I can't remember seeing this many wrong things on a single job...
I can't remember seeing this many wrong things on a single job...
On an industrial property that had been sitting idle & mostly neglected for several years, the owner decided he wanted the combination fire/security alarm brought back to working condition. What I found was a local Mirtone 790 fire alarm panel that had door switches, motion sensors (both wired normally open), smoke detectors, pull stations and fire alarm horn strobes seperately run back to said panel. All wire (I'm recalling between 20 and 30 pairs) were black 16 gauge TW, and all the wire labels had dried out, uncurled, and were laying on the bottom of the panel. No backup batteries installed. I found out that the system was armed at night by turning on the circuit breaker. An exterior light switch mounted on a bell box was wired in series with the exit door alarm contact, and was how one got out of the building without setting off the alarm. Everything was in conduit, except for the 16 volt plug-in transformers that locally powered the motion sensors. Miraculously, the Mirtone panel was ok.
I told the owner that the fire alarm would likely be salvageable, but it would be on a T&M basis, and would involve removing any security alarm wiring from the fire alarm. I identified & re-labeled the circuits, cleaned the smoke detectors, performed current draw calculations based on Mirtone 790 literature already in my possession (no drawings to work from!) & installed the correct size batteries. I also put a screw-on keeper on the circuit breaker. Tested the system, & everything worked, except for 4 horn/strobes in a high bay area. This high bay had one of those electric cranes that motors across pairs of horizontal girders painted yellow. No ground faults present. I could 'see' the EOL resistor installed at the last device with my meter at the panel, and I could read the supervision voltage from the panel at the terminals of the last device. Other devices worked on the same circuit, so I knew the output zone card in the panel was ok. I was thinking that perhaps voltage drop was the issue, which would have been consistent with what I was looking at. Maybe a bad device was clamping the reversed alarm current? But noooooo. What I found was an open junction box, not visible from the floor since it was obscured by one of the crane's horizontal girders. A Tandy analog volt/ohm meter from the 1970's with a severely corroded battery inside rested on top of this girder. Set to the ohms scale, it had its leads alligator clipped across the intact horn strobe circuit before the first device in that room. Removed the meter, closed the j-box, and I had a clean system. I can tell you that if there was a meter throwing event in the Olympics, that year I would have won.
To this day I don't have any idea if my predecessor fell, quit suddenly, forgot, or deliberately sabotaged the job.