Do I re rate mcb

[ih]

Hi
I have replaced all my halogen + other lights with led gu10.I added up all the bulbs & get total of 1091 watts.
(I am novice with electrics) my current MCB is 10amps
1.Am I right to convert 1091÷230=4.75 amps so need to replace MCB with 6amps if my conversion
is incorrect kindly advise the formula.
p.s.the cabling is mixture of 1.0 & 1.5 (reasons unknown to me)
2.Does the cabling have any bearing on MCB?
thanking in advance

 

[theprinceofdarkness]

The MCB is there to protect the cabling. Take a silly example :- If you some how connected a fan heater into a lighting circuit, so you are taking 10A through a 5A cable, the heater would work but the cable would overheat and potentially catch fire. So you put a 5A MCB in the way that would trip and save the cable (and your house). The equipment should have its own internal protection.
Frank

 

[ericmark]

In the main lighting should have a 6A MCB not because of the cable or any rules on lighting but because the standard ceiling rose which acts as a junction box with lighting is rated at either 5 or 6 amp. Also if a bulb goes faulty the holders are only rated at 2 amp in theroy there should be a fuse built into the bulb but from bitter experience this is not always the case. With a B6 MCB in the main the trip will operate before there is any damage to a holder, but with a B16 although still within the regulation the bulb contacts can weld themselves to the holder so both bulb and holder needs changing.

So in theroy if no ceiling roses used, you can use the B10 MCB fitted, but in practice better to fit a B6.

 

[Taylortwocities]

On a good day, and in ideal conditions, 1mm² cable is good for 14amps. 1.5mm² much more.

As Frank says, the MCB is there to protect the cable. It is fine as it is, leave it alone and stop worrying.


As an aside. I am wondering how you got to this figure

I have replaced all my halogen + other lights with led gu10.I added up all the bulbs & get total of 1091 watts

Even assuming each of your LEDs is 10 watts (they will be less than that) you would have 100 lights in your house.

100 lights, in one house?

 

[Taylortwocities]

So in theroy if no ceiling roses used, you can use the B10 MCB fitted, but in practice better to fit a B6.

True for GLS lamps, but these are all LED lamps now.

 

[ericmark]

The lamp which caused me all the problems was a very small one I think about 8W CFL from Ikea which is why I will not buy lamps from Ikea now. When it went it welded to contacts and this resulted in the outside light it was used with being rendered useless. It was my fault I should have know better than using a B16 MCB for a lamp. Although the built in fuse for GLS lamps was in case when they failed the gas in the bulb was ionised it really makes no difference most lamps will have diodes and other components which can fail and cause short circuits so having a small MCB will in the main stop them welding onto contacts if this should happen.

 

[JohnW2]

.... When it went it welded to contacts and this resulted in the outside light it was used with being rendered useless. It was my fault I should have know better than using a B16 MCB for a lamp. ...

You've told that story a number of times before, but, to be honest, I rather doubt that the outcome would have been any different had it been a B6 MCB - the sort of current we're presumably talking about would probably have tripped a B16 almost as quickly as a B6.

Kind Regards, John

 

[ih]

TTC
FYI besides other lights the house had 56 MR16 halogen which are now gu10 led lights on 240v(each with 6w bulb)

 

[ban-all-sheds]

56!

No doubt some people will see that and still think that lights like that are obviously designed for the job of lighting up rooms.

But anyway - 56 x 6 = 336W, so there's another 755W to account for. Another 125 6W lamps somewhere?

Does the house only have 1 lighting circuit? What wattage were the old halogens?

 

[winston1]

1.Am I right to convert 1091÷230=4.75 amps so need to replace MCB with 6amps if my conversion
is incorrect kindly advise the formula.

No. Typical LED lamps have a power factor around 0.65.

So your formula would be 1091/(240 x 0.65)=7amps.

 

[ih]

Apologies! the old halogen were 50w. figure of 1091 is incorrect .The correct figure is 671 this includes
outside pirlight .(my wife was adding up on calculator & got MR function wrong.
kindly note all the lights are on One circuit.
conclusion with the formula given by Winston 1 & if my maths is correct the new figure
should be 4.6amps equals MCB 6amps
thanking all

 

[JohnW2]

Apologies! the old halogen were 50w. figure of 1091 is incorrect .The correct figure is 671 this includes outside pirlight .(my wife was adding up on calculator & got MR function wrong.

I am trying to make the numbers add up. You said that you have 56 x 6W LEDs, which is 336W. Are you saying that outside PIR light amounts to 335W, to bring the total to 671W?

Kind Regards, John

 

[ih]

John
some LEDs are 5w some are 6w.to be added 3 bedroom+ 3floresent in loft+landing+passage +meter
cupboard+porch.outside pir is 120w. (not led)

 

[Taylortwocities]

Whatever the total eventually is, as had been said before, the MCB is there to protect the cable.
Otherwise everybody would be swopping MCBs everytime a new appliance was added or removed from a circuit.
If it is 10A then it is fine, leave it alone.