Heating Circuit Cabling

[mrscalex]

I'm modifying the supply cabling in my central heating system ready for a new boiler to be fitted (not by me I hasten to add). The old cable is 3-core and earth for supply live/neutral/earth plus a switched live.

The new boiler has a pump over-run facility which requires a 2nd switched live. I have various ceilings down and floors up for other work but nonetheless would like to keep the number of cables to a minimum.

The existing 3-core/earth looks like 6-amps rating which I guess is the correct thing to have (it's a typical Y-Plan system). So I'm wondering if there is such a thing as 4-core/earth rated at 6 amps. All the cable I have seen so far appears to be component connection flex at 3 amps. Is there such a thing at 6 amps?

If there is no such cable (or this isn't how it's normally done anyway) any advice would be appreciated. It just feels a bit clumsy banging up a couple of 2-core/earth cables but if that's how it's done...

Thanks,

Robert

 

[Lectrician]

Dont do what plumbers do and run flex - use 2 bits of T+E. The final connection to the boiler can be 5 core flex.

 

[felix]

You can get multi-core and earth mains cable - we use it a lot around here - but it's not easy to find. Moreover, apart from the earth, the cores are all black with little numbers on them. It's very easy to make mistakes with this stuff.

I agree with Lectrician; use two lengths of flat twin and earth. When somebody opens up the ceiling (or floor) years later they will see mains cable rather than some mysterious bit of flex. It'll be a lot cheaper too.

 

[mrscalex]

Okay thanks. I can't argue with that advice.

The overrun terminals on the boiler are for a live/earth/neutral anyway as opposed to just a live. So I suppose if I wire it like the manufacturers would like me to I'd need to dedicate a twin and earth cable to the pump anyway. Can't really see why I can't take the earth and neutral from the wiring centre (upstairs, boiler down) as it's on the same supply/isolator though!

Thanks,

Robert

 

[felix]

Can't really see why I can't take the earth and neutral from the wiring centre (upstairs, boiler down) as it's on the same supply/isolator though!

Neither can I. That's how mine's done. The second flat twin and earth cable carries switched live to the boiler and over-run live back to the pump. The two earths are in parallel.

 

[Lectrician]

Yea - the N and E to the pump are commoned at the boiler anyway.