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?

 

[philectrical]

In an ideal world yes. The reality is, if I wait I won't just have to pay a fortune to change the circuit late, considering it would be a lot harder to change then, than now, but I'd be taking a much bigger risk. The spur off the ring main should not be more than 13 amps, and hoping there's no dangerous overload until I can afford to hire an electrician is surely not a smart move.

What's wrong with learning how to do things properly? Everyone has to start somewhere, and I don't believe even the best electricians could be 100% safe and competent before they learned how to be.

I don't consider any work I have done to be complete, until I have tested for faults, surely this is especially true with testing for ring main faults.



Because simply putting in a 32 amp or more 4 pole double throw switch would solve the problem. I'm giving up with the idea of trying to make do with less than 4 poles because of the neutral problem. The problem now is I'm not finding very good results when I search for a suitable switch. Most switches don't even state how many throws they have, meaning I have to spend time considering switches that may not be suitable. A lot of switches that would work, have an off position in the middle. This would mean, every time I change over, there'd be a temporary break in the ring main.

What risk? What exactly is it you're trying to achieve and why? If it's just an extension that you want to be a ring and not a radial, you just put it on its own ring with its own MCB at the consumer unit. In houses we usually find a ring for the kitchen, a ring for the rest of the downstairs and a ring for upstairs. Why can't you just add a ring for your extension and then you won't have to turn off the other ring at all.

What about this switch (the 32 amp one)? LW42 20/25/32A 4Pole Rotary Selector Universal Rotary Changeover Switch Isolator | eBay - https://www.ebay.co.uk/itm/363422468983?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D237334%26meid%3D0335e5c0502e49d38a40b2ad4f530fe3%26pid%3D101195%26rk%3D9%26rkt%3D12%26sd%3D144256490302%26itm%3D363422468983%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv9PairwiseWebMskuAspectsV202110NoVariantSeed%26brand%3DUnbranded&_trksid=p2047675.c101195.m1851&amdata=cksum%3A3634224689830335e5c0502e49d38a40b2ad4f530fe3%7Cenc%3AAQAGAAACMKy7vEOvBI8Auv8QpEnxmxLXZS4es8rMPqHXyNkGqLRd5oFGCqYoxmH%252FqjQpK%252FWirOlnB9WVZFMpP6mhJ1kymU1M8jq5VvMoo31uLspbmeLeWT%252BfvsZpO2ahpxyDvgjOcdQx0iWHkpUoufOD4JjzKJbU98t748WYITGs2%252BeHRSELeuBy%252FyCI7u9eoSg%252FyNXo6qpQ%252B9wRFeo6UyaXdJYDwV94mYw4QgnSmE1bx5KdINZkADZypdDrGs8yaDZhodCpmI4TXp3TQzGjrnPsl2IpifElkTLwDh4fpTCNn3sDPMUCNeWxkDyRKqGusVtcmGpEIvNovGHxFfG%252BR%252Fl3y0pwOD32S8sd0wUgtbt3xNmvYAtu1v1w6uIJwip7VAS6rCrOwDOhjV0%252FLwSQgcql6aq1bC9vV5xsq2VoeOPSCntndugYChkHKZiTOPvv30ceZBWp7lOPmbbwUWNZx2K9FpNHuutKbseOQ9d%252FEquPHxfkl%252FfdUDv6Iqa2h4MKN7KRpovWk47BLFPnx%252BkgNEDWsVIqnyOd7U94q9H%252BRXO%252FbTuFYREJjBoleUS3kjX8VsQsQBrbERTVnyQpFogFkGfmVL0u6WRY3EM%252FO5n5QCVoHVswC90ypxmvKQbcNo94%252Fud4b%252F%252BdycUV8LXOtmbnSmhYdRVE6ydArc5uKZyrnObyPmv%252BAygPVREKKKG7mF%252BBlevH%252BLkO7hOR%252FQvQXI27l%252BThCaU8vw65s5r2YGpG7lFOkf%252Fj5cN4%7Campid%3APL_CLK%7Cclp%3A2047675

It looks like the cables will fit into it without being glanded. Could it be any more dangerous than connecting the cables via wago connectors in a junction box?

