Kussmaul Electronics 091-85-12 User Manual
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INTRODUCTION
NFPA 1901, Standard for Automotive Fire Apparatus, 1996 Edition, paragraph 9.3.3 requires a low
voltage alarm to detect whenever the battery voltage of a vehicle drops below a threshold for a 2 minute
interval. The Model 091-85-XX, Low Voltage Alarm/1901 is a voltage sensing device which is designed
to fulfill the requirements of referenced NFPA 1901 Standard.
OPERATION AND INSTALLATION
I. OPERATION OF THE LOW VOLTAGE ALARM 1901
The Model 091-85-XX contains voltage sensing circuits, a 2 minute timer, an output relay as well as
RED and GREEN colored LEDs to indicate status.
In operation the Model 091-85-XX continually monitors a system voltage present at J1-1 (+ VDC) with
respect to J1-2 ( VDC Return). When the system voltage is equal to or greater than the following “Low
Voltage Thresholds” the GREEN LED is illuminated indicating a normal system voltage.
Model Type
Nominal System Voltage
Low Voltage Threshold
091-85-12
12.0VDC
11.8VDC
091-85-24
24.0VDC
23.6VDC
Whenever the monitored system voltage drops below the Model Type “Low Voltage Threshold” a timer
internal to the Model 091-85-XX is started. If the Low Voltage condition continues for more than 2 minutes
the Model 091-85-XX output RELAY is energized, the GREEN LED will extinguish and the RED LED will
illuminate. The output RELAY will remain energized (COM makes NO) until the sensed system voltage
rises above;
12.8VDC for Model 091-85-12
25.6VDC for Model 091-85-24
The output relay has both normally open (NO) and normally closed (NC) contacts available providing
the installer with complete flexibility in wiring the alarm circuit. Any external alarm indicator or alarm
horn must be provided by the installer consistent with the output relay contact ratings provided in Model
specifications. The Model 091-85-XX is NOT waterproof so it is suggested that it be mounted in a
suitable location. Care should be taken to wire the +VDC
AND VDC Return sense lines to an electrical
point representative of system voltage monitoring requirements so that an accurate indication of system
voltage may be obtained. Fuse +VDC sense line as required using ONLY an ultra low resistance/voltage
drop device.
Refer to Figure 1 for illustration of a typical wiring configuration and output relay contact rating(s).
170 Cherry Avenue
West Sayville, NY 11796
www.kussmaul.com
Ph: 800-346-0857
Fax: 631-567-5826
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