How to correctly wire 2-way switch for ring main

[nicebutdim]

Assuming a suitable 4 pole double throw switch was available (and the fact that they aren't readily available should indicate that your problem might be better solved in another manner), how do you propose to connect it to work in the intended manner?

 

[philectrical]

Of course it does, and that's what I have been doing. There's always more to learn, but so I'd like my main focus on being learning everything I need to know to be safe at the task in hand. I'm aware that 2.5mm twin and earth is only rated for 17 - 27 amps depending on whether it's clipped into the wall or not, but in a non faulty ring main it's capacity is doubled so that it exceeds the maximum 32 amps the MCB will allow. I had a faulty kettle trip the MCB every time it was switched on so I don't believe it's wise to assume appliances always use the amps they are supposed to use.

It seems like fitting a 32 amp 4 pole double throw switch should be a simple task, and perfectly reasonable for maintenance and safety. Going from a faulty ring main to a safe ring main at the flick of a switch, certainly seems like a good idea to me. The problem is I've found no switches that state clearly they are 32 amp 4 pole double throw for single phase, no tutorials from fully qualified electricians about how to fit them. That's why the solutions I've thought of are "odd configurations to suit weird problems". It's also, why I am posting. It's better to make mistakes in the planning stage and correct those mistakes, than to follow through and learn the hard way. It seems to me that if the worst comes to the worst and there is a fault, being able to isolate the fault can only be a good thing.



A simply workshop but with power tools that will almost certainly exceed the 13 amp limit for a spur. A faulty power tool or accidentally running too much at once, no problem if the breaker trips, hence the need for a correctly setup ring main extension. 32 amps for the entire ring main is more than enough but I'd rather allow for it just in case. I'd rather have extra capacity that I don't need, than not enough capacity that I do need, or worse exceeding the safe capacity and risking a dangerous overload. When testing the ring main, if it fails, I'll still need to use the original ring main without the extension until I've fixed the fault. I can't do that without a cutoff switch. I wouldn't even be able to use the lights whilst I fix the fault.

If it's a workshop you would always wire that separately and most likely on its own CU. You would not do what you're suggesting. It's an overly bombastic and complicated non-solution to a very simple problem.

Get a spark in to run some armoured to your workshop and fit the CU on the wall. Will be half a day's work, full day with testing. ~£500 all in.

Depending on the machinery you can then fit isolators for each individual piece of machinery which you can use for maintenance purposes.

 

[AnonDIYer]

Assuming a suitable 4 pole double throw switch was available (and the fact that they aren't readily available should indicate that your problem might be better solved in another manner), how do you propose to connect it to work in the intended manner?

Considering an incomplete ring main will work but be dangerous, and I can't count on the switch even having easy to follow instructions, if I am even 95% sure, then I'll be rigging up a test circuit so I can be certain where to connect each wire. I can't decide right now because I don't know the labelling or configuration of the switch and don't have access to the information. Once I know for certainty, which wires are live and neutral in the off position, and the on position, wiring it up so that there's always a complete ring will be easy. I may need to use cable glands to connect the wires safety, and that would be the next step after if needs be. There's no reason why I can't test every single neutral wire to make sure it's neutral when it should be and dead when it should be and the same with the lives. I could even test both lives and neutrals together using simply 1 way switches.

Would confirming the wires are all connected in the correct places (off = complete ring main without extension, extension dead at both ends, on = complete ring main with extension, no lives or neutrals on either end bypassing the extension), the wires are secure, and the switch can support at least 32 amps, not be enough to for the switch to be safe?

 

[nicebutdim]

Considering an incomplete ring main will work but be dangerous, and I can't count on the switch even having easy to follow instructions, if I am even 95% sure, then I'll be rigging up a test circuit so I can be certain where to connect each wire. I can't decide right now because I don't know the labelling or configuration of the switch and don't have access to the information. Once I know for certainty, which wires are live and neutral in the off position, and the on position, wiring it up so that there's always a complete ring will be easy. I may need to use cable glands to connect the wires safety, and that would be the next step after if needs be. There's no reason why I can't test every single neutral wire to make sure it's neutral when it should be and dead when it should be and the same with the lives. I could even test both lives and neutrals together using simply 1 way switches.

Would confirming the wires are all connected in the correct places (off = complete ring main without extension, extension dead at both ends, on = complete ring main with extension, no lives or neutrals on either end bypassing the extension), the wires are secure, and the switch can support at least 32 amps, not be enough to for the switch to be safe?

You've received several responses from electricians who unanimously stated it's a very bad idea, yet you persist in asking questions in the hope that someone will give a contrary opinion and confirm what you want to hear.

You don't want to pay for the services of an electrician, but wish to learn by undertaking this project and intend buying test equipment, the cost of which will far exceed the services of any electrician. This leads me to ask in what way are you defining 'safe' and who you think might certify this work to satisfy your insurer?

I'm an apprentice so won't be giving any advice, beyond repeating that you need to engage the services of a competent electrician, but I did take a few moments to draw this out and it's not something I'd want any involvement with.

 

[AnonDIYer]

Get a spark in to run some armoured to your workshop and fit the CU on the wall. Will be half a day's work, full day with testing. ~£500 all in.

That's exactly why it's not possible.

Just having a switch is dangerous. I wouldn't trust about a 1/3rd of sparks out there to wire such a switch up safely

Would confirming all the wires are wired to the correct place and testing the circuit for continuity not be enough for it to be safe? How would just having the switch be dangerous? It would be operating way under the safe capacity.

 

[philectrical]

That's exactly why it's not possible.

Yes but you keep on plugging away with your frankly stupid idea and aren't actually acknowledging some of the good advice you've gotten.

Nobody is going to help you wire up this ridiculous set up you're after.

Can you explain why you won't just put it on its own separate feed? It will be much easier, much safer if done right and easier to figure out. People would actually be up for helping you to make it safe if money is such an issue and you're so hell bent on doing it yourself.

The standard for a workshop is to run its own feed in from the existing CU and have local isolation.

The problem is depending on your machinery and length of run it requires sound theoretical knowledge to do the design, since this is a workshop and not just a garage or shed with a few sockets in.

 

[goasis]

This thread is craziness... lots of qualified people have said this is a stupid idea for several reasons, don't do it.
Lack of funds isnt an excuse.
There's nlots of things I'd like but can't afford... that's life. Save up till you can.

 

[telectrix]

fortune for an electrician to do a complete rewire..

what fortune? average cost to install some extra sockets on a ring is under £80 each including materials . testing, and a certificate. but not rdecoration, which you'd have as an extra no matter who did the electrics.
and where did "complete rewire" come from.

post your location. maybe a member is close and would give you a reasonable quote.

FFS don't do what you are planning. you're a long time dead for the sake of a couple of hundred.

 

[philectrical]

fortune for an electrician to do a complete rewire..

what fortune? average cost to install some extra sockets on a ring is under £80 each including materials . testing, and a certificate. but not rdecoration, which you'd have as an extra no matter who did the electrics.
and where did "complete rewire" come from.

post your location. maybe a member is close and would give you a reasonable quote.

FFS don't do what you are planning. you're a long time dead for the sake of a couple of hundred.

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.

 

[littlespark]

Telling what can’t be done isn’t helping. We need solutions to what can be done.

New circuit back to board. Seemingly not possible.
13A fuse spur. Also not possible due to estimated load.
DPDT switch thing is just no.

So the options are….

1 Run the new circuit to where you want the sockets to be… then connect both legs

2 isolate the circuit you are extending from, for the entire time it takes to run the new circuit.
Run temporary supplies from other parts of the house in the meantime

3 Get someone else to do it

 

[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.