That's basically the same thing, it's a switch meant for industrial usage. Last time i connected some of these up it was for 3 phase machinery in a metalworking shop. They're not meant for domestic usage.

I don't know what idea you have in mind or what you're trying to do that you won't tell us about but you should abandon the idea. 'Starting somewhere' usually entails learning the basic science and principles, learning about how cable rating and mcb's work together, about how to terminate correctly, etc, etc. Learning how to do electrics doesn't start with coming up with odd configurations to suit weird problems, especially when there's a very easy solution to the problem of 'needing to turn the supplies on and off separately'.

Sounds to me like you've got a grow on tbh that you need to be able to disconnect from your supply if suspicions get raised, and it's probably why you won't get a spark in. Forgive me if i'm wrong and just being cynical.

 

[AJB Temple]

I am a DIYer too. In my case I have invested in modern test equipment, appropriate tools, safe isolation testers and read both regs and testing manuals. Therefore, I do understand that DIY people need to do things for themselves at times, and I am not judgemental about that.

My reaction when I read your suggestion was:

It’s potentially dangerous
It’s illogical
It’s over complicated, especially as you are avoiding explaining the need to isolate the ring extension.

If you are capable of safely installing the sockets and correct sized wiring for the ring extension, then it is difficult to see why you don’t simply do that. Then, cut the power and prove dead on the existing ring final circuit. Then, when certain it is safe, connect the extension.

If you do not have test equipment then you are taking a risk and I suppose that is a matter for you, but I would not expose my family (or anyone else) to using circuits where I had not done continuity, resistance, CPC, ramp tests etc.

I can’t for the life of me see any logic in fitting some kind of switching system to isolate and make dead part of a ring final circuit, whilst leaving the original circuit live. It made me wonder if you realise that current flows both ways around a ring final circuit. If it were me doing this and I had a load that exceeded the capability of a regs compliant spur, I would simply install a new radial with appropriately sized and suitably protected cable. I could switch that out at the CU. Simple and safe.

I also wondered from your post if you are clear what the purpose of the fuse is. You anticipate a load exceeding 13 amps in that section (suggesting some sort of large element or start capacitor perhaps) and your solution seems to be install a larger fuse. Even as a DIY person this seems to me to defeat logic: you need the correct sized cable for the job in hand, and a suitable trip device such as an RCBO rated to protect the cable from overload currents. I can’t see how some complex manual switching arrangement to isolate your ring extension is a sensible solution.

Anyway. I hope you arrive at a safe solution and a means of testing that you have installed it correctly.

 

[AnonDIYer]

'Starting somewhere' usually entails learning the basic science and principles, learning about how cable rating and mcb's work together, about how to terminate correctly, etc, etc. Learning how to do electrics doesn't start with coming up with odd configurations to suit weird problems, especially when there's a very easy solution to the problem of 'needing to turn the supplies on and off separately'.

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.

Sounds to me like you've got a grow on tbh that you need to be able to disconnect from your supply if suspicions get raised, and it's probably why you won't get a spark in. Forgive me if i'm wrong and just being cynical.

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.

 

[DPG]

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.

A properly designed circuit does not need a section of it to be isolated. Please take the advice you have been given. Your idea is not a good one

 

[timhoward]

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

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

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, and while you seem to understand many concepts you are also clearly blind to other ones.
It's also a bad idea having something so unusual in your house.

If you think through the scenarios you have mentioned...
In the case of faulty equipment consuming too much current - either fuse goes in plug, or over current protective device operates to protect wiring.
The wiring stays safe without a switch. You reset the circuit breaker and crack on.
A lighting circuit would not be affected by an over-current fault on the sockets circuit unless there was an earth leakage issue, and even then you just unplug things until until the RCD stops tripping.

If you are hell-bent on having isolation for this area, the right way to do it is a separate circuit, Some sparks would let you first fix to keep costs down.

 

[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