Bonding shed query

Xtrail14

I’m adding a extension to a shed and the structure is H iron, it’s to store two vintage tractors. One electrician said the poles need to be bonded but another electrican disagree and said since the shed is not for livestock there is no need.
How can there be two opinion? The poles are buried in ground in cement, it’s not a bolt down shed.

JL spark

Xtrail14 wrote: »

I’m adding a extension to a shed and the structure is H iron, it’s to store two vintage tractors. One electrician said the poles need to be bonded but another electrican disagree and said since the shed is not for livestock there is no need.
How can there be two opinion? The poles are buried in ground in cement, it’s not a bolt down shed.

Yes bond them , they are not part of the electrical installation but under fault conditions could come live , extraneous bonding

Risteard81

JL spark wrote: »

Yes bond them , they are not part of the electrical installation but under fault conditions could come live , extraneous bonding

Bonding has nothing to do with them potentially becoming live under faullt conditions. That is Earthing.

Bonding is there to ensure that extraneous-conductive-parts which can introduce a potential - generally Earth potential - are maintained at the same potential as the MET. So in a fault it makes these parts deliberately live so that no (or limited) current will pass when simultaneously in contact with these parts and Earthed metalwork which is live.

johnnyfruitcake

Risteard81 wrote: »

Bonding has nothing to do with them potentially becoming live under faullt conditions. That is Earthing.

Bonding is there to ensure that extraneous-conductive-parts which can introduce a potential - generally Earth potential - are maintained at the same potential as the MET. So in a fault it makes these parts deliberately live so that no (or limited) current will pass when simultaneously in contact with these parts and Earthed metalwork which is live.

If there is continuity between the H bars in the shed via the roof supports and metal sheeting, is bonding required?

EHP

You need to bond all exposed metal parts unless the steel is welded together you have to link all with bonding wires usually 10mm. Steel bolted together is not considered as continuous and needs bonding links.

JimToken

EHP wrote: »

You need to bond all exposed metal parts unless the steel is welded together you have to link all with bonding wires usually 10mm. Steel bolted together is not considered as continuous and needs bonding links.

Is there any regulation they says that?

2011

JimToken wrote: »

Is there any regulation they says that?

Whether a bolted connection is sufficient or not is a bit of a gray area.
Different people tend to have different views depending on a lot of factors.
In ATEX areas which are generally considered the most risky we would not bond across every bolted connection but we would record the resistance across pretty much every connection.

With the shed I would bond a few of the main structural parts but not ever sheet.

johnnyfruitcake

2011 wrote: »

Whether a bolted connection is sufficient or not is a bit of a gray area.
Different people tend to have different views depending on a lot of factors.
In ATEX areas which are generally considered the most risky we would not bond across every bolted connection but we would record the resistance across pretty much every connection.

With the shed I would bond a few of the main structural parts but not ever sheet.

I think bonding each H bar would be sufficient, if it's every part of a cattle shed you would have cable running everywhere, to each feed barrier and cubicle divider.

2011

johnnyfruitcake wrote: »

I think bonding each H bar would be sufficient, if it's every part of a cattle shed you would have cable running everywhere, to each feed barrier and cubicle divider.

I wired a milking parlor many moons ago. We welded all of the feed toughs together to reduce the bonding cabling requirements. Cattle are particularly susceptible to stray voltages.

johnnyfruitcake

2011 wrote: »

I wired a milking parlor many moons ago. We welded all of the feed toughs together to reduce the bonding cabling requirements. Cattle are particularly susceptible to stray voltages.

Would a milking parlor be more susceptible to stray voltage due to the milking units and the more than likely wet ground?

2011

johnnyfruitcake wrote: »

Would a milking parlor be more susceptible to stray voltage due to the milking units and the more than likely wet ground?

I would look at it differently. Everywhere in farmyards should be considered very wet.
Anywhere with cattle should be considered high risk. A cow will hop from foot to foot if there is a one volt difference between its hind and front legs. Just 25V can kill a cow.

So this can mean equipotential bonding cables everywhere.

2011

When I wired a farmyard I learned a few important lessons:

1) Earth rods / earth pits and areas around same need to be fenced off so that cattle can not access the areas. This is due to the risk of step potential.

2) Keep all electrical cables and accessories out of reach of cattle or chase into the wall. Cattle will deliberately rub against anything that sticks out.

3) Where possible use plastic enclosures. Anything that can rust will rust.

4) Always select the highest IP rating possible for all enclosures. Everything tends to get hosed down.

5) Everything should be as robust as possible. It is a very harsh environment.

6) Rodents have been known to chew cables!

7) NYMJ is not UV resistant.

8) Hager make a great IP rated board.

