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Hot water sensor open


I have a biomass panel that is showing a fault “code 20, HW sensor open”, so I have no heat or hot water at the moment .

It is a Trianco ,Greenflame Eco 26kw. With a Estyma electronic display.

I am assuming it is a faulty sensor in the biomass panel itself and not the At the HW tank.
There is a stat on the HW tank with a resistance of 20k apart from that I can’t see any sensors on the HW tank and surrounding pipes, so I am assuming it is a sensor in the biomass panel itself??

Any suggestions would be welcome, The Biomass panel is just out guarantee so being a electrician myself if the problem is just a faulty sensor somewhere I am hoping I can repair it myself if I can find it.

Thanks in advance


  • Jamie Hall
    Jamie Hall Member Posts: 23,287
    Before you start tearing into the panel, you say there is a hot water sensor -- presumably a thermistor, not a switch, since you quote the resistance -- in the tank? First thing I'd do is measure the resistance of that sensor at the tank -- and then measure again at the connection to the panel which is, I presume, separate. It is entirely possible that the panel is telling you exactly what the problem is: that somewhere in there there is an open. Bad contact, broken wire, any one of a number of possibilities.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,524

    The equipment provider can probably get you a resistance chart for the sensor which will show the resistance at different temperatures. May be in the manual if you have one.

    Sometimes disconnecting the sensor will force the equipment on at least temporally
  • rich1974
    rich1974 Member Posts: 2
    Jamie, I measured at the halfway point at a joint, I will measure at the biomass panel next and see what I get,

    Ebebratt I will try what you suggest.