Discuss Single & 3 Phase Wiring in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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K

Kevonius

Hello
I wondered if you could help?
I’m only domestic installer and have been asked aboutthe following
There is a 3 phase 200A metered supply into a factory unit.From the meter it goes straight into a pull handle isolator with fuses for eachphase (old Colours). All wiring from that point has been removed.
Some offices are being built inside the unit and need to be suppliedwith single phase power like within a domestic property with the following
1 x Ring MainOffice
1 x RingMain Kitchen/Hallway/meeting room (no Oven)
1 x Lightcircuit (Fluorescence)
1 x Lightcircuit (Security)
1 x AlarmCircuit
1 x Radial Circuit(Hand Driers)
1 x RadialCCTV

Then theyneed 3 Phase power to the workshop(not all M/C running at the same time)
3 x 64A Pointsfor M/C
6 x 32A Pointsfor M/C
5 x 16A Pointsfor M/C
8 x Doublesockets (220V)

My questionis should I use a 17[SUP]th[/SUP] Edition Consumer unit for the office area takenfrom 1 of the phases or should I use a 3 phase consumer unit to balance thephases?

I haveminimal 3 phase experience, so not sure what to do on the 3 phase side, can Iuse a high current carrying capacity cable for each phase + N & E (like aradial circuit) & drop this to each of the 14 x 3 phase points around theworkshop and fit breakers at these points (this means they would be in serieslike spurs) or put the breakers on a ring main type circuit with a 100A breakerat the CCU

Thanks foryour help
 
Hi mate. I know that no one likes turning away work, but I think with your knowledge of industrial work minimal then it would be advisable to maybe get someone else to help you out that has done this type of work before
 
I know what you mean!
Its just that it is for a friend. I can do the wiring just need some help on the circuit designs.

Thanks for replying
 
As its from scratch i would take a submains 3ph to offices and balance as best, it allows for future expansion like a 'no oven' you mentioned, query the no' of computers and decide whether a fuctional earth system needed on that ring, treat the circuits as individual 1ph in the offices, any light switch where you have 400v within will need to be marked with a warning 400v label and any other points like sockets within arms reach of each other but over different phases will need marking too.
As for the factory design it depends what machines been plugged in and there loading as to how the wiring is done, but usually supply all 3ph as radial points from a large 200amp 3phase dist' board, if you fit a 200amp busbar off incoming isolator you can then run 3ph to offices easily of hrc fuses maintaining discrimination and allows for further expansion, even the 63amp outlets run through sw/fused isolator off the busbar too.
Ps just a guide not a direction how to do it all.
 
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as a bove^^^ . and each 3 phase machine point should be in its own dedicated circuit for starters. honestly think that if you want this work, you need someone with more 3 phase experience to assist (share the job type of thing)
 
Mate you better get your :army: on , cause i think you are going to draw some fire on this one !
Good luck .
 
Ps as with others it is a steep learning curve to take on all at once, a knowledge of the machines your plugging in too may be needed for the sizing of mcb types thus affecting cable size, unless you been requested 63amp point only and other have worked out the machine requirements id work them to a type c mcb, but good advice to pull onboard someone with experience, sub them in explain and learn while you work ;)
Subbing in wont get you reaping in all the rewards but the experience is invaluable
 
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Thanks
Not sure of the loading on the machines, I would have to find that out, I know that it is only a refurbishment factory so the machines are only run for testing & demo purposes, so I suppose I really need 1 radial circiut for each point? Large distribution board!
 
Ive Pm'd you regards to the calculations etc if you need a hand sorting it out. :)
 
your 3 x 63amps and office board fed off busbar through fused isolators, 18way 3phase board with front end mccb 160amp main switch should do the job nicely, but lacking info as you haven't mentioned factory lighting, heating etc etc ..... dont be scared of big boards they like small boards just bigger :)
Talk to client about future plans if they plan on expanding then fit 400amp busbar then a supply upgrade is all thats needed no additional work in that area, its like a future proof safe guard.
 
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Oh dear lord. Electrical Trainee?

My thoughts exactly!!

Look, you have minimal training and experience, so if you want to help a mate out, at the very least, get another qualified and experienced electrician in to help you with this installation. That way, you will not only be helping your mate, but also yourself by learning a little bit more, about real electrical installations.

3 Phase installations aren't rocket science, but you really do need to know what your doing, ...more importantly the whys of what your doing!!!
 
No brainer, TP DB, 63A feed for CU, M/cs feed direct from TP DB, jobs a gud un

With respect i would have to disagree with you here, a onsite meeting with regards to the machinery side, will welders be used??? etc, or has machinery get a high inertial load, long start up current... this will all change the nature of the 63amp supplies requested. If it is deemed necessary to allow for any of the above then type D mcb would be required and it becomes unlikely on a 200amp supply that ZS could be met. To also note sub-ing a mains from a 63mcb will only give a small partial discrimination to the lower rated office breakers, so i would not run an office with possible computers and maybe a server, alarms etc from a 63amp mcb but an hrc fuse set instead, it would be better having a greater partial discrimination to reduce the threat of a fault tripping the supply mcb. Thus the busbar with dedicated isolators for the office and big 63amp outlets would be good design and more flexible.
 
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With respect i would have to disagree with you here, a onsite meeting with regards to the machinery side, will welders be used??? etc, or has machinery get a high inertial load, long start up current... this will all change the nature of the 63amp supplies requested. If it is deemed necessary to allow for any of the above then type D mcb would be required and it becomes unlikely on a 200amp supply that ZS could be met. To also note sub-ing a mains from a 63mcb will only give a small partial discrimination to the lower rated office breakers, so i would not run an office with possible computers and maybe a server, alarms etc from a 63amp mcb, it would be better having a greater partial discrimination to reduce the threat of a fault tripping the supply mcb. Thus the busbar with dedicated isolators for the office and big 63amp outlets would be good design and more flexible.

Actually agree with you - was being a little tongue in cheek just coming back from pub, would still run the cu on a SP63, probably radials for sockets. We dont know the size of the building so his 63A M/C runs obviously need to be short. End of the day, the guys got no chance - we know that... it needs a proper design. Onto the next.............
 
Gawd isn't it funny...........I was trained underground on 3 phase systems for 15yr and have been an Industrial spark since those days for another 21year and find it all pretty straight forward ( still learning though) and yet I had to ask a mate of mine the proper way of putting a fan in my bathroom lol:frown2:
 

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