Master switch for a circuit of sockets?

[akirk]

As a slight follow on to the excellent thread about sockets, I am having the workshop wired in the next few weeks, and amongst other plans will have a separate circuit for the main tools...

my question - is there an option to wire in a master switch I could use to turn off all plugs on that circuit as I leave the workshop? What should I be looking for - I would like to feel that all tools are turned off at a switch above child height!

 

[TheUnicorn]

if you had a consumer unit in the workshop surely you can just use that to switch off your dedicated tool circuit? or is the positioning of the consumer unit not suitable?

 

[akirk]

Consumer unit is there but a bit high for comfortable frequent access plus the risk of turning off the wrong circuit... would prefer a simple switch...

 

[Rorton]

something like a rotary isolator

https://www.screwfix.com/p/british-general-cprsd432-4-pole-rotary-isolator-switch-32a/8227r
from consumer unit into isolator, then into sockets

not in particular that one, but that type of thing

 

[akirk]

something like a rotary isolator

https://www.screwfix.com/p/british-general-cprsd432-4-pole-rotary-isolator-switch-32a/8227r
from consumer unit into isolator, then into sockets

that seems to be the idea - does that work on a ring / circuit versus a spur?

If I think of the electrical circuit like a railway I can see how on a spur an isolator would kill anything after it... but on a ring it would seem that the electricity could flow the other way around and bypass the isolator - or am I being really thick?!

 

[Rorton]

your correct, these are usually industrial use things, and in in commercial electrics, a ring isn't used (a ring is rubbish really, was a design used to save copper many years ago)

You should have your circuits as radials, and suitable size cable to handle. If you need the current capacity of a ring, then spark should be using 4mm or similar to create a radial from the consumer unit, to the isolator, then onto the sockets

 

[Spectric]

What tools are you thinking you may leave on by mistake? You said the installation is being done professionaly, therefore the fuseboard inlay card will detail what is being protected by each device so you could turn if OFF there but not good practice, and the toggles should be between 1350mm and 1450mm above floor level, high enough so kids cannot touch but low enough for an adult without using step ladders. The easiest way is to just have an isolator between the board and that circuit, something like 32 Amp TP&N Rotary Switch Insulated Weatherproof - IP65 and switch both L & N but not the CPC.

 

[TheTiddles]

I have a 13A switched fused spur run off the ring socket at the end of the garage, 4 double sockets run off this, bandsaw, router, tablesaw have all run through this fine (not huge machines mind, all run on 13A plugs)

This means all machines, tools etc are isolated on one switch that you have to go the length of the garage to switch on, I did that specifically to reduce the chances of someone pressing an appealing green button without having to go in, walk the entire length and take two actions to achieve this, all without me or anyone else noticing. It’s also got a light on it so I know when it’s on.

This is a small home workshop option, a more industrial option can be emergency kill switches by the door so when some twonk is being a fool you can kill the power to the entire shop floor because you’d consider going past the door as too dangerous yet he’s 100 feet away stood right next to the accident waiting to happen... I’ve only had to do that once

Aidan

 

[Spectric]

As Rorton said they should be radials and I would run as singles in PVC conduit rather than T&E. With a Ring you cannot fit an isolator because there is always a risk that you leave it broken, so you have a 32 amp PD on effectively just a 2.5 cable.

 

[akirk]

So why do we still build circuits rather than radials?

re tools - band saw / mitre saw / scroll saw/ thicknesser / sander / drill... if I have an isolator I can leave them all plugged in and switched on at the wall and just turn off one switch...

My builder will manage the work - either he will install and his sparky will sign off, or the sparky will install and sign off... however I like to also understand it partly to feel confident telling them what I want and also just for interest and understanding how the workshop is set up...

so it sounds as though running it all as a radial through the isolator is an easy way to do it... thank you

 

[AJB Temple]

I have an isolator switch in my workshop, exactly as per the photo above. I might be wrong about this, but I think the isolator is wired from the armoured before it goes into the consumer unit. It is right in the centre of the workshop back wall, and is very obvious, so if there is an accident this kills everything instantly. Much easier than having to find the CU, open it and switch off. I can also lock this isolator switch.

The consumer unit is one of several "slaves" in different buildings, all fed by armoured cable from the main entry point in the house. Professionally done.

 

[TheTiddles]

Why change? Rings work fine, copper is still expensive and we no longer own the country we mercilessly exploited for it till the end of the last war.
Aidan

 

[jimmy_s]

Rings work fine but issues can arise if one end of the ring gets broken then you are left with a radial cct which could be overloaded if its wired in 2.5mm T&E with a 32A protective device.

To be honest, I thought it was unlikely, but found that it had happened in the house here. Situation exacerbated by a large number of spurs of the ring cct that was actually a radial - serving electric heaters. Thankfully it didn't go on fire.

Quite like 4mm2 radials now.

 

[Sachakins]

You could just as easily overload radials too, even 4mm²

 

[Rorton]

If not provided with adequate protection, at least a radial is designed in such a way that the cable and mcb/protective device are designed to work together (4mm cable and 32a protection for example)

Ring usually has 2.5mm cable and the same 32a protection based on the fact the ring is in tact, but could inadvertently get overloaded should the ring be broken

 

[akirk]

So are we saying that the basic difference is that a radial is 4mm cable and a ring is 2.5mm? And that in a ring the last plug goes back to the breaker in the consumer board... Presumably breaking a ring gives effectively 2 radials from the same breaker but isn’t there still the same power consumption, same cable and same protective fuse over the two radials as there would be over the one ring main?

isolator switch needs to go after the consumer board as I only want to switch one of 10 circuits / fuses - to switch them all would kill the fridge-freezer and chest freezer...

 

[Sandyn]

I have a 2.5mm 16A radial running across the ceiling for my main power tools. It has a double pole upright cooker switch with neon. One switch puts everything off and when I do the rounds last thing at night, I can have a quick look in the garage and see the switch is off.

 

[HappyHacker]

You could run a 4mm or 6mm cable from the CU to the switch and then start your ring from the switch.

I prefer radials mainly due to the time I spend trying to fault find a ring when there is a problem. Also I find all sorts of bodges on rings when people have worked on them without understanding what needs to be connected to what. But I am usually inly seeing the faulty ones. Having said that they do work well when properly installed and there are installed in most properties in the UK without problems.

 

[RichieG]

As the isolator Rortin posted is four pole, couldn't you use it to isolate the live and neutral on both legs of the ring coming out of the consumer unit?

 

[Sideways]

An option.
Have them wire the ring in 4mm "singles" in conduit.
It is a robust solution.
It will still be safe to 32A if the ring suffers a single break anywhere.
It is easy to change to 2x 32A radials in future if you need even more capacity.