Cable to use on heating wiring
Lee Nowell
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)
This 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.
Tim W
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.
--
Tim Watts
You know you need more insulation when the snow blanket on the roof makes
the house 3 degrees warmer...
js.b1
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
>50mm is impractical unless you have internal wall insulation which
would be about 65mm PIR to current regs).
John
"js.b1" <js...@ntlworld.com> wrote in message
news:883845a2-ebd3-4ed5...@r5g2000yqb.googlegroups.com...
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!
Lee Nowell
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.
d...@gglz.com
interest:
http://www.tlc-direct.co.uk/Products/CA0dot75F7.html
Andrew Gabriel
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.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
js.b1
than Prysmian FP200 Gold) in 4C+E form, TLC carry it in white and red,
convenient for those more modern decor choices :-)