Consumer Unit Advice

[PaulS]

Hi, Just looking for a bit of advice on consumer units.

I've been replacing the old wiring (pre 1960)from my mums house and at trying to select the best consumer unit to replace the old fusebox.

It will have the following connections

1) Kitchen Ring
2) Living room/bedroom ring
3) Garage Ring
4) Lights
5) Immersion Heater
6) Cooker
7) Electric Shower

Everything but the shower unit seems fairly simple, (32,16 & 6A MCBs).
With the shower I understand an RCD is recommended, is this used in conjunction with a 45A MCB? I would probably want the garage ring on the RCD too.

Is a split load Consumer unit of any use here? I notice Screwfix has a prebulit unit by MK that is split load with a 100A DP in one side and an RCD in the other which is reasonably priced.

 

[plugwash]

yeah the screwfix fully loaded mk is a very good deal and should cover your requirements

sockets and the shower should generally be on the rcd

lights should not be on the rcd

a dedicated cuircuit for the freezer on the non-rcd side is also a good idea

other stuff i would generally put on the rcd unless there was a problem with doing so but some sparkys take the opposite approach

 

[dw3101]

just one point, the garage needs to be on a rcd - as it could power devices outside..

What size cable do you have to the garage... ideally swa and not T&E,

If you just have a ring in the garage and a 32a breaker, how are you powering the lights??

I would use a minimum of 4.0mm swa 6.0mm preferably.. and you have a few choices of how to wire it.. you could just have a 32a breaker and then have a ring in the garage and use a fcu for switching the lighting off the ring, personally I would have a metal clad cu in garage with a radial in the garage, and a 6a lighting circuit.. depends on garage requirements..

its a matter of pennys to go to larger cables with more (theoretically!) flexibility..

I just paid £1.72+vat per m for 2 core 16mm.

David

 

[plugwash]

he didn't say whether this was an attached garage

if you are burying cable then it pretty much has to be SWA (there are other options but they aren't really suitable for diyers

i would just consider an attached garage to be part of the house with the sockets rcd protected like the rest of the house

 

[dw3101]

good, point Ill get my coat.

Im not used to attached garages where I am from, and with me being into modifying cars in a big way and having 2x 32a welders a 16a compressor and a radial dedicated for tools, and a ring in the garage.. I tend to go OTT.



David

 

[ban-all-sheds]

Is a split load Consumer unit of any use here? I notice Screwfix has a prebulit unit by MK that is split load with a 100A DP in one side and an RCD in the other which is reasonably priced.

Before you buy what might be unsuitable (or, at least, would require components to be swapped) - is your Mum's supply a TT one?

 

[ban-all-sheds]

I just paid £1.72+vat per m for 2 core 16mm.

2-core. Are you running a separate cpc?

 

[PaulS]

Cheers for the advice guys.

The garage is attached to the house, so the light is on the lighting circuit.

I'm unsure what you mean by TT supply?

 

[PaulS]

Okay, I've found out about the TT system. Since we have and overhead power line entering the house and only two wires are entering the house its a TT system. So this will affect the components that can be used in the consumer unit? Your help is appreciated.

 

[plugwash]

you need a 100ma type S rcd

this can either be fitted in place of the main switch of the main isolator in the CU or in a seperate box before it

furthermore *ALL* sockets must be on a 30ma non delayed rcd

 

[PaulS]

I'm assuming with the TT supply its necessary to ensure that there is is an earth electrode fitted from the consumer unit to the ground?

 

[ban-all-sheds]

I'm assuming with the TT supply its necessary to ensure that there is is an earth electrode fitted from the consumer unit to the ground?

Absolutely.

I hope that there is already one there with the existing CU. Where does the earth cable from there go?

And isn't it scary how you came fairly close to installing the wrong thing, which would not have provided your dear old ma with the protection she should have....

As plug said, the whole installation must have a 100mA Type S RCD, and although this can be separate, it's more elegant to have it in place of the normal main switch in the CU, and all the sockets, not just downstairs/garage must be on a normal 30mA RCD, i.e. the one that comes with the split load board. AFAIK, MK do a suitable 100mA S incomer for that board, but I don't know if Screwfix sell them.

 

[PaulS]

Whats even scarier is that about 3 electricians have been in and done work to the system over the last 10 years. I'm off to the meter to track the earth cable

I was planning of putting in a small 5 way CU to replace a couple of ancient fuse boxes for the Storage heaters, will this also need a type S RCD in place of the DP isolator switch.

 

[ban-all-sheds]

Whats even scarier is that about 3 electricians have been in and done work to the system over the last 10 years.

Yeeeh haah!

I was planning of putting in a small 5 way CU to replace a couple of ancient fuse boxes for the Storage heaters, will this also need a type S RCD in place of the DP isolator switch.

The whole installation must be on a 100mA Type S..

Why not fit a bigger board than the MK you were planning?

 

[kai]

Note that the main 100ma TD RCD must be in a Plastic Housing, NOT a metal one, so one of those IP55 two way din-rail boxes can be used, if you have a metal consumer unit housing.