Boiler wiring - Flex or T+E

[Luke]

Hi all,

As some of you may know I'm installing gas central heating with the boiler in the loft. Things are progressing well, I've done all the pipework bar the last metre or so of the gas, and now I just have to finish off the wiring.

It's a standard Y-plan with the wiring centre in the airing cupboard. Thermostat in hall and programmer in the kitchen. The boiler is a Vaillant Ecotec plus 624 system boiler.

From the airing cupboard up to the loft I have run 2 * 1.5mm T+E, the first of which is the main feed to the boiler which is switched directly from a 3A switched spur, and the second feeds the programmer and all other associated switchgear, with the brown wire providing the live feed and the blue, the call for heat. This is as recommended by Vaillant - the idea being that if the boiler is switched off at the applicance, ALL other associated controls are no longer live.

So my question is how to I present these feeds to the boiler, in their existing T+E, or do I install a couple of accessories adjacent to the boiler and make the final run in flex? I am leaning towards flex, as the terminations at the boiler end are clearly designed to take flex, but essentially, I'm providing fixed wiring to a fixed appliance.

Assuming flex (and feel free to correct me) what accessories would I install? 1* unswitched socket for the boiler feed, and 1 * unfused flex outlet plate do you think? Or 2 * flex outlet plates? Any other suggestions?

I have put a photo here which shows the current wiring arrangements.

FCU to the left of the wiring centre feeds the boiler.

Thanks in advance.

Luke

[ARWadsworth]

I would terminate the T&Es with a fan isolator switch (relabelled BOILER) and use 4 core heat resistant flex to the boiler. This will allow local isolation of the boiler in the loft (ie you can then isolate perm live, switched live and the neutral)

Cheers

[Luke]

Thanks Adam, but I would need a 4-way isolating switch, and 5 core flex, as from my two T+Es, none of them are common, so could not merge them into a 3-way fan isolator. This is because the boiler presents a separate live feed to the programmer, and in turn a call for heat, in addition to its live and neutral supply, hence the 2 * T+Es. From a quick google I am not sure a 4-way isolator is available.

Luke

[ARWadsworth]

I'll bet that some of them are common!

You will have to explain a little bit more about your wiring set up. I am guessing that you are using terminal 4 on the boiler to supply power to the programmer etc. Where is the programmer getting the neutral from?

Terminal 4 is in effect a permanent live when the boiler is switched on and you could use a double pole switch as your isolator (just isolate the cable running from the fused spur in the airing cubpoard) and use heat resistant flex from the double pole switch to the boiler.

Cheers

[ARWadsworth]

I think I have worked out how you have wired it up (the clue was in the photo with the gripfill just before the plaster was stuck on)

All you need is 5 core flex, a double pole switch with a deep patress and strip connector (or crimps).

Use the double pole switch to isolate the live neutral feed to the boiler (local electrical isolation is required for boilers) and the two other cores in the flex need strip connecting to the other T&E behind the switch. You do not need a 3 or 4 pole isolator as when the double pole switch is off then there is no power down to your wiring centre in the airing cupboard

Cheers

[Luke]

Yes! That's exactly right - excellent deduction work! That makes good sense, I will take your advice and wire it as you suggest.

Thanks

Luke