Convector Heater Pilot Wire.

The French often use pilot wires to signal that off-peak tariffs are in force. Saves a lot of copper compared with separate full sized peak and off-peak supplies.  The French metering systems doesn't provide a switched off-peak supply like ours do - rather they provide access to a pair of volt-free contacts that signal peak/off-peak. The consumer then provides a low current circuit (typically on a C2 MCB) that runs back to the meter's contacts and drives pilot wires or contactors for anything that needs an off-peak supply. 

Makes isolation easier too - since the main DP isolator still isolates everything.

On the other hand it makes circuit protection tricker - you in effect have could have two circuits with a borrowed N to appliances that have pilot wires - so they can resort to tricks like auxiliary contacts on the circuit's normal MCB switching the pilot wire - and both circuits sharing the same RCD.

   - Andy.

Thanks Andy.

As an aside, the new consumer unit is huge. It has about 16 ways for a three bedroom new all electric house. The bad design part though is that it is a split load consumer unit.

Z.

Which regulation says that a split load CU is not satisfactory?

The unused pilot wire needs to be treated as a live conductor and terminated to make it safe.

I don’t understand why the system is not in general use in the UK, it can be retrofitted using a separate pilot wire controlled relay.

https://www.dimplex.co.uk/sites/default/files/assets//RXPWIF_Instructions_Issue_004.pdf

Obviously if you have a split load consumer unit all the heaters and controller need to be on the same RCD and isolating the heaters becomes an issue.

Sparkingchip: 
 

I don’t understand why the system is not in general use in the UK, it can be retrofitted using a separate pilot wire controlled relay.

https://www.dimplex.co.uk/sites/default/files/assets//RXPWIF_Instructions_Issue_004.pdf

Obviously if you have a split load consumer unit all the heaters and controller need to be on the same RCD and isolating the heaters becomes an issue.

I was looking for something like that a couple of years back, its a nightmare administering timers all over the place, these would have been ideal

Sparkingchip: 
 

I don’t understand why the system is not in general use in the UK, it can be retrofitted using a separate pilot wire controlled relay.

https://www.dimplex.co.uk/sites/default/files/assets//RXPWIF_Instructions_Issue_004.pdf

Obviously if you have a split load consumer unit all the heaters and controller need to be on the same RCD and isolating the heaters becomes an issue.

Last sentence of 314.4 perhaps?

   - Andy.

davezawadi (David Stone): 
 

Which regulation says that a split load CU is not satisfactory?

Would you run 8 separate diverse circuits through just one 30mA R.C.D? 120.1 “Proper functioning”.  and 314.1.

Z.

There’s no reason why you cannot have several heaters on the same circuit, particularly under floor heating which can have programmers with pilot wire controls.

A discussion from seven years ago

 https://www2.theiet.org/forums/forum/messageview.cfm?FTVAR_FORUMVIEWTMP=Threaded&catid=205&threadid=58537