Difficult to provide general advice on this, because of detail and nuance, so I'll have a go by making some general observations and referencing standards from where requirements can help address the detail for a specific building.

Peter Read said:

We have a natural smoke vent system on a project where the main supply cable to the SVCP has been taken from a local DB and wired in SWA. These systems have a 72 hour back up for the life safety element and all power & control cabling from the inverter is wired in FP200. However, the AOV contractor has just informed us that the main supply should also be wired in FP and afford the appropriate protection.

What if the inverter fails, and there's a fire? n this case if the primary supply is not protected against fire, the system can't act as designed? Clause 37.2.3.1 of BS 9999 says that protection is necessary for the primary supply too.

The relevant references for supply to safety services are Clause 15.7 and Section 37 of BS 9999, and Chapter 56 of BS 7671.

Peter Read said:

My question is should the main supply be installed in FP from the main panel board or can the protection be from just the local DB, bearing in mind that should the system 'fall over' the battery system will still give 72 hours of protection. Any insight would be appreciated.

See Section 37 and Table 29 (item 21) of BS 9999, Chapter 56 of BS 7671

Generally, safety services requires substantially separate distribution from other electrical services (see BS 9999 Clause 37.2.3.2)

Overall, though, for a given building, a competent person ought to have a fire risk assessment of the premises which details the relevant measures to be taken?

I did one two years ago, 5 storey blocks of flats with sprinklers in the communal areas, and of course, lots of vents connected to the fire detection system, as well as dampers for the air ducting.

I followed the Design, the 'Life Safety systems' were on a separate DB, fire separated in its own little room, with what should have been a totally separate supply from the street, but I found out the supply was taken off the main incoming supply cable, so the same supply for all intents, which is against the relevant Regs.

Anyway, the wiring to the main panels and sprinklers pumps/controls was in FP rated SWA from the separate Life Systems DB. The wiring to all of the vent controls was in FP200 cable, but the 230v wiring to the individual vent contactors was in normal T+E or flex, fed from any local DB.

I queried this a few times, but was told it was correct, in that if the supply is cut, the vents shut, so if the cable burns out, it will shut the vents even if the fire detection didnt work (that seems rather odd, and surely doesnt exist in any Regs explanation). Then there were the Firemans Vents, which when switched, open up the vents, these were all in FP200.

So I'd say, yes, you may need to fit FP cable to supply any controls. It is a pretty standard requirement in Commercial contracts. Also, I'd be checking the supply requirements. As it has battery back up, that may not affect you, but the supply to the control panel must not be able to be switched off by non-instructed people , I've been to a place before where they say the fire alarm has been bleeping for a week, and find the supply circuit breaker has been turned off, as something tripped, - they actually turned things off, rather than turning things on when trying to reset it!

In this case there is no much point in providing fire rated cable just between DB and SVCP since you have dedicated fire protected power backup system for SVCP. If the project has a parallel emergency power distribution system backed up with a secondary power source, this SVCP shall be connected in that and all cables including cable between DB and SVCP shall be fire rated.

Yasir said:

In this case there is no much point in providing fire rated cable just between DB and SVCP since you have dedicated fire protected power backup system for SVCP.

Whilst that is true, it doesn't answer the question as to whether the DB is the correct place to supply the 'primary power', given the requirements of BS 9999 that the 'primary power' ought to be supplied by fire rated circuits that are not unduly affected by faults on other circuits (as per my earlier post). Only a competently compiled fire safety risk assessment can answer that.

My apologies for missing the main point in the reply. My point was that they can't comply with BS 9999 just by providing fire rated cable from the local DB to SVCP. As you've mentioned, Only a competent site assessment can give a solution by assessing fire risks and comparing the cost between changing the existing cables and introducing a new fire rated supply from main panel till SVCP.