’s sort of ok for my application, since I’m really just using it to pre-heat a vacation house during the drive up there, but it makes me think my connections are incorrect. So far, the only way I can get the stove to go back into error mode is to depower the Insteon stat and start fresh. Definitely not something I feel I ought to do on a regular basis.

    Things I’ve considered: cycle time for furnaces (I waited at least 20 minutes for the Insteon/stove to finally send the “kill” signal, but it never arrived). Can I adjust the cycle time just to be sure?

    Thanks all.

  • #2
    You are using a 24 volt AC transformer?

    I don't have one but the FCC database photos. Show an electronic component controlling the outputs. Probably a Triac. Not relays with dry contacts.
    It is possible the Triac is not turning off correctly with a the control voltage from the stoves electronics.
    Maybe having the 2441TH wired to a 24 volt AC relay and having it connected to the stove may work.

    Does the stoves thermostat connections. Have a 'C' connection on it also. That way you could use its 24VAC common to power the 2441TH and not need the other transformer or having possible interactions between the power to the thermostat and the stoves power.
    Last edited by BLH; 02-04-2019, 05:24 PM.


    • #3
      I understood about 80% of that... 😂

      Yes, I’m using a 24v AC transformer to power the Tstat since it’s a WiFi “smart” Tstat. The stove doesn’t have a C wire— it’s built-in room sensor is a pretty basic unit with a probe on the end of it. I the probe must be connected to the stove at some point, thus wiring it in-line to the Tstat.

      So it sounds like what what you’re saying is the thermostat might not be actually making a clean break between the R and W terminals? Some residual electrons that keep the contact?


      • #4
        I suspect the power supply for the thermostat and the power supply for the stoves controls. Are keeping it from turning off. If by chance the stoves controls where not the normal AC and where DC.
        The triac in the thermostat would not go off. As it would still conduct until the applied voltage dropped below its minimum holding voltage.
        You may want to look at the Venstar 2 wire heat only kit. Smarthome sells. It isolates the thermostat and the stove controls. Even if you don't decide to get one. One of the two diagrams on the sales page shows you how it connects. The manuals tab also has the installation sheet if you care to see how it is used.


        • #5
          Thanks, I’ll check it out. On the pellet stove forum somebody pointed out that the Insteon is NOT millivolt compatible, and I need a milivolt Tstat. They were concerned that I was pumping 24v back into the stove’s control panel which might fry it.


          • #6
            If it is millivolt compatible controls. I would also say not to use it with a 24VAC transformer even it it was compatible.
            I believe the 2 wire heat only adapter uses a relay with dry contacts. That may work or getting a compatible thermostat.