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#142057 - 12/01/04 05:08 AM Siting UK Consumer Unit
davelloyd Offline
Member
Registered: 11/13/04
Posts: 24
Loc: U.K.
Hello,

I want to re-site the consumer unit in my garage so that I can install a "round the corner" garage door.

Is there any rule that says the consumer unit has to be close to the garage door itself or can I get it moved to the back of the garage?

At the moment the meter is to one side of the garage door with a separate isolator switch above it. 10 mm (I think) go from the isolator to the consumer unit which would need renewing and extending to the new position.

What should an electrician do with all the cablles that exit the consumer unit to feed the house? Can they all be terminated in some sort of junction box and then continued to the consumer unit?

I DON'T intend to do this myself but would just like a bit of info that will help me avoid the sort of bodger I posted about earlier

Thanks

David Lloyd
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#142058 - 12/01/04 11:50 AM Re: Siting UK Consumer Unit
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
Hi Dave!,
That sounds like a mission and a half, with a job like that.
Personally, I wouldn't like to see an Electrician use a heap of junction boxes to do a job like this, but at the end of the day, there are going to have to be some junctions made.
Is there a possibility of moving the Unit to suit the runs of cable, to minimise the number of joints required?.
Over here, you can pretty much put a Consumer Unit where you like as long as it's away from sources of moisture and it's easily accessible.
I've shifted switch-boards here before and believe me, it's not a job I'd like to wish on anyone!.
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#142059 - 12/01/04 12:14 PM Re: Siting UK Consumer Unit
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
There's no specific requirement for the unit to be near the door. I agree with Trumpy that extending every cable to the new location with junctions is going to make it rather ugly, although likely to be quite acceptable from a technical point of view (there's just a slight chance that the extra cable length might increase voltage drop beyond limits on some circuits, but most unlikely in an average domestic system if you're extending by only a few feet).

If you're lucky, some of the cable may take off in the direction you intend to move the panel (either in the garage or in the house on the other side of the wall), in which case you might be able to reroute and shorten them.

Quote:
10 mm (I think) go from the isolator to the consumer unit

If these are feeding the whole house, I would hope they're larger than that. 16 or 25mm would be the norm, depending upon the main service/fuse rating.
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#142060 - 12/01/04 12:41 PM Re: Siting UK Consumer Unit
davelloyd Offline
Member
Registered: 11/13/04
Posts: 24
Loc: U.K.
Trumpy, Pauluk,

There are just six breakers in the consumer unit and the job, I'm not saying it's easy, doesn't look too bad.

I imagined some sort of enclosure with ALL the conections made inside it or even simply some sort of metal box with a door and separate junction boxes inside to tidy things up.

The cables need to be extended by 12 feet so would this cause any problems with volttage drop?

I just stabbed at the size of the cables when I said 10 mm. These were put in by an electrician some years ago when the garage was extended and there are no problems so they must be 16 or 25 mm as you say

Regards

David Lloyd
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#142061 - 12/01/04 03:58 PM Re: Siting UK Consumer Unit
uksparky Offline
Member
Registered: 07/06/04
Posts: 200
Loc: UK
Hi Dave

There are no restrictions on the siting of CCUs; barring the obvious of course!!

Are you also moving the meter? This will incur significant expense from your utility provider...

It is possible to buy a metal enclosure and fit a terminal strip ( NOT choc-blocks! ) to join all the cables. A good sparky would be able to do this in a trice. However, it sounds to me as though space is going to be at a premium...

The minimum tails csa is 25mm. Some utility's DO have regs concerning the maximum length of tails to the CCU ( along with their own minimum csa requirements ) you need to check that. Also they may want them in a trunk... Also, check on their requirements for the main earth bond, which for a 100A TN supply is always at least 16mm, with 10mm for the supplementary.

Some thoughts: If you are moving the meter, and you can; put it outside in a service box. You can ( though it sounds radical! ) if this is a cavity wall, blatter out the inner leaf and mount the wooden board on the inside of the outer leaf. I have seen it done - but I can't vouch for the building regs on that bit!

Regarding voltage drop, it is unlikely that your circuits will be running at approaching critical load for the runs as they are. If they are, a way around this is to upsize the 'extension' to take account of this. However, if your loads are this 'tight', you might ask your spark to split some whilst you're on with this job...

Hope that helps a little!
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#142062 - 12/02/04 12:57 PM Re: Siting UK Consumer Unit
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
Quote:
Some utility's DO have regs concerning the maximum length of tails to the CCU ( along with their own minimum csa requirements ) you need to check that.


A good point. Dave, you mentioned an isolator switch feeding to the existing unit. Is this a switchfuse? If so, then there shouldn't be a problem in this respect.
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#142063 - 12/02/04 01:52 PM Re: Siting UK Consumer Unit
davelloyd Offline
Member
Registered: 11/13/04
Posts: 24
Loc: U.K.
pauluk,

Yes it is a 100 amp switch fuse. It is sited directly above the meter. Does this mean the cable from the switch to the consumer unit can be any length?

David Lloyd
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#142064 - 12/02/04 04:03 PM Re: Siting UK Consumer Unit
uksparky Offline
Member
Registered: 07/06/04
Posts: 200
Loc: UK
No it doesn't. What it technically means is that, if that switch is located between the meter and the CCU, then any cable between it and the CCU is not 'bound' by utility requirements.

Tails form a part of the consumer's installation, but must comply with the supplier's requirements. Where the protection is the supplier's cut-out this is obvious. However, where they are protected by an additional switch-fuse, rated the same as the cut-out, the same dimensions apply. The switch-fuse is deemed to be a matter of 'convenience' to isolate the whole installation, and not a "subsequent circuit".

It may be that an individual supplier may not be fussed, however most would be; a tail technically becomes a submain if it has a switch in it, but this is rather academic. It is worth being mindful that your tail - with or without the switchfuse ( rated 100A ) - must be able to withstand a fault current of 100A. You would not be permitted to use cable less than 16mm in any case.
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#142065 - 12/06/04 12:57 AM Re: Siting UK Consumer Unit
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
uksparky,
That's an interesting point you raise.
Just where is the set demarcation, between Consumer Equipment and Supply Authority Equipment?.
Here we have this statement:
Quote:
Where equipment is required to be isolated by the removal of the Mains Fusing to enable the disconnection of the Installation, this equipment is deemed the property of the Supply Authority

As heavy-handed as this seems, anything up to the Line-side of the Main switch is SA property here, including the Tails.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin
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#142066 - 12/06/04 03:48 AM Re: Siting UK Consumer Unit
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
Mike,

A typical modern external meter cabinet:


The meter and everything on the line side of it belongs to the PoCo. The tails which disappear into the wall (and up to the panel just above in this example) are supplied by and belong to the homeowner.

As John said though, even though these tails are the property of the homeowner, the PoCo has specific requirements for them. If somebody just ran a pair of 4 sq. mm tails into the box, the PoCo would (or at least should) refuse to hook them up.
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