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Thread: Heating + Hot water wiring

  1. #1
    Automated Home Sr Member eddr's Avatar
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    Mar 2011
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    Default Heating + Hot water wiring

    Hi All,

    Rather than explain myself really badly, to understand my problem, if you have the time take a look at http://www.diynot.com/forums/viewtop...033634#2033634

    Basically - If you havn't read the above, I am trying to automate the hot water and central heating.

    I have it setup so the controller/programmer has heating + hot water constantly on, and relays inbetween HW ON and CH ON after the programmer.

    This isn't fully working, as the Y plan wiring needs/expects a HW OFF and I think this is what is causing an issue with central heating not turning on. One possibility is to have yet another relay for the HW OFF ?

    I am not quite sure how to get past this one.

  2. #2
    Automated Home Legend Karam's Avatar
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    I'm not a qualified plumber so the following should be treated as a reasoned suggestion:

    I note you are using 2 separate changeover relays. So one of these could be used in place of the HW ON and OFF outputs. In other words disconnect the programmer's HW ON and OFF signals and instead connected the NC and NO relay outputs, probably best that NC connected as HW ON so that in event of failure you have HW. The relay pole being connected to Live. So now the relay replaces the programmer HW outputs. For the heating suggest put a NO relay output across the thermostat connections. The CH on the programmer is then left permanently on and thermostat turned very low. This way again you have a fallback position where you could use the existing programmer and thermostat if it should come to it.

  3. #3
    Moderator toscal's Avatar
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    Just get a relay for the CH that has a normally closed contact and a normally open contact when the relay is off (not energised). This when energised will switch off the HW (normally closed contact will open) when the CH is on (normally open contact will close). And when the ch is off it will turn it back on again.
    You will still need the HW relay as well.
    Last edited by toscal; 28th June 2011 at 09:49 AM.
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  4. #4
    Automated Home Sr Member eddr's Avatar
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    Thanks to the both of you for your help, I have gone with Karams suggestion and this has done the trick!

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