Bathroom Earth Bonding

[JohnW2]

one would probably never have to contemplate any bonding which was not 'earthed'.

What about in an IT system?

Hmmm - I was, as you will understand, talking in the context of 'normal' domestic installations This is, after all, a DIY forum!

Kind Regards, John

 

[Risteard]

one would probably never have to contemplate any bonding which was not 'earthed'.

What about in an IT system?

Hmmm - I was, as you will understand, talking in the context of 'normal' domestic installations This is, after all, a DIY forum!

Kind Regards, John

Fair enough!

 

[christof22]

Hi John

It does depend upon the installation as you say, though if MPB is required then for ADS to be safe MPB needs to be installed.

Hadn't read the full thread, missed the SB bit

Cheers Chris

 

[JohnW2]

Hi John ... It does depend upon the installation as you say, though if MPB is required then for ADS to be safe MPB needs to be installed.

I'm still not sure what you're getting at. If MPB is required, then MPB is obviously required for safety, as an issue is its own right - but what do you mean by 'ADS not being safe' if MPB (if required) is not installed? Do you mean that the installation as a whole is 'not safe' if it does not have MPB if required as well as ADS (which is clearly true), or are you suggesting that there is some way in which the ADS itself will be affected (detrimentally) by the absence of required MPB?

Kind Regards, John

 

[christof22]

Hi John ... It does depend upon the installation as you say, though if MPB is required then for ADS to be safe MPB needs to be installed.

I'm still not sure what you're getting at. If MPB is required, then MPB is obviously required for safety, as an issue is its own right - but what do you mean by 'ADS not being safe' if MPB (if required) is not installed? Do you mean that the installation as a whole is 'not safe' if it does not have MPB if required as well as ADS (which is clearly true), or are you suggesting that there is some way in which the ADS itself will be affected (detrimentally) by the absence of required MPB?

Kind Regards, John

I'm getting confused now


Yes, the first part of your post is the point i am making, maybe i misunderstood your previous post( that one can exist without the other)





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[JohnW2]

I'm getting confused now
Yes, the first part of your post is the point i am making, maybe i misunderstood your previous post( that one can exist without the other)

I thought I was just making a statement of fact As I said, there are properties in my village that have no need for MPB - so, in those properties, ADS can exist (perfectly safely) without MPB. Conversely, one can have satisfactory MPB (and maybe also SB) but without satisfactory ADS (e.g. if Zs was too high) - in this case 'not safe'.

Hence, it seems to me that one can 'have one without the other'. I never suggested that it had to be safe (which it isn't in the second of the above two scenarios), merely that the concept of ADS did not require any sort of bonding to be present (or vice versa).

Kind Regards, John

 

[christof22]

I'm getting confused now
Yes, the first part of your post is the point i am making, maybe i misunderstood your previous post( that one can exist without the other)

I thought I was just making a statement of fact As I said, there are properties in my village that have no need for MPB - so, in those properties, ADS can exist (perfectly safely) without MPB. Conversely, one can have satisfactory MPB (and maybe also SB) but without satisfactory ADS (e.g. if Zs was too high) - in this case 'not safe'.

Hence, it seems to me that one can 'have one without the other'. I never suggested that it had to be safe (which it isn't in the second of the above two scenarios), merely that the concept of ADS did not require any sort of bonding to be present (or vice versa).

Kind Regards, John

Hi John, i didn't quite grasp what you were saying


Conversely, one can have satisfactory MPB (and maybe also SB) but without satisfactory ADS (e.g. if Zs was too high) - in this case 'not safe'.



Notwithstanding thermal constraints, you can, it would be a challenge and you would definitely require SB.

So yes i agree in certain installations it is possible to have one without the other, though we do need disconnection unless we can guarantee touch voltages will be less the 50 V, so we need to be very careful with the touch voltages and what level of disconnection we do have.



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[EFLImpudence]

I agree with John.

What you are saying is that if the installation is not compliant then it may not be safe.
Probably correct.

However, that should not be the case.

 

[JohnW2]

Hi John, i didn't quite grasp what you were saying

Fair enough. I think your problem may have been (perhaps because, as yos said, you hadn't read the whole thread) you didn't understand that I was merely talking about the concepts of ADS and bonding - i.e that the concept of ADS did not require any bonding to be present, and that the concept of bonding didn't require any (satisfactory or at all!) ADS to be present.

Conversely, one can have satisfactory MPB (and maybe also SB) but without satisfactory ADS (e.g. if Zs was too high) - in this case 'not safe'.

Notwithstanding thermal constraints, you can, it would be a challenge and you would definitely require SB.

I'm afraid you've lost me again For a start, we might well be talking about a location (most locations) in which SB was never required. 'Inadequate ADS' (e.g., as I said because of a Zs which was too high) is surely 'very easy to achieve' (if one really wanted to), rather than 'a challenge', regardless of whether or not there is any MPB?

So yes i agree in certain installations it is possible to have one without the other, though we do need disconnection unless we can guarantee touch voltages will be less the 50 V ...

Lost again, I'm afraid I dont really understand that "...unless we can guarantee...". To be compliant with regs (and common sense) every final circuit surely has to comply with required disconnection times (even if that has to be achieved with an RCD) regardless of any consideration of touch voltages, doesn't it?

Kind Regards, John

 

[Risteard]

To be compliant with regs (and common sense) every final circuit surely has to comply with required disconnection times (even if that has to be achieved with an RCD) regardless of any consideration of touch voltages, doesn't it?

Supplementary bonding may be used instead of an RCD if disconnection times cannot be met. I presume this is the point being made. Therefore disconnection would be required for thermal reasons rather than shock protection.

 

[JohnW2]

Supplementary bonding may be used instead of an RCD if disconnection times cannot be met. I presume this is the point being made.

You are presumably referring to the fact that, in special locations (essentially bathrooms), SB must be installed if there is no RCD protection. However, as I implied before, I am unaware of any provisions in the regs for it to be permissible for any final circuit not to meet the generally required disconnection times (whether that is achieved by an OPD or RCD). Am I missing something?

In fact, as far as I can see, the test prescribed in the regs for confirming the adequacy of supplementary bonding is actually more demanding than the general requirement for disconnection times - effectively requiring satisfaction of the required disconnection times when there is a touch voltage of 50V, rather than the more general requirement that those same disconnection times be achieved in the event of a negligible impedance fault between L and CPC.

Kind Regards, John