Commercial TN-C-S earthing..???

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Question:

A commercial property has an illuminated sign, located approx 15 metres from the building.

The supply is TN-C-S - BS88/ 3036 - SWA from main DB

The sign does not have an r1r2, or Zs reading.

At the only junction you can find (3" below the grass), the supply is 2 core rubber flex.

Between the sign and the building is a car park.

The cable feeds only the sign.

Do you:

1. drop a rod next to the sign, as the earth shouldn`t be exported anyway?

2. go hunting for the "hidden" joint with a digicat - if the car park has to be excavated, we`re into the thousands at least!

3. if you do 1. , what about the rubber cable in the earth(2 core, remember)?

FYI. The "junction box" consists of ametal pattress, wrapped with insulating tape, with a double connector strip inside it. 4" below the ground. (there is also an IP65 socket fed from the "JB" - 1.5mm rubber flex again.). The 3036 supply fuse is 16A - the outgoing swa is 10mm - the rubber flex at the "accessible junction" is 2.5mm MAX

Your thoughts, please?

 
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Is the SWA to the sign or a rubber flex? Are you saying SWA leaves building and rubber flex arrives and this is the mysterious joint you are searching for?

If you put a rod in and there's only a L & N then you'd be safe AND there's no risk of earth leakage back to this rod as not connected to main supply.

What sort of sign is it? If double insulated does it actually need an earth?

 
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well its looks like the "Amateur Vet" is thinking straighter than me at the moment.....

so don't think I will even try to be cohesive on this thread at the moment...

had a few drinks already and..

Just opened a new bottle of beer I never tried before...

saw it when fillin up the motor earlier this evening....

"Captain Smiths Titanic" 5.2%

like to try a new thing every so often!

saves gettin in a rut!:DGuiness DrinkGuiness Drink

 
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You wouldn't think the SWA would be so far away? but in which direction??

Sign on a grassy area?

Aye

Could it be under there somewhere?

well, it`s SOMEWHERE!!!!

Grass sounds long!
Au contraire. Very little grass. The rubber cale to the IP socket is actually on the surface (visible!). Apparently , the landscapers cut a cable last year, with their mower.

I`m thinking that it may have to be a digicat +genny job.

(genny to swa cpc - find out where it disappears. I`m not happy leaving this carppy 2 core 3-4" below the surface!!!!

Right. That`s it!. I`m officially jaffered:)

Me goes beddiebyes now.

Please post a definative answer guys. I`ll be really, eternally grateful!!!

KME - until the morrow.............................

 
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The SWA likely taken shortest route? If you know where it leaves building and where sign is you should be able to narrow things down?

If car park and sign similar age then would be odd to terminate randomly under car park?

 

Admin1

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Bump - Intersting thread, KME. :)

I'd like to see more replies to this one and know the outcome when you are done, Mate.

 

steptoe

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have you tried for a Zs at the junction where the SWA changes to 2core flex? or am I being too obvious?

failing that change the flex to a bit of 3core hi tuff, joint in a plastic enclosure, RCD or DP RCBO the supply out with a 6a MCB/RCBO and spike the sign.

 

mikel

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Steptoe, Reading the thread I think his problem is that he can't find the point where the swa changes to the 2 core rubber cablePray

 

Admin1

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I agree Mikel. That is the impression that I get from reading it too.

 

steptoe

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Question:A commercial property has an illuminated sign, located approx 15 metres from the building.

The supply is TN-C-S - BS88/ 3036 - SWA from main DB

The sign does not have an r1r2, or Zs reading.

At the only junction you can find (3" below the grass), the supply is 2 core rubber flex.

Between the sign and the building is a car park.

The cable feeds only the sign.

Do you:

1. drop a rod next to the sign, as the earth shouldn`t be exported anyway?

2. go hunting for the "hidden" joint with a digicat - if the car park has to be excavated, we`re into the thousands at least!

3. if you do 1. , what about the rubber cable in the earth(2 core, remember)?

FYI. The "junction box" consists of ametal pattress, wrapped with insulating tape, with a double connector strip inside it. 4" below the ground. (there is also an IP65 socket fed from the "JB" - 1.5mm rubber flex again.). The 3036 supply fuse is 16A - the outgoing swa is 10mm - the rubber flex at the "accessible junction" is 2.5mm MAX

Your thoughts, please?
maybe Im missing something?

is this the ONLY junction?

or the ONLY junction LOCATED ?

 

steptoe

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Steptoe, Reading the thread I think his problem is that he can't find the point where the swa changes to the 2 core rubber cablePray
AH,

OK,

then its gotta be CAT&GENNY time,

cant have a 2core flex buried underground.

do we have good IR between P E & N E ? on 1000v. (with light disconnected of course)

 
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Good questions mate.SWA leaves building. 2 core flex arrives in vicinity of sign!

Rod in - sign is safe, but 2 core flex isn`t!!!!!

Sign is big metal jobboid, with 2 x fluoro.for illum.

You`re learning fast, m8.....
Is this big metal sign at ground level...

i.e. accessible whilst standing on the ground ?

or do you need ladders to reach it..

could it have been considered to be out of reach when installed?

 
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Thanks for the interest guys........

The sign is on 4" square metal legs, bolted to the ground; i.e. accessible by person walking by, on the path!!!

Steptoe, m8, We can only locate this 1 junction; by which time we`ve already lost the swa & any signs of a cpc.

The originating company have okayed hiring digicat & gen; to attempt locating route / interruption.

ins. reading - abysmal (<100K) - not surprising, given the location & condition of the "JB" we found.

Further info since o/p - the hotel car park had posts sunk 18" into the ground, for fencing, 2 years ago. One of them "interfered with" an underground supply cable for the entire area.

 
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