360077-1/O
114
Horizon Series™ - Laboratory, Pharmacy, and International Blood Bank Models
24.4.2
Control Sensor Offset
The temperature controller senses chamber temperature through a probe in the unit cooler. The chamber
setpoint typically varies from the measured temperature, so an offset value is used by the control system
to compensate for the difference.
►
Value is factory-preset and varies for each unit
►
Offset value can be changed from -10.0 °C to +10.0 °C
NOTICE
Control Sensor Offset is factory-preset and should not be changed unless directed by
Helmer Technical Service.
24.4.3 Hysteresis
►
Default setpoint for HLR111 and HPR111 models is 0.8 °C.
►
Default setpoint for HLR/HPR 120, 125, 245, 256 models, and all HHB models is 2.0 °C.
►
Allowable temperature variance on each side of the refrigerator setpoint.
NOTICE
Hysteresis is factory-preset and should not be changed unless directed by Helmer
Technical Service.
24.5
Test Alarms
Test alarms to ensure they are working correctly. The refrigerator has alarms for chamber temperature,
power failure, and door open (time).
24.5.1
Chamber Temperature Alarm
IMPORTANT
Perform the low alarm test before the high alarm test to control the temperature more
closely and complete the testing more quickly.
Obtain:
►
(1) 8 oz. (250 mL) glass half-full of chilled water.
►
(1) glass filled with crushed ice.
►
(1) 8 oz. (250 mL) glass half-full of warm water.
NOTICE
Temperature probes are fragile; handle with care.
Test the low alarm:
1
Identify setting for low alarm setpoint.
2
Remove chamber temperature probe from bottle.
3
Immerse probe in chilled water.
4
While stirring probe in chilled water, add approximately one teaspoon (5 mL) of ice every 20 seconds.
Ensure probe is at the bottom of the glass.
5
When low temperature alarm activates, note the temperature on the monitoring system display.
Test the high alarm:
1
Identify setting for high alarm setpoint.
2
While stirring probe in chilled water, add warm water so temperature increases 0.5 °C per minute.
3
When high temperature alarm activates, note the temperature on the monitoring system display.
4
Remove probe from warm water.
5
Place temperature probe in probe bottle, immersing it at least 2” (50 mm).
