Electrical Advice on Ring Mains

[Chems]

I'm in the process of deciding how to convert the original (1995) radial circuits in my workshop/garage to a ring main as advised by my friend the electrician. Fortunately the way it is laid out I can easily get the sockets all into a main and back to the consumer unit with a minimum of fuss. Once all said and done I will end up with the 2 sides of the ring coming back to the consumer unit. Now from reading I've read that they actually need to go into the consumer unit and just attaching the wires in a terminal block and then having a single 3 core wire going into the consumer unit won't constitute a ring main?

Some of the simple wiring will be carried out by myself but the friendly sparky will have to come at some point to check it over so I just wanted to ask about this as I won't see him for a few days now.

So just to outline the question clearly: Does the Ring have to have 2 three core wires going back into the Consumer Unit?

 

[Jake]

Short answer, yes.

In theory you could do other things, but it would be a non-standard circuit and would require the full gamut of design calcs to be done.

Seems a lot of bother to go to - do you need the extra 12A rating (I'm assuming it was a 20A radial which you are turning into a ring?

 

[Chems]

I'm not sure Jake, its worked fine how it is for years but since putting the 3hp SIP saw on it I wanted to make sure it was done properly. Runs the saw fine but dims the lights a bit on startup. If I can get away with keeping the radial circuit I'd rather do that.

 

[Digit]

Why convert two radials to a ring?

Roy.

 

[Chems]

Its not two radials, its just one with spurs.

 

[Jake]

If it were me, and I was going to run another cable (and had a spare way in the CU), I would prefer to run a second new radial for the saw than convert the existing into a ring.

Having said that, I don't know the full story or why your electrician friend has recommended what he recommended.

 

[Chems]

No spare slots in the CU I'm afraid. Did talk of bringing in a new CU but its all money money money.

 

[OLD]

Answer is yes the current will be shared by the cables to give a feed of up to 32 amps.
Just run a cable from the furthest on the radial to the CU and the sparks will connect both ends.

 

[Digit]

You state that the lights dim on start up Chems. Are the lights on the radial main as well or a separate MCB/Fuse?

Roy.

 

[Chems]

There on a seprate RCD on the CU.

 

[Digit]

Then I'm at a loss to see why the sparks suggests a ring chems. It certainly won't stop the lights dimming.

Roy.