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Thread: Evohome help please

  1. #1
    Automated Home Jr Member
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    Oct 2017
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    Default Evohome help please

    Hi! We recently did a knock down and rebuild project and have fitted Evohome throughout. Now it's cold enough to start testing the system properly and there are a few glitches, I think the installers weren't that familiar with Evohome so I'd like to understand what needs doing before getting them back in.

    Warning: I am a software guy, not skilled in plumbing or electrics so please forgive me if I use the wrong terminology - happy to post photos and answer questions.

    We have:
    Boiler: Worcester in S-plan
    Downstairs: UFH throughout, 7 zones, HCC80R + extension, DT92 thermostats per zone
    HW: Gledhill cylinder with Evohome control.
    Upstairs: HR92s throughout, 3 rooms with one radiator, one room with 3 radiators grouped into a zone

    The HR92s were added after the initial installation, previous we had a single DT92 upstairs bound to a relay box. My biggest issue now is that the only way I can get heat into the upstairs circuit is to go into the garage and press the button on the (now unbound) relay box. This opens the circuit for about 15 minutes.

    I think the HR92s call for heat via the controller, so I either need to remove the unused relay box and rewire somehow OR rebind somehow.

    Can anyone offer guidance please?

  2. #2
    Automated Home Ninja
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    Mar 2017
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    Quote Originally Posted by timgp View Post
    Hi! We recently did a knock down and rebuild project and have fitted Evohome throughout. Now it's cold enough to start testing the system properly and there are a few glitches, I think the installers weren't that familiar with Evohome so I'd like to understand what needs doing before getting them back in.

    Warning: I am a software guy, not skilled in plumbing or electrics so please forgive me if I use the wrong terminology - happy to post photos and answer questions.

    We have:
    Boiler: Worcester in S-plan
    Downstairs: UFH throughout, 7 zones, HCC80R + extension, DT92 thermostats per zone
    HW: Gledhill cylinder with Evohome control.
    Upstairs: HR92s throughout, 3 rooms with one radiator, one room with 3 radiators grouped into a zone

    The HR92s were added after the initial installation, previous we had a single DT92 upstairs bound to a relay box. My biggest issue now is that the only way I can get heat into the upstairs circuit is to go into the garage and press the button on the (now unbound) relay box. This opens the circuit for about 15 minutes.

    I think the HR92s call for heat via the controller, so I either need to remove the unused relay box and rewire somehow OR rebind somehow.

    Can anyone offer guidance please?
    Assuming you've got HR92s on all the radiators upstairs the motorised valve is redundant. You should either remove this, lock it open in the manual position and remove the BDR91 (however it won't be open fully) or wire the motorised valve in so that it's open whenever there is a heat demand (So wire the valve to the S/L for the boiler and remove the wiring for the micro switch from the circuit (Grey and Orange wires).

  3. #3
    Automated Home Jr Member
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    Oct 2017
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    Thanks, thatís helpful.

    Just before reading the above I tried multi-binding the heating demand on the evohome to both relay boxes and that is working fine. I guess the downside is that the upstairs circuit will be heated every time there is any boiler demand. As a plus this means towel radiators on in summer when the water is on!

  4. #4
    Automated Home Legend
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    Quote Originally Posted by timgp View Post
    Thanks, that’s helpful.

    Just before reading the above I tried multi-binding the heating demand on the evohome to both relay boxes and that is working fine. I guess the downside is that the upstairs circuit will be heated every time there is any boiler demand. As a plus this means towel radiators on in summer when the water is on!
    You should bind the upstairs zone valve as a heating zone valve in the stored hot water configuration - then it will only come on when there is heating demand, not when there is only hot water demand. (Make sure you clear its previous bindings first before rebinding)

    How many BDR91's do you have in total, what are they wired to and what are they bound as ? In an S-Plan configuration you normally have either 2 or 3 BDR91's - a hot water relay, a heating relay, and an optional boiller control relay.

    The hot water relay only comes on for hot water demand, the heating relay only comes on for heating demand, and the boiler control relay comes on for both. You're allowed to bind multiple BDR91's as heating zone valve relays if necessary, for example if you had multiple heating zone valves dispersed around the house. (They will however all switch on and off together, as the system relies on the HR92's for zoning, so its equivalent to wiring multiple zone valves to the same BDR91)
    Last edited by DBMandrake; 3rd November 2017 at 10:09 AM.

  5. #5
    Automated Home Jr Member
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    Thanks for this, I didn't mention the BDR91s in the original post at all did I?

    There are three BDR91s, one is marked boiler, one marked hot water and the other marked upstairs (this was previously bound to a DT92 before the HR92s went in). I can post a photo of the wiring if helpful.

    I think the hot water one opens the zone value to the cylinder. Not clear on the order of events for the other two.

    Last night I cleared the binding from both upstairs and boiler, then bound them both as heating demand on the controller.

    The other excellent discovery last night was that the reason some of the UFH zones weren't working is that the daughterboard for the HCC80R was not correctly seated!

  6. #6
    Automated Home Legend
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    So now you have two Boiler Relays? That should work. It effectively means you are opening the upstairs valve anytime there is a boiler demand but the actual HR92s are controlling any flow to the rads. You could disconnect one BDR91 too if you wanted and sell it. No point wasting power on two to do the same thing. Of course a little rewiring will be involved, which may not be your thing.

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