Green break-glass boxes

[Paul2886]

Your views please. Do you consider it necessary to link an electronic lock, on a final exit door, to the fire alarm system if its fitted with a green break glass box. Some varying views here at my neck of the woods. 

[jokar]

See the topic on BS 7273 part 4 and try to gain an insight from that.

[colin todd]

Nah, No one can understand BS 7273-4. Its all too difficult (apparently!!!!!!!!!)

[AnthonyB]

If you are asking for opinion rather than code, then I would say yes - default to the highest level of safety, unless your risk assessment can justify a lower standard.

Mag locks are increasingly used on doors where the occupancy & risk has previously deemed an anti panic fastening is required - if you are relying on someone identifying a little green box in a panic situation you might as well replace the panic bolts with a key in glass fronted box, as the exit is no longer panic proof. But if you have a fire alarm link then the mag locks should be dropped as people reach the door and it becomes panic proof on the bolts alone.

There is considerable ignorance about green & white override boxes by general staff and they are either totally overlooked and not understood, rarely being used in drills (where no alarm link is present) and peole either constantly using the normal push to exit or finding a different door - very little training seems to mention them.

[partymarty007]

This is the minimum standard I accept.

When considering the acceptability of electronically powered locks on exit doors ensure they meet all the following requirements:

they "fail safe" so that the door is unlocked in the event of power failure, system error or failure of the alarm system; and
they are unlocked automatically on the activation of the fire alarm; and
there is an easily operated override at the door.

The first of these points requires some clarification as it has come to light that some installations have been considered to "fail safe" when they failed to the locked condition for security reasons. Clearly in the case of fire exits this is never appropriate and "fail safe" must always mean failing to the unlocked position.
 
The third of these points also requires some elaboration, the standard requires them to be fitted only with a lock or fastening which is readily operated, without a key. This means the operating devices must be useable by anyone in the building and so would normally prevent the use of card operated locks, unless there was an emergency override (Green box).

Also

The Scottish guides technical annexe goes on to state:-

Electrically powered locks should not be installed on any door where it is:

The only route of escape from a building or part of a building
A protected door serving a fire fighting shaft.
Serving any room or storey with an aggregate occupancy capacity exceeding 60 persons.

[Wiz]

Your views please. Do you consider it necessary to link an electronic lock, on a final exit door, to the fire alarm system if its fitted with a green break glass box. Some varying views here at my neck of the woods. 

This is an interesting question.

BS7272-4 starts with 'It is now commonplace for there to be an interface(s) between the fire detection and alarm system and various forms of door hardware'

Therefore it would appear that BS7273-4 only contains the recommendations applicable where there is such an interface. It doesn't appear to provide the recomendation that you have to link the two systems.

Is the need for having any interfacing link between fire alarm systems and electrically release mechanism on doors covered by any other authorative document, rather than just the opinions of individuals?

Does anyone know?

[AnthonyB]

The Scottish guides technical annexe goes on to state:-

Electrically powered locks should not be installed on any door where it is:

Serving any room or storey with an aggregate occupancy capacity exceeding 60 persons.

Which implies doors liable to be fitted with anti panic fastenings - yet here in E&W they are spreading willy nilly.

Agree with your own requirements BTW

[FSO]

From a common sense point of view, why would you require a green box on an electomagnetic lock that will fail safe and is interconnected to the FA system?

[Wiz]

From a common sense point of view, why would you require a green box on an electomagnetic lock that will fail safe and is interconnected to the FA system?

FSO your question has previously been answered on this forum by Mr Todd. It has to do with the number of people who have been/or could be trapped and die in a burning building if the fire alarm system did not signal the fail-safe release properly and there was no Emergency Door Release available.

The British Standard version of recommendations for achieving what is required can be found in BS7273-4 : 2007.

But the original question asked was actually the other way around - If you have the green Emergency Door Release, who says you also need the link to the fire alarm system?  I think it is a good question and await the answer with interest.

[FSO]

Thank you Wiz.

I still fail to see why the system would not work.

If the FA system interlock worked, then job done.

If the FA system did not work then push the button that they do every day to open the door.

If the power fails, job done.

[David Rooney]

Thank you Wiz.

I still fail to see why the system would not work.

If the FA system interlock worked, then job done.

If the FA system did not work then push the button that they do every day to open the door.

If the power fails, job done.

The problem could arise where damage to the cabling to the locking device, or the rocker switch/button (generally single pole) or an earth fault could interfere with the "failsafe design" and prevent the locking mechanism from releasing. Hence the need for a double pole switch to physically disconnect all power from the locking device.

Of course this isn't necessary if you have a single action "turnkey" or similar that allows you to open the door from the secure side in the direction of escape.

If the door can be used to escape in both directions you wouldn't really want a turnkey on the secure side ..... or even a breakglass come to that.... see the various notes/commentary/clauses on secure locations etc..... hence risk assessment.

[David Rooney]

Is the need for having any interfacing link between fire alarm systems and electrically release mechanism on doors covered by any other authorative document, rather than just the opinions of individuals?

Does anyone know?

7273pt 4 mentions "Guidance on the security of buildings against crime, including the use of locking devices, is given in BS 8220" but I don't know this document or what it might refer to... and not spending £100 to find out....!

[Wiz]

Thank you Wiz.

I still fail to see why the system would not work.

If the FA system interlock worked, then job done.

If the FA system did not work then push the button that they do every day to open the door.

If the power fails, job done.

FSO, the 'normal' exit switch you are talking about is the switch I call the 'Request To Exit' Switch.

Firstly, not all doors have a Request To Exit switch i.e some electronically locked doors are only to be used in an emergency and have no switches.

Secondly, not all 'Request To Exit' switches are wired in 'series' with the power feed to the locking device. The ones that are, are those which unlock the door only as you depress the switch and where the door locks again immediately when you release the switch. If you had this type of switch you could possibly argue that it is only doing the same thing as the 'green box'  (which I call the Emergency Door Release) would do i.e breaking the power feed to the locking device. However all Emergency Door Releases meeting BS7273-4 recommendations need to be double pole and your RTE switch would also have to be double pole for the following safety reasons; Whilst it is true that an accidental disconnection of the wiring to a single pole RTE switch would release a fail-safe release mechanism, an accidental short of the wiring to a single pole RTE would actually short out the switch contacts and keep the release mechanism energised even when the RTE was operated!! The double-pole requirement is meant to avoid short circuits allowing this to happen.

Thirdly, many RTE switches are not wired as above. With the above scenario, it can be annoying when the door locks immediately you release the button (i.e if you are carrying something you have try to press the RTE switch with your elbow and open the door with your foot before you release the switch!)
The method of connecting RTE switches asscociated with a keypad/or proximity reader on the entrance side of the door is different. They normally have dedicated connection terminals for a RTE switch. If you wire the RTE to these terminals what happens, is that when you operate the RTE switch, it opens the door for the same period of time programmed into the keypad/reader controller for 'door open' time. i.e. pressing the RTE button causes the system to unlock the door for the same pre-programmed period of time as if someone has entered the correct code into the keypad/shown a valid token to reader that is on the entry side of the door. This makes the door much easier to use, press the RTE and the door stays unlocked for a few seconds.
However, the type of RTE switch usually required for this connection method is a Normally Open switch. This means its wiring is not monitored for disconnection i.e. a wire disconnecting from it won't cause the lock to fail-safe door open. Furthermore it is relying on the controller to accept the signal from the RTE switch and open the door. If the controller failed the door wouldn't open. In both these circumstances it is imperitive that a double pole Emergency Door Release is also provided and wired into the power feed to the door locking device. You certainly couldn't rely on just the RTE switch.

[Phoenix]

Your views please. Do you consider it necessary to link an electronic lock, on a final exit door, to the fire alarm system if its fitted with a green break glass box. Some varying views here at my neck of the woods. 

Wow! This has got technical....

Returning to the original question, I think AnthonyB and Marty, early on, gave the ideal answer.  But I've been in buildings that are huge (from Cathedrals to big sheds (and I mean big)) and to link every electronically secured door back to the alarm panel would mean literally miles of very expensive cabling.  In such cases, is it not agreed that a reliable one of these



is satisfactory as the sole means for ensuring that the door is always available for escape.....provided it also has one of these



Stu

[colin todd]

SEE WIZZY, you CAN understand BS 7273-4 just fine. And goddam it now that you do you like it so much that you want to extend its scope beyond that for which the BS 7273 suite was first invented. How cool is that. For your next task, I want to you to work on explaining Ohms Law to those amongst our enforcing authority chums who are arrogant enough to think if they cant understand it, it is not worthy of their attention. Use the analogy of water going through pipes cos they can relate to that.