Hi Alasdair

I will try to provide an abridge response

Whilst noting your definition quote the hazard in the instance of death through failure of the supply (part of the Group 2 definition). Furthermore the examples in 560.1 (and I know they are notes) states essential medical systems along with industrial systems etc. So goes beyond the world of fire fighters lifts fire alarm supplies etc.


In terms of Section 710 there are numerous references to connection to electrical supply system for safety  services or similar. Looking at this if the load needs to be connected to the safety supply then it will be part of that same system and the cable or cables that connects a load requiring a safety service supply will need to meet the requirement for a safety circuit. 


This thread is looking at fire resistance but there are lots of other requirements for safety circuits. 

As hospitals employ progressive horizontal evacuation (PHE) this means that there is the possibility that the patient end of the service may be in a separate compartment ( or sub-compartment or department)  than the fire and as such is held. If the cable or cables supplying the patient pass through a sub-compartment which may be in fire then it would be reasonable to expect that essential power remain on as long as the patient is expected to be held.


Therefore, this resistance to the effects of fire can be achieved by a number of methods (too much for this thread). as long as Section 710 and all the other general parts of BS 7671 have been satisfied.


Linking this back to the guidance in HTM 06-01, this follows on from lots of other HTM guidance regarding separating essential circuits  or where not feasible using fire resistant cabling so it offers an easy fool proof solution suggesting fire resistant cabling but if you are able to do it by another no less safe way then do that- This approach is applicable because of Clause 3.26 of HTM 06-01 which was originally based on the intended departure clause of BS 7671 120.3.


Paul


 

Hi Alasdair

I will try to provide an abridge response

Whilst noting your definition quote the hazard in the instance of death through failure of the supply (part of the Group 2 definition). Furthermore the examples in 560.1 (and I know they are notes) states essential medical systems along with industrial systems etc. So goes beyond the world of fire fighters lifts fire alarm supplies etc.


In terms of Section 710 there are numerous references to connection to electrical supply system for safety  services or similar. Looking at this if the load needs to be connected to the safety supply then it will be part of that same system and the cable or cables that connects a load requiring a safety service supply will need to meet the requirement for a safety circuit. 


This thread is looking at fire resistance but there are lots of other requirements for safety circuits. 

As hospitals employ progressive horizontal evacuation (PHE) this means that there is the possibility that the patient end of the service may be in a separate compartment ( or sub-compartment or department)  than the fire and as such is held. If the cable or cables supplying the patient pass through a sub-compartment which may be in fire then it would be reasonable to expect that essential power remain on as long as the patient is expected to be held.


Therefore, this resistance to the effects of fire can be achieved by a number of methods (too much for this thread). as long as Section 710 and all the other general parts of BS 7671 have been satisfied.


Linking this back to the guidance in HTM 06-01, this follows on from lots of other HTM guidance regarding separating essential circuits  or where not feasible using fire resistant cabling so it offers an easy fool proof solution suggesting fire resistant cabling but if you are able to do it by another no less safe way then do that- This approach is applicable because of Clause 3.26 of HTM 06-01 which was originally based on the intended departure clause of BS 7671 120.3.


Paul