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Thread: Evohome heating radiators and hot water the same time

  1. #1
    Automated Home Jr Member
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    Default Evohome heating radiators and hot water the same time

    Hi. Iíve had my evohome system installed for over a year now on my unvented system. My water cylinder is in the loft of my house. When it was first setup the relays were bound wrong and the hot water relay kept coming on the same time as the rad one. I soon sorted this out after reading advice on here. The hot water and rad relays are now separate. My question is I donít seem to be able to have the cylinder heat up the same time as the rads. The heating relay turns off when the water one comes on. Have I set something up wrong or is this the only way it works?

  2. #2
    Automated Home Jr Member
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    Can anyone assist please?

  3. #3
    Automated Home Legend
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    More info needed about your system (model of boiler, kind of cylinder, zone valves etc) and how it is wired up and configured...

    S-Plan or Y-Plan ?

    I presume you have only two BDR91's and one is configured as hot water relay and one as a heating zone relay, and those each operate either two 2 port zone valves or a mid port valve ?

    Are you sure the "heating relay" (BDR91) is turning off when the hot water one turns on, or do you mean the heating zone valve is closing ?

    As far as I know, Evohome doesn't have any software based hot water priority, so I'm puzzled by your comment that the "heating relay" turns off when there is hot water demand.

    Hot water priority is normally implemented by the wiring between the relays and zone valves. Hot water priority is typically done on purpose on systems with a very fast hot water reheat time where the boiler flow temperature is boosted for hot water re-heat, to avoid very hot water going through the radiators.

    What's the reason that you're trying to disable hot water priority ?

    On my system I don't use hot water priority, but that's because I don't boost the flow temperature for hot water demand, and have an old cylinder that is slow heating. (Just coiled copper pipe rather than a plate heat exchanger)

  4. #4
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    Thanks for the reply. I don't know it's is s plan or y plan. What I mean is there is never 2 relays on the same time (only 1 green light) even though the hot water is being heating on the timer in the app and the radiators have only just turned on. There is a zone valve (silver box)in the airing cupboard which has been left on auto. I can manually turn on both relays so the green lights are on both and both heating and water show on the ideal vogue gen 2 s32 boiler display but don't see why the system doesn't do it. I can see that the radiator heating turns off via the boiler display and the hot water starts to heat. When the water timer has finished the relay light goes off and the heating light comes back on.

    I wanted both relays on at once because the radiator temp drops a fair bit whilst the water is heating even if it's just for an hour. Don't know why they can't both be on the same time during that period.

  5. #5
    Automated Home Jr Member
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    I have asked a plumber who installed boiler and evohome. This is what he has said.
    "itís a s plan sort of. With unvented it has to have its own zone valve (in airing cupboard) for the hot water, that is wired up in series with an over heat stat. There is no zone valve for the heating as the rad valves act as zone valves"

  6. #6
    Automated Home Ninja
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    Quote Originally Posted by Tigermad View Post
    I have asked a plumber who installed boiler and evohome. This is what he has said.
    "it’s a s plan sort of. With unvented it has to have its own zone valve (in airing cupboard) for the hot water, that is wired up in series with an over heat stat. There is no zone valve for the heating as the rad valves act as zone valves"
    Even with that system you would still be able to have HW and CH at the same time as there's no software HW priority in Evohome. Are you sure it's not a binding issue and something is mis bound?

  7. #7
    Automated Home Ninja
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    The plumber says you've got no zone valve for your heating circuit, but you say there's a "rad relay". What's that relay controlling?

  8. #8
    Automated Home Legend paulockenden's Avatar
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    Could the thing that you've bound as a heating relay actually be a boiler relay?

  9. #9
    Automated Home Jr Member
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    Thanks. I'm an idiot. The hot water relay does come on the same time as the heating. I guess I never saw both lights the few times I checked because the heating was up to temperature and didn't need the relay on. I did a test and turned the rad valve up and they both came on.

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