RCDing & 3phase help

[electricmick]

Hi, im training as an electrician at moment and got a couple of questions if you wouldnt mind helping me.

If for example you had to install a new circuit which would be radial and say calculations worked out 6mm was needed, how would you go about satisfying the RCD regs without replacing for a 17th edition consumer unit? Someone was saying about splitting tails and separate board but couldnt quite understand. Couldnt the cooker cable just pass through an RCD fused spur to an appropiate rating?

Also were doing some work on 3phase, not me obviously but the bloke im with is scared il take his job i think and doesnt let much on about whats going on, is there anything to read on internet about 3phase? I understand that it comes into the workshop in 3phases at 400v and then its split and to be efficient should be balanced, is each of these splits 230v like you get in domestic? Its like an apprentiship im doing but its more of a dogs body getting his steps and passing tools to be honest lol

Thanks, Mick

 

[Andy™]

Hi, im training as an electrician at moment and got a couple of questions if you wouldnt mind helping me. If for example you had to install a new circuit which would be radial and say calculations worked out 6mm was needed, how would you go about satisfying the RCD regs without replacing for a 17th edition consumer unit? Someone was saying about splitting tails and separate board but couldnt quite understand. Couldnt the cooker cable just pass through an RCD fused spur to an appropiate rating?for one circuit i would probably add an external RCD fed from fuse/MCB. os split the tails & install a 2nd CU for other stuff

Also were doing some work on 3phase, not me obviously but the bloke im with is scared il take his job i think and doesnt let much on about whats going on, is there anything to read on internet about 3phase? I understand that it comes into the workshop in 3phases at 400v and then its split and to be efficient should be balanced, is each of these splits 230v like you get in domestic? Its like an apprentiship im doing but its more of a dogs body getting his steps and passing tools to be honest lol

domestic supply is fed from three phase

Thanks, Mick

my red

 

[SLIPSHOD & SLAPDASH]

You could fit an RCBO in the existing board. If the cables are not buried and not for 13a sockets you may not need RCD protection.

The electricity is distributed in 3 phases. Most domestics only use one. Although officially 400v now you normally find its still 415v for 3 phase. 3 phase equipment is far more economical than if that machine was single phase. yes you should balance the phases by trying to put equal amounts of loading per phase, for example if you have 3 fluorescent lights, put one on each phase.

 

[electricmick]

what about if its got bs3036 fuses? do they do an RCBO to replace the fuse?

 

[m4tty]

what about if its got bs3036 fuses? do they do an RCBO to replace the fuse?

If it's got bs3036 fuses it would be a board upgrade or split the tails using a Henley block then new small cu with rcd mainswitch and mcb for cooker or rcbo with mainswitch.

 

[SLIPSHOD & SLAPDASH]

what about if its got bs3036 fuses? do they do an RCBO to replace the fuse?

Not that i know

 

[m4tty]

If it was for say a lighting circuit you could put one of them rcd fcus in the lighting circuit as it's under 13a. Just a thought

 

[Andy™]

If it's got bs3036 fuses it would be a board upgrade or split the tails using a Henley block then new small cu with rcd mainswitch and mcb for cooker or rcbo with mainswitch.

not always.

you can easily take a cable from fuse to an external RCD and then to circuit

 

[electricmick]

i assume you mean the main service fuse, is there enough room in there to get two tails? Also our tutor told us not to cut a seal that they have on them but everyone i spoke to says they do, can you get in trouble for cutting it?

 

[m4tty]

By external rcd do you mean one of them ones the size of a single socket. Powerbreaker?cheers

---------- AUTO MERGE Post added at 18:46 ---------- Previous post was at 18:40 ----------

what about if its got bs3036 fuses? do they do an RCBO to replace the fuse?

i assume you mean the main service fuse, is there enough room in there to get two tails? Also our tutor told us not to cut a seal that they have on them but everyone i spoke to says they do, can you get in trouble for cutting it?

Not the mainfuse mate. From the cutout to the meter then into Henley blocks (connector blocks for big cables/rated accordingly) then split to old bs3036 board and new small board for shower.

It is illegal to cut seals as it's the dnos equipment but it goes on. To get them to come out and pull fuse then put it back in when finished on every board change would be a nightmare. Plus waiting for them can take weeks and there's more costs involved with cu change.

 

[SLIPSHOD & SLAPDASH]

i assume you mean the main service fuse, is there enough room in there to get two tails? Also our tutor told us not to cut a seal that they have on them but everyone i spoke to says they do, can you get in trouble for cutting it?

Why would you want to cut one of these

Possibly a clubbing joke here but not from me

 

[electricmick]

on a 3phase would you just use one of the phases and neutral then to get the standard 230v required in domestic? Also with 3phase what happens about earthing? is it combined with the neutral or earth rod to make it a tt system or is there an outer sheath like tns?

thanks