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Brain Teaser: What makes a Network Room's internal doorknob hot?

Yep, it sounds silly, like maybe it's a joke?  But it's really something I'm trying to discover.

A couple of my 250+ network rooms have internal doorknobs that are noticeably warmer than expected.

The air conditioning is working perfectly inside the room and also out in the hall.

Anyone inside the network rooms comments about the brushed-aluminum-looking doorknobs being warm.  Not hot, but warmer than expected when you're in a cooled room.

The rooms are good sized--12'x16' or bigger, with 14' ceilings.  There's not a lot of network equipment or other electronics in them--maybe six Cisco 2960XR's in network racks in the middle of the room, a few wall-mounted intercom and electronic security boxes, and that's it.

This particular building has eight network rooms, only two of which have warm doorknobs.

The building is a cancer treatment center and clinic that's only eight years old.  I jokingly asked our Radiologists and Physicists whether loose neutrons might be a cause; they were thoughtful, then smiled and shared that the treatment rooms are encased in six to twelve feet of concrete on all sides, with thick concrete neutron baffles for their halls, and thick lead doors isolating them.  They didn't think their equipment would be a possible source of the heat.

There are motion sensors over each internal door.  Could some form of infrared motion detection emit enough radiation that a door handle might become just slightly warmer than the surrounding air?

But other doors have the same detectors, and don't have warm doorknobs.

I've not measured the temp on the handles--yet.  ;^)  But the air temp is probably 68F around them, and they are probably 85F or warmer, at a guess.

Apparently I need a way for NPM to measure and track and report on doorknob temperatures.  Maybe I should relabel this for a Halloween story . . .


  • Said he wasn't familiar with this particular experience, but would look into it.  I've not heard back from him.  Yet!

  • I will admin, I was expecting a joke.  Something about the sweaty palms of a Unix admin or something...

    Have you looked into the mag-locks as recommended?  I've had that happen a few times.  Based on the picture it looks like the door opens into the room, so that's the side the lock would be on.  Does the lock feel warm? 

    One simple test would be to tape some paper or something over the handle to make a sort of baffle.  Basically make a U shape around it.  Then, if the heat is coming from inside the room the paper should warm, not the handle.  If it is the lock then the handle would still be warm.

  • I've left it with the electrician for further troubleshooting.  Once I hear back, I'll update the tale.  The striker plate and magnetics and electronics don't seem hot at all--only the inside handle of the door.  It's a little freaky, and I'm waiting for a full explanation.

  • I've seen automatically locking/unlocking knobs get noticeably warm. This particular pair (in a stairwell, one on each floor) had a card swipe, and instead of an electromagnetic strikeplate, the kn0b itself would lock and unlock. I'm not sure how it worked, but there must have been either a battery or a wireless power source for the kn0b. With as much heat as it generated, I'd think a battery would only last a few days though. It sort of felt like the designers used the kn0b as a heat sink.

  • jemertz wrote:

    ...the **** itself would lock and unlock.... power source for the ****.... **** as a heat sink.

    Does the Jive platform really think k-n-o-b is a naughty word that needs to be blanked out for the safety of the UK user community?

  • Clearly. Although their plural is just fine. I'll edit the post to make it more legible.

  • Yes, exactly what John said.  I worked with key card control doors and depending on how hey are set up, need current through the locking/magnetic mechanism to remain locked.  (they unlock with loss of power for safety/fire reasons)