Bonding metallic pipework

[adammid]

I have just been reading through a specification for a job and the Consultant has requested that exposed metal pipework is bonded, which is obviously fine, but it says that a connection is made for every 230m2 of floor area even though the metallic pipework is continuous. I cannot and have never heard of this in the regs. Surely one connection for the whole building will suffice.

This is what the Spec says:

'Exposed metallic pipes shall be bonded to the protective conductor but where metal to metal joints exist and form a continuous electrical circuit of negligible impedance when tested, one bonding connection for a group of pipework installations may be made. At least one such connection shall be made for every 230m2 of floor area served by the pipework.'

Any thoughts guys?

Cheers

 

[44ALLAN]

Adam,

My first thought was....... what if that 'one' connection for the whole installation was removed?
Bit belt and braces really for somewhere that sounds pretty large.......alterations in the future etc.

 

[adammid]

Thanks Allan,

So you think its wise to have a connection every 230m2? Why then in the regs does it not mention multiple connections for large installations? What about it creating parallel earth paths?

 

[44ALLAN]

Thanks Allan,

So you think its wise to have a connection every 230m2? Why then in the regs does it not mention multiple connections for large installations? What about it creating parallel earth paths?

Adam,

These pipes are being 'bonded' as you would any other extraneous or exposed conductive part to limit touch voltages.
Have a read of pages 51-53 of Guidance note 8.

Parallel earth paths are brilliant mate the more the merrier I say lol

 

[Deleted member 26818]

I recently wired a switchroom.
All the containment was metal, the walls and the ceilings were metal and all the panels and enclosures were metal.
Every run of containment had to be earthed/bonded back to the earth bar, I even had to use BS951 earth clamps on conduit.
I sometimes think that some designers really don't have a clue.

 

[adammid]

Sounds like you are trying to pull our legs there Spin!! Why would you have metal walls? and are you trying to say a separate earth for each run of containment?

 

[Engineer54]

I cannot and have never heard of this in the regs. Surely one connection for the whole building will suffice.

This is what the Spec says:

'Exposed metallic pipes shall be bonded to the protective conductor but where metal to metal joints exist and form a continuous electrical circuit of negligible impedance when tested, one bonding connection for a group of pipework installations may be made. At least one such connection shall be made for every 230m2 of floor area served by the pipework.'

Any thoughts guys?

Cheers

It is a normal requirement to bond extraneous metallic pipework as it enters and exits a building on large projects. An example would be, heating or steam pipes from a central boiler house that supplies several buildings. Medical gasses, again from a central storage/supply area that serves more than one building. So single point bonding isn't ''always'' going to be the case.


Now tell us what sort of installation/systems your working on??

 

[adammid]

Its a care home. One building, and the consultant has requested one connection for every 230m2 of the floor area. There are not multiple buildings, the pipes will not leave and then re enter the building.

 

[Deleted member 26818]

Sounds like you are trying to pull our legs there Spin!! Why would you have metal walls? and are you trying to say a separate earth for each run of containment?

Here's one picture.
You should be able to make out the metal wall behind the ladder rack and the SWAs:

Here's another picture of the earth bar, not yet connected all the earths:


Again you should be able to make out the metal wall.
Yes each run of containment had to be earthed/bonded, either from one to another, or back to the earth bar.

 

[Engineer54]

Its a care home. One building, and the consultant has requested one connection for every 230m2 of the floor area. There are not multiple buildings, the pipes will not leave and then re enter the building.

My post was merely trying to explain to you, that single point bonding isn't ''Always'' going to be the case on a larger project. I'm not saying i agree with the clause either, not without knowing the reasoning behind this clause anyway!! What is the total square metre area of this building??

If your not happy with this Specification clause, or want clarification, then it's standard practice to raise a SQ(C)O (Site Query(/Clarification) Order) with the Resident Engineer. Who should then respond with a written explanation for you in the response area on the form submitted. But then it all depends what sort of information system you have on this project!! lol!!

 

[SYKRAPS]

If it is part of the specification and does not compromise BS7671 just do it and charge for it accordingly

 

[adammid]

Yes will do but then could omit it and then when they argue and say why have I not done it, I will say that it does not require bonding every 230m2 in order to comply with regs and therefore thats why I have not done it.

 

[snowhead]

Yes will do but then could omit it and then when they argue and say why have I not done it, I will say that it does not require bonding every 230m2 in order to comply with regs and therefore thats why I have not done it.

It's a request or rather a compulsory spec of the proposed contract between client and contractor, for whatever reason doesn't matter as long as it doesn't conflict with any regs.

