camelot-forum.co.uk

Something that has been bugging me for while following a report I read of a place with a fire where the ventillation kept running hereby supplying the fire with fresh oxygen ans making maters much worse than if the ventillation system had shutdown.

We have an MVHR system and mains powered smoke/heat detectors as separate systems. I have read that some installations have the MVHR switched off if the alarm is triggered. I was wondering what those with MVHR systems on this site had approached this ?

__

I'm sure a decent fire alarm system would have an "alarm state" connection giving 5V or 12V or whatever in "alarm" condition or a contactor that does similar. And many MVHR systems would probably have a suitable terminal to accept this and turn off in the event of an alarm.

However the reality of a domestic dwelling is that you need a fire to be successfully detected (via smoke, heat, rate of rise of heat, etc.) and you need sounders or flashing lights that will reliably wake/alert people anywhere in the property. The people then need to vacate to a safe distance and contact the emergency services.

I cannot imagine any MVHR system would displace so-much air that it would defeat a smoke alarm! And most houses are small enough that 2-4 sounders would wake/alert the occupants reliably.

The MVHR system feeding the fire with fresh air would only be a concern if the house was fitted with fire-doors and a fire that would otherwise be constrained by lack of oxygen was sustained with air from the MCHR. The reality is that domestic fires are not constrained by lack of oxygen!

Basically: don't worry about it!