Low bay lights

[Jimmyb]

hi all, can someone please help as i anit 100% sure not really done any commercial work on my own before,
i im putting some lights up on a small barn for outside lighting, 2 x 250w HID Metal Halide lights (see link) im just think i will still require a plastic cover for the bulb even though it says no safety glass required im I right

Im i reading it right, does this require 2.9A for startup (2.7x250w not 1.8x250w), it just seemed a lot but i have work with these before so would really like some guidance/info.

also would i use the 1350w or 900w for voltdrop calc.

many thanks

 

[Guest123]

Hi there.

The load of each lamp needs to be multiplied by 1.8 as they are discharge lamps.

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.

A little confused by the volt drop querie???? depends on the type of cable, protective device and length of run.

Cheers.

 

[Jimmyb]

Hi there.

The load of each lamp needs to be multiplied by 1.8 as they are discharge lamps.

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.

A little confused by the volt drop querie???? depends on the type of cable, protective device and length of run.

Cheers.

it just confused me when they say the lamps are rated at 2.9 but there only 250w and 250x1.8/230 doesnt equal 2.9a it about 1.95a.

with voltdrop do i use the firgue after ive x1.8 or is it the same as motors and allowed a big voltdrop on startup so rating of lamp (1.09a)

many thanks

 

[Guest123]

Ok

Volt Drop = (mV/A/M) x Ib x L / 1000

mV/A/M for your cable, from Appendix 4 of BS 7671
Ib = rating of fuse / circuit breaker
L = length of run.

 

[Jimmyb]

Ok

Volt Drop = (mV/A/M) x Ib x L / 1000

mV/A/M for your cable, from Appendix 4 of BS 7671
Ib = rating of fuse / circuit breaker
L = length of run.

what about design current, Ive always used that not the rating of the fuse im i missing something ?

 

[Guest123]

Yes that is fine.

I always tend to use the breaker rating for lighting as a worst case scenario to make sure what I'm installing will be ok if I need to add / extend in the future.

 

[crazyelec]

hi all, can someone please help as i anit 100% sure not really done any commercial work on my own before,
i im putting some lights up on a small barn for outside lighting, 2 x 250w HID Metal Halide lights (see link) im just think i will still require a plastic cover for the bulb even though it says no safety glass required im I right

Im i reading it right, does this require 2.9A for startup (2.7x250w not 1.8x250w), it just seemed a lot but i have work with these before so would really like some guidance/info.

also would i use the 1350w or 900w for voltdrop calc.

many thanks

we've just put up 5 x 400w low bays in a factory to find the start up current was 28.9amp. it dropped to 14.8 running, luckily a C16 held in but could hear it trying clicking trying to trip.

 

[Frenchsparky]

I know it may confuse some of you a little but bear with me due I am well verised with both Americian and French ballast on the HIDs.

Anyway what type of ballast you are using due I noticed that you have starting current higher than running amps if that correct that is reactor ballast some case I know you may called " choke " ballast

Typically I am not crazy with reactor ballast IMO it ok for most light duty useage but for myself I used CWA { constant wattage autotransfomer } ballast the starting current is much lower than running current levels is.

The other thing about the " Choke " or reactor ballast that they are pretty senstive with voltage dip if the system voltage dip down to something like 80% of line voltage the HID lamp go out while the CWA will not affect until you get pretty serious voltage drop like almost low as 55% of line voltage before it will drop out { arc out }

The last question I will ask you UK sparkys what is the most common HID ballast manufacter you have in your area ?

I know in USA have half dozen manufacter but the most common one is Advance ballast company

In France it will varies a bit. { Yes I can get European spec of Advance ballast }

Thanks for your time

Merci,Marc