lighting load

[johnmf]

in an industrial unit ive just rented theres 6 400watt high bay lights all fed from a 1.5mm 2 core armoured cable. i work the load out to be 10.5 amps. the protection is a 16 amp mcb type c. havent got a copy of the regs to check this out so am not sure what 1.5mm 2 core swa is rated at but i think its borderline! is this set up ok? the cable is just about impossible to change n i cant cut down on the lights but the next mcb down i believe to be 10 amp. any suggestions?

 

[Lectrician]

Load wise it's fine.

Whats the length of the run?? Volt drop may be an issue, and possibly your Zs.

I always go for 2 x 400watts on a C10, or 3/4 x 250watts on a C10. Never bother with 6amp breakers in commercial. Even C10's can trip occasionally on startup.

 

[johnmf]

cheers, thats reasurring, just thought 16amp breaker was pushing it a bit for 1.5 but suppose its only 10 amp load.

the runs about 80 mtrs at a rough guess. ya ever had any problems wi type b's nuisance tripping with this kind of light unit tho? wa thinkin just in case have to change the breakers say to get the zs.

 

[Lectrician]

1.5 pvc swa is rated to around 20amp.

80 meters is a long way for this size!

I would check the calc if I where you!

Are the lights linked one to the next, or star wired etc? Reason I ask is volt drop will be different between each fitting as you loose current each time......if you see what I mean!

 

[johnmf]

worked the volt drop out to be 17 volts with the load im pulling. believe the maximum aloud drop to be 9.2 volts????? am i right in thinking that the only effect this will have is that the lights wont work to full capability so to speak?

 

[johnmf]

the length of run was 60 mtrs incase any of you were wondering not 80! guess my first guestimation was a bit out!!!

 

[Spark123]

BTW, don't forget to multiply your load by 1.8 for discharge lighting

 

[johnmf]

so your saying the cable size is not adequate enough for whats running off it? and the issue of the voltage drop?

 

[securespark]

very dim lights....

 

[Spark123]

It depends on how they are wired, you are unlikely to have all of the loading at one end of the circuit, volt drop is worked out using design current hence as the current is not as large after the first fitting volt drop will be less per meter in this leg, ditto in the third leg and so on. I think with such a long run you may have problems with your max Zs, for a C16 breaker being 1.2ohms for a 70deg C cable measured at 20deg C.