DIY Doctor

upgrade of mcb in consumer box

Postby salmo » Sat Jan 02, 2010 2:28 pm

I would like to change a 6amp mcb to a 10amp in my consumer board
but what i would like to do is change it by just switching off this mcb.Am i correct in saying that i am safe to do so so long as i use an insulated driver and i can safely unscrew the mcb from the busbar.
thanks for any help.
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Simply Build It

Postby ericmark » Sat Jan 02, 2010 8:29 pm

This is like saying "If I look both ways am I safe to cross the road" and of course the answer is no. As looking does not stop the traffic.

There are provisions for working live. But for most of us, that includes electricians, it is against the electricity at work act and is a big "NO".

Second one must ask why would anyone want to change a 6A MCB for a 10A? In the main 6A MCB's are used for lights. Although one is allowed up to 16A on lighting this would only be allowed where are the hardware is rated to 16A. In most cases we use ceiling roses as junction boxes and these are only rated 5/6A so in most cases we have no option but use 6A MCB's on lighting.

I theory all bulbs should be internally fused so on blowing ionisation within the bulb will not trip MCB. As a result using BA22d lamp holders rated at 2A is considered as OK. However some cheap imports of CFU one being Ikea are not fused and although at 6A very little problems are found at 10A to 16A it has been found when they fail they weld themselves to the bulb holder meaning the whole fitting not just bulb needs changing. As a result I would say it is better to limit to 6A MCB's and type B at that.

When ever changing a protective device one must also check the earth loop impedance to ensure if there is a fault the MCB will trip within the prescribed time. However the meters required to measure this are around the £250 so unlikely any DIY person can afford the meter.

If a PIR (Periodic inspection report) has be completed you may find the reading there. However although they are to be completed every 10 years or on change of occupant often they are not done so you will likely need to measure yourself.

Once you alter a circuit you will need to raise a minor works certificate to show all the tests have been carried out.

I hope I do not need to go further. And you will see it's not just a case of undoing a couple of screws.

Even if you ignore what I have said. Be aware often you need to slack off all the breakers on the bar and have to fiddle with the DIN rail clip to get it to release so you would need to remove the supply anyway. So may as well do it first as last.

Do insure there is some one available to call emergency services with a phone that will work without power and they have numbers to hand.
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Postby salmo » Sun Jan 03, 2010 1:28 pm

thanks ericmark will get someone else to do it cheers for youre help
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