. a defect in the wiring between the abort
switch and the main control unit, or
. an improper abort feature installation or
an improper timer setting (low).
During troubleshooting, disable the ex-
tinguishing agent release and the computer shut-
down feature, if provided. Check the abort timer
setting according to the manufacturers instruc-
tions. If the timer setting is quite low, 15 seconds
or less, increase the setting to 20 seconds or more
(as determined by local authorities to be adequate
to prevent unnecessary discharge of the agent).
If actuating the abort switch has no effect,
check the switch continuity with an ohmmeter
while actuating it disconnected from its wiring.
If the switch continuity shows alternating readings
of zero ohms and infinite resistance, as it should
when being repeatedly actuated, check that the
OFF and ON positions of the switch are not
reversed. (Such reversal may be caused by
connecting the wires to the wrong pair of switch
terminals or inverting the switch when mounting
it.) If the switch has no defect, check its circuit
continuity with an ohmmeter at the control unit
and with at least one wire disconnected from the
control unit. Observe switch action at the ohm-
meter by actuating the switch repeatedly. Correct
any circuit defects or wiring errors. Replace the
switch if it is defective.
DRY CHEMICAL EXTINGUISHING
Dry chemical extinguishing systems are very
similar in construction and operation to gaseous
extinguishing systems. There are three general
categories of chemical extinguishing systems: total
flooding, local application, and hose line systems.
Total flooding systems are arranged to
discharge the agent into enclosed spaces. Such
systems are used for the protection of flammable
liquid storage rooms and paint drying ovens
(fig. 8-36). Ventilating equipment, conveyors,
Figure 8-36.Total flooding dry chemical system installation.