Does this metal post need to be earthed or bonded or neither?

[HappyHippyDad]

I have 5 x 6m metal posts sticking out of the ground used for 200w floodlights to light up a manege.

This is a domestic stables. The posts test as 35ohms to earth. The installation is TNCS and has 30mA RCD protection on all circuits.

The floodlight will be earthed and in doing so the post will become earthed as the bracket holding the floodlight to the post is metal.

I just cant quite work out if the post is an extraneous conductive part and needs a 10mm bonding cable or if it's an exposed conductive part as it's housing the cable up the middle of it and is holding the light, in which case it is earthed, however is the 1.5mm earth feeding the floodlight sufficient.

The cable feeding the arena lights is 6mm 3 core SWA.

Just when i think I've got earthing and bonding completely sussed I get a situation that confuses me!

 

[James]

ok, so the post on its own is no risk to anybody.
just a metal pole sticking out of the ground.

there is no risk of someone being in contact with the earth to light fitting and a different potential earth from the post itself.
I presume the circuit is rcd protected?

personally I cant see an issue.
it would seem ridiculous in my mind to bond the posts with a 10mm cable.

I am happy to wait for constructive criticism if my interpretation is incorrect.

 

[mart spark]

I'd say it would be an exposed conductive part at most as it's forming part of the electrical system. but if unsure IR test to earth and if greater than 0.02mohms it's just a piece of metal

 

[MFS Electrical]

Earth it, it’s containment

 

[HappyHippyDad]

I'd say it would be an exposed conductive part at most as it's forming part of the electrical system. but if unsure IR test to earth and if greater than 0.02mohms it's just a piece of metal

It's measured 35ohms to earth so just a tad under 0.02Mohms
There is a weatherproof junction box 40cm above the base of the post (attached to the post) which houses the terminations going up to the floodlight and on to the next post.

 

[AJshep]

IMO as long has it has a connection to a cpc and the entire length of the cable that is in contact with the pole is 30mA rcd protected. you don't need to take a main bond to it..

If it wasn't RCD protected before coming in contact with the pole then it would require bonding.

 

[jackhammerJIM]

IMO as long has it has a connection to a cpc and the entire length of the cable that is in contact with the pole is 30mA rcd protected. you don't need to take a main bond to it..

If it wasn't RCD protected before coming in contact with the pole then it would require bonding.

If the metal work becomes live due to a broken PEN conductor how will an RCD affect the outcome ?

In my opinion you should insulate the physical connection between the floodlight bracket and the post .

 

[Lucien Nunes]

By connecting the TN-C-S earth to the post, you could create a voltage gradient from the post across the soil, since the TNCS PEN could be a significant voltage away from true earth. It won't be much of a gradient because of the low Ra of the post, however horses are very sensitive to voltage gradients. It might be better to isolate the post and/or fitting from the supply earth.

Post crossed with Jim's

 

[Toneyz]

Without checking I think that when you do lamp posts the minimum to earth the post is 6mm.

 

[Midwest]

Section 714 outdoor lighting, 714.411.203 (BYB), applies I think. As its for stables, I'd also have a look through Section 705.