Supplementary bonding

[j-lextricks]

With the advent of Rcds is it still necessary to (I) supp bond in bathrooms and (ii) at pipe work from boilers? My logic would say 'yes' so that in the event of Rcd failure, zero potential continues to be achieved. There has been much discussion with myself and colleagues on this issue. I would welcome other sparks' opinions on this.
Thank you comrades,

Joe.

 

[craigday]

I would always bond gas and water services, a bit of overkill never hurt anyone

 

[oldtimer]

O yea I take it you are not running a business then because your the people you are competing with wont do it and that will reflect on the cost

 

[craigday]

No but for the sake of a bit of single green and yellow and a backlash if a problem arises I think it's worth it

 

[HappyHippyDad]

I was about to start a similar thread!

I dont think its quite as simple as saying supplementery bonding (SB) can be omitted if there is RCD protection. Reg 701.415.2 says SB can be omitted in locations containg a bath or shower provided 3 conditions are met:

(iv) All final circuits comply with requirements for automatic disconnection
(v) All final circuits in the location have RCD protection
(vi) All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2

ALL of the above conditions have to be met, not just one. I'm just abit confused about (vi), does that mean conductive parts in a bathroom still have to be connected to MET terminal in some way??

Hope this helps a little, I'm sure the experienced chaps will soon have it explained..

 

[Geoffsd]

With the advent of Rcds is it still necessary to (I) supp bond in bathrooms

Not now 'required' if other conditions are met - disconnection times and main bonding.

and (ii) at pipe work from boilers?

Never necessary (unless in bathroom) but plumbers demand it.

My logic would say 'yes' so that in the event of Rcd failure, zero potential continues to be achieved.

You can still 'supplementary' bond if you want but DO NOT bond isolated parts.

There has been much discussion with myself and colleagues on this issue. I would welcome other sparks' opinions on this.
Thank you comrades,

There are no 'opinions' just the measurements and facts and regulations.

 

[Geoffsd]

(vi) All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2

ALL of the above conditions have to be met, not just one. I'm just abit confused about (vi), does that mean conductive parts in a bathroom still have to be connected to MET terminal in some way??

Yes, by the main bonding of ecps.

 

[hermetic]

This is more common sense that regulations, and in my estimation the answer is, if there is a possibility of a potential difference arising in a fault situation, which would be removed by bonding, then BOND IT. We should never use regulations as an excuse NOT to do something which enhances safety. The above comment about not doing it because you competitors won't is irresponsible and irrelevant. Safety is paramount, not regulations.

 

[craigday]

this is more common sense that regulations, and in my estimation the answer is, if there is a possibility of a potential difference arising in a fault situation, which would be removed by bonding, then bond it. We should never use regulations as an excuse not to do something which enhances safety. The above comment about not doing it because you competitors won't is irresponsible and irrelevant. Safety is paramount, not regulations.

well said

 

[Geoffsd]

I agree with hermetic BUT -

this does not mean that all metal parts should be bonded 'willy nilly'.

It is just as dangerous to 'bond' an isolated part that should not be 'bonded'.

In fact you cannot 'bond' an isolated part - you would be earthing it and providing a current path of negligible resistance where one did not exist before.

 

[D Skelton]

I'm just abit confused about (vi), does that mean conductive parts in a bathroom still have to be connected to MET terminal in some way??

It means all extraneous conductive parts need to be effectively connected to the protective equipotential bonding. A classic example of this commonly carried out by plumbers with no due regard to the impact on electrical safety their work has is where PVC tee junctions have been used in bathrooms to join copper to copper. Say for example during a renovation the placement of the bathroom sink is to be changed to the other side of the room, the existing copper pipes are capped under the floor and a PVC tee put in place to facilitate a vertical copper feed to the new sink. Well those taps are still extraneous conductive parts but they are no longer effectively connected to the protective equipotential bonding, therefore meaning that the pipes should have supplamentary bonding linking between them bypassing the PVC tee. You can even buy the maintenance free supplamentary bond links especially for this purpose that don't even require a tool to fit from your local plumbers merchant and yet how many do you ever see fitted?!

In short, without an effective connection it is possible to reach a potential difference far higher than 50V between extraneous conductive parts.

Hope this helps?

 

[hermetic]

"It is just as dangerous to 'bond' an isolated part that should not be 'bonded'."

Can you give me an example of this?
The problem is that everyone thinks the RCD is the universal cure all and makes all installations safe. There is a rule in engineering that states that "all mechanical devices will eventually fail, and the time they last is in direct proportion to the quality of their manufacture and the amount of maintenance they get" the RCD is such a device, and DOES NOT fail "safe". Installations should remain safe even if the RCD has failed.
​

 

[Deleted member 9648]

It means all extraneous conductive parts need to be effectively connected to the protective equipotential bonding. A classic example of this commonly carried out by plumbers with no due regard to the impact on electrical safety their work has is where PVC tee junctions have been used in bathrooms to join copper to copper. Say for example during a renovation the placement of the bathroom sink is to be changed to the other side of the room, the existing copper pipes are capped under the floor and a PVC tee put in place to facilitate a vertical copper feed to the new sink. Well those taps are still extraneous conductive parts but they are no longer effectively connected to the protective equipotential bonding, therefore meaning that the pipes should have supplamentary bonding linking between them bypassing the PVC tee. You can even buy the maintenance free supplamentary bond links especially for this purpose that don't even require a tool to fit from your local plumbers merchant and yet how many do you ever see fitted?!

In short, without an effective connection it is possible to reach a potential difference far higher than 50V between extraneous conductive parts.

Hope this helps?

I dont entirely agree....extraneous means 'liable to introduce a potential,usually earth'. Supplementary bonding is only required in special locations as defined in Bs7671. If metallic pipes coming in to a special location are supplementary bonded at the point of entry,the hazard has been dealt with. Once within the location metallic pipes are no longer likely to introduce an external potential,therefore there is no requirement for effective continuity for pipework within the location.
The key part of this is the term EXTRANEOUS....there is a tendency to believe that all metallic pipes are extraneous,in general the only extraneous pipes are those coming into the location from outside the location.

 

[onions1066]

We should work to regulations that's why they are there, they are written by people considerably more intelligent than us ( well most of us, maybe not tony and MDJ ) . If it does not require bonding then don't we should all work safely but there is a point where you can take it too far.

 

[Deleted member 9648]

"It is just as dangerous to 'bond' an isolated part that should not be 'bonded'."

Can you give me an example of this?
The problem is that everyone thinks the RCD is the universal cure all and makes all installations safe. There is a rule in engineering that states that "all mechanical devices will eventually fail, and the time they last is in direct proportion to the quality of their manufacture and the amount of maintenance they get" the RCD is such a device, and DOES NOT fail "safe". Installations should remain safe even if the RCD has failed.
​

The whole idea of bonding is to reduce the possibilty of a PD between conductive parts and extraneous conductive parts. IMO supplementary bonding has always been a waste of time. Provided main bonding is effectively carried out at the point of entry there is no realistic possibility of any pipework within the confines of an equipotential zone getting an external potential....external potentials come from outside by definition.