3 phase factory lighting

[nickblake]

Fuses sound a good idea to prevent loosing all the lights , what still concerns me is the amount of lights per mcb 10 thats alot of load as you can see from previouse message .on drawing its a B6 , i am correct is saying 250 watt each or am i mistaken and they are son / MH . I take it you mean a 50amp MCB dont get mixed up with isolator and MCB , MCB's dont like being used as switches , so you could always use a switch fuse say 63 amp switch fuse and derate the fuses accoring to your loadings then you can protect the circuit and isolate as well ,instead of using an MCB for isolation

 

[pmac10]

bal, cant see your diagram mate, but wouldnt bother fusing neutral as it provides a safe current return path for imbalanced loads. if the fault doesnt blow a fuse on the way in, its not likely to blow one on the way out having done work

 

[mogga]

on street lighting circuits we had problems when running anymore than 6 no400w son t fittings if one went faulty it would take out the mcb rather than the fuse in the fitting due to the additional fault time req for fuse against mcb


ie 400wx1.8 /230v = 3.14a per fitting 5 per curcuit =15.6a each fused @ 10A the mcb trips taking them all out as nick says

 

[bal]

Fuses sound a good idea to prevent loosing all the lights , what still concerns me is the amount of lights per mcb 10 thats alot of load as you can see from previouse message .on drawing its a B6 , i am correct is saying 250 watt each or am i mistaken and they are son / MH . I take it you mean a 50amp MCB dont get mixed up with isolator and MCB , MCB's dont like being used as switches , so you could always use a switch fuse say 63 amp switch fuse and derate the fuses accoring to your loadings then you can protect the circuit and isolate as well ,instead of using an MCB for isolation

Thanks for the pointers Nick - on further investigation the lights are mercury vapor 250w single phase.

I'm thinking of changing the MCB's from B to C rated and increasing the supply to the whole box (see reply to Mogga below- "you reckon I should up the whole supply?? ie 60amp feed, C30 MCB to 30A contactor to C10 MCB's to lights to cover any current surges".

Good idea about the switch fuses, I didnt know that MCB's dont like being used as isolators - can you recommend a manufacturer??

Thanks for all your input.

regards

 

[bal]

bal, cant see your diagram mate, but wouldnt bother fusing neutral as it provides a safe current return path for imbalanced loads. if the fault doesnt blow a fuse on the way in, its not likely to blow one on the way out having done work

As per Nickblakes suggestion - I'm going to install switch fuses, understand your suggestion about not having to fuse the neutral - thanks for the suggestion, I'll change my scheme.

regards

 

[bal]

on street lighting circuits we had problems when running anymore than 6 no400w son t fittings if one went faulty it would take out the mcb rather than the fuse in the fitting due to the additional fault time req for fuse against mcb


ie 400wx1.8 /230v = 3.14a per fitting 5 per curcuit =15.6a each fused @ 10A the mcb trips taking them all out as nick says

Mogga, I've change the configuration to utilise C rated MCB's, also reduced the lights to 9 x 250w per contactor which would now be 3 pole. Thats 3 lights on a radial per pole of contactor. The 3 light radial 250wx1.8/230v=1.95a - 3 fittings per circuit=5.86A.

I take your point - you reckon I should up the whole supply?? ie 60amp feed, C30 MCB to 30A contactor to C10 MCB's to lights??

regards

 

[nickblake]

MCBs are designed for protecting the circuits yes they are designed to handle inrush depending on type but the contacts arent designed to switch on that load imagin the arch when contact is made changed many MCB's due to worn contacts , Square D ,Proteus , Crabtree , Merlin gerin or MEM ,

When you add all the lights together its quite a load you could you's a 32 amp switch fuse , and just de rate the fuses , noe you have reduce the quantity of lights per contactor the 25 amp is well adiquate