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Power robbing thermostats

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  • Power robbing thermostats

    After I started experiencing issues with furnace/thermostat (see another thread) I opened a manual for my furnace and found this:
    THERMOSTAT POWER ROBBING THERMOSTATS IMPORTANT: There are three basic types of thermostats. They are: mechanical, battery powered and power robbing. Thermostats that are powered by furnace transformer voltage, referred to as “power robbing,” may not be used. Use of a power robbing thermostat will result in intermittent operation.

    It seems to me that wired insteon thermostat is in fact power robbing and is not allowed with my unit? I have 5 wires running up and all the terminals match. Except the weird shutdown on heat issue everything functions normally, but now with the above statement I wonder if I am causing unnecessary wear on the furnace??
    Attached Files

  • #2
    I reviewed the Honeywell R7184 and I don't see that warning. Do you have a link for the manual that you have?
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    • #3
      yep, here you go:
      It must be important because its on the very first page right in your face... Then page 11,13,etc.
      I just received 24vac transformer from amazon and wired it up - no more thermostat shutdowns/reboot, no more coming up in "off" position if the furnace keeps power off for longer than 60sec.

      The house came with the furnace and I added insteon later... I learned more about furnaces/thermostats/etc than I ever wanted to know :-)


      • #4
        How old is this oil fed furnace?
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        • #5
          it was produced in 2006, installed a bit later


          • #6
            2006 is pretty recent so am a little surprised this furnace doesn't support what is considered basic in the TSTAT industry.
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            • #7
              That is not so basic nor standard, it is just one of the many different configurations that are out there for HVAC control systems. There are many systems that keep power to R constant always but also several that cut the power at the R terminal for several different scenarios and reasons which are tied to how the system is supposed to function. Why it happens doesn't matter, the solution is the same. Just get a 24 VAC transformer that plugs into the wall or is wired to the side of a junction box and use that to power the thermostat. The 2 wires from the transformer will connect to the R and C terminals in the Insteon Wired Thermostat and keep constant power going to it so that it does not power down and reboot when the HVAC system shuts off the power temporarily.


              • #8
                turns out the furnace was hitting a high heat limit, which was fixed after changing the nozzle from 1g to 0.75g which reduces oil supply of course. Why it suddenly started happening without any changes to furnace is still a mystery, but all good now and saving on oil...