If an Architect wanted Triple glazing and the bulding regs only ask for double glazing would you only supply double glazing?

 

[Engineer54]

Yes will do but then could omit it and then when they argue and say why have I not done it, I will say that it does not require bonding every 230m2 in order to comply with regs and therefore thats why I have not done it.

As your contract quotation price is based, ....and therefore includes complying with everything as noted in the contract specifications. You will find yourself in some very deep contractual trouble if your just going to omit what you don't think is necessary.

And don't for a second think that quoting BS7671 will get you out of trouble, contract law will not even consider it!! The ONLY way to change a contract specification, is via a ''Change Order'' which is, or has been agreed between all the interested parties along with any costing changes against that order!!

 

[1shortcircuit]

First question, What size building are you dealing with (m2)? How many floors?

If it was four floors for example, then it could just be a simple run to the first pipe on each floor so no big deal

You could politely request that the designer reassess the spec to confirm that it is essential (probably is on a large building just in case someone throws in a piece of plastic over time) but may be something that was spec'd on another job and entered onto the design sheet for this particular job by mistake?

I certainly would NOT dream of omitting ANYTHING on the spec without prior written agreement. That's just asking for trouble that could potentially ruin you... That's if the guy in the prison doesn't when you drop the soap in the shower

 

[MDJ]

therefore thats why I have not done it.

You won't get repeat business from this consultancy if you attempt to argue with the electrical engineer who designed the job and wrote the specification, unless it is a dangerous situation get on and do it, and smile whilst carrying out the work as well, at this level any trouble you cause will not be forgotten, and IME a lot of engineers are buddies and play golf together, if word gets around you are difficult you may not get much future work at all, get on with it man!!!

 

[telectrix]

it's a bit like an alarm company i worked for once. if the "consultant" specifies a magnetic contact on the karzi lid, then he gets a magnetic contact on the karzi lid.

 

[Engineer54]

I get the impression that the OP doesn't have much experience with Spec'd job's/projects!! As i stated before the specification forms a large part of the contract, as well as will contract procedures. Any quotation price submitted to win a contract, should be based very much on the specification required. So the cost of materials and man hours associated with particular items of work, will be taken as covered by the winning contractor to the client. Start omitting work, or disregarding specifications and your well and truly in breach of contract. Penalties can be crippling under the umbrella of contractual law. Stating minimum BS7671 requirements, or any other recognised code /reg or BS wouldn't be entertained as a defence, unless it can be proved the contract/specification was in contradiction/compromised that standard!!

Thing's can and often do get changed within specifications during the course of the contract, but only via following the contracts laid down procedures. ALL changes will be in writing and agreed between both parties, BEFORE such changes are incorporated into the work. But remember any changes will have a cost implication one way or the other!! lol!!

 

[PRR]

> a connection is made for every 230m2 of floor area

So if the facility is 230m long, and a conduit runs crossways, it has to be bonded every meter?

Area-based sure is odd. If the goal were RF interception, area is part of it, but also length of run. If the goal is to limit step-touch fall-of-potential shock hazard from some large electric source to remote earth, then the critical measure is distance in direction of that source. In extreme cases you would grid the whole lot, floor, even grid the walls (metal walls are pretty extreme, but I have seen rooms enclosed in tight mesh.) Also all suspended-ceiling metal, all metal water pipe, metal door-frames......

If the job is that earth-happy, then even if you aren't asked to do the walls pipes doors, you should be prepared to accept their bonds in your earth-bus. (See spinlondon's massive earth-bar.)

> Its a care home

So, old/sick people? Extra caution is warranted.

It WOULD be distressing if somebody died and your name came up in the investigation.

I'd do all the joints extra good, AND do an explicit bond every 50 feet (which is what 230m2 seems to imply). What the heck, it is THEIR contract and thus their money. Extra work for a quasi-reasonable reason and clearly specified in contract is just extra money for you.

 

[snowhead]

> a connection is made for every 230m2 of floor area

So if the facility is 230m long, and a conduit runs crossways, it has to be bonded every meter?

NO, there's no care home in this country that's 230mtrs long.

Bonding is every 230m2, so every area 23 x 10 needs 1 bond.

The home my Mother is in is made up rooms 5 x 4 mtrs either side of corridors 3mtrs wide.
So each opposite pair of rooms and section of corridor = 52mtr2.
That's bonding approx every 9 rooms.
In a 60 bed home with several lounges and dining rooms that would probably be a dozen bonds.