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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?

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0 euringharris over 5 years ago

I think in reality this this needs addressing in the next version of the HTM otherwise Contractors will continue to be scared of non-complying to the regulations unless they use fire rated cabling.

Hi Matt

Adding a UPS increases the fire risk so that in itself needs further consideration - but regardless of that the guidance is there to make a fool proof solution (based on Firecode requirements from the 1990s through to today) Obviously lots of electrical designers have not read HTM 81 or any of its successors or they would be aware of this.

If you don't want to use fire resistant cabling and you have sufficient mitigating measures to provide an alternative solution you can follow the procedure in Clause 3.26 of the HTM, However, you will need to get that departure agreed (and take responsibility for that departure if it turns out not to be correct)

.....Any proposed departures, including any equivalent or mitigating measures to be applied, should be discussed with the relevant stakeholders

including the Electrical Safety Group....

If it doesn't stack up when you present your risk assessment (ensuring all risks including the addition of the UPS to the space which will more than likely change the space assessment) then you will need to apply further mitigation or revert back to guidance.

regards

Paul
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0 euringharris over 5 years ago

I think in reality this this needs addressing in the next version of the HTM otherwise Contractors will continue to be scared of non-complying to the regulations unless they use fire rated cabling.

Hi Matt

Adding a UPS increases the fire risk so that in itself needs further consideration - but regardless of that the guidance is there to make a fool proof solution (based on Firecode requirements from the 1990s through to today) Obviously lots of electrical designers have not read HTM 81 or any of its successors or they would be aware of this.

If you don't want to use fire resistant cabling and you have sufficient mitigating measures to provide an alternative solution you can follow the procedure in Clause 3.26 of the HTM, However, you will need to get that departure agreed (and take responsibility for that departure if it turns out not to be correct)

.....Any proposed departures, including any equivalent or mitigating measures to be applied, should be discussed with the relevant stakeholders

including the Electrical Safety Group....

If it doesn't stack up when you present your risk assessment (ensuring all risks including the addition of the UPS to the space which will more than likely change the space assessment) then you will need to apply further mitigation or revert back to guidance.

regards

Paul
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BS 7671 interpretation of clause 560.7.7

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