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Thread: Evohome Help Please.

  1. #11
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    Yes, but I don't see any reason not to have a central C/H zone valve and it could be useful if one of the HR92s misbehaves, gets removed, or replaced with a TRV. Also, the zone valve is needed if you move house and want to revert to a timer+stat and take the expensive evohome system with you. I'm not trying to be argumentative, but I don't see why the OP should remove their zone valve - what have I not understood?

  2. #12
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    Quote Originally Posted by DorrisMancer View Post
    Yes, but I don't see any reason not to have a central C/H zone valve and it could be useful if one of the HR92s misbehaves, gets removed, or replaced with a TRV. Also, the zone valve is needed if you move house and want to revert to a timer+stat and take the expensive evohome system with you. I'm not trying to be argumentative, but I don't see why the OP should remove their zone valve - what have I not understood?

    Even without a CH Zone Valve if a HR92 misbehaves you can remove it and that Rad will heat whenever there is a heat demand which would be the same result as having a CH Zone Valve and removing HR92

    In the ops position the Easy option is to disconnect CH Valve Electrically and Lock open it is then simply a matter of reconnecting to revert to original but be aware Valve can seize due to lack of movement

  3. #13
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    It isn't the same result ... with a CH zone valve rads without an HR92 will not heat up when there's just a DHW heat demand.
    I can't see any downside to having a zone valve and it's potentially beneficial to have one, that's why I was surprised at the recommendation in the responses to the OP and wondered whether I'd misunderstood some aspect of the system.
    Last edited by DorrisMancer; 12th November 2017 at 10:58 AM.

  4. #14
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    I don't think there is any harm in keeping the CH Valve, it just isn't required. If you keep it in then you are just introducing yet another dependency in the chain. Anyway, I don't like the mechanical locking of CH Valve suggestions. It doesn't open the port completely and could cause the Valve to seize. Best to wire it up to the boiler relay or pump.

  5. #15
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    Quote Originally Posted by DorrisMancer View Post
    It isn't the same result ... with a CH zone valve rads without an HR92 will not heat up when there's just a DHW heat demand.
    I can't see any downside to having a zone valve and it's potentially beneficial to have one, that's why I was surprised at the recommendation in the responses to the OP and wondered whether I'd misunderstood some aspect of the system.
    And Conversly If a CH Zone Vlv Fails then no Rad heats its really up to the op no harm in having a Zone Valve just adds another possible point of Failure

    I had Zone Valves I just removed Heads and opened Valves this way they are fully open all the time and HR92s do the individual Rad control but Could be reversed if needed

  6. #16
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    That's certainly true, but there's only one zone valve in the path and (in my case) there are 23 HR92s, all relying on: batteries, electronics, gears and magic. I don't have any MTBF data but intuitively an HR92 failure must be more likely than an S-plan zone valve failure (seems not to be true for Y-plan valves). If the zone valve does fail it can be locked open or decapitated.
    So ... for all but small new systems I think a zone valve has value, and that decapitation (your solution) is best for existing systems.

  7. #17
    Automated Home Ninja Dan_Robinson's Avatar
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    Crack on then.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

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