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Burnham ES27 no heat - FIXED!!

EricPeterson Member Posts: 79
edited December 2018 in Gas Heating
Woke up to a cold boiler (Burnham ES27).
The boiler reports the following on the IQ Boiler Control:
StA (Status) 1 Standby
hr (Heat Request) OFF

The system though is calling for heat (through TT terminals on IQ Option Board).
The Option Board connects with a wiring harness to the IQ Boiler Control.

I swapped out the IQ Boiler Control with a spare - same results.
So that leaves either the wiring harness, or the IQ Option Board (neither of which I have spares for).

The boiler was installed in 2011 and has been reliable until now.
Anyone got any ideas for troubleshooting this?

Eric Peterson


  • EricPeterson
    EricPeterson Member Posts: 79
    A close inspection of the wiring diagram led me to jumpering the points on the control board for the two thermostat contacts.
    And voila the boiler kicked on.
    See photos. StA 8 = Running
    So there is either a problem with the wiring harness or the Option Board, as the signal is not getting through.
    I have both parts on order.

    Very strange that this failure would suddenly occur after seven years of operation.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,306
    A problem with the wiring harness or the board is not that uncommon, especially with the Molex connector. Heat being the biggest contributor. Are you sure your thermostat wires going into the board/connector are ok too?
    You'll be bummed to replace those parts, and find out it doesn't work and it was a loose/bad connection somewhere.
  • EricPeterson
    EricPeterson Member Posts: 79
    I checked the wires coming in and they are fine. Since closing the connection on the logic board fires the boiler that isolates the problem to either the harness or the Option Board. At least that's the way it seems to me.
  • Ironman
    Ironman Member Posts: 6,555
    No, that isolates the boiler from the thermostat and wiring. How did you check the wires coming in?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EricPeterson
    EricPeterson Member Posts: 79
    Wires coming in - there are three zones controlled by zone valves (White Rogers 1361 2-wire), wired similar to Figure 9 (T1 / T2 correspond to T/T on the Burnham board):
    I've checked this wiring, and verified that if any of the zones calls for heat then the TT contacts are closed.
    So with the thermostat(s) calling for heat, yet the control board reporting no heat request, then the problem must lie between the control board and the TT contacts - which means either the option board and/or the wiring harness.