BMS WTF



  • So I do quite a lot of BMS (Building Management Systems) work, including the system for a big London councils City Hall. We only took this system on recently, and I was sent to examine the current state of play and devise a maintenance program etc. Now as you may know, most BMS's these days are just Off the Peg PC's with some specialised interfaces, and of course a UPS or two to keep it running when the power goes off.

    This particular units UPS was a standard APC jobbie, with a plug-less IEC lead snaking in through the bottom panel. Now i should make it clear that this BMS sits in the main building Switch Room, which contains a 3 phase substation, and this BMS also controls the Switching Arrangement for the substation.

     So anyway, I arrive in the switch room, set out my gear, walk over to the BMS Panel and crack open the door, no alarms start going off so i continue to open the door to its fullest extent. This was my mistake. About halfway through its travel i feel a light pressure pulling the door back, assuming its just lack of use i pull a bit harder.....BANG....BANG....BANG the three massive switches behind me (each about the size of a small car) have all flipped. The lights go out... OH SHIT OH SHIT OH SHIT OH SHIT, the emergency's come on, I listen for the generator.... panels dead, no dice. I'm sweating heavily trying to work out WTF is going on when I look down at the bottom of the BMS panel and notice that the output lead from the UPS is hanging out...... I trace the cable back and discover that ITS ZIPTIED ROUND THE *&##@@ Door Hinge. I quickly plug it back in and  3 minutes later everything is hunky dory (apart from all the people shouting at me).

     

    Morals Of The Story:

    don't use IEC leads when there is no real need for easy removal / movement. 

    don't zip tie cables round things that move.........

    don't route your entire 24 story buildings power through a known to be flaky BMS using relays that default to off.

    and the most important of all - Dont have your generator control system be dependant on incoming power (How the **** they ever thought this was wise i'll never know.)

    Bosses Interpretation:

    My Fault - Dont open panels until you know what's inside (like that's even remotely possible in the real world.....



  • @VisualD said:

    don't route your entire 24 story buildings power through a known to be flaky BMS using relays that default to off.

    And don't route it through a system dependant on an equally flaky APC UPS. Those things are NOT APPROPRIATE for this sort of job, they're designed to keep mid-range servers and small datacenters from being damaged and nothing more. They are not designed to provide continuous operation or even smoothing for a generator - they're just to give you time to shut down cleanly. There are real continuous operation power systems, and none of them are made by APC. It's quite impressive that they could buy a generator and not get a proper power management system along with it - I didn't know that anybody would even sell you that.


    and the most important of all - Dont have your generator control system be dependant on incoming power (How the **** they ever thought this was wise i'll never know.)

    The other parts were dumb - but this is the real WTF here. This system is a complete waste of money, and lawsuit material if I ever saw it. (It wouldn't meet the electrical system codes here - I don't know about your jurisdiction, whatever it is)

     

    Bosses Interpretation:

    My Fault - Dont open panels until you know what's inside (like that's even remotely possible in the real world.....

    Ask to see the documentation of what was inside the panel. (There won't be any documentation)



  • "It's quite impressive that they could buy a generator and not get a
    proper power management system along with it - I didn't know that
    anybody would even sell you that."

     

    Standard behaviour, remember this is the local government, they probably bought it from the 3rd son of a councillors brother, who was a "BMS Specialist" by virtue of knowing how PC's work

     



  • How do you find out what's inside without looking!?  Next time he asks you to check on anything in the server room, tell him the door was closed and you aren't sure what's on the other side.



  • Consider yourself fortunate that the system restarted when you plugged it back in.  A frightening number of long running embedded systems don't.  Taking them down to test that they come back up is not something anyone wants to risk.  Except during commissioning, and then its often forgotten.

    Mark.

     

     



     


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