Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 72 replies
  • Subscribers 32 subscribers
  • Views 11004 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Bonding a metal bath

David-Adams
Good evening


I am having one of those moments where I can’t sleep because I am worrying about something I probably don’t need to. That’s the rational part of me talking, unfortunately the anxiety monster won’t b***** off. 


We have just had our old cast iron bath replaced with a nice new shiny steel one. The old bath was bonded back to the terminal block by main consumer unit over 6mm earth cable via the airing cupboard. We also have an electric shower. 


The new bath has no taps on it (they are wall-mounted and fed by copper pipes). The waste is all plastic. The electric shower has been replaced with a new electric shower. The copper pipes in the airing cupboard have been connected via a new 4mm earth cable. My electrician says that according to the 18th edition, there is no requirement for the metal bath to be bonded. 


I have no reason to doubt him, except for the anxiety monster eating away at my brain I mentioned earlier. What limited literature I have found seems to suggest this is correct, but in some circles it is a hotly debated topic with contradicting views. I was just wondering if someone could confirm this for me please. I would also be interested in understanding why this is the case to satisfy my own natural curiosity of all things!


Many thanks in advance
Parents
  • 0

    AJJewsbury:




    To prove the necessity of supplementary bonding within each indivual case would it not be the most obvious solution to take measurements for both continuity and insulation resistance and then compare them against recognised acceptable safe values?



    Ah, but what are the "recognised acceptable safe values? I'm thinking especially of R≤50V/Ia when not all the circuits in the premises are 30mA RCD protected...

      - Andy.


    For older installations you'd have to look at the worst case which would depend on the size of the protective device protecting the bathroom circuits. from what I remember it could be as high as 500A. Guidance suggests 0.05 Ohms between extraneous metalwork giving a maximum voltage difference of 25V. for the 5secs the fault is active.

    I can't see how you could anticipate this accurately without some form of measurement.


    Legh

Reply
  • 0

    AJJewsbury:




    To prove the necessity of supplementary bonding within each indivual case would it not be the most obvious solution to take measurements for both continuity and insulation resistance and then compare them against recognised acceptable safe values?



    Ah, but what are the "recognised acceptable safe values? I'm thinking especially of R≤50V/Ia when not all the circuits in the premises are 30mA RCD protected...

      - Andy.


    For older installations you'd have to look at the worst case which would depend on the size of the protective device protecting the bathroom circuits. from what I remember it could be as high as 500A. Guidance suggests 0.05 Ohms between extraneous metalwork giving a maximum voltage difference of 25V. for the 5secs the fault is active.

    I can't see how you could anticipate this accurately without some form of measurement.


    Legh

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines