Back to the well on electrics again!
I'm in the process of sorting out a purchasing list for the bits to wire my one man workshop. I've an electrician lined up to check it all out before connecting up, but he's on holidays and so i've a few questions i'd appreciate some help with bottoming out in the meantime.
The most basic ones relate to consumer unit, MCBs, RCD, circuits and isolator arrangements. The shop has an existing RCD and MCB equipped 8way consumer unit (CU), but given the need to supply most of my machines and the inverter driving the dust system fan directly (3 and 4Kw single phase) i'll need more ways/circuits than it can support.
Plus i'd like to be able to shut down all power in the shop (i.e. machine supplies and 13A sockets but not lights and alarms) on a single switch, while leaving the laundry room (under the same roof), lights and alarms fed from the original CU so that they stay on at all times.
To minimise wiring I'm thinking in terms of leaving the existing CU in situ to feed everything that does not require to be isolated as listed above. I thought then that i could take a spur from the feed to it to feed a new CU (to be placed directly below it) with its own RCD and MCBs. Putting the feed through a 65A isolating switch (the CU will have an isolator, but they are not i think meant for everyday use?) would make it possible to isolate the new CU.
The questions coming to mind are:
1. Is this general arrangement OK in principle?
2. How should the incoming feed to the existing CU be tapped into, and is this OK to do? What sort of junction box? The existing incoming cable is armoured, runs up the wall to the CU in a small galvanised steel duct, and has an OD of about 12mm.
3. Will a correctly sized MCB adequately protect the 4kW Yaskawa single to 3 phase inverter driving the dust system fan, or should i also fit the fast acting 80A class T fuse suggested in the manual? (actual max output by the book is only 21A - the ramp function will minimise start up current)
4. Will the inverter or any of the other typical loads in the shop cause problems with MCBs or the RCD? (i.e. are they suited, or do i need a split type e.g. some channels without RCD protection?)
5. Will a suitable CU be in any ways special?
6. The plan is to use 32A wall sockets on dedicated circuits for the larger machine supplies. (all > 13A, some > 16A) They have their own on/off switches. Do i need to use a wall mounted isolating switch as well?
Some incidentals:
6. Any thoughts on using flex vs. the solid conductor grey cable for misc. fixed wiring?
7. Is 2.5mm2 cable OK on socket ring mains (should handle 30A by the book - there's a max of 6 X 13A sockets on any circuit), with 4mm2 for spurs?
8. The lighting is split into 3 circuits, with the most heavily loaded running 6 X 116W fluorescent battens = 700W approx. The book suggests 5A/1mm2 cable, but is this a little marginal given it can handle 1100W max?
Anything else to watch out for with this sort of installation?
Pardon the length....
I'm in the process of sorting out a purchasing list for the bits to wire my one man workshop. I've an electrician lined up to check it all out before connecting up, but he's on holidays and so i've a few questions i'd appreciate some help with bottoming out in the meantime.
The most basic ones relate to consumer unit, MCBs, RCD, circuits and isolator arrangements. The shop has an existing RCD and MCB equipped 8way consumer unit (CU), but given the need to supply most of my machines and the inverter driving the dust system fan directly (3 and 4Kw single phase) i'll need more ways/circuits than it can support.
Plus i'd like to be able to shut down all power in the shop (i.e. machine supplies and 13A sockets but not lights and alarms) on a single switch, while leaving the laundry room (under the same roof), lights and alarms fed from the original CU so that they stay on at all times.
To minimise wiring I'm thinking in terms of leaving the existing CU in situ to feed everything that does not require to be isolated as listed above. I thought then that i could take a spur from the feed to it to feed a new CU (to be placed directly below it) with its own RCD and MCBs. Putting the feed through a 65A isolating switch (the CU will have an isolator, but they are not i think meant for everyday use?) would make it possible to isolate the new CU.
The questions coming to mind are:
1. Is this general arrangement OK in principle?
2. How should the incoming feed to the existing CU be tapped into, and is this OK to do? What sort of junction box? The existing incoming cable is armoured, runs up the wall to the CU in a small galvanised steel duct, and has an OD of about 12mm.
3. Will a correctly sized MCB adequately protect the 4kW Yaskawa single to 3 phase inverter driving the dust system fan, or should i also fit the fast acting 80A class T fuse suggested in the manual? (actual max output by the book is only 21A - the ramp function will minimise start up current)
4. Will the inverter or any of the other typical loads in the shop cause problems with MCBs or the RCD? (i.e. are they suited, or do i need a split type e.g. some channels without RCD protection?)
5. Will a suitable CU be in any ways special?
6. The plan is to use 32A wall sockets on dedicated circuits for the larger machine supplies. (all > 13A, some > 16A) They have their own on/off switches. Do i need to use a wall mounted isolating switch as well?
Some incidentals:
6. Any thoughts on using flex vs. the solid conductor grey cable for misc. fixed wiring?
7. Is 2.5mm2 cable OK on socket ring mains (should handle 30A by the book - there's a max of 6 X 13A sockets on any circuit), with 4mm2 for spurs?
8. The lighting is split into 3 circuits, with the most heavily loaded running 6 X 116W fluorescent battens = 700W approx. The book suggests 5A/1mm2 cable, but is this a little marginal given it can handle 1100W max?
Anything else to watch out for with this sort of installation?
Pardon the length....
