Split Load Consumer Unit

[gt900uk]

Do i need to have a split load consumer unit or can i just use an RCD main switch unit? This is to replace an old stye cartridge fuse unit.

 

[andy]

Do i need to have a split load consumer unit or can i just use an RCD main switch unit? This is to replace an old stye cartridge fuse unit.

my mystic cat is on holiday for the week. looks like well have to wait before we can help you

 

[Big_Spark]

What type of supply do you have, if you live in a town or city, then you will be very unlikely to have a TT supply (Overhead) and thus there is no requirement for you to have an RCD main switch..which is a bad idea anyway.

 

[johnad]

if you live in a town or city, then you will be very unlikely to have a TT supply (Overhead)

i have a TT supply and it is not overhead but underground.

go for split load so you keep the lights on in the event of a fault.

 

[andy]

if you live in a town or city, then you will be very unlikely to have a TT supply (Overhead)

i have a TT supply and it is not overhead but underground.

go for split load so you keep the lights on in the event of a fault.

just because you have split load doesnt mean that the lights will stay on if there is a fault. if you have a TT supply then everything must be rcd protected so if there is a fault on the 100mA side you will lose your lights

 

[johnad]

sorry im talking about two different things,
what i mean is my supply is TT and i will have rcd protecting the whole istalation.

gt900uk was asking about using a single rcd as a main incomer,
what i was trying to say was if he has not got a TT supply then i would go for a split load and use the rcd to protect some circuits (garden etc) and put the lights on the non rcd side.

 

[gt900uk]

You can borrow my mystic cat , Its rural location so if i went with a CU that was RCD switched it wouldnt do any harm? As split load is only partially covered by the RCD? Am not sure what type of supply it is. Just looking to buy the right stuff before i get someone in to fit it.

 

[plugwash]

thats generally a bad idea

1: most sparkys will probablly be able to get stuff cheaper than you can
2: most sparkys will have thier preffered brands and may refuse to install anything else or charge you a lot more because of the extra time it will take working with a brand they are familair with
3: you can end up buying the wrong thing.

 

[johnad]

i have had the same problem myself look at the for reference at the top of this section and you can see how to identify your supply type,
if you do have a TT supply then you will need to protect the whole lot with a rcd but you can use a split load unit and use a time delay rcd for the main incomer,
that way if the 30ma rcd trips then you can have the lights on the time delay side and not be plunged into darkness,
it will help if you get a fault at night as i have...

 

[gt900uk]

So basically there is no requirement for split load its just hand that the lights wont go out in the event of a fault? If everything is on RCD then all is well?

 

[andy]

So basically there is no requirement for split load its just hand that the lights wont go out in the event of a fault? If everything is on RCD then all is well?

if you have a TT supply, everything must be RCD proteted. if you have tnc(s) then you should RCD protect sockets which could supply areas outside (i.e downstairs ring) and shower

 

[plugwash]

the wiring regs don't explicitly require a split load but.

1:mains powered fire alarms must not be on a rcd with a trip point less than 100ma (i think this rule is relaxed a bit if there is battery backup but i'm not sure)
2:the wiring regs do require fault protection be designed to give discrimination now i know split loaders aren't brilliant for this but at least the lights stay on).

personally i do not belive either a split load board or a single 30ma rcd protecting everything is doing things properly but to do it properly is far far more expensive.

 

[johnad]

a 30ma rcd main switch is fine but you will kick youself if you get nuisance trips,
do as plugwash says get your sparks to supply your unit ,

 

[kai]

Why can't you have TWO separate RCD sections - the 100MA section feeding the Lights, Freezer and Smoke Alarm, and the 30MA section feeding the Sockets and Shower and Cooker (If it has a socket point)?

This way is a fault appears on one section, it won't affect the other half.

 

[plugwash]

you can but most manufacturs boards aren't specifically designed for it so you would have to get two sets of large cores into the output of the main switch

i think it could be done quite easillly with 16mm xple cores (strip em out of a bit of XPLE swa if you can't get them any other way) but i'm not positive about it.