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13
Hydrogen Out-gassing Switch (“HOT” Switch) (optional)
The HOT switch option prevents battery charging when a system exhaust fan is not
functioning. This option incorporates the usage of a “sail switch” (Honeywell # S688A
1007 , provided by others) in the exhaust ducting of the facility. Upon exhaust fan
failure, the sail switch will close a contact which will eliminate the battery charging of the
Defender.
Connect the Normally Closed and the Common contacts of the sail switch to the Hot
Switch terminal block (1 & 3) shown in the picture below.
To verify function, ensure that the system has been started up and is fully operational.
With the system battery breaker OPEN, turn off the facility exhaust fan (the sail switch
will return to its “at rest” position). Measure the DC bus voltage at the battery breaker
(the bottom of the breaker, not the top). This voltage should drop to apprx. 220 VDC in
an 18 battery system and to apprx. 120 VDC in a 10 battery system. Turn on the facility
exhaust fan. Measure the DC bus voltage at the battery breaker. The voltage should
rise to apprx. 237 VDC for an 18 battery system and to appx. 132 VDC in a 10 battery
system.
