Bonding to pipes

[Flanders]

Fair comments I always do a continuity test and pipe work and metal parts in a bathroom / shower room / airing cupboard anwyay

AM I correct about the cross bonding of boilers and sinks ?

 

[Geoffsd]

Refer back to my previous post and point 2 Geoff

I wasn't querying any of your excellent post :smiley2: merely trying to point out to the OP that the situation may be satisfactory.

 

[D Skelton]

Yes indeed. If there are no extraneous or exposed conductive parts within the bathroom then the requirements of 701.415.2 have been met by the very nature of the fact that there are no extraneous or exposed conductive parts within the bathroom to supplementary bond!

 

[hoppy]

Am I right in saying if you test between an exposed and extraneous conductive part and the resistance is less than 1666 ohms then bonding in the bathroom is not required, or does the figure have to be 0.05 ohms or less

 

[D Skelton]

The result measured has to be less than or equal to 50V/Ia or 50V/I(delta)n in a.c systems. However, if you were using 30mA as your I(delta)n and using a resistance of 1667ohms as your reference then I would argue that those two parts are not effectively connected to earth and would need supplementary bonding.

0.05 ohms is a quoted and suggested figure to ascertain an effective connection to earth, anything greater than that in a bathroom would require supplementary bonding. Only once you have provided supp bonding can you apply the aforementioned formula.

 

[Geoffsd]

The result measured has to be less than or equal to 50V/Ia

That is correct - Ia for the highest rated opd on the circuits of the location.

415.2.2 Where Ia is the operating current in amperes of the protective device.
For overcurrent devices, the current causing automatic operation in 5 seconds.
For RCDs, IΔn.

For example if the only circuit in the bathroom is a lighting circuit on a B6A MCB then R(must be)≤/Ia = 50/(6x5) = 50/30 = 1.66Ω
Measurements between parts of less than 1.66Ω confirms that the supplementary bonding is satisfactory.

However, if that measurement is obtained before bonding is applied then it is not required.

If there is a shower circuit on a B40 MCB then the value used would be 50/(40x5) = 50/200 = 0.25Ω.

or 50V/I(delta)n in a.c systems. However, if you were using 30mA as your I(delta)n and using a resistance of 1667ohms as your reference then I would argue that those two parts are not effectively connected to earth and would need supplementary bonding.

Not so.
That is why supplementary bonding is not required when RCDs protect ALL the circuits of the location (AND the other conditions are also met).
The value is merely a limit obtained from 50/0.03, such a high reading is most unlikely

0.05 ohms is a quoted and suggested figure to ascertain an effective connection to earth,

Not so.
0.05Ω is a figure generally considered to be negligible impedance and is used to confirm a good connection between the bonding conductor and the part to which it is connected.

anything greater than that in a bathroom would require supplementary bonding.

Not so - see above.

Only once you have provided supp bonding can you apply the aforementioned formula.

Not really - as above.

 

[D Skelton]

I'm sorry mate, I have to disagree. If you are in a bathroom measuring 1.5kohms between a tap and the light swtich then at least one of those parts is NOT effectively connected to earth, therefore just adding an RCD at 30mA would not be enough. Ascertaining the effectiveness of a connection to earth in a bathroom isn't as simple as just using R=or<50V/I(delta)n. Those are the only points I was trying to make.

0.05 ohms is a stated value that CAN be used to ascertain the effectiveness of a connection between an extraneous conductive part and the MET

 

[hoppy]

Thanks for the guidance guys. So basically it is better to use the formula with the highest rated mcb in the bathroom to measure resistance to check supp bonding is effective or if it is required.This then should be done even if rcd protection is present. In you opinion is best to ignore the 1666 ohms resistance allowed for an rcd and always use the highest mcb and calculated resistance! Sorry to keep going on I just like getting other people's opinions and experiences who have a better knowledge and understanding.

 

[D Skelton]

If there is no supplementary bonding, how can you use the formula for ascertaining whether or not a supplementary bonding connection is suitable?! You need to first assess the effectiveness of an exposed or extraneous conductive part's connection to earth.

 

[Geoffsd]

If you are in a bathroom measuring 1.5kohms between a tap and the light swtich then at least one of those parts is NOT effectively connected to earth,

That's what I said.
1666 is just a nominal value obtained from 50/0.03. It is unlikely to be that high.

(Much the same as using 23kΩ to determine isolation.) It's actually going to be only a few ohms or almost infinite.

therefore just adding an RCD at 30mA would not be enough.

