Electric Meter Switch Isolator wiring orientation

[Raptor0014]

Having a discussion the other day with a kitchen fitter who “also does electrics” and he is adamant that a NIC contractor told him that a meter isolation switch has to have the supply go in the bottom and the load out the top, same as a MCB. This convo came about as he said the property we were both at was wired wrong as the supply went in the top of the EMIS.

I tried to explain that unless the manufacturer instructions stipulate it only goes one way (like a KMF) then it won’t really matter, if there is any ambiguity it should be labelled which way it is wired and any sane electrician would test it was dead before working on it. Plus it would usually have the larger of the two covers over the supply side.

However he was adamant I was wrong. So I opened up the CU I was working on and asked him to look at the 100A switch and pointed out the supply for that goes in the top and the same 100A type switch is usually found in the EMIS.

I‘ve installed various make EMIS and don‘t ever recall one stipulating which way the supply side must be. But he is adamant that they can only go one way.

Am I being thick?

 

[nicebutdim]

However I think you can just swap it around so the enclosure is up the other way to feed in the top.

They can indeed. The covers are designed to ensure incoming tails are enclosed no matter which side they come in.

 

[mainline]

Having a discussion the other day with a kitchen fitter who “also does electrics” and he is adamant that a NIC contractor told him that a meter isolation switch has to have the supply go in the bottom and the load out the top, same as a MCB. This convo came about as he said the property we were both at was wired wrong as the supply went in the top of the EMIS.

I tried to explain that unless the manufacturer instructions stipulate it only goes one way (like a KMF) then it won’t really matter, if there is any ambiguity it should be labelled which way it is wired and any sane electrician would test it was dead before working on it. Plus it would usually have the larger of the two covers over the supply side.

However he was adamant I was wrong. So I opened up the CU I was working on and asked him to look at the 100A switch and pointed out the supply for that goes in the top and the same 100A type switch is usually found in the EMIS.

I‘ve installed various make EMIS and don‘t ever recall one stipulating which way the supply side must be. But he is adamant that they can only go one way.

Am I being thick?

100A 1 Pole + Neutral Electricity Meter Isolator Switch

proteusswitchgear.com

Facility to seal the enclosure cover and incoming ‘bottom’ connections, allowing the outgoing ‘top’ connections to be
made at a later stage

Wylex 100A DP Isolator With Enclosure - Screwfix

Order online at Screwfix.com. Ideal for use where local isolation is required. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Load /Supply either way.

 

[Simon47]

I've come across some "interesting" "facts" from supposedly competent electricians in teh past. One of my favourites was the one who told me that data had to be in the top section of the dado trunking - because if the power went in the top and data in the middle then they wouldn't be insulated*. Had to re-route some of the cables on that job as the top section wasn't big enough for all the cables.
* No this wasn't about open-back mounting frames, he genuinely believed the PVC divider only insulated one-way.

 

[Dave OCD]

I was once told by an ex navy Electrician that if common and L1 were swapped over in a one way switch it would then operate upside down ?!

 

[Other_Tucker]

I'm sure it doesn't matter if the supply goes in the top or bottom of the isolator, we've had this debate at work. It's a switch which disconnects and reconnects a conductor. Yet we still put supply in the top and load in the bottom out of habit, as it is in a CU main switch. The tiny diagram on the front of a RE2 isolator shows the top as main and the bottom attached to the switching poles, see pic, still sure electrically it doesn't matter

 

[Simon47]

It doesn't matter. The electrons don't care which contact they arrive at and find an air gap. But then. 1/100th of a second later, other electrons will arrive at the other contact and find the same air gap.

 

[Mike Johnson]

The problem is there are muppets in this world who don't know to test what side of the switch is live, just assume that the covered terminals are the live side, which is not unreasonable, but only make that mistake once.

 

[mainline]

I did ask him to explain and I did mention about the line and neutral being right. I explained about KMFs etc for the very reason about the fuse terminals being live.

But he was so insistent that it was wrong and should be bottom in top out that I actually started to doubt myself hence running a sanity check on here. I normally have a couple on the van but didn’t have one to show him.

When I was in infant school, he would be the one standing in the corner with the hat on.

 

[Mike Johnson]

When I was in infant school, he would be the one standing in the corner with the hat on.

Now days called an infringement of your human rights.

 

[brianmoooore]

Came across a stand alone RCD once that had been wired N - S on one pole and S - N on the other. Still worked perfectly as an RCD, of course, and the layout of things around it made it obvious why it had been done, but the problem was the test button circuit. These are normally wired to take the neutral from one end and the live feed from the other, so that the power to the test circuit is disconnected as soon as it trips. Unfortunately, in this case, the neutral and the live were both taken from the 'in' side, so the test resistor had been fried by the button being held in too long.

 

[Simon47]

Came across a stand alone RCD once that had been wired N - S on one pole and S - N on the other. Still worked perfectly as an RCD, of course ...

It shouldn't have worked - should have tripped under any load as the sense coil would read the sum of the currents rather than the difference.

 

[brianmoooore]

It shouldn't have worked - should have tripped under any load as the sense coil would read the sum of the currents rather than the difference.

You could well be right. It was back in the day when RCDs were still pretty much a novelty and this one had been added in front of an old MEM rewireable fuse board. I only got as far as testing it by the inbuilt button, which it failed and then started emitting smoke (which was when I realised how it had been connected.)
Board and RCD were replaced by DIN rail type CU, with a RCD main switch and MCBs and a couple of extra ways for the new circuits that I was there to install.

 

[baldelectrician]

I really like the Hager VC02SW REC isolators
The cover can be rotated to allow the supply at either side

They are also slimmer than others on the market, as well as having terminals that tighten to 3.6 Nm and cord clamps for the meter tails
All in a decent bit or kit.

 

[nicebutdim]

I really like the Hager VC02SW REC isolators
The cover can be rotated to allow the supply at either side

They are also slimmer than others on the market, as well as having terminals that tighten to 3.6 Nm and cord clamps for the meter tails
All in a decent bit or kit.

Is it much slimmer than wylex RECSW2S?

I like the twin screws provided by wylex and wonder if Hager provide the same?


Edit: Can't find info on terminals, but note that it's 15mm narrower than the slim wylex enclosure. Seems a touch expensive, but smaller profile would be invaluable in many homes where incoming supply is afforded a ridiculously small
amount of space.

 

[mainline]

Is it much slimmer than wylex RECSW2S?

I like the twin screws provided by wylex and wonder if Hager provide the same?


Edit: Can't find info on terminals, but note that it's 15mm narrower than the slim wylex enclosure. Seems a touch expensive, but smaller profile would be invaluable in many homes where incoming supply is afforded a ridiculously small
amount of space.

REC2S 150mm 63mm 79mm (H W D)
VC02SW 145mm 50mm 78.5mm