# Tripping Circuit Breaker

#### Meblin

I have just replaced a transformer for a flexi track light with 12V halogens. The old transformer was rated at 150W and I was using 5 x 20W lamps. I fried this by changing the lamps to 50W. I have got a replacement but this is a 200W transformer and I have it loaded with 2 x 50W and 3 x 20W (total 160W).

My problem is that when I switch the light on it trips the circuit breaker, but not every time. The breaker that is on our light loop has B6 on it (so I assume this is 6A the maximum for a lighting circuit). My question is how do I stop this happening? and no I don't want to go back to the smaller power unit as it doesn't give enough light.

The Transformer has a 1.6A fuse in it if this is of any further help.

Many thanks

Meblin

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#### hammy

Meblin,

The leccy guys will probably shoot me down on this one, but
with my elementary gasp of electronics/electrical theory:-

P = V x I (power equals voltage times current)
therefore I = P / V (current equals power divided by voltage)

In your original state: the current used would be:-

I = P / V = 100watts from 5x20 bulbs divided by 12 volts = 8.33 Amps current.

In your revised state

I = P / V = 160 watts from your bulbs divided by 12 volts = 15 amps current.

Like I said i'm no electrician, but thats a significant jump in current....

I might be wrong, but at least it'll tempt some bright spark out of hiding
who'll no doubt tell me how wrong I am and supply you with the right answer!!

Regards Hammy

#### securespark

Hamster

That is the current on the secondary (SELV) side of the tranny.

Is this a dom set up?

B6 (guess it is Wylex plug-in breaker) is a 6A type B MCB.

Are there other fittings with trannies being switched on at the same time?

#### Meblin

securespark said:
Is this a dom set up?

Not sure what you mean?

securespark said:
B6 (guess it is Wylex plug-in breaker) is a 6A type B MCB.

It's a Legrand and I'm not sure that it's plug-in (we had the whole board replaced)

securespark said:
Are there other fittings with trannies being switched on at the same time

No other devices with transformers are being used on the lighting circuit. We have enegy saving lamps in most of the lights, so low Wattage useage.

I will try tomorrow to return it to the original 5 x 20W lamps and see if it still has the same problem.

Meblin

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#### Meblin

I have just spoken to a technician @ micromark (the company that manufatures the transformer) and he informed me that it needed to be modified. Unfortunatly he told me that he could not tell me because I am not a qualified electrician

I'll have to get one of the electrician at work to call them for me to find out what needs to be done.

Meblin

Here is a link to the actual transformer that I have.

#### securespark

Sorry Meb, dom short for domestic.

#### Meblin

securespark said:
Sorry Meb, dom short for domestic.

Yes it's in our kitchen

Meblin

#### Meblin

I have spoken to some of the Electrician Lecturers at work and they tell me that I need a C type breaker. Would this be suitable?

It looks bigger than the ones I have. I only see the middle section size bit on my board. is the remainder hiding under the cover?

Meblin

#### plugwash

generally the brand of the breaker should match the brand of the board

so if the board is a wylex that breaker is suitable

#### ban-all-sheds

Meblin said:
I have spoken to some of the Electrician Lecturers at work and they tell me that I need a C type breaker. Would this be suitable?
No - you've got a Legrand board, that's a Wylex breaker.

It looks bigger than the ones I have. I only see the middle section size bit on my board. is the remainder hiding under the cover?
Yup

#### Meblin

Bought a Legrand c6 MCB for just over £5 and it has sorted the problem.

Meblin

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