Well, it would but the situation isn't going to arise where you find 1665 or 1668Ω but if the measurement was slightly above the required maximum then an RCD (on ALL circuits AND other conditions) would remove the need for supplementary bonding.

Ascertaining the effectiveness of a connection to earth in a bathroom isn't as simple as just using R=or<50V/I(delta)n. Those are the only points I was trying to make.

But supplementary bonding is not about ascertaining the effectiveness of a connection to earth.
(That should have been done already with the main bonding and effective cpcs.)
It is about ensuring minimal potential difference in the event of a fault.

0.05 ohms is a stated value that CAN be used to ascertain the effectiveness of a connection between an extraneous conductive part and the MET

Well, obviously it CAN and WOULD BE but it is not an upper limit.
0.05Ω is only 3m of 1mm or 11m of 4mm conductor so not likely to be achieved anywhere.

 

[Geoffsd]

If there is no supplementary bonding, how can you use the formula for ascertaining whether or not a supplementary bonding connection is suitable?! You need to first assess the effectiveness of an exposed or extraneous conductive part's connection to earth.

First you measure between all the extraneous and exposed parts.

If the values are below 50/Ia then either the parts are already bonded (elsewhere) or do not require bonding.
If the values are above 50/Ia then the parts require bonding unless ALL circuits (AND the other conditions are met) are protected by RCDs.

 

[D Skelton]

That's what I said.
1666 is just a nominal value obtained from 50/0.03. It is unlikely to be that high.

It could easily be that high if polyplumb has been used.

Well, it would but the situation isn't going to arise where you find 1665 or 1668Ω but if the measurement was slightly above the required maximum then an RCD (on ALL circuits AND other conditions) would remove the need for supplementary bonding.

Not if there were parts that weren't effectiviely connected to earth.

But supplementary bonding is not about ascertaining the effectiveness of a connection to earth.
(That should have been done already with the main bonding and effective cpcs.)
It is about ensuring minimal potential difference in the event of a fault.

I know it isn't, but specifically in a bathroom it is needed if exposed/extraneous CPs are NOT effectively connected to earth.

Well, obviously it CAN and WOULD BE but it is not an upper limit.
0.05Ω is only 3m of 1mm or 11m of 4mm conductor so not likely to be achieved anywhere.

If water is bonded and no plastic fittings used, the chances are supp bonding wouldn't be required in a bathroom as 0.05ohms between parts is a very acheivable value.

- - - Updated - - -

That's what I said.
1666 is just a nominal value obtained from 50/0.03. It is unlikely to be that high.

It could easily be that high if polyplumb has been used.

Well, it would but the situation isn't going to arise where you find 1665 or 1668Ω but if the measurement was slightly above the required maximum then an RCD (on ALL circuits AND other conditions) would remove the need for supplementary bonding.

Not if there were parts that weren't effectiviely connected to earth.

But supplementary bonding is not about ascertaining the effectiveness of a connection to earth.
(That should have been done already with the main bonding and effective cpcs.)
It is about ensuring minimal potential difference in the event of a fault.

I know it isn't, but specifically in a bathroom it is needed if exposed/extraneous CPs are NOT effectively connected to earth.

Well, obviously it CAN and WOULD BE but it is not an upper limit.
0.05Ω is only 3m of 1mm or 11m of 4mm conductor so not likely to be achieved anywhere.

If water is bonded and no plastic fittings used, the chances are supp bonding wouldn't be required in a bathroom as 0.05ohms between parts is a very acheivable value.

 

[D Skelton]

First you measure between all the extraneous and exposed parts.

If the values are below 50/Ia then either the parts are already bonded (elsewhere) or do not require bonding.
If the values are above 50/Ia then the parts require bonding unless ALL circuits (AND the other conditions are met) are protected by RCDs.

If the values are above 50/Ia then the parts require bonding full stop! It is irrelevant whether or not an RCD is used.

 

[Geoffsd]

If the values are above 50/Ia then the parts require bonding full stop! It is irrelevant whether or not an RCD is used.

Not so.

701.415.2
Where the location ...
(iv) ...
(v) ...
(vi) ...

 

[D Skelton]

If the values are above 50/Ia how can they be considered to be effectively connected to earth?!?

Supplementary bonding can ONLY be ommitted if the requirements for ADS have been met, parts are effectively connected to earth AND 30mA RCD protection is provided on all circuits within the location.

I think I have illustrated this exact same point two more times throughout this thread!