Today most panels have a negative or common terminal for
each zone that is an earth-grounded terminal. I am constantly finding
technicians installing the EOL on the positive or high side of the zone.
In most cases this doesn’t seem to be an issue until a wire,
in a grounded metal door frame, is cut into by a burr caused by drilling. As
you will see in the accompanying diagrams, this can make the difference between
detection or no detection.
I hate to think about how many security zones are out there
that will not work because the control panel sees a normal zone. –
Contributed
by Lee Bernardo, technical training manager, Per Mar Security, Davenport,
Iowa.
