Consumer Unit Query

[tworoads]

I am helping a friend who has just moved house and wants a shower fitting. The consumer unit is not wired as I have seen before. Can anyone comment on the following questions?

Should there be a seperate ring main for the kitchen?? The cooker is seperate but then only 1st and ground floor ring mains.

The ground floor ring main is the only one to have RCD protection (an RCBO)Should I be concerned about this? I know that in my house the RCD feeds all the MCBs (exept lights)so the shower, oven and all ring mains are protected.

Can an electric hob use an RCD or is there too much earth leakage?

Ditto an immersion heater.

The plan is to install a shower, needing 40A. It's an average size house with electric cooker and immersion. What diversity should be applied - will the main 100A switch be OK?

Would I want to RCD protect the shower?

As there is only a single slot left in the consumer unit if I do want to RCD protect the upstairs ring or the shower I need a bigger box. Can I take a spur to a smaller consumer unit and transfer say the lighting to that and group all the RCD protected circuits in this box with a big RCD on?

Thanks in advance for any help.

LEe

 

[amtodd]

Hi Lee,
Should there be a seperate ring main for the kitchen?? The cooker is seperate but then only 1st and ground floor ring mains.
Most domestic systems evolve, looks like your friend's has too. Hence less rings than in a modern install. (rewiring my 30's semi recently ended up with 6 rings + shower + cooker + lights, previously only spurs + immersion).

The ground floor ring main is the only one to have RCD protection (an RCBO)Should I be concerned about this? I know that in my house the RCD feeds all the MCBs (exept lights)so the shower, oven and all ring mains are protected.
You can ignore the old stuff if you choose to, but can be prosecuted for ignoring anything new (ie the shower)

Can an electric hob use an RCD or is there too much earth leakage?
yes

Ditto an immersion heater.
ditto yes

The plan is to install a shower, needing 40A. It's an average size house with electric cooker and immersion. What diversity should be applied - will the main 100A switch be OK?
yes. theory is your random stuff - tv hi fi, kitchen kit etc is all quite low power, and all the hi-power kit (kettle, shower, cooker, washer etc) are rarely on together so total power doen't get too high at any time

Would I want to RCD protect the shower?
yes, see above

As there is only a single slot left in the consumer unit if I do want to RCD protect the upstairs ring or the shower I need a bigger box. Can I take a spur to a smaller consumer unit and transfer say the lighting to that and group all the RCD protected circuits in this box with a big RCD on?
your solution is perfectly acceptable, but best solution is to ditch the old box and get a new split load box (re-use the trips if they fit). tidy, easier to trace later, you get to re-do the lot so you know it's ok but costs about £100 + your labour. either way, you'll likely need to disconnect the main incoming fuse (the big one the electric board protect with seals) To get them to reseal it, you'll need to show your install is safe, and a new box might help here.
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