Cable size

uksparks · Jan 5, 2015

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?

spark 68 · Jan 5, 2015

uksparks said:
Can I not connect it to the armouring to take it back to the MET or the CPC of the circuit? Do I have to run in another 10mm earth, I then have the hassle of protecting the earth cable when it leaves the wall and into the ground...

I thought you were going 16mm^ now ?

uksparks · Jan 5, 2015

spark 68 said:
I thought you were going 16mm^ now ?

Yes I am using 16mm 3 Core SWA for the entire length.

davesparks · Jan 5, 2015

UKESRail said:
I hear you all. I just cannot believe this is not a standard practice. Seems like sense in all PME supplies.

You'll have to ask the regulations committee about that one.
But it is common in many larger PME supplied installations. And if an installation has extensive underground metallic services or structural steelwork then via the main bonding this will act as an earth electrode.

telectrix · Jan 5, 2015

all this hassle for charging a toy car. :icon6:

Leesparkykent · Jan 5, 2015

what about connecting to the rebar in the reinforced concrete base?

uksparks · Jan 5, 2015

spark 68 said:
I thought you were going 16mm^ now ?

Sorry I don't know why I said 10mm, hang about, would it have to be 16mm as its strictly speaking a main earthing conductor.

uksparks · Jan 5, 2015

telectrix said:
all this hassle for charging a toy car. :icon6:

I know, its silly isnt it!

davesparks · Jan 5, 2015

uksparks said:
Can I not connect it to the armouring to take it back to the MET or the CPC of the circuit? Do I have to run in another 10mm earth, I then have the hassle of protecting the earth cable when it leaves the wall and into the ground...

It is up to you, I have presented my reasoning for connecting it directly back to the MET. If you think this is wrong or whatever then you don't have to follow it.

uksparks · Jan 5, 2015

Leesparkykent said:
what about connecting to the rebar in the reinforced concrete base?

This is the base, its only about 300mm deep.

spark 68 · Jan 5, 2015

Leesparkykent said:
what about connecting to the rebar in the reinforced concrete base?

Dave mentioned that way way back lol

uksparks · Jan 5, 2015

davesparks said:
It is up to you, I have presented my reasoning for connecting it directly back to the MET. If you think this is wrong or whatever then you don't have to follow it.

I accept what you are saying and fully understand why you have come to that way of thinking, but just to put a charger in, it seems a little like I am suddenly taking on the entire installation and trying to protect that opposed to just my bit of work.

davesparks · Jan 5, 2015

uksparks said:
Sorry I don't know why I said 10mm, hang about, would it have to be 16mm as its strictly speaking a main earthing conductor.

Of course not, I'd be inclined towards 10mm as it will be subjected to the same currents as the main bonds.

Guest125 · Jan 5, 2015

uksparks said:
You say not to the MET...

You say at the end of the circuit.

You say to the MET

You are now saying to the MET.

Which is it??

Me personally right now would earth at the end of the circuit. BUT, Wednesday when I am in the office I am going to look at what the other guys said, compare this to what I can find in the BYB and make a decision about how I would do it in the future.

Remember. YOU need to be happy that it complies.

Leesparkykent · Jan 5, 2015

spark 68 said:
Dave mentioned that way way back lol

trying to steal dave's thunder lol

uksparks · Jan 5, 2015

UKESRail said:
Me personally right now would earth at the end of the circuit. BUT, Wednesday when I am in the office I am going to look at what the other guys said, compare this to what I can find in the BYB and make a decision about how I would do it in the future.

Remember. YOU need to be happy that it complies.

My BYB will arrive on Wednesday too so will look then. I think it will probably end up just being a rod(s) at the end of the circuit.