Boiler spur and timeswitch wiring

[Alfie25]

Firstly, I’m not going to be undertaking any of this work myself, I’m just trying to get an idea of what can and can’t be done.

At the moment I have the boiler spur, with the timeswitch/programmer right beside it and the boiler above it. The wiring is chased into the wall so it’s not easy to see what goes where. Will it be wired in sequence? i.e. boiler spur wired to timeswitch then timeswitch wired to boiler?

The reason I’m asking is I’m looking to move the timeswitch to a different room when the boiler is replaced, however leaving the spur where it is (underneath the boiler). Is this do-able, or not easily? On most properties I’ve seen, the timeswitch/programmer is right beside the spur, which makes me think it’s wired in sequence.

 

[ALCPlumbing]

You can put the programmer wherever you want as long as you are able to get a length of five core cable from junction box to the new position.

 

[stem]

It depends upon many factors. for example

Most boilers require a permanent live supply for as well as the switched live supply from the timeswitch. Your existing one might not have this, but most likely your new one will.

If there are any other peripheral items connected, such as thermostats and motorised valves

How the original installer decided to wire it up.

Having said that it should be fairly easy for a suitably skilled person.

The timeswitch could be removed and replaced with a terminal box and the existing cables terminated. Then a new cable (or cables depending on the complexity) could run from there to the new location.

Or simply rewire the whole thing, which is probably the easiest it you are changing the boiler anyway, especially if the permanent live is required.

Or another alternative, if you have a combi boiler (i.e. one that doesn't need time control for the hot water) may be to use a wireless programmable thermostat. The receiver would replace the existing timeswitch and use the same wiring, whilst the programmable thermostat is located remotely.

 

[Alfie25]

Good points there stem. It's going from a traditional boiler to a combi but I'm wanting to keep hard wired controls, so a separate wall mounted thermostat and a hard wired timeswitch for the heating. I'm just not a fan of these RF programmable thermostats.

There's currently the junction box in the upstairs airing cupboard beside the motorised valve/pump/cylinder, but all of that will of course be going when the combi is fitted.

Are there 2 cables needing to go to a timeswitch/programmer? Power in and power out?

 

[stem]

It's a little more complicated than that. If you have a 'Y' plan system with a single three port valve, it's wired thus:

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• stem
• 2 Feb 2010
• 2

As a minimum, at the programmer there will be 5 wires required as ACLPlumbing stated earlier:

1. Live supply
2. Neutral supply
3. Live out 'Heating on'
4. Live out 'Hot Water on'
5. Live out 'Hot Water off'

There may also be an earth, plus other live, neutral or earth connections going out to other devices, depending on where the original installer decided to make the connections. Although this is unlikely if you have a wiring centre in the airing cupboard.

If you are going for a combi, then likely all of the existing wiring will be decommissioned and the combi wired from scratch. One of the advantages of a combi is that electrical installation is very simple. Normally it will only require a mains supply to the boiler and connection from the boiler to a room thermostat. That's it. All of the other functions will be taken care of inside the boiler.

If you insist on a remote programmer, a set of terminals are provided for remote control. Because the hot water function will be missing, then a three core cable will be sufficient (Live, Neutral & Switched Live) It could even be shared with the thermostat wiring, if local, as both the programmer and thermostat will likely be wired to the same boiler terminals, with their respective switching devices being wired in series.

As timeswitches are usually incorporated into the boiler, make sure you don't select that option when ordering it, if you are planning on having a remote programmer installed.