Installing mains pilot wire for storage heaters

[phatboy]

I will soon be replacing some aged storage heaters with Dimplex Duoheats, or possibly Quantum.

The existing wiring is in place but will be changed from surface fixed to flush. This gives the opportunity to run in the pilot wire. How would this usually be done? I assume as it is mains it must have 2 sheaths so a single wire will not do?

Thanks
Tim

 

[stem]

For new installations usually a 3 core and earth cable is installed from the start, but to upgrade an existing system you can run an additional cable for the pilot wire. Something like this, which is normally used for lighting circuits. As the pilot wire is just used for control purposes, it shouldn't be carrying much current, but might be best to check with the heater manufacturer.

 

[phatboy]

Thanks stem.

I cannot find 2.5mm 3+E cable, only 1 & 1.5 for lighting

Could 1mm single+e be used? Does it count as part of a power circuit if it's for signalling? Unfortunately TLC don't seem to stock it

 

[stem]

The pilot wire utilises a 230V signal to turn the heater on and off, so although it doesn't carry much current, it is still at mains voltage. The Dimplex Duoheat instructions state:

"Any 240V insulated cable may be used to link pilot wires around the ring main. A low signal current is used. Suitable connections would be either an additional single core wire marked or colour coded appropriately or use a 4 core cable throughout the radiator ring. As a mains conductor, the pilot wire should be isolated in accordance with the IEE regulations."

 

[ban-all-sheds]

The existing wiring is in place but will be changed from surface fixed to flush.

Do take note of this:

[wiki]electrics%3Awalls[/wiki]

 

[EFLImpudence]

Are these actually storage heaters?

If so what does the pilot wire do.

 

[securespark]

"As a mains conductor, the pilot wire should be isolated in accordance with the IEE regulations."

Should that be "isolated" as in the excerpt, or "insulated"?

 

[OwainDIYer]

Possibly both. You used to be able to get a dual switch / flex outlet for peak and off-peak supplies to a storage heater where one 4-pole switch and two flex outlets would provide total isolation to a heater.

You'd need a 5-pole switch for a Quantum if there's a pilot wire as well. If such a thing isn't made, is it actually possible to install the heater in full compliance with the regulations and good practice?

 

[Echo the husky]

I've seen these things installed with 3 isolator switches by each heater, not very nice. I have also seen them done with a 20A DP switch for the off peak, and a 13A fused spur for the normal electric, with the neutrals in a separate connector, and the pilot wire switched with the fused spurs neutral contacts.
You could fit a 6 pole isolator such as one of these nice MK ones, probably not to most peoples tastes aesthetically, but as neat as you are likely to get. I rather like industrial switchgear though.

 

[Adam_151]

I came across one setup (this was with panel heaters rather than NSH) where the pilot line did not have any isolation at all, it was just connector blocked to the pilot line in the heater flex in the back of the spur. That got changed around I think (as it was a separate 1.5mm twin and earth coming in from a central joint box near the time clock) to be a switch leg wired from the live on the load side of the spur, switched through one pole of a 4 pole contactor fitted next to the time clock and the back to the point wire in the back of the spur, so that the spur killed the heater entirely.

 

[stem]

Are these actually storage heaters? If so what does the pilot wire do.

The pilot wire provides a control signal from a remote controller, which can operate on several zones, so that the bedroom heaters can operate at different time settings to the lounge etc., I worked on one comprised just of panel heaters though, not storage heaters.

Having said that, those specifically mentioned by the OP are storage heaters. There's a description of the 'pilot wire' from Dimplex here. if you scroll down a bit.

 

[EFLImpudence]

Thank you.

Yes I know how they work for panel heaters but they can surely only work with storage heaters if they have additional convection heating as well - i.e. not solely storage heaters.

 

[phatboy]

Thank you.

Yes I know how they work for panel heaters but they can surely only work with storage heaters if they have additional convection heating as well - i.e. not solely storage heaters.

I believe it controls the charge on them too. These heaters uase electronic controls, not the manual knobs...

 

[EFLImpudence]

Ok. Thanks. I haven't come across any of them.

So, it just saves you turning down all of them individually if the weather is warmer.