Increasing the wattage on a lighting circuit

[miki]

Hope someone can answer my questions?
My consumer unit has a 5amp MCB for the lighting circuit.
I am adding some low voltage downlighters which means the total wattage will be just over 1400w, for the whole house. For some reason, both upstairs and downstairs are running off one 5amp fuse. I may need to change this so that they have their own fuses, but could i get away with it by added a bigger fuse? I may need to split the circuit anyways.

Thanks.
M.

 

[plugwash]

5A mcb that sounds old

you could use a 6A mcb if you can get one for your board or are planning to replace the board

you can use a 10A mcb on a lighting cuircuit but the cuircuit must be designed for it (10A switches 1.5mm cable) so it's not really something you can retrofit

failing that you have a few options

1: split the lighting cuircuits
2: put the new downlighters on a 3A fused spur from the ring
3: put the new downlighters on thier own cuircuit from the CU

option 2 seems the easiest soloution especially if theese are light positions (as apposed to a replacement job)and would be needing a new switch anyway

if you do go with option 2 though remember to use 2.5mm from the socket on the ring to the fcu

 

[Big_Spark]

There is nothing to say you cannot run both upstairs and downstairs lights from one protective device so long as the circuit still complies with all other Regulations.

However, splitting the upstairs and downstairs lights is considered to be a "good installation design" and should be done wherever possible.

If it is a case of two seperate circuits sharing a common protective device, the solution is easy in that they can be sperated in the board and put on their own device.

If, however, the circuit was wired as one, then it is a little more complicated, a lot will depend on exactly how the circuit has been wired originally.

1400W via a 5A MCB is too much, you could, as a temporary solution up the breaker to a 10A, but it should not go higher than that for lighting.

 

[miki]

Thanks guys, lots of options to think about.
M.

 

[ZenStalinist]

Wait... is it your whole house that adds up to 1400 watts? If so, then I somehow doubt you'll have all of the lights on at once!

 

[plugwash]

i'm sure it's happened in this house before

i would stroungly advise against uprating the breaker on an existing cuircuit and i think either split the cuircuicits if it's easy if not then put the new lights on a fcu from the ring

 

[Big_Spark]

i would stroungly advise against uprating the breaker on an existing cuircuit and i think either split the cuircuicits if it's easy if not then put the new lights on a fcu from the ring

Plug, there will be no danger to upping the MCB from 5A to 10A for a lighting circuit, even 1.0mm(though recently downrated like a lot of cables) can still safely handle 11A as a single phase lowest potential maximum rating.