Hello,

I have just had a quick look at a job I have been asked to test. It is a large office area that was designed by a consultant and installed to a decent standard. There is evidence of some additions - and I have noticed that the lighting circuits are 2.5 / 1.5 singles on a 16 amp type C mcb feeding 600x600 grid fittings with 4 x 14watt lamps - however, in some areas four of these fittings are connected together via a plug in and out system on a 1.00m flex - I feel this may just comply - but Im not too happy with it though.

Opinions please.

Thanks

What are your thoughts on the current rating of the switch they have used?

Regards

BOD

Probably fine from an overload point of view as the current will be limited by the load, and if Zs is OK then disconnection time should be fine. If v.d. is OK, then that just leaves the question of fault protection. From memory 1mm2 is too small for any C type MCB from an energy-let through point of view using generic MCB data, but you'd have to check the manufacturer's data for the actual MCBs in use before condemning it as theirs is usually a lot tighter than the generic standards.

- Andy.

Forgot to say - the are on ceiling sensors and these do not appear to be overloaded.

Also, the client mentioned nuisance tripping in an other area - where a similar lighting set up was supplied by a 10 amp type C mcb.

Thanks

16 lamps each of 14 watts certainly wont overload a 1.0mm flex.
Whilst in theory the let through energy of a C16 MCB might be too high, in practice it does not seem to be a problem.

No one worries about portable appliances with 1.0 or even 0.75mm flex on C16s, and this is the norm in Europe and AFAIK permitted here.

HI

I had a good look today - the 16amp type B mcb - serves an open plan area and a few small offices each with 4 light fittings in.

The only issues are that 6amp Danlers sensors have been used - the max load I measured on any circuit was 4.7amps and that from the ceiling lighting box a 1.00mm flex has been used to supply each individual fitting.

Im not sure if I have a problem or not?

so these are the 1500w load version.

has any allowance been made for the starting current of the fittings?
last time i spoke to danlersi seem to remember they stated that the 1500w was to include this criteria,so 3a[more or less] was the running load.

I don't think you have a problem as far as BS 7671 is concerned - although it's a crap design. Those 16A MCB's are there for a reason - probably inrush current - and you are putting that inductive little lot across switching contacts that are 6A rated (and probably a lot less inductivly) - BoD highlighted this above.

I suspect the initial design was fine - it's the later botching by the designer/installer that's a bit suspect.

Obvioulsy if you have a number of PIR's switching much smaller groups (as ideally you would) then ignore my comments above.

Regards

OMS

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Failure is always an option

Thank you for all the replies.


In most areas the PIRs are only switching on four fittings and in open areas 7 fittings.

Im tempted to try these circuits on a 6amp type C - As I will feel better if this is a successful solution