Controller overheating ??

[ban-all-sheds]

Fused Connection Units.

Your socket circuit will have a protective device rated at more than the BX is, so you'll need two of these for each one, one on each feed to it.

A bit messy.

Swapping plugs from off-peak to peak sockets is simpler, but not very sophisticated.

How about this, which won't need any timers, so you can keep them as spares for the immersion, (as they seem to have short lifetimes ):

Wire the utility room with 2 radials, one peak, the other off-peak, via a suitably rated double pole changeover contactor, with the coil supplied (via an FCU) by the off-peak supply. Off peak also to the NO terminals, peak to the NC, socket circuit from the common terminals.

Then whenever the off-peak is available, the contactor will close and the sockets will be connected to the off-peak supply. When the off-peak is not available the contactor will open and the sockets will be supplied from the peak supply.

Do make sure you document it well, and have instructions at the CU to warn people that they should isolate both supplies before poking knitting needles into the sockets.

 

[peweuk]

Sounds a really simple solution - when it's brought to your attention.

I seem to remeber doing something similar many years ago at a previous house - but had forgotten all about it.

 

[peweuk]

Having given some thought to this I have been wondering if the contactor route would be best suited to the project I am currently working on.

In the extension I have built I need to have 3 hot water tanks all heated by immersions overnight - but also having a 'daytime boost facility.

So for these I am considering having a feed from the off peak meter and a feed from the standard meter to a contactor.
From the contactor then individual feeds to each immersion would be fed through individual immersion time switches.

For the contactor feeds from the CU's I need to use cables suitable for carrying up to 33amps (ie 3 immersions), and the contactor also needs to be suitably rated.

So I am thinking I need 6mm cable to one of these, with 2.5mm cable to each immersion.

Or would it be better to have 3 feeds from the CU's to 3 of these - one for each immersion.

 

[ban-all-sheds]

Neither - you need double pole changeover , aka double throw (sometimes abbreviated to DPCO or DPDT) contactors.

And surely 1 has got to be better than 3, but the people here who build control panels might have a proper list of pros'n'cons.