New consumer unit

[starfire]

Hello,

Just moved into a property and looking at getting the old style consumer unit replaced by a qualified electrician, just want to check a few things:

1. Does a new CU have to be dual RCD?
2. Once complete I should get a electrical install certificate straight away from the electrician and a compliance certificate from my local council after a few weeks?

Also, is it easy to relocate a CU to say a different wall as there doesn't seem to be a lot of space width ways where my existing unit is and the new dual RCD seem to be quite wide?

Thanks!

Fusebox

• starfire
• 4 Jun 2013
• 1

 

[Lectrician]

Not particularly easy to relocate, especially if no access above.

You can get small 6 and 8 way dual splits which are compact.

Why would you want to upgrade a CU to something that is not completely upto date? You should go for a dual split

You could even consider a straight consumer unit (mains switch only), and then use RCBO's. Would be more expensive, but likely more compact.

You should receive an Installation Completion Certificate and a BCO notification.

 

[starfire]

OK,

Did not realise you can get 6 and 8 way dual RCD, just googling they mostly seem to be 10 way and 350mm+ wide and only have 290mm where existing unit is.

 

[ban-all-sheds]

You can get small 6 and 8 way dual splits which are compact.

Is that 6/8 MCBs plus 2 RCDs, or 2 or 4 MCBs plus 2 RCDs?

You could even consider a straight consumer unit (mains switch only), and then use RCBO's. Would be more expensive, but likely more compact.

 

[Lectrician]

MK did a 3+3 dual split, but I cannot find reference to it in their cat now. It was pretty much bang on 300mm I recall.

Hager do a 3+3 dual split, but 310mm wide.

Hagar do a 6way 100amp incomer for 6 RCBO's at 240mm wide.

Wylex looks a winner - They do a 3+4 dual split at 290mm wide. Max of 7 ways.

Looks like you will need 8 ways minimum though, unless some of your ways are unused under the cover?

 

[starfire]

I haven't lifted the cover to check how many circuits there are and don't want to remove power at the moment, unless its safe to remove cover and leave main switch on?

Could you confirm once complete I should get a electrical install certificate straight away from the electrician and a compliance certificate from my local council after a few weeks?

 

[Lectrician]

You can remove the fuse cover to see if the fuses are all in, but to remove the main cover, you need to turn the main switch off, and remove the fuses, remembering that incomer to the main switch will still be live.

An electrician does not need to give you a completion certificate immediately. We post ours on with the bill, or even a few days after, depending on the work load.

 

[plugwash]

1. Does a new CU have to be dual RCD?

The 17th edition of BS7671 now requires most concealed cables* to be protected by a 30ma RCD. In practice this means in a domestic install that most circuits need to be RCD protected.

There is also a requirement that "Requires that every installation shall be divided into circuits as necessary to avoid danger and minimise inconvenience, in the event of a fault."

Many electricians and electrical suppliers seem to think that while losing the whole installation to a RCD trip is unacceptable losing half of it is. I personally consider this hogwash but the powers that be seem to be going along with it.

A CU with a plain main switch and RCBOs protecting the outgoing circuits is the way to go IMO.

* Exceptions include cables in earthed metal conduit, cables burried more than 50mm deep, cables incoprorating an earthed metal layer and cables that are in an installation that is under the supervision of a skilled or instructed person.

 

[JohnW2]

Hagar do a 6way 100amp incomer for 6 RCBO's at 240mm wide.

Even that probably includes more space at the sides than is strictly necessary - 8 modules only amounts to 144mm.

Kind Regards, John

 

[securespark]

Way for way, Wylex are more compact than Hager.

 

[JohnW2]

Way for way, Wylex are more compact than Hager.

Yes, that's certainly true in terms of the examples you quoted. Assuming the 3+4 dual split Wylex (290mm) has a main switch as well as 2 RCDs, there's only 56mm 'spare space' at the sides, as compared with 96mm for the (240mm) Hager 6-way+main switch one.

Kind Regards, John

 

[EFLImpudence]

Many electricians and electrical suppliers seem to think that while losing the whole installation to a RCD trip is unacceptable losing half of it is. I personally consider this hogwash but the powers that be seem to be going along with it.

Why is it hogwash?

The whole installation includes all of the lights.

As long as the lights don't go out where you are working with hazards what else is so bad?

 

[SimonH2]

You could even consider a straight consumer unit (mains switch only), and then use RCBO's. Would be more expensive, but likely more compact.

+another one for that. There's no reason a new CU with RCBOs can't be the same size as your existing one.

As to moving it, that may be easy, it may be "impractical without ripping the building to bits". It all depends on where the cables run, how much spare length there is, where the current and new positions are relative to the meter, and a few other factors.