How to correctly wire 2-way switch for ring main

[AnonDIYer]

Currently I have a spur from the ring main, but I'm planning on adding more sockets. I can't add a 13 amp fuse because I expect to be using more than 13 amps, therefore, I am going to convert the spur into a ring main extension, as in the following diagram:

I'd like to put in a 2 way switch so that I can isolate the ring main extension whilst I'm doing work on the extension, and as an emergency off switch. When the switch is off, A should connect to B. When it's on, A should connect to C, and D to B.

I'm planning on buying a 45 amp double pole 2-way cooker switch to use for this. This is the back of the switch:

And the instructions:

I thought about how I can wire this up. The best configuration I can think of is to connect the 4 lives inside the switch, A to L2, B to N1, C to L1, D to N2, and the 4 neutrals joined together. I believe this would be perfectly safe in the off position because the lives A and B will be connected via L2 and N1, and the neutrals C and D would not cause a problem because the circuit they are part of would be dead.

However, in the on position, lives A and C will be connected via L1 and L2, and lives B and D will be connected via N1 and N2, which is perfect, but what about the 4 neutrals? This gives the neutrals a shortcut from A to B, as A and B will always be a live circuit.. Would this not create an unbalanced circuit and be dangerous?

Can someone please let me know the correct way to wire this up?

 

[DPG]

I really don't see the point of the OP asking his question if he isn't going to take notice of the replies and blindly plough on anyway. God help whoever buys this house in the future.

 

[timhoward]

The problem is i don't think many electricians will be willing to do what he's expecting. They can get power to his workshop but i don't think i know any spark that would do this weird switch thing he seems insistent on and he doesn't seem for turning.

I'm sure Tel was just suggesting extending the ring in the normal fashion.

How would just having the switch be dangerous?

1) It would require an unusual switch
2) Many people wouldn't connect it properly, including some sparks
3) the ring final circuit would be wired in an unusual way
4) test results would vary depending on the position of the switch
5) Failure of the switch could result in neither normal or extended ring being connected. Then you have a 32amp breaker protecting two legs of cable rated for 20 amps.

The regs say that you can have a ring final circuit if the load in any part of the circuit is unlikely to exceed the current carrying capacity of the cable for long periods. (433.1.204)
The presence of a switch doesn't affect that - the extended circuit is either safe to use or not.
In fault conditions it makes no difference, ADS will occur before you get to a switch. It makes no material difference to resolving any fault either as I described earlier. It truly does nothing for you at all.

Many people from all areas of the country, with different training and experiences have unanimously tried to convey to you that the switch is entirely pointless and dangerous.

My final comment is that in a small workshop you tend to just use one thing at a time. It's pretty unlikely that more that 13A will be drawn unless welding and/or heating is plugged in. Plenty of workshop consumer units only have a 16A breaker for sockets after all.
Frankly I'd suggest that if a DIY approach is needed then either :
a) just put a 13A fused spur in and wire up some sockets.
b) just prepare the wiring, turn off, extend the ring, and turn on.

I'm done with this thread now, there's no point in commenting further.

 

[philectrical]

I'm sure Tel was just suggesting extending the ring in the normal fashion.

What i mean is i'm sure any spark that turns up and suggests a normal solution would find OP insisting on his switch thing, and would subsequently walk away without doing the work anyway. I don't know any spark who would carry it out.

OP i would urge you to folllow timhowards suggestions in his closing statements above.

 

[UNG]

In terms of safety what the OP is proposing needs to be properly risk assessed and the outcome of that would most certainly be that it is dangerous in so many ways
When workshop is mentioned that to me that generally means that some expense has been made to equip it and now the OP having spent the budget has nothing left for the important part of supplying it with electricity and is now trying to concoct some half baked method of providing it with power
No matter how much initial testing is carried out every operation of the "switch" will no doubt have some impact on the overall performance of the switch especially if it is under load of the the time of operation and this will no doubt show up in future test results or when someone gets hurt because of a failure
I would not want to work in any property with a DIY hybrid circuit as is proposed by the OP, my advice to the OP is isolate your workshop until such time you have sufficient funds to do the wiring job properly before you or somebody else in your property is seriously hurt or killed and then the cost will be a lot higher

 

[westward10]

@AnonDIYer you have had plenty of advise suggesting that what you intend to do is not practical and no one is going to give you a method for carrying out your proposal. Your best course of action is to consult an electrician and as already stated no electrician is likely to connect these socket outlets in the manner you suggest.
Thread closed.