lamp post earthing

[binky]

Was working on a lamp post today and wondering why the post itself is bonded when all contents /cabling is class II./ armoured. Whilst I appreciate the post forms an extraneous conductive part, if all electrical items are Class II what's the chance of shorting to the casing, which also, effectively, is a large earth rod.

 

[Andy™]

its not all class 2. the head will usually be class 1 so the post is indirectly an exposed conductive part through the fixings at the top. its also common to have an earth to the door too

the column is usually coated in bitumen type material too where is int he ground, so its not always as good of an earth rod as you might expect

its unlikely, but the cable is also unsupported and can rub against the column internally to the point of failure (you can often hear it when the post is moving in the wind)

 

[Sidewinder]

its not all class 2. the head will usually be class 1 so the post is indirectly an exposed conductive part through the fixings at the top. its also common to have an earth to the door too

the column is usually coated in bitumen type material too where is int he ground, so its not always as good of an earth rod as you might expect

its unlikely, but the cable is also unsupported and can rub against the column internally to the point of failure (you can often hear it when the post is moving in the wind)

2nd'd

 

[Blue Duck]

lampposts have doors!!!???

Well I never...

I thought the oval hole in the side was some kind of bin that when full was sealed up with green and yellow tape and a peice of cardboard.

:innocent

 

[kerching]

its not all class 2. the head will usually be class 1 so the post is indirectly an exposed conductive part through the fixings at the top. its also common to have an earth to the door too

the column is usually coated in bitumen type material too where is int he ground, so its not always as good of an earth rod as you might expect

its unlikely, but the cable is also unsupported and can rub against the column internally to the point of failure (you can often hear it when the post is moving in the wind)

Turded

 

[SLIPSHOD & SLAPDASH]

I foolishly phoned the nic helpdesk about a block of flats with numerous metal illuminated bollards and a few lamposts dotted around the grounds. All were supplied by pyro bonded at both ends, connected to a PME  supply, i like normal  never got an answer if this was acceptable.

Or if the 1.5l pyro satisfied the bonding rules

 

[kerching]

I foolishly phoned the nic helpdesk about a block of flats with numerous metal illuminated bollards and a few lamposts dotted around the grounds. All were supplied by pyro bonded at both ends, connected to a PME  supply, i like normal  never got an answer if this was acceptable.

Or if the 1.5l pyro satisfied the bonding rules

I may be able to assist in your plight....

A) were  you expecting an answer from them?

B) did they suggest you refer to the  Bad Book?

i have NEVER had an answer from them yet!

did they try to sell you a label printer instead?

 

[binky]

its not all class 2. the head will usually be class 1 so the post is indirectly an exposed conductive part through the fixings at the top. its also common to have an earth to the door too

the column is usually coated in bitumen type material too where is int he ground, so its not always as good of an earth rod as you might expect

its unlikely, but the cable is also unsupported and can rub against the column internally to the point of failure (you can often hear it when the post is moving in the wind)

makes sense, but if it all were Class II would it really be required to bond the steel. Can't help thinking the pole would make a bloody good earth rod in some locations, and so that must have an affect on the earthing system

 

[Andy™]

probably helps the DNO with their PME.in some areas each column has its own DNO feed. in other areas there is one DNO feed then council wiring between multiple lights.

 

[Blue Duck]

makes sense, but if it all were Class II would it really be required to bond the steel. Can't help thinking the pole would make a bloody good earth rod in some locations, and so that must have an affect on the earthing system

Dog piss makes it a bad earth rod. 

 

[binky]

LOL,

 

[binky]

with regards to sizing a bond, am I still right in thinking it's half the neutral size with a minimum of 4mm.

 

[Andy™]

 generally its not less than half the earthing conductor size with min of 6mm, unless its TNCS.

however, street lighting earthing has slightly different requirements, 559.10

 

[binky]

trying to find what electrical cabinets come under ie the metal cabinets used for containg the supplies to outdoor lighting, sockets for regular events, I've read the index about 10 times but nothing seems to relate to these? Anyone know what these come under?

 

[Andy™]

street lighting etc used to have its own section in special locations (or am i going mad?) but was removed. generally, the usual regs now apply

 

[Essex1]

Street lighting comes under street furniture in BS7671. 

 

[Andy™]

yep. long gone...

 

[Sidewinder]

 generally its not less than half the earthing conductor size with min of 6mm, unless its TNCS.

however, street lighting earthing has slightly different requirements, 559.10

There is no section 559.10 in Amd 3!

It's now Section 714 BTW.

 

[Andy™]

oops. thats what happens when amd3 is at the office and you quickly look through an old version you have at home...

 

[binky]

Street lighting comes under street furniture in BS7671. 

sounds like a sofa and 2 comfy armchairs...