Ring main advice please

[ColJack]

but if it's one 4 pole contactor then it's ok..

the quote is from Fig 15A..

or another solution is to split it into 2 20A radials..

 

[holmslaw]

..

 

[SUNRAY]

I have been onto the NICEIC help line, their advice is quite simple.

The RFC must be continuous and have a single point of supply, the comparison he made is with a RCD which may and can be fitted after the OCPD & before any any outlet. His concern, like several on here, is the is ease of fitting another outlet in the parallel feed but can see no reason why the arrangement as currently fitted should fail a PIR as long as it is correctly identified at all reasonable points.

I had to describe the original systen twice as his reaction was of disbelief.

Apparently appendix 15 is guidance notes only.


Not forgetting the advice was the operators opinion and interpretation of the regs.

 

[ban-all-sheds]

Its not ok, because you are breaking the ring circuit and thereby turning the cables from the cu to the contactor into two individual 2.5 radials on a 32A MCB, when the contactor is open.

So?

 

[davelx]

As I said earlier and Holmslaw agreed - you can have any config you like providing you comply with the regs - so why not just STOP calling it an RFC??

 

[holmslaw]

..

 

[ban-all-sheds]

Which regulation makes it so?

 

[holmslaw]

..

 

[ban-all-sheds]

They are not regulations.

Which regulation, i.e. xxx.y.z makes a 2.5mm² cable on a 32A breaker unacceptable?

 

[holmslaw]

..

 

[ban-all-sheds]

Are'nt they? you learn something new everyday.

They are in the regulations, but that's not the same thing.

Can't be bothered with you to-day, bye bye.

OK - feel free to return if ever you think you can answer my question - until then we'll all proceed on the basis that you are wrong.

Which you are.

 

[SUNRAY]

Its not ok, because you are breaking the ring circuit and thereby turning the cables from the cu to the contactor into two individual 2.5 radials on a 32A MCB, when the contactor is open.

So?

2.5 cable is not acceptable on a 32A circuit.

I kind of have a bit of trouble with this statement and see both sides of the argument.

2.5 is rated somewhat lower than 32A therefore should not be on a 32A supply which I agree with!

2.5 is suitable in the regs for a parallel feed on 32A supply.

2.5 is suitable in the regs for a RFC on 32A supply.

2.5 is described in the regs for an unfused spur, of unspecified length, on a RFC using a 32A supply.

The regs otherwise indicate a conductor can be used, with limited length, on a circuit where the OCPD rating exceeds that of the conductor providing it is followed by a OCPD of a rating lower than that of the cable.


In the circuit in question I'm not comfortable with any issue or risk and want to get it right. We certainly don't want any chance of it coming back to hit us in the face, again, in the future.

 

[ban-all-sheds]

2.5 is rated somewhat lower than 32A therefore should not be on a 32A supply which I agree with!

It should not be used to carry a load of 32A.

 

[JohnD]

A long time ago i used to do electrical work in a licenced theatre

Now I am just a householder

I would certainly have put a submain to the stage area, and I would probably have run it at inaccessible height, like the stage lighting supply and controls cables. With a small CU feeding your stage outlets, and if you want, some EPO buttons and a contactor at the stage end. I would have had the stage CU where it was visible and accessible to the stage manager for RCD and contactor resetting but not easily interfered with by others. You could take working lights off the stage CU as well.

If there was to be a ring, it would only start at the stage area. However I would probably not use a ring as I would not want sockets across the front of the stage. There would be no sockets taken off the submain. There would be no sockets in the stage area fed from other circuits.

BTW I would also have preferred different coloured, or identified, sockets on the stage circuit to reduce the risk of confusion with auditorium sockets when a circuit was isolated for maintenance.

 

[SUNRAY]

As I said earlier and Holmslaw agreed - you can have any config you like providing you comply with the regs - so why not just STOP calling it an RFC??

I don't care what its called but it was wired as a circular circuit incorporating 2 switched points.
It is currently (assuming it is still as we left it) a contactor supplied using 2x2.5mm cables & 32A rcbo feeding a circular circuit.
For convenience I have been using RFC as the final (part of the) circuit is formed with a ring, just happens to be that the start of the circuit is the output of a contator not the RCBO.

I dont understand the problem that this has caused as there are thousands of similar circuits in use across the land, are they all wrong?