Cable size

[uksparks]

Hi,

I am going to be connecting an out door power supply, away from the building, its all metal casing.

The supply is 10mm, I am using a 3 core SWA for part of the run, the inside part was going to be in twin and earth, but then I was just thinking, going on table 54.8 section 544.1, am I looking into this too much or does it need to have a 10mm earth as its extraneous metal which is fixed into the ground?

In which case I was just thinking of running 3x 10mm inside the building so the earth is 10mm too to them comply with min size of bonding conductor.

I am right to make it 10mm throughout the entire run aren't i?

 

[uksparks]

My main point still stands, look closely at the formula in the associated annexe to exemption I) to see if you can get within the paramaters, you may have to juggle the loading about a bit, this is a starting point

Ill check the BYB in the morning when it arrives.

 

[spark 68]

it is a bit more than that, there are rules specifically for PME, you need to follow these, if TSHTF it will be you in deep doo doo

 

[ImpededLoop]

it is a bit more than that, there are rules specifically for PME, you need to follow these, if TSHTF it will be you in deep doo doo

I'll admit my lack of experience for vehicle charger installations, but what exactly is the danger here? There's an external socket that connects to the charger unit in the car which I assume is double insulated.

I know there are specific regulations about this application and that I haven't fully read them, but why is this anymore likely to harm anyone than mowing the grass with a Flymo?

Personally, I think the greatest risk would be to solely TT the charger socket if it can be simultaneously touched with the steel building cladding which is connected to the PME terminal.

 

[spark 68]

Don't forget when doing the calcs to add the new chargers load to whichever phase, if you can comply with exemption I) then it don't really matter about the Ra of the steelwork, you have already complied with BS7671, if the steelwork has a fortuitous low Ra then great

 

[spark 68]

I'll admit my lack of experience for vehicle charger installations, but what exactly is the danger here? There's an external socket that connects to the charger unit in the car which I assume is double insulated.

I know there are specific regulations about this application and that I haven't fully read them, but why is this anymore likely to harm anyone than mowing the grass with a Flymo?

Personally, I think the greatest risk would be to solely TT the charger socket if it can be simultaneously touched with the steel building cladding which is connected to the PME terminal.

The main concern as always is a broken suppliers N, where anything connected to the local CNE link can rise to phase voltage, read the caravan/marina regs

 

[Silly Sausage]

First off I would be looking at the formula in the annexe associated with exemption i), then clamping the individual tails to see how balanced the building actually is when it is normally loaded, and adding up any further loads from the DB to see if it is possible to severely unbalance it, this would be my starting point.

I hinted at this last night when I said "Archies suggestion is looking better by the minute"

I feel we might be being ignored here a smidge!
But having now seen some loading figures, I reckon your suggestion of the isolating tranny is by far the best solution!

 

[ImpededLoop]

The main concern as always is a broken suppliers N, where anything connected to the local CNE link can rise to phase voltage, read the caravan/marina regs

Thanks Spark 68.

I totally agree with what you are saying, but the only additional risk is surely the metallic enclosure for the car charger sockets.

In the case of marinas and caravan parks there is little control over the use of the sockets and the combination of bare feet and extension leads/home built electrics. With this car charging installation the cars are likely to be connected with purpose made leads and the charger units in the cars most likely double insulated.

I'm not questioning the regs, just trying to understand the background thinking behind them.

 

[spark 68]

Thanks Spark 68.

I totally agree with what you are saying, but the only additional risk is surely the metallic enclosure for the car charger sockets.

In the case of marinas and caravan parks there is little control over the use of the sockets and the combination of bare feet and extension leads/home built electrics. With this car charging installation the cars are likely to be connected with purpose made leads and the charger units in the cars most likely double insulated.

I'm not questioning the regs, just trying to understand the background thinking behind them.

In the event of a broken suppliers N (on PME) and Depending on the EVC the metalwork may become live, either the charger itself, or depending on mode possibly the vehicle itself (live DC ?), else why would they have all of these regs associated ?

I was in a IET seminar before AMD2 and originally (allegedly) the IET did not want PME connected to these chargers at all!, then there was argy bargy about the vehicle connection socket allegedly, I don't know if some of the decisions we ended up with were political at EU level rather than technical or what, then we had AMD2

 

[uksparks]

Ill be honest, I am looking at this in two ways, on one hand I accept and agree with what you are saying, but on the other, I feel its making a mountain out of a mole hill.

I really do not know what to do now.

 

[uksparks]

The main concern as always is a broken suppliers N, where anything connected to the local CNE link can rise to phase voltage, read the caravan/marina regs

WPD don't even record it, I have spoken to them about lost neutrals before and they say there is more chance of finding a needle in a haystack.

 

[ImpededLoop]

Ill be honest, I am looking at this in two ways, on one hand I accept and agree with what you are saying, but on the other, I feel its making a mountain out of a mole hill.

I really do not know what to do now.

You've got a range of suggestions for both options. Only you can decide how you choose to install it.

 

[uksparks]

You've got a range of suggestions for both options. Only you can decide how you choose to install it.

Which option would you go with?

 

[Engineer54]

Ok but how would you actually test the steel structure, it will not be possibles to guarantee that the water service is 100% disconnected and you are only testing steel as probably cannot access every single part.
what would you do? Disconnect the main earth and try doing a Ze to the steel bond?

Can't think of any other way to test the steel structure....

 

[uksparks]

Can't think of any other way to test the steel structure....

Is that a serious or sarcastic answer? I can only presume thats your genuine answer?

 

[Simlec]

Ill be honest, I am looking at this in two ways, on one hand I accept and agree with what you are saying, but on the other, I feel its making a mountain out of a mole hill.

I really do not know what to do now.

Welcome to been the boss and having peoples safety come first.. Its a crap club really but with up's & downs on the way, chin up:smiley2: