On Wed, 16 Apr 2008 08:28:04 +0100, "Mr Sandman"
wrote:
To have a final exit door which
requires either a carried device to open from the inside or a smoke
alarm to function is not terribly bright.
There is a final door exit button, but its pretty useless if you cant see
it. Some of us have visual impairments.
In a fire at night (the most common time for fatal fires) everyone has
visual impairment. If you are used to it that gives you an advantage.
The three most common places to find bodies after a fire are under
beds and in wardrobes (usually children) and against the front door
(mostly adults looking for a key to get out).
If you want to wire things up to smoke alarms that's fine - but don't
do it at the expense of far more useful functions like exit releases.
If they are not easy to find where they are now then moving them and
making them easy to find in the dark by feel should be a much higher
priority than playing with smoke alarms.
As for the smoke alarm wiring - personally I'd put a single relay
controlling a no volt release switch on the input side of the power
supply or mains feed to the door magnets. That way once the smoke
alarm goes off the doors open and can't re-lock. Using relays alone
on the smoke alarm circuit to control the locks simply means that when
the smoke alarms stop working the doors can re-lock - not a good idea
as the fire is developed by then.
I assume you are talking of magnetic plate door locks such as:-
http://www.screwfix.com/prods/72119/Security/Access-Control/Electromagnets/Standard-Single-Magnet-Door-Lock-12-24V
http://tinyurl.com/52pcum
and not the sort shown here :-
http://www.screwfix.com/prods/19768/Security/Access-Control/Door-Entry-Systems/Door-Entry-Kit-Rim-Lock-Release
http://tinyurl.com/3uhplw
An NVR switch unsets on power failure and won't restore the lock
supply until manually reset by physically pressing the on button..
There is therefore no possibility of the door lock re-energising when
you don't want it to after the alarm has gone off.
http://www.axminster.co.uk/pricing/INC/recno/4/cid/JVR7W1QUAQR7KGMAA97FQW0GZXGBN435/product-Axminster-Light-Duty-NVR-Switch-21280.htm
http://tinyurl.com/3lty73