split load CU setup correct?

B

benholme

Hi,
We recently had our CU replaced by a spark. The old one was fuses only, the new one is a split load with breakers. He connected it in such a way that only the ring main is protected by the 30mA RCCB and its own RCD. All other circuits are connected to RCD which in turn are connected to a 100A switch. Which if any of the follwoing sould be protected by the RCCB?

lights 6A
Shower 32A
kithen sockets (radial circuit) 16A
boiler 6A
security alarm 6A

I started to think about this after reading that all new showers should be protected by a 30mA RCB. If we had our shower replaced, whould the spark install a seperate RCB of simply use on the the spare RCCB protected ports in the CU?

Thanks in advance.
 
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What the feck are you going on about!?

He connected it in such a way that only the ring main is protected by the 30mA RCCB and its own RCD. All other circuits are connected to RCD which in turn are connected to a 100A switch
???

???

whould the spark install a seperate RCB of simply use on the the spare RCCB protected ports
???
 
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Mr.DangerMouse there is no need to be so rude to someone who has come here for advice and probably does not posess the technical knowledge that a sparky does. He has tried to describe his problem and it is not very clear what he means but with a bit of coaxing I'm sure we can help him out.

Benholme the information you have provided is not very clear. Are you sure what you have written is correct? Is it possible to post a picture of your board so we can try and determin the setup you have and any problems there may be with it?

Rob
 
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B

benholme

Sorry if I have not explained it correctly. Here is a photo of my CU.

cu.jpg


I basically was wondering which of the MCB should be on the left rather than the right.

If the shower was replaced for a 8.5kW one, would the spark replace the MCB for a higher rated one and would it be on the left or right hand side of the board?

Thanks.
 
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Benholme,

Your split board should have the kitchen sockets and shower on the left protected by the rccb. Why a spark would not use the rccb side for such circuits is beyond me. Be careful those circuits had not caused the rccb to trip so he planted them on the isolator side.

hth
 
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It is as I suspected.

Ben used RCD, when he meant MCB. And he used RCCB to describe the RCD, just as Square D have done on his new CU.

I would be sorely tempted to swap things around a bit. To my mind, all socket outlets should be RCD protected, including the cooker circuit, if there is a CCU incorporating a S/O.

I would also put the shower on the RCD.

Boiler lights and alarm should be on the incomer side.

I would also up the mcb for the kitchen S/O to 20A.

As for the circuits being on the wrong side, look at the installation cert. and see what the IR readings are for those circuits.

Oh, and the MCB's should be in descending order from the incomer or RCD. Ie the biggest closest to the switch and the smallest further away.

Hope this helps, Ben.
 
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Thanks for the picture benholme. Right there was a bit of confusion from your earlier post as you were refering to a Minature Circuit Breaker (MCB) as an RCD. (Residual Current Device)

The setup you have could be correct according to the regs, providing that it is not likely that any socket outlet in the kitchen will supply equipment for use out doors. There is currently no regulation that says a shower must be RCD protected.

I would have thought though that it is a standard practice for all electricians to protect all socket circuits and higer risk circuits such as showers with an RCD when fitting a new consumer unit unless there is a specific circumstance where this setup would not be suitable. I would thing that providing you get a decent electrician to fit your new shower that he would transfer the circuit to the RCD protected side of the C.U. It may need an upgraded cable / MCB as you currently have a 32A MCB fitted which is too small for alot of newer higer powered showers. Also I would get him to check if there is any reason for the kitchen sockets to be on the unprotected side of the C.U. The way it is is not unsafe, but it could be safer.

<edit> securespark beat me to it as usual :D
 
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Yeah, but James beat us both!!

I agree with you: showers are not required to be RCD protected, but most shower mfrs strongly recommend it in their install. instructions.
 
K

kai

The B16 feeding the kitchen socket could be the Fridge Freezer Circuit, as is the case in my home, in that case DO NOT change it for a B20 or indeed anything higher than a B16 for safety reasons - the B16 breaker is just right for a single socket circuit feeding the freezer.
 
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kai said:
The B16 feeding the kitchen socket could be the Fridge Freezer Circuit, as is the case in my home, in that case DO NOT change it for a B20 or indeed anything higher than a B16 for safety reasons - the B16 breaker is just right for a single socket circuit feeding the freezer.

...and, if that's what it is used for, it can be an advantage not to have the freezer circuit on an RCD, in case it trips while you are away and all your food defrosts and rots. Few people though have the luxury of a dedicated circuit for the freezer (but I have as well! ;)

On the other hand if it also supplies the socket that you plug your kettle and toaster into, 15A is a bit low, and an RCD does provide an extra level of safety.
 
B

benholme

thanks for all your replies, and sorry for the earlier confusion.....

the kitchen MCB supplies all sockets in the kitchen, currently a fridge freezer, washing machine, microwave, gas oven, tumble drier and kettle. From what you have said, i guess i should get it changed for a 20A breaker on the left of the board. We hope to replace the whole kitchen within a year and I would like to have a ring installed then.

I think my current shower is 7kW. Its connected using 6mm2 cable that is no more than 10m long. If I got the shower replaced for a 8.5kW one, would the breaker and / or cable need to be replaced?

Thanks for your help guys.
 
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benholme said:
the kitchen MCB supplies all sockets in the kitchen, currently a fridge freezer, washing machine, microwave, gas oven, tumble drier and kettle. From what you have said, i guess i should get it changed for a 20A breaker on the left of the board. We hope to replace the whole kitchen within a year and I would like to have a ring installed then.
A lot of load even for a 20A circuit, I agree you would be better with a ring main or a 32A (using 4mm² cable) radial for the kitchen.
I think my current shower is 7kW. Its connected using 6mm2 cable that is no more than 10m long. If I got the shower replaced for a 8.5kW one, would the breaker and / or cable need to be replaced?
An 8.5kw shower requires a 40A circuit. 6mm² is rated max 47A before de-rating for factors such as thermal insulation, grouping and ambient temp (as you are using MCBs no rewirable fuse correction is req'd). How is the cable run i.e. clipped direct, away from thermal insulation, what ambient temp through loft etc?
 
B

benholme

The shower cable is currently clipped to wooden joists or walls all the way. It does not pass through the loft space as the isloation switch is in the airing cupboard directly behind the shower. Is 6mm2 enough for this?
 

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