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Thread: Evohome - Radiator coming on outside of schedule

  1. #1
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    Default Evohome - Radiator coming on outside of schedule

    Hello all.

    Our system has been 'set up' for about 6 months but we've only been learning to use it for the last 2.

    It's been ok, one or two teething problems but nothing reading up on here hasn't helped sort out.

    However, in the last few days some of the radiators input setup have started coming on outside of the schedule.

    They are due to come on at 6.30am but are coming on much earlier and I can't work out why.

    Also, today some, but not all, of them have been coming on.

    There has been a fault on the error log that says:

    COMMS FAULT, BOILER RELAY

    Any ideas?

  2. #2
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    A couple of possible reasons:

    * The temperature in the room has dropped to your nighttime set-back temperature so the radiator comes on to maintain that temperature. If it's this, you might want to lower your nighttime temperatures.

    * Optimum start: the radiators come on in advance of the scheduled time so that the room has reached temperature at the scheduled time. If it's this, you could embrace it, or disable optimum start, or set the schedules to match your use of the room (i.e. "I get up at 7am on Saturdays") rather than what you think your heating needs ("I'll set it to 6:15 so the room is warm by 7").

  3. #3
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    How would I check those possibilities?

  4. #4
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    We had a COMMS FAULT, BOILER RELAY warning come on when the power to the boiler was off for a few hours - have you had any power-cuts? Ours did seem to 'recover' without any interferring?
    If you click into the optimisation setting you can check whether you have optimisation switched on or not.

  5. #5
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    Optimisation was on but had been switched off since this morning.

    However, throughout today some radiators have been coming on when they haven't been scheduled.

  6. #6
    Automated Home Legend paulockenden's Avatar
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    But there's no 'on' or 'off' in the schedule, only target temperatures. Perhaps those rads needed some heat to keep them on target?

    P.

  7. #7
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    Quote Originally Posted by paulockenden View Post
    But there's no 'on' or 'off' in the schedule, only target temperatures. Perhaps those rads needed some heat to keep them on target?

    P.
    Indeed.

    What was the scheduled set point and current measured temperature of the radiators that should have been "off" ?

    If you really want a radiator to be "off", schedule it to 5C. This is the lowest you can schedule a set point to, and ensures that there is always frost protection active in every zone. (Just be careful not to set the HR92 dial itself to "off" as that disables frost protection and also prevents it from following the schedule or remote set point changes of any sort)

  8. #8
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    Quote Originally Posted by DBMandrake View Post
    Indeed.

    What was the scheduled set point and current measured temperature of the radiators that should have been "off" ?

    If you really want a radiator to be "off", schedule it to 5C. This is the lowest you can schedule a set point to, and ensures that there is always frost protection active in every zone. (Just be careful not to set the HR92 dial itself to "off" as that disables frost protection and also prevents it from following the schedule or remote set point changes of any sort)
    Sorry. When the radiators aren't scheduled to be 'on' they are set a 5C.

  9. #9
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    Quote Originally Posted by Hammers80 View Post
    Sorry. When the radiators aren't scheduled to be 'on' they are set a 5C.
    So by "coming on" you mean they are getting hot, even if the HR92 is set to 5C ?

    That's going to be a mechanical problem, probably one of the following:

    1) HR92 base not screwed onto the valve body properly. Lift the HR92 off the base, make sure the black wheel is turned anti-clockwise then screw the white bit down onto the valve body. I then sit the HR92 in place then give the HR92 a little extra turn as well. Then make sure the latch is latched over. If you need an adaptor for your type of valve bodies it may not be fitted properly.

    2) The locking latch not latched - it's not there just to lock the HR92 on the base, if it's not latched the HR92 will not function, in particular it will make no attempts to control the pin position which could result in the radiator running when it shouldn't. So check it is latched.

    3) The valve body may not be fully compatible (such as wrong pin length exposed) resulting in it not being able to properly close or open the valve. What make and model are your valve bodies, if you know ? Or what make and model of TRV's were previously fitted ?

    4) The valve body if old may be starting to seize, or could have some debris (like metal shavings, strips of shredded o-ring etc) stuck in the valve seat preventing it from sealing.

  10. #10
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    Quote Originally Posted by DBMandrake View Post
    So by "coming on" you mean they are getting hot, even if the HR92 is set to 5C ?

    That's going to be a mechanical problem, probably one of the following:

    1) HR92 base not screwed onto the valve body properly. Lift the HR92 off the base, make sure the black wheel is turned anti-clockwise then screw the white bit down onto the valve body. I then sit the HR92 in place then give the HR92 a little extra turn as well. Then make sure the latch is latched over. If you need an adaptor for your type of valve bodies it may not be fitted properly.
    Yes the heating is coming on even when set to 5 on some of the radiators. I had assumed it was happening to random radiators but will keep an eye on them to see if it is always the same ones.

    Thanks for the advice.

    I'll be taking a look at all the valves.

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