Consumer Unit Safety

[taycast]

I have an MK consumer unit. If I switch off the main switch, I am ok to rewire my garage lighting circuit, which feeds from the consumer unit from a dedicated mcb? i.e to work safely in the mcb with the lives and neutrals

OR

Should/can I switch the supply off at the meter, which has a white recessed button saying push to off, an arrow pointing clockwise, and a flat slot in it for a screwdriver. Would this make everything dead beyond the meter and be safer, as surely there is a risk that I could touch a live at the meter side of the main switch.

I have no other switches to shut off the supply. Thanks once again. Perahps you can see my pictures which may help

Consumer Unit

• taycast
• 29 Jan 2009
• 1

Meter

• taycast
• 29 Jan 2009
• 1

[/img]

 

[rebuke]

If you switch off the main switch, then the only live terminal is the one at the incoming side of the main switch. Whether you're happy to work in the CU at that point is up to you.

I don't know if the button/screw in your meter is an isolator, I've not seen that sort of meter before and your picture is a bit too blurry to make it out. What I will say, is if it is, then make sure you turn the CU off at the main switch first, as I would suspect that it is not designed to isolate under load...

 

[sparkyspike]

That switch on the meter will turn off the supply, meaning the top of your CU isolator won't be live. I don't know whether it is double pole or single pole though (i.e. whether it opens both line and neutral).

 

[GaryMo]

If you switch off the main switch, then the only live terminal is the one at the incoming side of the main switch.

This will be the case after you've proved for dead therefore erasing the risk of a potentially faulty main switch that could have isolated the neutral only.

Always follow a safe isolation procedure.

 

[ban-all-sheds]

I don't know if the button/screw in your meter is an isolator, I've not seen that sort of meter before and your picture is a bit too blurry to make it out.

It is:

And someone recently posted photos of one which they had opened up - it's single pole.

 

[Taylortwocities]

The isolation switch only cuts line.

For some curious reason, the DNO round here (SNS) usually seals this isolation switch

 

[rebuke]

GaryMo: good point, always test for dead, don't rely on the fact a switch/breaker appears to be off - this is what happens when I do a post in a hurry

Taylortwocities: Perhaps to avoid people turning them off under load, and potentially destroying their meter (not sure if they're rated for it, but assuming they're not, then turning off a large load could cause a big arcing event, which could at best damage the meter, at worst cause a fire etc...)

 

[ban-all-sheds]

From the memory of the photos here a few weeks ago it certainly isn't the most sophisticated switch mechanism ever built....

 

[Taylortwocities]

The spec is here. No data on the contact rating though......

 

[taycast]

Thanks for all that. For clarification. I could turn off the main switch and work with care in the consumer unit once I have checked all is dead? I assume that the CU main switch should isolate the neutral too?

When you say the meter is single pole, what does that mean - does it mean when switched to off its only the live that is isolated?

 

[kai]

That meter is single pole (I had one in my previous house), and is rated at AC21B, i.e. occasional switching of Resistive loads only, so its better to turn off the CU main switch first, before touching the meter switch.

Perhaps someone else here can enlighten you on the terms of AC20B, AC22A, and AC23A etc.