9) Consider using 3 phase everywhere that it is possible.

10) We ensured that the entrance to the “power room” was too narrow for a cow to enter. They made a number of attempts:)

Tuco88

I've never seen Earth links across bolts for structural RSJs before, not to say it is not wrong. You'd have to do alot of drilling becase those bolts are very large, ive never seen a lug that size ~24mm hole? I also wouldn't dream going near it mechanical certs etc...

The way we did it recently was 2 single 120mm^2 main earth cables is installed to form a ring, Earth bars mounted on the main RSJs. We would usually take a link from the Earth bar back onto the steel also.

Older ways you would see is with a 120mm^2 link onto the RSJ to the earthbar via Cadwelding. They use the steelwork as an Earthing highway if you will, probably handy to install at the time but not ideal.

Point to point Main Earth test then.

2011

Tuco88 wrote: »

I've never seen Earth links across bolts for structural RSJs before

It is common enough. Often earth bosses with an M10 or M12 tapping are provided especially for this reason.

Tuco88

I've seen bosses, never across joints tho, everyday is a school day. Even on a new 150m extension its not been done on that, must be a site requirement.

2011

Tuco88 wrote: »

I've seen bosses, never across joints tho, everyday is a school day. Even on a new 150m extension its not been done on that, must be a site requirement.

The bosses can be used to cross bond and / or link back to a local earth bar.
Like I said in an earlier post, it is a bit of a gray area. When dealing with cattle (as per the OP’s situation) bonding is far more important than when dealing with people.

Tuco88

I've only seen the bosses where to attach the main earth to the steel, so say the main supports not on all the steel joints. Another one is the use of bolts with star/serrated washers on PTFE lined pipework.

I don't think its for livestock only vintage tractors. A nice fordson super major I hope ��

2011

Tuco88 wrote: »

I've only seen the bosses where to attach the main earth to the steel, so say the main supports not on all the steel joints. Another one is the use of bolts with star/serrated washers on PTFE lined pipework.

Yes, this is a very common solution in pharma plants. We generally accept any reading across a joint like that that is <0.5 Ohms.

I don't think its for livestock

Reading back, I think you are correct.

JimToken

Do we have a figure here here in ET101 for the max.resistance of the main bonding conductor allowed

I've seen a figure quoted of 0.05 ohm

2011

JimToken wrote: »

Do we have a figure here here in ET101 for the max.resistance of the main bonding conductor allowed

No. What would you consider to be the main bonding conductor?

I've seen a figure quoted of 0.05 ohm

Where? As measured between what 2 points ?

JimToken

2011 wrote: »

There is no single bonding conductor maximum resistance value.



Where? As measured between what 2 points ?

Of course not I'll have to look up the info

JimToken

2011 wrote: »

No. What would you consider to be the main bonding conductor?



Where? As measured between what 2 points ?

Let's say the main bonding here was for an outbuilding

How far can the main bond run from the MET in 10 sq for example

2011

JimToken wrote: »

Let's say the main bonding here was for an outbuilding

How far can the main bond run from the MET in 10 sq for example

I think you are talking about the CPC to the outbuilding from the main board. In which case you would have to consider the rating and type of upstream protective device. Then you would be looking at the maximum earth fault loop impedance that would ensure that the maximum disconnection time was not exceeded. In other words the lower the rating of the upstream MCB the longer the 10 sq. CPC could be (if everything else was equal).

JimToken

2011 wrote: »

I think you are talking about the CPC to the outbuilding from the main board. In which case you would have to consider the rating and type of upstream protective device. Then you would be looking at the maximum earth fault loop impedance that would ensure that the maximum disconnection time was not exceeded. In other words the lower the rating of the upstream MCB the longer the 10 sq. CPC could be (if everything else was equal).

It's a reading for the main bonding , it doesn't seem to be a regulation

JimToken

https://www.voltimum.co.uk/articles/how-long-should-main-protective-bonding

link there which i can't read

Tuco88

2011 wrote: »

Yes, this is a very common solution in pharma plants. We generally accept any reading across a joint like that that is <0.5 Ohms.

The site that I am on, the standard for static on pipework is <1.0 Ohm for welded pipe lines. This reference from a local Earth bar to earh point (Flange/Valve etc..)

PTFE lined pipework is actually <10 Ohms. On new installed pipework usually have a stud tack welded on to attach a lug/washer/nut so a low value is possible <1 Ohm.
The problem is the nature of the swivel type flage used on PTFE pipework, its impossible to get low readings especially on old pipe with the stud broken off or just not on it.

Not to mention the bonding strap is to 16mm^2, it looks cat when done, takes time to be done well.

Interesting to hear other site standards.