How can I identify my supply type?

[goosander]

I'm trying to identify what type of electricity suppy I have, its either TN-S or TN-C-S but I can't tell for sure because the earth connection to the incoming supply is hidden under a plastic cover.

Can anyone tell from these photos, or do I have to lift the plastic
cover (green arrow on 2nd photo) below the service fuse to be sure?

 

[andy]

it has a very good chance to be TNCS

 

[goosander]

My thoughts as well, but aren't they supposed to label PME supplies?

If it helps, the supply is approx 2.5 years old and is in Fife (Scottish Power).

 

[plugwash]

its either TN-S or TN-C-S probablly TN-C-S but you can't tell for sure without opening the cutout or asking them (which i don't reccomend).

i wonder why they didn't put the neutral through the isolator looks like shoddy workmanship to me.

 

[Adam_151]

Also if you look at where the neutral leaves the meter, you can see the inner isulation is red instead of black

 

[goosander]

Did you mean you don't recommend lifting the cover or you don't recommend asking Scottish Power?

As for shoddy workmanship, I wouldn't be surprised at all, given my experiences of some of the other hammer merchants (sorry tradesmen) used by the builder.

 

[plugwash]

sorry i did mean that i didn't recommend opening the cutout

you don't really need to know if its TN-S or TN-C-S anyway unless you are running a caravan or something.

P.S that kit would have been fitted by scottish power not your builders spark. I guess they just ran out of black tail or something dunno why they put the neutral on a seperate henly though maybe it was to reduce confusion given that they were using only red tail

 

[goosander]

you don't really need to know if its TN-S or TN-C-S anyway unless you are running a caravan or something.

True, but I am planning on installing outdoor sockets for a patio and/or shed and I've seen posts on this forum that lead me to believe that the earthing requirements can be different for the two systems. Is this the case?

...dunno why they put the neutral on a seperate henly though maybe it was to reduce confusion given that they were using only red tail

I've just had a flick through the regs and have found the following which may explain the unswitched neutral:

460-01-03 "Except as provided by Regulation 460-01-05, neither an isolator (disconnector) nor a switch shall break a protective conductor or a PEN conductor."

460-01-04 "Except as required by Regulation 476-01-03, in TN-S or TN-C-S systems the neutral conductor need not be isolated or switched, where the neutral conductor can reliably be regarded as being at earth potential..."

476-01-03 "A main switch intended for operation by unskilled persons e.g. of a household or similar installation, shall interrupt both live conductors of a single phase supply."

Perhaps Scottish Power interpreted 460-01-04 very rigidly and decided that 476-01-03 did not apply as they did not consider their cutout isolator to be a 'main switch', the 'main switch' being in the consumer unit.

 

[plugwash]

460-01-03 "Except as provided by Regulation 460-01-05, neither an isolator (disconnector) nor a switch shall break a protective conductor or a PEN conductor."

but once it leaves the CUT-OUT its no longer a PEN conductor

460-01-04 "Except as required by Regulation 476-01-03, in TN-S or TN-C-S systems the neutral conductor need not be isolated or switched, where the neutral conductor can reliably be regarded as being at earth potential..."

yes so they don't absoloutely have to switch it but it still seems odd not to especially as that looks like a double pole switch. and it used an extra henly. My guess is that he was out of black tail and needed to keep them seperate to avoid confusing the guy who connected up your houses supply (i'm guessing that the supply was put in first with the isolator or neutral henly and then the aprky connected to them later)

476-01-03 "A main switch intended for operation by unskilled persons e.g. of a household or similar installation, shall interrupt both live conductors of a single phase supply."

Perhaps Scottish Power interpreted 460-01-04 very rigidly and decided that 476-01-03 did not apply as they did not consider their cutout isolator to be a 'main switch', the 'main switch' being in the consumer unit.

yeah does it by any chance have a for maintinace use only or similar notice on it?

 

[mapj1]

Your REC/DNO should be able to tell you - it has a good chance of being PME, label or not, looking at it and the age of intallation. ! http://energylinx.co.uk/electricity_distribution_map.htm

Other wise a measurement of neutral earth voltage step at the CU while switching on a large load (shower?) should tell you if the N-E resitance is less than the L-N loop resistance... and that can only mean PME.

 

[the electrican]

It does not matter what short of earth you have for an outside socket, but you MUST have the socket protected by an RCD

 

[plugwash]

it CAN matter depending partly on what you wan't to use the socket for.

you are not allowed connect a caravan or camper van to a PME supply (though i'm convinced this rule gets brokwn all the time) and many recs reccomend against using PME for anything outside.

almost all garden kit is class 2 anyway so if thats all the socket will ever get used for its a non-issue.

 

[Big_Spark]

The Supply is TNC-S (PME), and there is no restirction on an outside socket being connected to such a supply so long, as has been pointed out, it is either an RCD faceplate socket (Suck as the MK SEAL range) or the socket is protected by an RCD at the Consumer Unit.

Plug, REC's recommend, and in fact do not install, PME services for Caravans, you are correct, but this is not the same as pluging one in at your home. The Caravan situation is the same as construction site temporaries where the REC's will not supply the Earth, the end user has to have an Earth Rod installed. There is a big difference between a single caravan at someones house and a park full of Temporary accomodation..which is essentially what a caravan park is legally..if not in practice!

 

[Lectrician]

REC's will predominantly install TN-S services to caravan parks and farms, if, due to network restrictions (middle of a distribution run) they can't supply TN-S, they will supply no earth at all.

 

[kai]

Why is the Red coloured meter lead in the Neutral side too? - it looks like shoddy workmanship to me - If I did an inspection - it would be a Cat 1 Fail.