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Discuss Adding a relay to Thermostat in the DIY Electrical Forum area at ElectrciansForums.co.uk.

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  1. Nevbox
    Offline

    Nevbox New EF Member

    Location:
    York
    Hi forum,

    I am trying to fit a relay to my boiler and then to a raspberry pi zero. The pi has a humidity and temperature sensor to moderate the heating. This is basically a DIY 'Nest' project.

    The current setup is an age-old thermostat and analog timer.


    [​IMG]
    [​IMG]

    I've wired my relay with Common and NO (Normally open).

    I attempted to link the relay directly to the thermostat, but my test was unsuccessful.

    My attempt looks like this:
    The analogue timer was set to constant and the thermostat to 0C
    [​IMG]

    Any suggestions?
     
  2. davesparks
    Offline

    davesparks Trusted Advisor

    Location:
    guildford
    For a start that cable is too big so it is preventing the terminals tightening properly on the original wiring, this loose connection needs rectifying ASAP before it starts a fire.
     
  3. Matthewd29
    Offline

    Matthewd29 Regular EF Member

    Location:
    Belfast
    Some insulation damage and poor termination on the brown there
     
  4. gnuuser
    Offline

    gnuuser retired Industrial wire monkey DIY

    Location:
    nw.Pa. USA
    before wiring a relay into the circuit you would need to study the schematics carefully and understand everything involved.
    and consider that altering control circuits in a heating system can void any warranty and may violate safety regulations.
    creating control circuits should be done with simulators (lamps and or buzzers) to indicate the state of the output. and verify that the circuit is operational.
    while experimenting is an admirable trait you need to ask yourself this question "Why complicate a simple control system?" and if i do change things how many things may cause it to fail?
     
  5. davesparks
    Offline

    davesparks Trusted Advisor

    Location:
    guildford
    Or at the very least wait until the summer when breaking your heating won’t have such an unpleasant effect!
     
    • Agree Agree x 2
  6. Andy-1960
    Offline

    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    Also noticed you have not connected the CPC instead choosing to cut it back, not a good idea!
     
    • Agree Agree x 1
  7. Nevbox
    Offline

    Nevbox New EF Member

    Location:
    York
    Thank you for the tips guys. I have installed smaller wires, bought an enclosure for the relay. (with regards to safety). Testing the circuit has been successful.

    The original system still works, but I have disabled it by setting the thermostat to zero. In the event of my controller crashing, losing power etc.. the relay remains open and the thermostat can be turned up.


    If you're wondering the motivation to install this system, it has been done due to the age of the original thermostat controller (inaccuracy, limited control & high gas bills from heating being left on)
     
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