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?

 

[SparkyChick]

If that were the case, you would only be able to assemble the case in one way to facilitate that. The Line/Neutral orientation is important because it could be opening/closing the line before/after the neutral.

If it was a switch fuse it's obviously different because you don't want the fuse terminals to be live with the switch in the off position, but for a standard (is it 60947-3 compliant) isolator, unless stated on the device itself, it shouldn't matter which side is the load and which is the supply.

Ask him to explain why it matters. And ask him what qualifies him to be providing such 'guidance'

 

[SparkyChick]

p.s. in short he's talking out of his.... you can guess the rest

 

[Raptor0014]

If that were the case, you would only be able to assemble the case in one way to facilitate that. The Line/Neutral orientation is important because it could be opening/closing the line before/after the neutral.

If it was a switch fuse it's obviously different because you don't want the fuse terminals to be live with the switch in the off position, but for a standard (is it 60947-3 compliant) isolator, unless stated on the device itself, it shouldn't matter which side is the load and which is the supply.

Ask him to explain why it matters. And ask him what qualifies him to be providing such 'guidance'

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.

 

[SparkyChick]

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.

Don't buy into his delusion. Unless I'm messed in the head, what he's saying is complete rubbish. As you pointed out... if it required a specific way, it would be labelled as such or there would be a wiring diagram on them and the cases would only go together one way.

 

[James]

Don't buy into his delusion. Unless I'm messed in the head, what he's saying is complete rubbish. As you pointed out... if it required a specific way, it would be labelled as such or there would be a wiring diagram on them and the cases would only go together one way.

I am not able to tell from here if you are “messed in the head”

however I would put my vote in for it really makes no difference, an isolator is just that, it isolates one set of terminals from another.

It might be more “normal” for it to be one way round rather than another but either way is just fine, after all it is able to do its job as an isolator.

 

[Lucien Nunes]

Might be Chinese whispers:

DNO person says 'Our standard configuration is to put the feed in the bottom.'
NIC spark says 'DNO person says they put the feed in the bottom.'
Kitchen/spark says 'NIC spark says the feed has to go in the bottom'

By the time you get to the 20th person, the remark still refers to bottoms but not in the context of wiring isolators.

 

[davesparks]

It is possible this comes from something like the wylex REC2 isolators where the enclosure is designed so that the incoming supply goes in the bottom and then the lid goes on and gets sealed, the top outgoing terminals have a smaller seperate lid. This allows the DNO side to remain enclosed when the electrician is connecting to the outgoing side.

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

Also an MCB doesn't have to have the feed in the bottom, it can go tbe other way. Some DBs have the MCB's fed from the top such as single phase schneider/Merlin Gerin boards.

 

[Mike Johnson]

Most if not all European double pole MCB's and RCD's are fed from the top, the terminals are staggered to allow bus bars to be used on both line and neutral.

 

[swaRRR]

You're right, wiring can go in either top or bottom. It's just a switch closing the circuit at the end of the day.

 

[telectrix]

with the KMf type switch fused units,s. 1 way isolates the fuse when turned off, the other leaves it live. choice allcomes down to where you can dress the cables in neatly. can't leave something that looks like a ktchen fitter has done it.

 

[timhoward]

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

Think about that a moment, then think about solar installations. None of them would work if that were true!

 

[Lucien Nunes]

Hopefully no-one calling themselves an electrician is trying to claim that it won't work the other way, rather that there is some regulation requiring it to be installed a particular way.

 

[Raptor0014]

Hopefully no-one calling themselves an electrician is trying to claim that it won't work the other way, rather that there is some regulation requiring it to be installed a particular way.

Having seen and had to rectify this guys work previously. It’s clear he’s no electrician. At a stretch he’s done a part P course at some point.

I’m far from perfect by any stretch of the imagination. But I do have some idea of what I’m doing. And if I’m ever in doubt, even in cases like this, I’m not afraid to ask more knowledgeable people and/or consult the BBB.

 

[swaRRR]

Think about that a moment, then think about solar installations. None of them would work if that were true!

When i first started doing solar the fact that the feed fed the MCB which then fed the busbar really confused me.