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Thermostat Wiring?

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  • 11-04-2005 4:33pm
    #1
    dee mm
    Closed Accounts Posts: 62 ✭✭


    OK have got myself a new room thermostat for my central heating. The thermostat i am replacing is old Danfoss unit, with wiring marked 1 2 and 4. 4 has two wires on it. Now the question is on the new one there are three conections NO, NC, and COM. What wire goes where?
    Any ideas would be nice. :)


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    #2
    fred funk }{
    Registered Users Posts: 6,827 ✭✭✭fred funk }{


    The one with two wires in it will wire into the com on the new unit.

    You should only have one wire over from the old unit and that should wire into the NO.

    COM = Common NO = normally open NC = normally closed

    So the two wires that are together are permanently live and when the unit switches it gives the NO power thus turning what ever it controls on.


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    #3
    Borzoi
    Registered Users Posts: 2,876 ✭✭✭Borzoi


    No offence Silver, but I'm not sure what you're on about, though at least this is right
    Silver Knight wrote:
    COM = Common NO = normally open NC = normally closed
    .


    dee mm

    Feed your live wire supply into the COM connection.

    Wire out from either the NC or NO but usually the NO - it's just a polarity issue. It's a bit like any switch, one way is on, one is off. And like any electrical switch all you're really doing is controlling the Live wire feed.


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    #4
    dee mm
    Closed Accounts Posts: 62 ✭✭dee mm


    Right this is all good, but I do have two wires one marked 1 and the other 2 . So and this is where I am confused, which one goes where? If the two together are live (com) I am now left with two wires :confused:


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    #5
    fred funk }{
    Registered Users Posts: 6,827 ✭✭✭fred funk }{


    Probably the best and safest way to deal with this is to post a diagram,Then we can truly see whats what.


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    #6
    Lex Luthor
    Registered Users Posts: 11,220 ✭✭✭✭Lex Luthor


    dee mm, if you can let us know what exactly the wires on the old unit were connected to...did the old unit actually have all 4 wires terminated?

    As the lads say, you really should only have 2 wires to switch on your boiler. However the chances are its possible the 2 wires that are connected together, one of them is probably a live feed that is needed somewhere else in the house.

    You will only need the COM & NO contacts on the new unit. Also, try get us the model type or number of the old one so we can have a look at its operation.

    Just don't electrocute yourself...make sure your boiler is knocked off before you go messing around.


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    #7
    dee mm
    Closed Accounts Posts: 62 ✭✭dee mm


    Right had a look at this, the unit is a Danfoss, with three terminated conections, they are marked 1,2, and 4, (with two wires together terminated on 4.) So I appear to have an extra wire!


    I'm begining to get a bit cold at night now so might give it a go this afternoon. :D


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