The Boiler Switch gets installed into the "Room Thermostat" cables on the boiler wiring diagram

If you have an existing external wired thermostat, it will replace the cables placed there

We're unable to advise on specific boilers legally, as we are not heating engineers or electricians. The boiler switch will make and break connections between the NO and COM terminal. If your diagram shows "RT", then these are the ports for an external Room Thermostat. This is where the connections go for our Boiler Switch unit. It would be the same terminals as where any previous hard wired room thermostat would have been, if applicable.

It is normal to use the NO and COM connections on our boiler switch, but we are not aware of the operation of the boilers on the market. We wouldn't be able to advise on the wiring of these boilers as they are not our products and so we are not fully aware of their operation. Ordinarily, the COM and NO will connect to the cables which would be present on any pre existing Room Thermostat, or alternatively go to the terminals where a "jumper" cable was placed if an external stat was not in use.

If the Switched live and Permanent Live was connected to the boiler before to do the switching of central heating on and off, then our Boiler Switch will be able to do the same control. The Switched Live would be placed in the NO terminal, whilst a "jumper" cable should go between the right hand L terminal and the COM cable, with the permanent live and the neutral cable going to the left hand side L and N terminals.

This will allow you to have the control of the boiler, replacing the pre-existing timer.

If in any doubt, we would recommend contacting the boiler manufacturer advising them that you are looking to install an external thermostat controller and would like to know the terminals to use on the boiler you have.

What are the terminals behind the boiler switch? Which wire goes where ?

Terminals behind the boiler are exactly the same as the LW821

Live Neutral goes into it, Jump the live over the COM, if the boiler uses mains voltage to switch on or off, or don't jump if it doesn’t Then inside the boiler switch, there's a relay that connects COM and NO together when you turn it on

What do I do to my existing Thermostat ?

If you have an existing external wired thermostat, the boiler switch will replace the cables placed there

Existing thermostat gets removed, or turned onto permanently on, if it can't be removed