Why would an elevator run away when I press the call button?

December 9, 2023 10:09 AM

Sometimes the elevator call button in my lobby makes the elevator on my floor leave and then come back before it lets me on. Why?

I live in a mid-rise building (nine floors) served by a two-elevator bank. The two elevators are idle 90% of the time, and it's common for one to be idling on a higher floor (5 or 6) and the other to be sitting in the ground-floor lobby with its door closed.

Usually if I press the "Up" call button in the lobby, the ground-floor elevator will immediately open its door and all is right with the world.

But about once per week when I press the "Up" call button in the lobby, instead of opening its door the elevator that is right in front of me will "run away" to a higher floor (usually the third or fourth), pause for about 20 seconds, and then return to the lobby (empty) before letting me in. (The other elevator just remains on an upper floor without moving.)

This "running away" happens too frequently to be a case of coincidence with someone on an upper floor pressing the call button and then not getting on. It's clearly triggered by the pressing of the lobby "Up" button because it always happens the instant after you press it.

This is a minor inconvenience at worst but I am curious about what could be happening. If it's an obvious programming issue I may raise it with building management.

The elevators are Otis brand if that matters. Any elevator experts who can solve this mystery?

posted by hayvac to Technology (6 answers total)

Hypothesis: there is some kind of wiring or logic fault that occasionally makes a press on the lobby call button create a ghost button press on the interior panel. The elevator then thinks it already has a passenger inside that needs to be taken up first before it can come back for you. Is it always the same elevator that exhibits this behavior?
posted by agentofselection at 11:26 AM on December 9, 2023 [2 favorites]

I live in a 12-story building with two elevators that have a similar quirk. What seems to happen is that the left elevator is the dominant one, so if it is on the ground floor or within a few floors of the ground, the one on the right will not just open when you press the call button even if it is already there. There are also two call buttons on the ground floor and the elevator on the right won’t open unless you press the call button next to it (but even when you do, the left elevator will still prevent it from opening if it is nearby).

At one time they were working toward making the two elevators serve different sets of floors. There was actually a wall between them on the ground floor. I’ve always chalked up the strange behavior to leftover configuration/programming from that.

I remember elevator programming being a very intro-to-programming exercise so trying to think about what the logic must be is one of the ways I spend my time when I’m waiting for the elevator to show up.
posted by jimw at 11:40 AM on December 9, 2023

Can you put someone on the 3rd floor and have them watch the button as you press the lobby call button? Maybe it lights up or something and you can tell for sure it's a wiring issue.
posted by JoeZydeco at 1:06 PM on December 9, 2023 [3 favorites]

Elevators have counter weights. Is it possible that when you press the button the weights are on your floor and what you hear is them going up in order for the elevator to come down?

And yet, I would swear I have heard this happen with certain elevators too, including a rather old one that is the only elevator in the building, because counterweights don't usually sound exactly like the elevator itself, and I thought I could tell the difference.

I'd experiment with standing by the elevator and listening to it go up and down to try to make sure I'm not hearing the counter weights.
posted by Jane the Brown at 4:03 PM on December 9, 2023 [1 favorite]

The elevator has limit sensors to make sure the floor of the elevator is level with the floor outside and/or sensors to prevent opening the doors when the elevator isn't just in the right spot. When you press the Up button the elevator determines that it's just a bit out of proper position and goes up and then back down to try and land at the right spot. Maybe while it's sitting there unused it drifts a little bit up or a little bit down, but ends up out of proper position. (Totally just another wild guess.....)
posted by zengargoyle at 4:57 PM on December 9, 2023 [2 favorites]

On of my hobbies is chatting with the elevator repair crews. This is all office building experience but - elevators can be set up about 300 million ways. And sometimes they're set up in the least optimal way for the building they are in - such as a small building like yours.
But most likely what zengargoyle says and not a glitch or a setting that's designed to be optimal in giant office building that goes wonky in a small building.
posted by Lesser Shrew at 6:45 PM on December 9, 2023