Thread: Wiring a room thermostat into a combi boiler ?

  1. #1
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    Wiring a room thermostat into a combi boiler ?

    I have been asked a Q on this - (I am a spark but im 500 miles away from the "problem lol)
    Anyway the better half's sister wants to self install a room thermostat. Now any i have done in the past its just been a simple T+E cable from stat to the boiler - But its always system dependant. So with that said she needs a step by step guide to connections -
    She has a Gloworm Ultracom 30cxi Combination Boiler
    And a simple Honeywell Room thermostat
    Does anyone here reguraly install these ? I cant seem to find a wiring diagram that i can e-mail her so the job is simple.
    Can anyone offer any help in finding a circuit diagram for this boiler ? Like i say without me seeing the boiler - im a bit of a loss. Any help/tips are welcome.

  2. #2

    Re: Wiring a room thermostat into a combi boiler ?

    Ask them for the 2 connection points or diagram/pdf booklet for boiler. Only 2 wires and prob 24v.

    Not sure whether it would goto the n/o or n/c contacts on thermostat though. If wrong just swap them over.

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  3. #3
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    Re: Wiring a room thermostat into a combi boiler ?

    does she have aprogrammer aswell? has she got the 10 way junction box?

    i installed all mine but i didnt install the thermostat as they are quite useless and had to re-draw part of the drawing.i just used thermostatic valves on the rads, that way, you can control each rooms heat independantly rather than one thermostat. the problem i find with stats is, if the room with the stat gets warm, the other rooms may still be cold and the heating will go off or the room with the stat may be cold but the other rooms like an oven then you will still have to get up and turn off manually anyway, waste of time if you ask me. spend the money and get the thermostatic valves on rads, saves wireing, saves chasing for the wireing and you will probably save money in the long run with the thermostatic valves.

    hope you understand this this, if not just ask and ill try a bit harder to explain lol

    Last edited by manutd4life; 23rd January 2009 at 18:51.

  4. #4
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    Re: Wiring a room thermostat into a combi boiler ?

    First off it should be heat res cable and you can use a .75mm flex, the reason for this is not because the walls will catch fire but because it will be coming back into the boiler (if combi) and if system boiler it will go into a junction box that will connect the system and valves... This cable will have to pass pipes and for that reason you should always use a heat resistant cable- plus they are piss cheap

    Gloworm - There will be a "link" in the boiler you can take this link out and replace it with the connections to the stat, inside the stat its normally 1/3 if honeywell (sometimes there is a neutral to 2).

    If the link is already missing then you will need the manual as i do not know off my head the connections but they are pretty standard on the gloworms - if you put a meter on one of the terminals then you turn the heat up on the radiator stat (on the glowworm) you will get either 24v or 240v swithcing and that will be the live that kicks it on but you will still need to find where it goes to (normally the next pin)

    I will look and see if i can find a manual in my van tomorrow pal (its being serviced) and then print out the diagram.

    Mickie D
    Electrical Exam Papers and Simulators

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