3 Phase Advice

[GarryT]

Hi All

I haven't done any 3 Phase work for some time but I have just been asked to wire up a new woodworking workshop.

There will be 6 - 7, 3 pahse machines all ballanced load machines (4 pin plugs, 3 ph & e)

3 - 4 single phase machines, 2 x 32A ring socket cicuits and a couple of lighting circuits

The main incomer (35mm SWA) is protected back at the mains board by a 100A 100mA ELCB.

I need to install a new 3 phase board in the workshop (any recommendations for a good board?)

I know all sockets up to 32A require RCD protection now, so do I install a mains incomming 4 pole RCD in the new board (I know with this if anything tripped he would loose everything!), separate RCD's to all the 3 phase sockets (expensive, also I can ony find 4 pole rcds so I would need to spec a much bigger board & how would they work on a balanced 3 phase load with no neutral?), or can I hardwire all the 3 phase machines in to avoid fitting RCD's to all the circuits? and just fit rcbo's to socket and lighting ciruits and possibly the single phase machines and then would you keep the 4 pole RCD incomer?

Thanks
Garry

 

[LewisM]

Use a 100ma main switch then 30ma for sockets etc and use the commando sockets with a 30ma

 

[DefyG]

The main incomer (35mm SWA) is protected back at the mains board by a 100A 100mA ELCB.

I need to install a new 3 phase board in the workshop (any recommendations for a good board?)

I know all sockets up to 32A require RCD protection now, so do I install a mains incomming 4 pole RCD in the new board (I know with this if anything tripped he would loose everything!), separate RCD's to all the 3 phase sockets (expensive, also I can ony find 4 pole rcds so I would need to spec a much bigger board & how would they work on a balanced 3 phase load with no neutral?), or can I hardwire all the 3 phase machines in to avoid fitting RCD's to all the circuits? and just fit rcbo's to socket and lighting ciruits and possibly the single phase machines and then would you keep the 4 pole RCD incomer?

Why is there a RCD at the source, is it a TT earthing system?
What is the wiring system, why RCD for lights?
Doubt RCD's are needed for machines

 

[GarryT]

Why is there a RCD at the source, is it a TT earthing system?
What is the wiring system, why RCD for lights?
Doubt RCD's are needed for machines

Yes mains is TT System, No RCD's for machines even if through a socket?

 

[DefyG]

Best change main RCD to S type then.
RCD required on socket if upto 32A

 

[pc1966]

On TT you really have little choice but to have a delay (S-type) RCD as an incomer otherwise you won't disconnect on a earth fault. 100mA is fine, some cases you might go for 300mA.

Hard-wire the machines if you can, avoids the RCD need and unless they are really likely to move all you need is a local isolator switch for safe maintenance.

For the single phase stuff you can probably put in one or two RCBO for a ring and/or the odd radial. Again if it is fixed position then hard-wire and no RCD needed, but you might just find it easy to put small stuff on 13A plugs.

Ideally the RCBO would be double-pole so a N-E fault won't trip the incomer, but that is unusual to find for a TPN board. Given any risk of faults taking out the lights while machines are running I would put in at least one or two with emergency battery back-up built in (or from a even a power cut).

I don't do this commercially so can't really say much beyond I found the Hager boards to be fine, and they have matching DIN enclosures for anything fancy you need to add. Schneider also are well regarded.