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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Seetek on January 09, 2023, 03:20:57 PM
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Hi all, I have been asked why there is a need for a GBGU on a powered sliding door, when, if the power fails, the door, fails-safe to the open position. The question is if the power has failed, what does operating the break glass actually do? I have tried explaining BS 7273-4 and other posts on here but the guy needs a definitive. Any offers?
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It's not for power failure (although it operates by cutting the power) but could arguably is to make the doors stay open to facilitate uninterrupted flow.
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Just wondering how the sliding door returns to the open position on power failure. Is it a mechanical or back-up electrical arrangement?
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I recall some are held under spring tension by the powered part of the mechanism - loose the power and there is nothing to stop the springs opening the door.
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I remember researching this same subject when I was an inspecting officer and finding that a type A break-glass unit wasn't required. From memory, I think it was in the British Standard....
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:o really?????????????
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I remember researching this same subject when I was an inspecting officer and finding that a type A break-glass unit wasn't required. From memory, I think it was in the British Standard....
You don't mean the BS that is actually specifically for these doors that says "In the case of electronically secured doors and powered sliding doors, it is normal,
particularly in the former case, to provide a suitably identified manual control adjacent to the doors to operate the release mechanisms if they have not already been released automatically."
or ADB which says
"5.8 Electrically powered locks should return to the unlocked position in all of the following situations.
a. If the fire detection and alarm system operates.
b. If there is loss of power or system error.
c. If the security mechanism override is activated.
Security mechanism overrides for electrically powered locks should be a Type A call point as described in BS 7273-4. The call point should be positioned on the side approached by people escaping. If the door provides escape in either direction, a call point should be installed on both sides of the door."
looks like they don't agree with your recollection. The BS does give examples of when they can be omitted (prisons, certain boundaries in airports etc) but the preumption is to provide.
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:)