3 phase supply, advice required

[lurch]

Some advice please. . . I have a local community centre (old prefab) that has a 3 phase TNS supply from the local DNO. I have carried out a EICR which has unsatisfactory on various points, however I am trying to locate the regulation that covers isolation. . . . the scenario is 3 phases in to 3 phase meter, and then 3 separate single phase domestic Consumer units, all located within a cupboard.

My concern is that there is no single point of isolation on the 3 phase supply. I want to give this a C2 but not having come across this scenario before and want to know the regulation that covers this . . . if there is one. Or is it totally acceptable to have this setup as it is. . . . constructive answers always welcome.

 

[telectrix]

Could happen anywhere switching off the wrong Mains Switch, just an important question, was the Plumber trained in the Safe Isolation Procedure? seems not in this
instance.

plumber trained? contradiction in terms there, pete. you can train a dog, but never a plumber.

 

[Spoon]

but all it takes is for joe public to look in cupboard and isolate wrong board

Unskilled personal who do not use safe isolation and testing procedures should not be working on Electrical installations full stop.

As above, 'joe public' should not be messing with the boards.

 

[streamer]

If you were to fit an isolator, then really you should get the supply company to fit an isolator in order to allow you to fit an isolator, in which case you wouldn't have to fit an isolator at all!

 

[suffolkspark]

it is in the regs that there should be a single point of isolation for an electrical installation,,,, but its definition of an installation is poorly worded meaning you can have more than 1 "installation" within a premise.... so its a grey area, imo it at the most warrants a C3

 

[hightower]

537.1.4 is the reg I think relates to this, but I'm with @Pete999 and the others - what you've got here is 3 SP installations rather than a TP install. I'm failing to see how it's unsafe.

 

[Pete999]

this highlights the point I am making. . . if there was a single point of isolation then this wouldn't of happened. we are obsessed in this country on cutting into meter tails and hooking in additional cu's .

You could argue that Mate, but in this case the Plumber was at fault for not observing the correct isoation procedures.

plumber trained? contradiction in terms there, pete. you can train a dog, but never a plumber.

OK I'll give you that one.

If you were to fit an isolator, then really you should get the supply company to fit an isolator in order to allow you to fit an isolator, in which case you wouldn't have to fit an isolator at all!

The circle of life continues

it is in the regs that there should be a single point of isolation for an electrical installation,,,, but its definition of an installation is poorly worded meaning you can have more than 1 "installation" within a premise.... so its a grey area, imo it at the most warrants a C3

You have isolation at the three inputs to the three SP&N CUs no need to code imo.

 

[Pete999]

this highlights the point I am making. . . if there was a single point of isolation then this wouldn't of happened. we are obsessed in this country on cutting into meter tails and hooking in additional cu's .

Still doesn't distract that the "Safe Isolation Procedure" should have and should be adhered to at every point of isolation in my opinion, regardless of how many switches are involved.

 

[suffolkspark]

You have isolation at the three inputs to the three SP&N CUs no need to code imo.

I wouldn't code it either pete, but this subject of single point of isolation for an installation has come up before

 

[westward10]

I would definitely Code it.

 

[Pete999]

I would definitely Code it.

So what would you code it as and why?

 

[westward10]

I tend not to discuss what Code I would list it under as that that is personal opinion and different circumstances may give different outcomes. As in #35 by HT I would refer to Reg 537.1.4 and I certainly don't sway with this more than one installation in an installation where there is only one source of supply.

 

[telectrix]

i would not code it, but maybe fit a notice " ensure that the correct isolation procedure is carried out before working on this installation". a bit like " all the right notes, but not necessarily in the right order".

 

[Ian1981]

It’s all down to interpretation again.
Each DB has a linked main switch and as such has a single point of isolation for each DB.
However the regulation points out that each installation shall have a point of isolation as close to the origin of the installation capable of switching the supply on the load side as a means of isolation.
I recall Napit put out a column in professional electrician magazine saying that a standard consumer unit supplying final circuits and a separate consumer unit supplying say a shower circuit or economy 7 can be classed as separate installations.
I myself did an EICR a couple of years back but failed to mention the single point of isolation on the Eicr.
An Niceic inspector who did a site visit as part of the company annual assessment said although it didn’t warrant a code , a comment should have been made in the relevant section of the Eicr.
But I get the view of ‘they can only be one installation etc’
My opinion....... I wouldn’t code this example but I’d mention it on the report.

 

[davesparks]

If it was my job, i would fit a 4 pole 100a isolator, much the same as your electrical utilities supplier would fit. Not expensive, and sorts out the "one point of isolation" reg. Hope this helps.

That should be either a TP isolator or a TP&N isolator if it is intended for on-load switching.
A straightforward 4 pole isolator won’t necessarily have late break/early make on the fourth pole.

 

[Dillb]

An Niceic inspector who did a site visit as part of the company annual assessment said although it didn’t warrant a code , a comment should have been made in the relevant section of the Eicr.

Since when is it any business of the NICEIC what the regs state? Its either compliant or its not, yet they make a comment that neither confirms it or isnt. Yet people still fall over themselves for these scams.