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Replace a simple room thermostat for a time control one?

Discussion in 'Plumbing and Central Heating' started by astiling, 28 Jan 2015.

  1. astiling

    astiling

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    Hi, I have a pretty traditional setup with a gas powered boiler for heating and hot water with a single room thermostat which is just a simple dial to set the trigger temp for the radiator heating.

    I would like to replace the thermostat with a time controlled one so that I could get it to trigger the boiler to heat the radiators at set times and at set temperatures so overnight at 18 degrees, during the day (weekdays) at 15 degrees and early evening at 20 degrees.

    This product looks suitable:
    http://www.salus-tech.com/products/thermostat/programmable-room-thermostat/_c1_23_st620pb/

    But I wanted to check if I'm over-looking any other relevant products. I'm not really looking for internet control, wifi etc.

    My simplistic (possibly overly so!) view is that the current thermostat is just making a circuit that causes the boiler to start heating the radiators (via the programmer which is set to "always on"). So, a new unit with more flexibility is just replacing the outputs so should be an easy swap?

    Any help/suggestions appreciated.

    Thanks
    Adam
     
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  3. stem

    stem

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    That will do exactly what you want. I have seen some criticism of the Salus range of controls usually relating to malfunction, but I have a wireless one and it works just fine.

    If you have an existing two channel programmer (IE for hot water and heating) and don't want to change it for a single channel hot water only unit, or alter the existing wiring, you can just set your existing programmer to have the heating permanently 'on' and let the new programmable thermostat take total control.

    You don't say what existing wires you have at your present thermostat. Most likely you will have a live, a switched live and a neutral. With the Salus being battery powered, you won't need the neutral, so it will need to be terminated safely, which usually means putting the wire in an insulated screw connector and tucking it in a corner.
     
  4. bathjobby

    bathjobby

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  5. astiling

    astiling

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    OK, many thanks for the helpful replies. Not sure what wires go to the thermostat but will take a look, with it isolated.
    Thanks again
    Adam
     
  6. scoobydo123

    scoobydo123

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    Is your boiler a condensating one? I quite like the Myson MPRT this works slightly different to a simple on/off stat it will maintain a set temp far more accurately than the on/off stats. It also calculates the termal load of the building and will come on early if temps drop overnight quickly so your target temp is achieved at the time you want it. Honeywell also do these features. When working like this the return temps will stay below the dew point so savings could be had.
     
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  8. astiling

    astiling

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    Thanks guys, I have the new thermostat that needs just a live in/ out.

    I opened up my current one and it has the following:



    What do I need to do to replace this with the new one? I was hoping to see a similar live in/out so bit stumped.

    Thanks
    Adam[/img]
     
  9. stem

    stem

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    The thermostat you have is an old mechanical type. they have a little internal heater called an accelerator that improves their switching accuracy. In order for this to work, it needs a neutral connection. Your new one doesn't need the neutral, so it needs to be isolated. Usually this is done by fitting an insulated screw connector and tucking it out of the way. Do not connect the neutral to your new thermostat or you will cause damage.

    The usual method of wiring is.

    Red = Live
    Yellow = Switched Live
    Blue = Neutral

    I have come across the odd rogue installation which uses a different convention, so it will be best to either check the wires with a multimeter, or trace them back to see what they are connected to.
     
  10. astiling

    astiling

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    Great thanks, was wondering why it needed power.
     
  11. stem

    stem

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    I had already said that you may not need the neutral. ;)
     
  12. astiling

    astiling

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    Ha - yes quite right :)
     
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