8ft lights

[moose man]

I was called to the offices today with the light out mcb triped when i reset

the mcb all ok but triped again when all 3 offices were put on together

cu used to be 3036 fuse all work fine board change to mcb typ

on the circuit are 8. 8ft double fittings total power is 2000W

Ib 8.6A *1.8PF =15A there is a 10Atype c mcb could this be a overload fault

not a fault current as all the circuits was tested 3weeks before all reading are fine its wired in 1.5singles thing it used to be on a 15A 3036

moose man

 

[Riggy]

Of course a 15A load will trip a 10A MCB.

The fault is with whoever changed the board!

 

[moose man]

Of course a 15A load will trip a 10A MCB.The fault is with whoever changed the board!

we had a company come in to to do the job who done the testing

would it be a good idea to split the circuits or the fittings

 

[Riggy]

Get them back to sort it is the short answer.

I'd make the split wherever's easiest to achieve getting the load below the MCB rating.

 

[NozSpark]

Would the circuit comply if you put it on a HRC fuse instead of a MCB???

 

[tom1]

Would the circuit comply if you put it on a HRC fuse instead of a MCB???

what about a 16 amp mcb?

 

[Andy™]

what about a 16 amp mcb?

circuit may not be capable of it. but a fuse may be an easier alternative, as nozspark has suggested

 

[tom1]

[quote name='Andy

 

[Andy™]

if it was a long circuit or they required a type c for the florecence, along those lines?

in some cases, a fuse of similar rating to an MCB can hae a higher Zs too

 

[kme]

I`ll apologise in advance if I`m being daft here (stella artois sampling in progress!).

I was of the impression the 1.8 multiplication factor was only applicable under startup?

Or are we actually stating that 2KW of fluorescent lighting is going to draw a sustained current of 15A?

3 offices. Lets suppose, for the sake of this thread, that the lighting is spread equally between them. Further, lets up the current from 8.6 to 9A.

If the offices are switched on individually, to my mind, by the time the third office is reached, you will have:

office 1: 3A

office 2: 3A

office 3: 5.4A at switch on; dropping back to 3A when running.

Making the maximum if started seperately 11.4A (and we rounded the figure up!)

I don`t have the curves in front of me, but I would expect the C10 to hold that.

In the O/P`s position, I`d be trying them individually.

If the circuit is not capable of being split, and cannot take a B or C16, it may be worth changing **some/all** of the tubes for 100W

KME (hard hat at the ready)

 

[SteveH37]

Might be a good time for them to replace the old 8ft fittings, getting a bit scarce now and 8ft tube prices going up all the time.

 

[PC Electrics]

An 8ft 125W fluorescent light fitting draws 175W total. Thats 125W for the tube and 50W for the electromagnetic ballast.

So your actual current on this circuit is 16 x 175 = 2800W (12A), 21A on start up if they are all started together.

You need to either split the circuit up or reduce the power comsumption.

On the latter, you could offer to convert the units to T5 tubes. There is a product that adds a convertor to the standard 8ft fitting to which you then fit 2 x T5 tubes. The light output is the same (or better) and the power consumption is reduced from 175W to 77W. Go to your local CEF and ask about their "linear convertors". Tripping problem solved and customers lighting bill reduced by 56% with a payback of about 16 months for the investment. I've fitted several myself and am about to do a local shop out with 5ft convertors. They are very good (unusually for CEF!!).

 

[moose man]

would a 16 amp be ok on a 1.5 circuit as i ask the company and thay said no

 

[Lurch]

would a 16 amp be ok on a 1.5 circuit as i ask the company and thay said no

It would depend on the circuit arrangements, but I would suspect not on a reasonable sized lighting circuit.

 

[PC Electrics]

You'll have to check how the circuit is run and the reference methods employed in the construction and then look it up in 7671.

If the circuit is clipped direct with no insulation covering, then it would be okay.

When you say "the company" who do you mean?

 

[moose man]

An 8ft 125W fluorescent light fitting draws 175W total. Thats 125W for the tube and 50W for the electromagnetic ballast.So your actual current on this circuit is 16 x 175 = 2800W (12A), 21A on start up if they are all started together.

You need to either split the circuit up or reduce the power comsumption.

On the latter, you could offer to convert the units to T5 tubes. There is a product that adds a convertor to the standard 8ft fitting to which you then fit 2 x T5 tubes. The light output is the same (or better) and the power consumption is reduced from 175W to 77W. Go to your local CEF and ask about their "linear convertors". Tripping problem solved and customers lighting bill reduced by 56% with a payback of about 16 months for the investment. I've fitted several myself and am about to do a local shop out with 5ft convertors. They are very good (unusually for CEF!!).

thay are all double fittings would it reduce the load by fitting 6ft HF fittings

 

[moose man]

it runs in 3*3 trunking with with about 5 other circuits

 

[Andy™]

would a 16 amp be ok on a 1.5 circuit as i ask the company and thay said no

maybe. depends on cable length etc. look in OSG - there are tables with max length for various cable CSA & MCB type.