Wiring High bay lighting

[YoungBart]

Good Morning all,
Just scratching my head a bit, Doing a bit of preliminary design for a large factory and I've come to sizing cables for the lighting, The lights are 4 x 80w These can't be changed unfortunately, They are controlled by sensors in banks of 6 giving each bank a load of around 8.4A. With the shortest circuit being around 34meters, Within high level lighting trunking. After running the details through our magic software We are getting a cable size of 6mm! Which do not connect into the light fittings. I can't change the fittings, or the locations of them etc.

In my experience on the tools I haven't really had a lot to do with wiring such a system so was wondering how they are normally wired. I didn't know whether it would be best to wire the 6mm to a marshalling box/Klik rose type system and then flex out to the light? But then was thinking that Connecting 2 x 6mm's into a such a system may be difficult.
How have you guys done this in the past?

 

[telectrix]

Or you could wire a 2.5mm rfc and spur off using click roses.

 

[YoungBart]

Cheers Tel, I'll put that info Through Our machine!, But It should work.

 

[Lucien Nunes]

4 x 80w These can't be changed unfortunately, They are controlled by sensors in banks of 6 giving each bank a load of around 8.4A

Assuming power factor of unity. Are you certain that this is the case for the existing fittings, before getting too committed to 8.4A Ib?

I'll put that info Through Our machine

What sort of machine do you need to work out voltage drop? I normally use a smoke packet.

 

[YoungBart]

Assuming power factor of unity. Are you certain that this is the case for the existing fittings, before getting too committed to 8.4A Ib?



What sort of machine do you need to work out voltage drop? I normally use a smoke packet.

My dear old mother would be most upset if I took up smoking just to work out volt drop, So I just use Hevacomp Connect software.

I'd never even considered power factor to be honest, I'll look into that!

 

[Lucien Nunes]

I'd never even considered power factor

On corrected electonic ballasts it might be very near unity, on uncorrected wirewounds the current may be 50% higher than you've allowed.

Re outsize cables, I remember designing some circuits for 120V discharge followspots in a theatre built to US wiring code. The spots were plugged into 20A NEMA outlets, but the length of the cable and low permissible drop lumbered us with 4AWG (21mm²) cable, which obviously had to be terminated in a separate box with a 14G link to the outlet.

BTW I don't smoke either.

 

[telectrix]

On corrected electonic ballasts it might be very near unity, on uncorrected wirewounds the current may be 50% higher than you've allowed.

Re outsize cables, I remember designing some circuits for 120V discharge followspots in a theatre built to US wiring code. The spots were plugged into 20A NEMA outlets, but the length of the cable and low permissible drop lumbered us with 4AWG (21mm²) cable, which obviously had to be terminated in a separate box with a 14G link to the outlet.

BTW I don't smoke either.

do you want me to send you some of my old smoke packets to do your calcs. on? you can ignore the Polish health warnings. where can you buy smokes named "eithers"?:35:

 

[Lucien Nunes]

Don't worry Tel, I've got an app for my phone. You can select between Marlboro, B&H and Silk Cut, you can do trig in either degrees or radians, ten memories, optional scientific notation and it has a special function for making little sketches of tricky conduit bends.

 

[YoungBart]

Is That the equivalent of an E cig packet?

 

[Risteard]

After running the details through our magic software We are getting a cable size of 6mm!

Have you considered the fact that apart from the first section of cable the rest won't be carrying the full current?

 

[HandySparks]

The lights are 4 x 80w These can't be changed unfortunately, They are controlled by sensors in banks of 6 giving each bank a load of around 8.4A. With the shortest circuit being around 34meters, Within high level lighting trunking. After running the details through our magic software We are getting a cable size of 6mm!

Are you saying that, even at a circuit length of 34m, you need to use 6mm²? If so, is it cable grouping that's forcing this size of cable? It can't be volt drop at this length unless you're using a very low volt drop figure?

 

[YoungBart]

Re: Wiring High bay lighting

Originally Posted by YoungBart
After running the details through our magic software We are getting a cable size of 6mm!



Have you considered the fact that apart from the first section of cable the rest won't be carrying the full current?

Yep, That's all been taken into account, it's the first section I'm referring to.

HandySparks, unfortunately we are already tight on Volt drop due to the length of incoming cable and supply to the DB feeding the lighting.

 

[Darkwood]

Just looking at your Signature YoungBart, this is a famous Einstein quote but he was unaware at the time that there is actually a fish that does climb tree's as a survival instinct when its natural water habitat drys up - Mangrove Killifish be the strange creature and means Einstein on this occasion slipped up as that so called genius fish exists

 

[YoungBart]

Just looking at your Signature YoungBart, this is a famous Einstein quote but he was unaware at the time that there is actually a fish that does climb tree's as a survival instinct when its natural water habitat drys up - Mangrove Killifish be the strange creature and means Einstein on this occasion slipped up as that so called genius fish exists

Youll be telling me next E doesn't equal mc2 :49:

 

[davesparks]

Yep, That's all been taken into account, it's the first section I'm referring to.

HandySparks, unfortunately we are already tight on Volt drop due to the length of incoming cable and supply to the DB feeding the lighting.

If the volt drop is already tight on the distribution circuit then no amount of messing around with the lighting circuit is going to cure that and you will be stuck with big cables.


But look on the bright side, at least you don't have to worry about grouping factors

 

[YoungBart]

If the volt drop is already tight on the distribution circuit then no amount of messing around with the lighting circuit is going to cure that and you will be stuck with big cables.


But look on the bright side, at least you don't have to worry about grouping factors

That's what I figured unfortunately, Just wasn't sure if there was a certain way of wiring this type of circuit, Looks like wiring as a 2.5mm Ring has sorted it.
Thanks for all the help guys.