BMS Shutdown- Air Intake/ Extract Air

[Tony.]

Good Evening,

Can someone point me in the direction of any info on the above.

We have a bms system controlling a ahu, in the event of a fire activation everything shuts down, except the air extract in the commercial kitchen.

this installation is approx 10 years old, there is no paperwork except for a panel schematic.

this schematic show the fire alarm relay only killing power to the air intake and not the extract?

Is this correct?  

would the designer think that this was to aid  evacuation of the kitchen?
This installation is in Scotland, if that makes any difference.
Thanks in advance for any pointers

[BLEVE]

Makes sense to extract smoke only rather than intake or recirc don't you think.

i.e. would be advantageous to extract on smoke evolution rather than shutdown and accumulate fire efluvia

[Tony.]

Bleve,

yes i agree it makes sense, but commercial ventilation isn't my field so i'd rather double check with the appropriate reg and make a recommendation based on fact.

I have asked the panel builder to see if they were given a design brief / control philosophy for this ahu, but as i said earlier its 10 years old.

Will have another look at IHS later.

Thanks Tony

[Tom Sutton]

Tony

Have you checked out BS EN 12101-3:2002 Smoke and heat control systems. Specification for powered smoke and heat exhaust ventilators.

Although not directly associated they may be using the same principles to control the products of a fire in the premises.

I think BLEVE gave the stock answer you wouldn't want the products of a fire recirculating.

[Tony.]

Tom,

Thanks for the pointer, as you say its not the right field, but i looked at it anyway.
Further investigation required.
I found more info on the original client who was the m&e contractor to the panel builder so will see if they can provide some info.
Thanks for all the help
Tony

[Tom Sutton]

BS 5588-9:1999 Part 9: Code of practice for ventilation and air conditioning ductwork

6.6 Recirculating distribution systems

On triggering of the smoke detection system, the supply system should be switched off and the exhaust system should continue to run. This mode of operation will allow smoke to be extracted from the space and away from exitways until the system breaks down or a fire damper closes.
NOTE 1 Care should be taken that this action will not cause excessive negative pressure within the space and require a force in excess of 100 N to be applied to the door handle to open the doors on the route of escape.
NOTE 2 If the smoke detectors are connected to the general fire alarm system, the method for resetting the ventilation plant after operation of the fire alarm should be completely separate from the method for resetting the fire alarm.

It was a relevant document ten years ago before BS 9999 may be worth a look.

[Tony.]

Tom,

Just looking at bs5588-9:1999

Page 31. Thanks very much.

As a side note, is thete a good way of looking for standards?  I looked for a while on ihs and couldnt find anything.

Tony