400 Watt Security Lights Problem

[SFT223]

Hi everyone,

I wired a pair of 400 Watt security Lights (Master/Slave) to an existing, but not working, single 400 Watt security light connection last weekend and everything worked fine when testing and setting up. However, the property owner has just told me that when they get home from work, the circuit breaker has tripped requiring them to reset it.

I asked whether they always get home in the dark, which will obviously switch the security lights on. But apparently this problem has occurred even when they get home in daylight hours. They say that they didn't have any issues prior to my installation, so naturally I must have done something wrong!

The circuit breaker is rated at 6 amps and only covers the downstairs lighting, so should be just about fine when including the security lights as well. But I don't understand why it should trip during the day as well, when the security lights aren't even drawing any power.

Is it just a case of fitting a bigger breaker, or could something else be the obvious problem?

Thanks for your help.

Steve

 

[Marvo]

You can only install a larger MCB if the cable sizes used on the downstairs lighting circuit are large enough to allow it. Rather test the entire circuit first and check the load current with a clamp meter.

 

[SFT223]

You can only install a larger MCB if the cable sizes used on the downstairs lighting circuit are large enough to allow it. Rather test the entire circuit first and check the load current with a clamp meter.

Thanks Marvo,

I forgot to say in my OP that I installed 2.5mm T&E, rather than use standard 1.0mm or 1.5mm T&E. But that's only because I prefer 2.5mm T&E on anything outside a house.

Steve

 

[Spoon]

Does the consumer unit have an RCD?

 

[BlueToBits]

The cold resistance of the two 400W TH lamps may be causing enough in-rush to trip a type B MCB.
If the circuit is RCD protected it should be possible to fit a type C breaker. A better solution would be to fit lower wattage or low energy lamps. Is 800W of TH light really needed?

 

[SFT223]

Does the consumer unit have an RCD?

Sorry for the delay in getting back Spoon, but I've only been able to get back into the property this morning. Yes the consumer unit does have an RCD and the consumer unit and all components are Wylex manufacture. The circuit breaker is a NSB6, which I presume is a 6 amp?

Steve

 

[SFT223]

The cold resistance of the two 400W TH lamps may be causing enough in-rush to trip a type B MCB.
If the circuit is RCD protected it should be possible to fit a type C breaker. A better solution would be to fit lower wattage or low energy lamps. Is 800W of TH light really needed?

Sorry for the delay in getting back BlueToBits, but I've only been able to get back into the property this morning. Yes the consumer unit does have an RCD and the consumer unit and all components are Wylex manufacture. The circuit breaker is a NSB6, which I presume is a 6 amp?

Excuse my ignorance, but what is the advantage of a type C breaker over a type B? Oh and in response to your question about is 800W necessary, the answer is yes, due to cost of purchasing in stock clearance sale at Screwfix and the fact that one light covers the rear of the property, with the other covering the side and driveway.

Steve

 

[telectrix]

if it's tripping in daytime, then it's not inrush current of the lamps, as they don't com on. answer is to clamp the circuit and get customer to walk the PIR and see what current is being drawn, or if it trips.

 

[Deleted member 9648]

Before doing anything else I would suggest an IR test of the circuit is required,and an RCD test to check the RCD is functional.It may be that there is an earth fault and the RCD is inoperative causing the MCB to trip. Terminating 2.5mm cables into lighting terminations is tight at best,and you may have caused an earth fault somewhere.
Type C mcb's are less sensitive than type B's to inrush currents,and are often used where motors or transformers cause tripping on energising.However you cant just swap without first testing that the different mcb will still meet disconnection times.

 

[SFT223]

Thanks to everyone who contributed to this post. I swapped the breaker over to a type C, which some of you had suggested correctly that this would be less sensitive and all now appears to be functioning correctly.

When pressed, the property owner confirmed that the problem HAD only occurred after the lights had come on upon returning home from work (light sensor was a little too sensitive and went off, even when there was only a little daylight!). Therefore, this definitely made the breaker the most obvious item to concentrate on.

Pleased to report that problem now sorted!

Steve