This discussion is locked.

You cannot post a reply to this discussion. If you have a question start a new discussion

BS 7671 interpretation of clause 560.7.7

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?

Parents

0 Roy Bowdler over 5 years ago

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.

When I was first trained around the 14^th Edition (1974 amendments), the limitations of the scope of the regulations was emphasised (I was in a Power Station Apprentice) and that they formed part of a raft of relevant laws, codes and standards. The (CEng) trainer also emphasised in his words "that they did not preclude any other methods determined by a suitably qualified electrical engineer”. I don’t know if the phrasing was his own, or a quotation?

When some years later I was responsible, an “Electricity Supply Industry Electrician’s Guide” was available, which covered most common situations to the extent that a Electrician/Technician/Engineer not primarily responsible for significant design would usually need. With the modern emphasis on risk management and a more litigious environment, these issues can be complex and require significant expert judgement/control. My example also illustrates how responsibility has been fragmented by the tendency to compartmentalise and sub-contract. This “shares” risk, but requires considerably more than pure technical skills to manage.

Perhaps this anecdote helps? One of the UKs leading Leadership Training organisations, has its roots in “outdoor development” carried out in The English Lake District. Its first three significant customers were Post Office Telecom (now BT), The National Coal Board (no successor) and the Haden Group (absorbed into Balfour Beatty). Presented with similar challenges, each illustrated a different approach. One would acquire every possible bit of equipment, ie “throw money at it”, another would use their collective physical strength if possible and the third would nominate a representative to negotiate with those managing the challenge.
Cancel
Vote Up 0 Vote Down

Cancel

Reply

0 Roy Bowdler over 5 years ago

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.

When I was first trained around the 14^th Edition (1974 amendments), the limitations of the scope of the regulations was emphasised (I was in a Power Station Apprentice) and that they formed part of a raft of relevant laws, codes and standards. The (CEng) trainer also emphasised in his words "that they did not preclude any other methods determined by a suitably qualified electrical engineer”. I don’t know if the phrasing was his own, or a quotation?

When some years later I was responsible, an “Electricity Supply Industry Electrician’s Guide” was available, which covered most common situations to the extent that a Electrician/Technician/Engineer not primarily responsible for significant design would usually need. With the modern emphasis on risk management and a more litigious environment, these issues can be complex and require significant expert judgement/control. My example also illustrates how responsibility has been fragmented by the tendency to compartmentalise and sub-contract. This “shares” risk, but requires considerably more than pure technical skills to manage.

Perhaps this anecdote helps? One of the UKs leading Leadership Training organisations, has its roots in “outdoor development” carried out in The English Lake District. Its first three significant customers were Post Office Telecom (now BT), The National Coal Board (no successor) and the Haden Group (absorbed into Balfour Beatty). Presented with similar challenges, each illustrated a different approach. One would acquire every possible bit of equipment, ie “throw money at it”, another would use their collective physical strength if possible and the third would nominate a representative to negotiate with those managing the challenge.
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

BS 7671 interpretation of clause 560.7.7

Join us to get the best from IET EngX.

Community Rules & Guidelines