Adding a relay to Thermostat

[Nevbox]

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.


https://i.Upload the image directly to the thread.com/fwN9hty.png
https://i.Upload the image directly to the thread.com/MwvdNGl.jpg

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
https://i.Upload the image directly to the thread.com/9xD9BBb.png

Any suggestions?

 

[davesparks]

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.

 

[MJPD29]

Some insulation damage and poor termination on the brown there

 

[gnuuser]

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?

 

[davesparks]

Or at the very least wait until the summer when breaking your heating won’t have such an unpleasant effect!

 

[Andy-1960]

Also noticed you have not connected the CPC instead choosing to cut it back, not a good idea!

 

[Nevbox]

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)