3 Phase help please

[AndyStobbs]

Recently bought a two post lift for the workshop. Its a 3 phase motor, so will have to equip the unit with 3 phase.

Currently I have 3ph as far as the distribution board. My plan is to also convert the compressor to 3ph at the same time - or atleast get a supply upto it in readiness, and also to add 1, perhaps 2 5 pin sockets.

Just after a little info regards what kind of stuff is out there and what rules and regs are.

Point 1, as I understand it, every 3 ph machine is required to have a dedicated supply and breaker ( no ring main as with 1ph), is this the case?

Point 2, my DB is a crabtree, and has RCBO protection on all single phase circuits. Will the 3ph aslo need RCBO's or is MCB acceptable?

Point 3, I have some 2.5mm square single's left over (from the single phase wiring). Providing current requirements are within scope of 2.5mm, can I use up these singles, and mark them with tape to indicate which phase is which? I have 100m roll of blue un-opened - can I even mark this up as a live phase?(I would like to use up what I've got laying around where possible)

Point 4, Where 5 pin sockets are concerned, do they still need isolation - given that unplugging the plug would be an isolator in itself? Are the combined sockets and isolators any advatage over separate items?

Point 5, Is plastic conduit acceptable, for un-armoured cabling?

Thanks Gents

 

[Exuptoy]

Recently bought a two post lift for the workshop. Its a 3 phase motor, so will have to equip the unit with 3 phase.

Currently I have 3ph as far as the distribution board. My plan is to also convert the compressor to 3ph at the same time - or atleast get a supply upto it in readiness, and also to add 1, perhaps 2 5 pin sockets.

Just after a little info regards what kind of stuff is out there and what rules and regs are.

Point 1, as I understand it, every 3 ph machine is required to have a dedicated supply and breaker ( no ring main as with 1ph), is this the case?

.........it SHOULD! Not that everyone does!

Point 2, my DB is a crabtree, and has RCBO protection on all single phase circuits. Will the 3ph aslo need RCBO's or is MCB acceptable?

.......it doesn't NEED one, MCB has been the accepted protection for years. 17th edition regs just adding further complications and confusion.

Point 3, I have some 2.5mm square single's left over (from the single phase wiring). Providing current requirements are within scope of 2.5mm, can I use up these singles, and mark them with tape to indicate which phase is which? I have 100m roll of blue un-opened - can I even mark this up as a live phase?(I would like to use up what I've got laying around where possible)

.......the regs state any circuit using non standard colour and not in compliance must be marked at each outlet to verify to someone following on.
If you are not getting this installation tested all this is a moot point really just good practice!
http://www.elecsa.co.uk/Technical-L...ting/Current-Carrying-Capacity-of-Cables.aspx

Point 4, Where 5 pin sockets are concerned, do they still need isolation - given that unplugging the plug would be an isolator in itself? Are the combined sockets and isolators any advatage over separate items?

..........Isolation is an advantage as a disconnection source. Pulling the plug is not advised to effect isolation.

Point 5, Is plastic conduit acceptable, for un-armoured cabling?

............Conduit is suitable in your situation.

Thanks Gents

Lyn

 

[AndyStobbs]

Thanks for the advice. The installation is unlikely to be inspected and will be carried out by me. But I still want it by the book. There are enough risky things in a workshop without adding to the list by shortcuts in wiring.

Thanks
Andy

 

[madkayaker]

Then get it inspected by a competent electrician

 

[Exuptoy]

Then get it inspected by a competent electrician

He's not wrong you know.

In the reply above I included a link. http://www.elecsa.co.uk/Technical-L...ting/Current-Carrying-Capacity-of-Cables.aspx

This goes to show how grouping and thermal effects of the installation have an outcome in reducing the current carrying capacity of copper cable. Also distance of the cable runs will have an effect in the form of volt drop. These tables can be found in the current regs and probably online.
Where the ccc of the cable is border line you'd be better off going to the next size up. It's not worth having a fire risk for the sake of £120 worth of cable!

http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Singles/index.html#2.5mm_Singles_6491x_7

 

[AndyStobbs]

Thanks for the advice guys. I have taken that on board.
Recently bought an 18 way DB to use exclusively for 3ph machinery, retaining my original crabtree 12way for all single phase installations.
Two 5 pin sockets 16A with isolators built in, and a good few metres of 2.5 SWA 5 core and 6 SWA 5 core.
All second hand but it'll serve.