Two points of isolation - Consumer Unit Wiring

neilneil2000 · Nov 20, 2016

Hi guys,

In my garage there are two Consumer units, one connected off the other like a daisy chain. I expected therefore for the secondary Consumer unit to be electrically in series with the first, allowing me to isolate the entire garage using the master switch on the primary unit. However, it turns out that the two units are electrically in parallel, meaning I need to turn off both master switches (one in each unit) in order to isolate the garage.

Is this normal/acceptable?

Tony S · Nov 20, 2016

Are the two boards fed off the house you recently bought?

Murdoch · Nov 20, 2016

Nothing unusual about this. People fiddling with lecky normally check for isolation, and I can tell you never assume anything.

Rob_the_rich · Nov 20, 2016

The main switch in a CU only isolates the circuits included in the CU, not also another CU elsewhere, unless it says it does.

Andy™ · Nov 20, 2016

you can have more than 1 main switch in a property

ProDave · Nov 20, 2016

Describe what you have in more detail, i.e how many circuits on each, and what do the labels on each circuit say about what circuits they feed?

Evans Electric · Nov 21, 2016

NeilNeil ( So good they named him twice) You have fallen for the classic mistake for the Electrician ........ assumption . Never assume is what we had drummed into us . You were assuming that ONE of those boards killed the other , I think we all learn , some sooner than later , never to assume that something is now Brown Bread 'cos one day it you'll get it wrong .

Its the same in general life too, my brother was called out to the hospital late one night , set off on his motorbike , at a T junction an approaching bus was indicating a left turn , our kid pulled out , bus went straight on . Brother got to the hospital but in an ambulance. Never assume.

neilneil2000 · Nov 21, 2016

ProDave said:
Describe what you have in more detail, i.e how many circuits on each, and what do the labels on each circuit say about what circuits they feed?

The main feed in comes up from the ground and into the bottom of the primary box. The primary box then has two circuits, one labelled "lighting" and another labelled "sockets". There is then a length of cable out of this box to another about 10 inches away which has a single unlabelled circuit. I have traced the unlabelled circuit and it appears this runs to a single socket.

The house (and garage) have had several issues I have had to address, including all earth wires snipped off at both ends (switches and sockets) so I just wanted to see if this was a normal thing or not, as nothing would surprise me!

Murdoch · Nov 21, 2016

Me thinks you need a competent man with a MFT to do some basis tests.... sounds a shambles IMHO

Andy™ · Nov 21, 2016

+1. probably best get someone to do an EICR

steptoe · Nov 21, 2016

Murdoch said:
Me thinks you need a competent man with a MFT to do some basis tests.... sounds a shambles IMHO

A dangerous shambles

Tony S · Nov 21, 2016

neilneil2000 said:
The main feed in comes up from the ground and into the bottom of the primary box. The primary box then has two circuits, one labelled "lighting" and another labelled "sockets". There is then a length of cable out of this box to another about 10 inches away which has a single unlabelled circuit. I have traced the unlabelled circuit and it appears this runs to a single socket.

The house (and garage) have had several issues I have had to address, including all earth wires snipped off at both ends (switches and sockets) so I just wanted to see if this was a normal thing or not, as nothing would surprise me!

Sounds like my first house 40+ years ago. Two MEM metal switch-fused units one for lighting the other power……….. sort of.

TT with a 30A rewireable cutout.

Earthing? Two 6” nails with a bit of bare 3/.029 wrapped around them, one for each of the 15A sockets on the ground floor.

I’ll not go in to how the shed was supplied

ProDave · Nov 21, 2016

What is needed is one of the admins to come along, and allow you as a new member to post some pictures.

Either that or keep making meaningful posts until you reach a post count of 10.

But it does sound from what you say about cut earth wires that at best it needs a serious check out and probably some remedial work, at worst a rewire, but we don't know.

binky · Nov 21, 2016

neilneil2000 said:
The main feed in comes up from the ground and into the bottom of the primary box. The primary box then has two circuits, one labelled "lighting" and another labelled "sockets". There is then a length of cable out of this box to another about 10 inches away which has a single unlabelled circuit. I have traced the unlabelled circuit and it appears this runs to a single socket.

The house (and garage) have had several issues I have had to address, including all earth wires snipped off at both ends (switches and sockets) so I just wanted to see if this was a normal thing or not, as nothing would surprise me!

As per other comments, it sounds like your electrics are quite dangerous, snipping out earths is most certaily not normal - similar to driving without seat belt, you might not need it for years, but if you had an accident, your protection has been removed.

Doctor · Nov 24, 2016

Has the incoming feed been split before the main c/u ? Tail blocks ?

Andy™ · Nov 24, 2016

Virus said:
Has the incoming feed been split before the main c/u ? Tail blocks ?

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Two points of isolation - Consumer Unit Wiring

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