fused spur

[harv54]

I'm currently installing a separate ring for my kitchen but I've run out of ways in the consumer unit. Currently, the immersion heater is fed from its own 15A MCB in the consumer unit. If I re-wire the water heater as a fused spur off the upstairs ring this will free up the MCB that I need (re-rated to 30A). My question is - is it acceptable to wire the spur directly at the consumer unit

 

[Adam_151]

Immersion heater should be off its own circuit, its a large fixed load and should not be off the ring, if you tried hard enough you could probably jusify it by saying the circuit has plenty of free capacity, etc, but very bad practice, think also there is a reg that states that water heaters for vessels over a certain capacity (15 litres??) should have a dedicated circuit, but not entirely sure?. I certainly wouldn't do what you are proposing though

 

[harv54]

Thanks Adam. I guess I'll have to install a small consumer unit for the kitchen ring

 

[Steve]

You CAN fit a 45A MCB in your existing CU, run 10mm² supplying a NEW CU, and put a 15A and 32A MCB in this CU, for the immersion and the new ring, or any 2 circuits of your choosing.

Also, you can do this with the 2 lighting circuits (if you have 2) - fit a 20A MCB in the main CU and run it to 2 x 5A FCUs for the lights. Then you have a free MCB way where one of the light circuits used to be.

 

[andy]

or better still, replace CU with larger one...

 

[Steve]

or better still, replace CU with larger one...

i'm trying to save them money . . you know what these DIYers are like!

 

[harv54]

Thanks guys. believe it or not this is not about the money. I really don't want the hassle of replacing a perfectly good modern CU for the sake of 1 MCB.

 

[Adam_151]

what circuits have you got? and then we might be able to suggest something

one that springs to mind is light circuits, if they are not heavily loaded it may be possible to convert to a single lighting circuit

 

[harv54]

It's an 8 way RCD protected CU allocated as follows:-
Immersion Heater - Shower - Upstairs lighting - Downstairs lighting - Garage feed - Upstairs ring - Downstairs ring - Cooker.

 

[Steve]

Like I said, take the 2 lighting circuits out. Put a 20A MCB where one of them was. Run 2.5mm² cable to 2 fused connection units (preferably switched units). From these 2 FCUs, run the 2 lighting circuits, making sure to label which is which! (dont forget to put 5A fuses in the FCUs)

This frees up one MCB way, and is by far the simplest thing to do without installing additional consumer units or combining other circuits . . .