HA Immersion heater control

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  • jpdw
    Automated Home Guru
    • Oct 2007
    • 169

    HA Immersion heater control

    Has anyone added control of their immersion heater to their HA scheme? If so, do you know what rating the switching relay is?

    As a result of my CH zoning, I'm going to have a 1 spare relay in the airing cupboard.. either 4A or 13A rated; I'd like to have the ability to boost the HW with electric on some occasions, so it seems useful to use the "spare" relay. Clearly a spare 4A wont be good enough for the immersion but, as my immersion is rated at 3Kw (ie 12.5A) I wondered if even the 13A is high enough (ie taking max consumption and adding some 'safety' margin).

    If anyone else has done this I'd be interested to know if they've used 13A relays or something higher.

    ta!
    Jon
  • TimH
    Automated Home Legend
    • Feb 2004
    • 509

    #2
    Here's a tutorial for replacing a time switch with an X10 module:


    But, is your immersion heater fed separately from the consumer unit? If so, what's the rating of the fuse/MCB in there? It's that fuse/MCB that protects the circuit so you shouln't be installing anything that has a lower rating than that (cable, terminals, etc.).

    If you're immersion is protected by a 16A fuse/MCB you'll probably need to put in a 16A relay driven from your relay bank. This new "relay" could be a contactor as they can usually handle higher currents. Look at part no. 729-903 from http://rswww.com as an example.

    Essentially you wire one of your relay outputs to the coil of the contactor and then the immersion heater supply through the contactor contacts. Energising your relay then energises the contactor coil, which in turn pulls-in the last set of contacts and powers the immersion.

    If in doubt, contact a qualified electrician blah, blah, blah

    HTH,

    Tim.
    My Flickr Photos

    Comment

    • jpdw
      Automated Home Guru
      • Oct 2007
      • 169

      #3
      Originally posted by TimH View Post
      Here's a tutorial for replacing a time switch with an X10 module:


      But, is your immersion heater fed separately from the consumer unit? If so, what's the rating of the fuse/MCB in there? It's that fuse/MCB that protects the circuit so you shouln't be installing anything that has a lower rating than that (cable, terminals, etc.).

      If you're immersion is protected by a 16A fuse/MCB you'll probably need to put in a 16A relay driven from your relay bank. This new "relay" could be a contactor as they can usually handle higher currents. Look at part no. 729-903 from http://rswww.com as an example.

      Essentially you wire one of your relay outputs to the coil of the contactor and then the immersion heater supply through the contactor contacts. Energising your relay then energises the contactor coil, which in turn pulls-in the last set of contacts and powers the immersion.
      The fuse is 15A (maybe it's 16A and I mis-read it), though given the state of some of the other electrics in this place (supposedly installed by professionals a few years ago & before we moved in), I would not take the fuse rating to be what it SHOULD be !!

      I thought that relaying the relay (as you suggest) might end up being the solution. It means driving 2 coils rather than just one but that would be cheaper than adding another Idratek unit with a digital output.

      I was hoping there might have been a simpler way that I had missed :-)

      Originally posted by TimH View Post
      If in doubt, contact a qualified electrician blah, blah, blah
      Who will most likely say "dont know about that gov, why not just use a switch".
      That said, I'll try and get our plumbers' electrician to fit this along with the heating electrics.
      Jon

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