24 x 400w metal halides advice

[solo2771]

Hi all,
just a quicky, I have to quote for a job lighting a large grain store 5000 square feet.
due to the layout of the store i am thinking 24 x 400w (max) metal halide low and high bays.
supply to the building is 3 phase.
i was thinking of dividing over the 3 phases 8 each controlled by 1 switch via contactor.
I am thinking of using swa clipped direct to the columbs to jbs above each lamp. lights are between about 16 ft and 30 ft high. Owner has offered use of fork lift.
Does this all sound about right?
and also i am fishing for a price to charge him as i never seem to charge enough (clients have said).
any help much appreciated.

 

[ghost]

It is difficult to advise on pricing without looking at the job.
Are you planning on working off the fork lift? I think I would rather be pricing the job with a MEWP for safety reasons.
Obviously without seeing the job it is difficult to offer a lot of advice.

 

[Mr Mark Sparks]

watch your loadings 8x400 3200w/14amps but its even more than that with discharge lamps i suspect someone will tell us the correction factor for these

 

[solo2771]

yeah 8 x 400 is max 1/2 will be 250w. will be on 2.5mm and 20A breaker

 

[Darkwood]

A little advice here you need to know, decide what mcb brand your installing then get product book for the tech' info in the back, it should tell you what max load is when using metal halide on each size mcb. If you dont get this info you will end up with nuisance tripping and a large bill to rectify, you will be supprised how few light can go on each mcb most sparkies assume weighing up the load inclusive off inductive correction factors is the way of choosing the rating of mcb,s but this is not the case as inrush of multiple fitting needs to be accounted for when picking the size.
More than likely you will find you have to increase cable size to compensate the larger mcb's needed.
This is also the case when picking contactors, switching devices of any nature etc and once youve dont this a few times you,ll find the tech sections in the product books indispensible as they do all types of lighting, motors, transformers etc.

 

[pennywise]

Might be an idea to put each individual light on a industrial klik rose or 13amp point so you can disconnect the fitting during maintenance and still keep the rest of the lights on etc.

 

[Guest123]

Hi

An additional factor of 1.8 is required for discharge lighting, i.e - (3200 x 1.8)/230 = 25A.

 

[Darkwood]

If it is possible to switch individual rows then you will have to wire 3 circuits balanced over the phases per row this stops large phase imbalance if all rows are not on or if a row trips with fault etc, the balance is still maintained in most circumstances this way.

 

[ian.settle1]

Check that you will not need explosive proof fittings, a grain store can be a very dusty atmosphere which is highly explosive.

 

[Darkwood]

Check that you will not need explosive proof fittings, a grain store can be a very dusty atmosphere which is highly explosive.

Good point made. Hope we dont scare this guy off.

 

[sparky paul]

16A is the maximum you can have on a lighting circuit under the 17th

 

[Sintra]

What about a 3 phase busbar system.

Fittings will have individual fuse protection via tap offs and phases can be alternated to suit.

Lighting busbar trunking, Busbars, Plugin busbar systems, feeder busbar system, Conductors, sliprings, cable reeling drums

 

[solo2771]

just got all replies, glad i had bottle of red or might be a bit worried lol
it is no longer a grain store (going to be an engineering workshop)
where does the 1.8 come from?
and also 16 amp lighting, what if they all plug in as another poster said does this still apply?

 

[Guest123]

where does the 1.8 come from?

Basically the 1.8 factor is to allow for the inductive nature of the load, the control gear needed to start the lamp (chokes, ballasts, auto-transformers etc) and also the power factor correction capacitors.

By multiplying the total load of the lamp by 1.8 then you are allowing for the effect of all the above on the circuit.

 

[sparks1234]

Do yourself a favour and wire it in FP200 or equivelent. If you need some mechanical protection on the vertical rise put it in some conduit. It is so much quicker than SWA,
Straight into beza boxes with stuffing glands.
The cost of a scissor lift will pay for itself, just drive along, girder clipping the cables, tek screw the beza boxes, hang the lights and plug in, get your lad to make them up on the ground. job done

You could easily get the high level work done in a day. we have installed bundles of these and tried all methods and this is by far the easiest / quickest

 

[solo2771]

why fp 200?

 

[sparks1234]

why fp 200?

Some use T & E which I am not really in favour of up there but there is no reason why not. FP does clip down and sits nicely. Either way it is a lot easier than SWA

 

[Darkwood]

16A is the maximum you can have on a lighting circuit under the 17th

What if each light is fused down through a connection unit?

 

[pennywise]

Hi tuff all the way.

 

[Darkwood]

Checked the SQ-D mcb tech' section, if you have a 16A (D) then the max is 4 * 400w metal halides.
All the mcb brands usually sing a similar tune, making this a type (c) or (b), increasing the no' of lamps or decreasing the mcb rating will all make you prone to nuisance tripping on start up.Note using to type (d) will limit your allowable ELI dramatically so take this into account when running long runs.

 

[solo2771]

Checked the SQ-D mcb tech' section, if you have a 16A (D) then the max is 4 * 400w metal halides.
All the mcb brands usually sing a similar tune, making this a type (c) or (b), increasing the no' of lamps or decreasing the mcb rating will all make you prone to nuisance tripping on start up.Note using to type (d) will limit your allowable ELI dramatically so take this into account when running long runs.

so 8 x 250 W on a 20 should be about the max, Still don't fancy all that conduit work

 

[Darkwood]

so 8 x 250 W on a 20 should be about the max, Still don't fancy all that conduit work

It doesnt calculate like that its what the mcb's inrush can withstand with multiple inductives loads and this doesn't calculate uniformly thats why you need to pick your method then refer to the tech on your brand of mcb.
Ive followed so many sparkies who think 1.8 factor applies when working out mcb rating and type on inductive loads and this is not the case, then they scratch their heads when the get a call about mcb's tripping when lights switched on.
College dont touch on this subject and i believe they should. Well they didnt in my days.

 

[sparks1234]

I have always put mine on C type breakers and never had a problem