Set The Undertemp Safety Thermostat - Thermo Scientific 3907 Operating Manual

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Chapter 6
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6-2 Model 3907 & 3948
2. Turn the overtemp control knob clockwise at least 2°. The alarm should be silenced
and the overtemp indicator light should go out. The overtemp safety thermostat is
now set a few degrees above the control temperature setpoint. When the chamber
temperature rises to the overtemp control point, the alarm system will activate, power
to the heaters will shut off, and the chamber temperature will be maintained at the
overtemp control point.
NOTE
When an overtemp condition occurs, the cause must be determined and
corrected before normal operation under the main temperature controller can
be resumed.
NOTE
When the chamber temperature control setpoint is changed, the overtemp
safety thermostat must be reset to accommodate the change.
NOTE
The overtemp control is not directly calibrated. The numbers on the dial are for
reference only.

Set the Undertemp Safety Thermostat

Allow the chamber temperature and humidity to stabilize, then set the undertemp safety
thermostat as follows:
1. Turn the undertemp control knob slowly clockwise until the audible alarm sounds and
the undertemp indicator lights.
2. Turn the undertemp control knob counterclockwise at least 2° on the scale. The
alarm will silence and the undertemp indicator light goes out.
The undertemp safety thermostat is now set a few degrees below the control temperature
setpoint. When the chamber temperature drops to the undertemp control point, the alarm
system activates, power to the compressor shuts off and the chamber temperature is
maintained at the undertemp control point.
When an undertemp condition occurs, the cause must be determined and corrected
before normal operation under the main temperature controller can be resumed.
Thermo Scientific