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Thread: Can anyone help my wife? (With a question about our system ;))

  1. #1
    Automated Home Jr Member
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    Default Can anyone help my wife? (With a question about our system ;))

    Why do our rads come on in the morning even though the whole house is currently warmer than the setpoints?

    Our valves keep motoring during the day even though the rads are displaying temperatures higher than the setpoint? E.g. this morning the kitchen was at 19 with a start of day setpoint (optimised) of 17.5 and the valves were heard to motor. (Kitchen calibration setting is -3 if its relevant)

    The effect of this from Mrs Codgers PoV is that ďthis b*****y system is turning the rads on when we donít need them Ė the old system didnítÖ. ď

    Why does the system motor when it does seem to be necessary?


    Thanks

  2. #2
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    Is the radiator in question actually heating up ? If not, and all you hear is the motor turning a bit, it is working as designed.

    It's a proportional system and the motor has to turn about 30% of its total travel before it gets to the point where the valve actually starts to let water flow through the radiator.

    So say your room is at 19 degrees and your set point goes from 5C over night to 17.5C the radiator valve pin position may go from 0% (pushed right down) to about 20% up - but this is not enough to allow water to flow through the radiator so it won't actually get hot, nor will it call for heat from the boiler - this doesn't happen until the pin position goes above 30%.

  3. #3
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    Yes. Thatís what annoys her. The rads do actual heat up. (Ie the boiler is firing as well)

  4. #4
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    If the radiator is actually coming on and heating up when the set point is 17.5 and the actual temperature is 19 degrees that suggests a problem, perhaps with the HR92 not being fully compatible with the radiator valve body.

    Next time this happens go into the HR92 menu option 10 just as the radiator is warming up and see what valve position is reported. Anything below 30 should not get hot, if it is signifcantly below 30, say 20 or less, and still getting hot, that suggests that the valve body is not properly compatible or that the HR92 has not calibrated itself for the valve body properly.

    You could try a valve position re-calibration - remove the HR92, turn the black wheel fully anti-clockwise then refit the HR92. After about a minute it will say cycle - it is winding the motor down on the pin to find the fully closed position.

    Are the valve bodies that the HR92's screw onto relatively new, or fairly old ? Do you happen to know what make and model the valve bodies are ?
    Last edited by DBMandrake; 10th June 2018 at 09:59 PM.

  5. #5
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    The valves are a couple of years old. They were Honeywell TRVs fitted in anticipation of upgrading to evohome.

  6. #6
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    Iíll try the valve position recal in a while. Iím away with work again!

  7. #7
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    After 2-3 years I'm starting to have issues with my cheap peggler bulldog valve bodies where they won't stop flowing water until they get down to about 15-20% indicated position, despite calibration attempts, this results in those zones going over temperature and still heating in some conditions.

    What happens is because it doesn't call for any heat demand until 30%, if that's the only zone active (for example bedroom radiator at night) the valve position has to reach at least 30% to start calling for heat from the boiler and probably more to call for enough heat to get the room up to temperature. So the valve position settles around 30-40% to maintain the night time set point, and does so more by modulating the boiler output rather than the water flow through the valve.

    But then as soon as some other zone comes on and starts calling for heat (downstairs in the morning) the bedroom starts to overheat and the valve position starts to be closed down again. However instead of the water through the valve stopping flowing relatively soon at about 30% indicated position it keeps flowing until closed down to 15% - by this time the room temperature is about 1 to 1.5C past the set point and yet the radiator is still actively heating the room. This is not normal behaviour.

    Eventually it will find the new equilibrium when other zones are calling for heat but it takes quite a while, so the room goes over temperature for quite a while. At night when other zones go off the reverse happens - because the valve is closed down to about 15% it then has to open up to 30% again to start calling for heat from the boiler.

    So when the downstairs zones go off the bedroom goes under setpoint by nearly 2 degrees before it starts firing the boiler again as it then has to re-adapt in the other direction for the new point of equilibrium.

    Most annoying, but should be fixed by new, better quality valve bodies which I keep saying I will fit one day!
    Last edited by DBMandrake; 10th June 2018 at 10:52 PM.

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