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BS 7671 interpretation of clause 560.7.7

MS01
Within BS7671 there is the following clause:-

560.7.7 Safety circuit cables, other than metallic screened, fire-resistant cables, shall be adequately and reliably separated by distance or by barriers from other circuit cables, including other safety circuit cables.

Now I read this in two ways, the first is this is specifically talking about fire rated cables only… or

This is insinuating that unless I use a metallic screened fire-resistant cable I must provide separation by distance or by barriers including from other safety circuit cables. Does this mean a common dedicated medical IT final circuit trunking is not acceptable as each IT circuit in its own right is a safety circuit, therefore if I was to move away from fire rated cable I would need to ensure each IT circuit is installed in its own individual piece of containment (conduit) to give the correct level of separation or would a common galvanised trunking dedicated to the IT cabling be sufficient.

I appreciate no one will give me an answer to the question above, but can people let me know how they interpret this clause to see if I’m on the right lines.  

Can I ask how do you interpret this clause?

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    Roy Bowdler:
    I recall a situation some years ago in which Bed Head Trunking produced by a particular supplier had been specified by the designer, on the basis that it had been “approved as a medical device”. Our design department pointed out that other supplier’s containment was substantially the same, but available at much lower cost.  I can’t recall the overall cost difference, but it would have been 100K plus. So we have an ambiguous situation involving several powerful stakeholders, with one or more potentially standing to lose money.


    Graham makes the point well and illustrates that engineering judgments are often about coming to an optimum solution (aka compromise) not theoretical “perfection”. I also don’t recall the outcome, although readers familiar with current policy around HTM 08-03 may be more familiar.  


     




    Hi Roy


    I am not a great fan of manufacturers who capture a market and then capitalise on this trying to exploit the sector . However, what is often the case is that contractors often see specific pieces of equipment as standard commodities such as cable tray or trunking. I refer to that by your reference to 'containment'.


    Medical Trunking systems are not medical devices (covered by the BS EN 60601 series of documents)  but instead is covered by the Medical Supply Unit standard BS ISO 11197 and as such are slightly more than a piece of containment in fact in most instances if the installer uses the trunking as containment by adding cabling that is not intended then it will probably invalidate any conformity certification. 


    However, if your £100k was for another BS ISO 11197 compliant system then that is a different matter.


    Ultimately, the responsibility for compliance with Standards rests with the designer under Regulations  511.1 and 511.2 and the designer is correct to specify the equipment to the correct standard. 

    regards


    Paul

     

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  • 0

    Roy Bowdler:
    I recall a situation some years ago in which Bed Head Trunking produced by a particular supplier had been specified by the designer, on the basis that it had been “approved as a medical device”. Our design department pointed out that other supplier’s containment was substantially the same, but available at much lower cost.  I can’t recall the overall cost difference, but it would have been 100K plus. So we have an ambiguous situation involving several powerful stakeholders, with one or more potentially standing to lose money.


    Graham makes the point well and illustrates that engineering judgments are often about coming to an optimum solution (aka compromise) not theoretical “perfection”. I also don’t recall the outcome, although readers familiar with current policy around HTM 08-03 may be more familiar.  


     




    Hi Roy


    I am not a great fan of manufacturers who capture a market and then capitalise on this trying to exploit the sector . However, what is often the case is that contractors often see specific pieces of equipment as standard commodities such as cable tray or trunking. I refer to that by your reference to 'containment'.


    Medical Trunking systems are not medical devices (covered by the BS EN 60601 series of documents)  but instead is covered by the Medical Supply Unit standard BS ISO 11197 and as such are slightly more than a piece of containment in fact in most instances if the installer uses the trunking as containment by adding cabling that is not intended then it will probably invalidate any conformity certification. 


    However, if your £100k was for another BS ISO 11197 compliant system then that is a different matter.


    Ultimately, the responsibility for compliance with Standards rests with the designer under Regulations  511.1 and 511.2 and the designer is correct to specify the equipment to the correct standard. 

    regards


    Paul

     

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