Why do elevator doors beep when held open?
Answer:
security issues.
So it doesnt hold up the elevator when other people are trying to use it. Its just like the subway when the doors start to close without everyone on the train. It has a schedule that it is trying to keep.
People are waiting on other floors, the beep tells you to get out of the way.
the beep is in place to censor out what the elevator is really saying: "Get your damn hands off my doors!!"
Functionally: There's a sensor that is triggered when the door is open. It's probably the same sensor that prevents the elevator from moving when the door is open.
The sensor is connected to a timer that triggers an alarm after so long.
Logically:
Because the elevator is not supposed to be able to move with the door open, as has been stated, it prevents other people from using the elevator.
the noise you are hearing is what we in the trade refer to as the " nudge " buzzer. It sounds when someone ( or something ) holds the doors open ( interrupting the light barrier ) longer than the preset time. This noise is intended to warn that the doors are going to close no matter what.
However, the light barriers can and do go faulty. I would place a call with your service company and ask them to investgate the problem. But I have seen a situation where fluorescent lighting in the lobby has been the cause of the problem. Some of the older light barrier systems were susceptible to different light frequencies close to the infra red they use. One building upgraded their lobby lighting and all of a sudden, we had door problems.
So, like I said, talk to your service company, that is usually the best advice one can give. It's what YOU pay them for after all !
Almost all newer elevators come with a feature called "door nudging". If you block the infra-red beams on the detector edge(the black strip located on the inner car door), after about 30-40seconds, the elevator goes into nudging mode.
In nudging mode, you cannot make the door open by waving your hand across the beams on the detector edge, the door will continue to close no matter what. The only way you can stop it, is by hitting the door open button(on some elevators).
In nudging mode, the doors close at a reduced torque (according to ASME A17 code, doors MUST close at reduced torque) to prevent someone from getting hurt.
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