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Fire alarm triggers hand dryers

Discussion in 'Electrics UK' started by seasickstevie, 25 Jun 2017.

  1. seasickstevie

    seasickstevie

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    Staff came in this morning to discover fire alarm been going for several hours (false alarm - security hadn't bothered to report it, but that's another story).

    Bizarre thing is the hand dryers in both toilets had been running all night it seems, as the place was like an oven. In fact, it seems it's not the hand dryers triggering the fire alarm, but the other way around.

    Staff says every week for the last (x) number of years when they do a fire alarm test, the hand dryers automatically switch on of their own accord.

    Seems it hasn't bothered anyone 'till now when the alarm kicked off in the night.

    Anybody got any clues?
     
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  3. deadshort

    deadshort

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    I would check if the power went off overnight , i have had a fire alarm go off when power fluctuated. Handryers will switch on after power cuts and also trigger of the room is dark and then thelights are switched on in the room.
    It may have been a surge which has knakered the sensor in the dryer.

    DS
     
  4. flameport

    flameport

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    What type of hand dryers? How are they activated - switch, IR beam, ultrasonics, microwave sensor etc.?
     
  5. deadshort

    deadshort

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    Waving !:D

    DS
     
  6. seasickstevie

    seasickstevie

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    The hand dryers are activated by IR beams.

    Not concerned what triggered the fire alarm, that's not an issue (not to me anyway). It's why every time the fire alarm is triggered by the standard test procedure (or any other reason), the hand dryers instantly come on.
     
    Last edited: 26 Jun 2017
  7. seasickstevie

    seasickstevie

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  8. 333rocky333

    333rocky333

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    fire alarms often get linked to shut down the aircon which may be why it was hot in there and often links to the supply for the music usually via a socket,
    We have come across things spurred off or computers plugged in to these circuits, that also go off when alarm tested.
    Though if they know definetely they ran all night, with the alarm triggered then obviously not the case.
    As DS says some dryers do trigger when repowered up.

    I would check what actually happens rather than take there word for it and see if they have bells or sounders, maybe if sounders near, they trigger it somehow and possibly just changing the tone may help.
     
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  9. seasickstevie

    seasickstevie

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    Thing is, the toilets were stinking hot. The dryers were obviously on for hours. They literally do come on instantly the fire alarm is triggered, and stay on. I've stood there and watched it.

    Nothing to do with power going off overnight. It's instant.

    I think the suggestion that the tone, intensity, and resonance of the sounders triggering the sensors is a possibility.

    Fire alarm guy coming tomorrow. Interested to see what he says.
     
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  11. Lectrician

    Lectrician

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    Strobes are often used in toilets on fire alarms?
     
  12. seasickstevie

    seasickstevie

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    Yes, one in each loo. Would that trigger the hand dryer?
     
  13. bernardgreen

    bernardgreen

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    If the Hand Drier uses a PIR type sensor for hands under the drier then a strobe may well false trigger the sensor. Flash photography in a laboratory had to be banned as it triggered PIR based sensors in the adjoining room ( glass partition )

    Maybe the dryers switched on to help blow the fire out :mrgreen: ( sorry Monday morning humour )
     
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  14. Lectrician

    Lectrician

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    I've seen the sounder-beacons trigger PIR detectors on intruder alarms, so assumed it may do the same on hand driers.
     
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  15. flameport

    flameport

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    Proper course of action:
    a. cover strobes with kitchen foil
    b. test alarm system
    c. do dryers activate?
    d. remove foil
    e. test alarm system
    f. do dryers activate?

    Or a much quicker option is to just remove the unhygienic dryers and install paper towel dispensers and a bin.
     
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  16. Alec_t

    Alec_t

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    But do they turn off by themselves when the alarm stops (or shortly thereafter)? If not, then the dryers themselves may have a fault.
     
  17. seasickstevie

    seasickstevie

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    Yes they turn off soon after the alarm stops.
     
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