Cylinder 'Stat Wiring

Peter Rhea

I take it this shouldn't be in 3-core flex, with the blue wire used as a live?

Also, flex for fixed wiring (to room stats) should be minimum 1.5 mm sq.?

tomdempsey200

you have to use the correct phase colours for the stat

fixed wiring is a minimum 1.5

I have in the past wired stats in 0.75 off a heating spur for practical reasons.. I think technically it may not be allowed though

Irish Steve

Life would be so much easier if there was free web access to the regulations, but that's another of these clever ways that the regulatory clubs keep their stranglehold on things, and keep the consumer in the dark. I would have to admit to not knowing exactly what's in the current regs on this.

A long time ago at home, I put in a central management panel that is fused internally at 3 Amps in the hot press, and all the wires to programmers, pumps, thermostats and motorised valves and the like go from that, and are in the main 1 mm Flexibles, with sleeving on live returns to indicate they are lives where appropriate. There is no way that the management panel could or would take multiple 1.5's in the screw terminals, which is how the different devices are connected, and with a 3A fuse protecting the whole panel, 1.5 is way too heavy.

I have yet to find a source of 3 core 2 live and earth flex, which would be ideal for tank stats and the like, I have seen 3 core 1.5 solid for lighting, but it's not really suitable for this application.

There can be "issues" with 1.5 (especially if it's solid, which I've seen used before on stats Yeah), it is so inflexible, if brushed against by the house owner, it can overcome the spring that holds the stat against the tank, which then causes the hot water system to run continuously, as the stat never gets up to switch off temperature. One option may be to use a covered junction box, with solid from the central panel to the box, and then a short tail of flex to the stat. Also provides somewhere for the termination of the Motorised valve tails as well. The location of the other controls and junction box or time switch/programmers will be a factor here.

Peter Rhea

Thanks for the replies.

I just thought I'd replace the flex to the cyl. stat with a longer length, so it can be tidied out of the way & not have to be negotiated when I want to get at the stop valves behind the cylinder (not that I have to do this often). What's there ATM is just 3-core.

Then I had a look at some of the other wiring. The main runs from the 'wiring centre' in the hotpress, back to the boiler & control panel, seem to be 1.5. The run to the room stat looks like what comes with the motorised valves: maybe 1.0 or .75?

Is the 1.5 for fixed requirement just for mechanical strength reasons?

2011

I would have no issues with using a 0.75 mm sq. flex provided:
1) It has the desired mechanical strength
2) The flex is heat resistant (important for a hot press)
3) It is protected with a suitably sized fuse or MCB

0.75 flex is a standard cable between most ceiling roses and bulb holders.

After all the stat should only be switching a very small current.

Peter Rhea

Yes, all the power for the heating system comes from a plug with a 3 amp fuse.