Cable size

[uksparks]

you should be able to see if it is PME without calling them.

I wont help even if it's not anyway.

 

[uksparks]

Not the same. No.

Thats only on the basis you can get s guarantee from the DNO it will never change.

 

[spark 68]

Even if it is PME you may well find there are earth rods already fitted, a lot of newer PME industrial units have earth rods fitted, a look around the perimeter of the building often you will see the inspection pits

 

[Guest125]

i like the idea but there just isn't the option to do this unfortunately due to it being a car park immediately outside the building.

I would say tough. To much risk.

 

[uksparks]

I must say I didn't notice any having walked all round it a couple of times.

 

[Guest125]

I seem to think this is going to be more problematic than planned for.

i think other than connecting the rod to the met there's probably not a lot of choice.

Not to the MET. The rod would earth the VCP only.

 

[davesparks]

I seem to think this is going to be more problematic than planned for.

Where's the problem?

-Install the charging point.
-Install this little length of SWA, connect it to the charging point.
-Install earth rods, utilise the root of this charging point and the rebar of the concrete pad as part of this, test it and add more rods as required then connect it to the MET.
-Test and fill in the paperwork.
-Send your invoice and get your money.

 

[uksparks]

Not to the MET. The rod would earth the VCP only.

Point two suggests connecting it to the MET

 

[davesparks]

Not to the MET. The rod would earth the VCP only.

Why not? It'll be much better for the installation as a whole to have a decent earth nest connected to the MET than it will to have what is effectively a big external socket connected to its own earthing reference in such close proximity to the metal building bonded to the PME earth.

 

[uksparks]

I'm so I'll just run 16mm swa to the charge point, connect it to the met, and also connect an earth rod in for good measure.

Ok so we have a plan of action, it says in point two, a rod of very low resistance. Can anyone telld what if says in 722 of the regs as have not got a BYB yet.

 

[Guest125]

Why not? It'll be much better for the installation as a whole to have a decent earth nest connected to the MET than it will to have what is effectively a big external socket connected to its own earthing reference in such close proximity to the metal building bonded to the PME earth.

I cannot answer that TBH. Just does not sound right.

 

[uksparks]

I guess I could put a rod or two in the base of the unit as looking at it, I'll be able to do this quite nicely, make connecting it easy.

 

[Guest125]

I guess I could put a rod or two in the base of the unit as looking at it, I'll be able to do this quite nicely, make connecting it easy.

As long as the connection is accessible.

 

[spark 68]

I guess I could put a rod or two in the base of the unit as looking at it, I'll be able to do this quite nicely, make connecting it easy.

You need to space your rods apart more than 1.5 X the length of the rods mind.

 

[davesparks]

I cannot answer that TBH. Just does not sound right.

Why doesn't it sound right? Adding an extra earth electrode to the PME supply is only going to improve it and make your installation safer in the event of an external neutral fault. This is exactly what is recommended in the regulations for swimming pools fed via a PME supply and is required practice for PME supplies in other parts of the world.

 

[davesparks]

I'm so I'll just run 16mm swa to the charge point, connect it to the met, and also connect an earth rod in for good measure.

Ok so we have a plan of action, it says in point two, a rod of very low resistance. Can anyone telld what if says in 722 of the regs as have not got a BYB yet.

I always start with 2off 8'x5/8" rods spaced 10' apart and then test that and work up from there.

The earth electrode(s) should be connected back to the MET, not to the end of your new circuit.

 

[uksparks]

I always start with 2off 8'x5/8" rods spaced 10' apart and then test that and work up from there.

The earth electrode(s) should be connected back to the MET, not to the end of your new circuit.

not even if connected with a 10mm cpc?

 

[Guest125]

Why doesn't it sound right? Adding an extra earth electrode to the PME supply is only going to improve it and make your installation safer in the event of an external neutral fault. This is exactly what is recommended in the regulations for swimming pools fed via a PME supply and is required practice for PME supplies in other parts of the world.

It just does not. I am not dismissing you or belittle your post. I am all ears and would like to understand more. I would have though somewhere in BS7671 it would say something like to earthing systems cannot be in one location. Guess guess guess. Not fact!!!!

don't get many swimming pools on the railways although the unions are thinking about this 'right' in there current talks.

 

[Guest125]

I always start with 2off 8'x5/8" rods spaced 10' apart and then test that and work up from there.

The earth electrode(s) should be connected back to the MET, not to the end of your new circuit.

Wont the fault then take the path with least resistance which is bound to be the PME earth which pretty much makes the earth rod pointless?

 

[spark 68]

Wont the fault then take the path with least resistance which is bound to be the PME earth which pretty much makes the earth rod pointless?

If the Rods can achieve around sub ohm Ra they will be effective, also the way I read it they are as backup in case of a broken DNO Neutral to keep Ut low.