CK Tools :) The professionals choice when it comes to Electrical Tools
This official sponsor may provide discounts for members

Discuss Grid switches on 32A ring in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

I've been trying to work out whether grid switches (ie. a 20A switch) are acceptable on a normal 32A ring. I've read many threads online. Very few people seem sure whether it's acceptable but many sparks seem to do it in kitchens etc.

The argument seems to be that the switch is rated at 20A but there could be 32A flowing through the ring. However, how much of that 32A would actually go through the terminal? The majority of the current would go straight from one wire and into the other as they will be touching. I can't see it being an issue but the real question is whether it meets regs. Does anybody have the official answer to this?
 
Bulk Workwear - Clothing Suppliers for the Whole Forum Network
This official sponsor may provide discounts for members

Andy78

-
Mentor
Arms
Esteemed
Have a read up on the regs surrounding ring final circuits with the start off point being that 2.5mm cable clipped direct is only rated for 27A.
Also think about how the 20A DP switch is to be connected into the circuit and the load that would be drawn through it.
 
T

Toneyz

If a bank of grid switches supplying a few high current used appliances this should be located as close as practically possible to the midpoint of the kitchen ring final circuit.
 

Taylortwocities

-
Arms
Esteemed
Your grid switch will be on a spur (LOAD) output from a ring

So that will not be 32A, will it? The only place where it might be anything near 32A is at the MCB in the CU.
 

ChrisElectrical88

-
Mentor
Arms
Esteemed
The load across the switch will be 13A maximum as you would imagine that they feed a single socket or spur each.

However i am not a fan of them and have been called out to a few crackling due to poor termination. Takes a lot of care and a 47mm backbox to get them perfect, something not many people do.
 
  • Thread Starter Thread Starter
  • #6
Have a read up on the regs surrounding ring final circuits with the start off point being that 2.5mm cable clipped direct is only rated for 27A.
Also think about how the 20A DP switch is to be connected into the circuit and the load that would be drawn through it.
That all makes sense now. This is what I had originally though but my mind had been led astray by some convincing replies I had read.
 

telectrix

-
Mentor
Arms
Esteemed
grid switches...spawn of the devil. rated at 20A yet burn out on 13A max. .... need to knock a brick out to get all the cables in. never can get the faceplate on right.... and the 1 marked fridge controls the dishwasher.
 
  • Thread Starter Thread Starter
  • #8
However i am not a fan of them and have been called out to a few crackling due to poor termination. Takes a lot of care and a 47mm backbox to get them perfect, something not many people do.
This is my biggest fear. However, they look great when they are done well and will take up a lot less space in my small kitchen.
 
Me personally not a big fan of grid logic switches

But if done correct do serve a purpose

but as telexctric mentions the amount of wonky badly installed ones is frightening , and never assume they are wired correct

turn off the one marked fan and you probably just isolated the washing machine
 

Taylortwocities

-
Arms
Esteemed
I really do not like a bank of grid switches fed from a ring final. The whole point of a ring final is to distribute the loads round the ring. With a grid bank you’ve got all of the high power items coming from a single point on the ring.

If you MUST have a mission control panel like this, then it is best fed from a 32A 4mm radial. That finishes the sermon on the mount for today.
 
I am not a fan of this method. The last few firms that I have worked for do this method, even having a fuse holder in the grid switch along with the socket by the appliance, so having 2 fuses in series and making it more fiddly, along with them mounted in a cupboard. Also as has been said before they are fiddly and prone to issues. Especially when under pressure to get jobs done as quickly as possible.
 

Midwest

-
Arms
Esteemed
I think the only reason these are used in new builds, is to comply with Part M, with all the sockets for appliances in cupboards or behind appliances.
 
Your grid switch will be on a spur (LOAD) output from a ring

So that will not be 32A, will it? The only place where it might be anything near 32A is at the MCB in the CU.
I know this is a few months old but I found it quite an interesting thread.

Presumably each switch is on a spur and doesn't that mean the supply side of each switch module will have 2xL and 2xN cores - continuing the ring in and out.

So there could be more than 13a flowing through the terminals on the supply side of the switch. But maybe that's ok because its not flowing through the switch ?

EDIT CORRECTION: Apologies I corrected this a couple of times !
 

Midwest

-
Arms
Esteemed
Don’t think so. Each DP switch will have feed in and a feed out, for each live & neutral terminal, thus completing the RFC. The load side of the switch will feed the appliance.
 
Don’t think so. Each DP switch will have feed in and a feed out, for each live & neutral terminal, thus completing the RFC. The load side of the switch will feed the appliance.
Thanks for that but the feed in surely has to continue the ring thus would need two cores per terminal? (And the load side as you say off to the socket). So each DP switch controls a single spur with a single socket.
 

Midwest

-
Arms
Esteemed
Thanks for that but the feed in surely has to continue the ring thus would need two cores per terminal? (And the load side as you say off to the socket). So each DP switch controls a single spur with a single socket.
Yep, as said feed in and feed out per terminal. And each DP switch feeds an appliance via a single cable. We at cross purposes?
 
Yep, as said feed in and feed out per terminal. And each DP switch feeds an appliance via a single cable. We at cross purposes?
Sorry yes might be my fault - I had to change my original post.
So if there is feed in and feed out that could easily go beyond 13a (and possibly beyond 20a depending on where it is in the ring?). Not sure if its an issue in practice though?

ANd in any case no more than 13a would be going through the switch.
 

Strima

-
Arms
Esteemed
So if there is feed in and feed out that could easily go beyond 13a (and possibly beyond 20a depending on where it is in the ring?).
Both cables will be in the same terminal and clamped together so the current is flowing through the cables and not the terminal block.

Most switches would normally feed a single socket for an appliance however you could potentially use a double socket-outlet for two appliances, these are normally rated for a maximum of 20 amps hence the 20 amp rating on the switches.

This is down to diversity of the loads and unless you have two three bar heaters plugged in it's doubtful you'll ever exceed 20 amps on a switch.
 

telectrix

-
Mentor
Arms
Esteemed
might never exceed 20A through the switch but why do i keep finding them burnt out and occasionally bridged? spawn of the devil, would never fit myself.
 

Taylortwocities

-
Arms
Esteemed
might never exceed 20A through the switch but why do i keep finding them burnt out and occasionally bridged? spawn of the devil, would never fit myself.
They burn out because they’ve been installed badly, often by fitters of kitchens. And I agree, pain in the whotsit, and mostly pointless.
 

Midwest

-
Arms
Esteemed
might never exceed 20A through the switch but why do i keep finding them burnt out and occasionally bridged? spawn of the devil, would never fit myself.
There's thousands out their with no problems. Perhaps those that have caused issues are like problems RFC's have, to the unanitiaive. (cant be arsed to spell it correctly)
 
Electrical2Go - Online Electrical Supplier
This official sponsor may provide discounts for members

Reply to Grid switches on 32A ring in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Scolmore Electrical Products
This official sponsor may provide discounts for members
Top Bottom