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Thread: Underfloor heating control problem.

  1. #1
    Automated Home Lurker
    Join Date
    Apr 2008

    Default Underfloor heating control problem.

    Hi, I have just finished self installing my underfloor heating into my conservatory (I did it myself, as all the local heating companies were obviously blagging it, when they quoted).

    Things have gone smoothly, but I have fallen at the final fence.

    I have a WorcesterBosch CDi35 II Combi in the kitchen powering my heating, hotwater. The underfloor heating is taken off the standard radiator flow and return, into a 3 port manifold, with actuators on all 3 sections, there is also a circulation pump here. The 3x actuators and pump are powered by a Honeywell CM927 wireless room thermostat (in the conservatory), and the matching reciever next to the pump/actuators.

    My WB boiler also has a wireless room thermostat, which is located in the main house (the hall), and that is what fires the boiler up when heating is needed.

    The problem is, there is a very real scenario that the conservatory will require heat, but the hall is fine, so the boiler won't be heating up, and hence the underfloor heating will simply be circulating cold water!!

    There is no easy way to get wiring back from the conservatory to the combi in the kitchen, without major disruption (Kitchen is quite new, and the misses will kill me, if I need to lift up tiled flooring and such...)

    One possible solution, I can see, and I am not sure if it will work, is to pair up another Honeywell CM zone system reciever unit on the back of the boiler. Now all the documentation says about pairing up multiple transmitters (room stats) to a single receiver, but I want to do it the other way around, 1 room stat to 2 recievers (one on the UHF and one on the boiler). Can this be done?

    Anyone have any other bright ideas as to how I may solve this?

    Many thanks...

  2. #2
    Automated Home Sr Member NeilUK's Avatar
    Join Date
    Jul 2005


    I don't know if you have already tried, but it would be easier to buy another receiver and test it in the way you need it to work.

    If you find out that it does not work because the 927 can only bind to one receiver then the simple if inelegant solution is to use another CM927 or CM67 bound to your second receiver as the boiler feedback and keep both room units synchronised. Bit of a pain to change as you need to do it n both units but at least you don't need to run a cable and mess around with interface relays at the boiler to electrically isolate the UFH heating demand signal from the radiator heating.

  3. #3
    Automated Home Jr Member
    Join Date
    Apr 2008


    I take it you also put a thermostatic mixer valve in?

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