Cable to use on heating wiring

Hi All,

I have a number of zones in my new heating system and need to run some

4 core and earth cable from the boiler to the room where the timers are going to be fitted. Looking in Screwfix they only sell flex rather than the solid core mains cable type (if you see what I mean)

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looks like the right one to use but the plumber believes that you have to run solid core wire. I can't see how it makes any difference to be honest and given this is heat resistant would imply it was made for the job.

Does anyone know if this is ok or not?

thanks in advance for your help

Lee.

Reply to
Lee Nowell
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Lee Nowell wibbled on Saturday 09 January 2010 16:05

I'm not 100% sure on the concept of running flex through the building in general (though it is normal in some other countries), but the easy get out is to use this stuff in the hot areas, and terminate into a junction box and back to normal T+E to complete the run to the timers. If the flex were going to be in conduit or clipped to a surface, I see no issues with it. Issues

*may* occur is you need to bury it in plaster. Wait around for some more opinion.

It would certainly be better to use heat resistant flex anywhere that is actually running hot.

On an aside, I went one better with the SELV feed to my bathroom halogen lights - using silicone flex which is much higher rated than the normal heat resistant stuff. That's all clipped to the joists.

Reply to
Tim W

Your plumber is incorrect.

Flex is permitted provided either... a) - Terminals are designed for flex b) - Flex ends are suitably prepared (bootlace ferrules)

Haven't got the 17th regs to hand re regulation number & page (I'm not going out to the shed :-)

Now if you have seen inside a fused spur wiring accessory recently you may notice there is no difference between the "load" terminals (which require flex) and "supply" terminals (which are usually supplied by solid twin & earth).

What does matter is that the cable is run in zone if buried (since

would be about 65mm PIR to current regs).

Reply to
js.b1

It would be interesting to see a diagram of the circuits. I would go for using cables and bringing them into a terminal strip in a box and then into a short run of flex into the boiler. I guess a cable is needed for a timer and one for a thermostat.

Thought - why not have a programmable thermostat - only 2 wires + earth are needed. Timer not required. Also consider a Wireless Thermostat.

If determined to have a timer - then how often does it need to be accessed - I touch mine twice a year to set the GMT / Summer time. It lives next to the boiler. As the boiler is a combi and my thermostat is programmable the thing is on 24 hours a day!

Reply to
John

I essentially have 4 central heating zones, secondary return pump, and hot water to time.... My wife wanted it set up so she could switch any zone on from a central location.

The cable essentially needs to go from the boiler in the garage, into the ceiling above, run for about 3m then down a wall (in conduit) to the timers.

How do I tell if the terminals are OK for flex? The boiler end has a couple of standard CH wiring centres (Honeywell white boxes with terminal strips in them) and the timers are the Horstmann ones (if that helps).

thanks for you help all

Lee.

Reply to
Lee Nowell

If you haven't already found it, this stuff from TLC may be of interest:

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Reply to
dom

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You can use flex for permanent wiring. It's not normally done because it's more expensive, and because it won't stay in a straight line when clipped. Wiring terminations need to be suitable for flex, or you need to use bootlace ferrules.

Sheathed multicore mains control wiring is always flex AFAIK.

Control wiring is often low current rated compared with T&E, and you need to be careful that you provide fault current protection which is consistant with the higher impedance of the cable runs. Note that for mains wiring, you must always run an earth conductor, even if it's not required at the far end.

Reply to
Andrew Gabriel

Actually you could use FP200 (referring to its generic type rather than Prysmian FP200 Gold) in 4C+E form, TLC carry it in white and red, convenient for those more modern decor choices :-)

Reply to
js.b1

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