Models 3940 and 3949_________________________________________________________________Start-Up and Operation
Audible Humidity Alarm and Indicator Display (Figure 3-3)
The humidity alarm is a function of the humidity con-
troller, Figure 3-4. When the cabinet humidity goes outside
the set parameters of the controller, L3 indicator on the
controller lights, the audible alarm sounds, and the humidity
alarm indicator (Figure 3-3, Item I) on the control panel lights.
Hold/Run Key
Pressing the Hold/Run key (Figure 3-4) on the con-
troller silences the audible alarm and extinguishes the
humidity alarm indicator and the L3 indicator on the con-
troller. A3HI/A3LO flashes on the lower display until the cabi-
net humidity returns to the system setpoint.
Note:
The humidity controller’s high
and low limits are set by the factory
at 100% and 0%. Therefore, the sys-
tem will go into the alarm state when
the humidity exceeds these percent-
ages by one percent. When operating
the incubator near these high or low
humidity levels, frequent alarms may
occur. This will require that the con-
troller’s high or low limit be reset to
three or four percent over the high
limit or three or four percent under
the low limit. Refer to the Watlow
User’s guide provided. Refer also to the
factory configuration records located at
the end of Section 2 of this manual.
Undertemp Safety Control, Indicator Light and Audible
Alarm (Figure 3-2)
The undertemp safety thermostat should be set
slightly lower than the operating temperature of the
incubator. In the event of an undertemp condition, the
undertemp safety thermostat will:
• Activate the audible alarm and the undertemp indicator
light.
• Interrupt power to the refrigeration system and maintain
the incubator’s cabinet temperature at the undertemp safety
control point.
Note:
As with the overtemp safety control, the undertemp con-
trol is not directly calibrated. The numbers (0 to 10) on the dial
are for reference only and do not correspond to any specific
temperature.
If an undertemp condition occurs, the alarm can only be
silenced by lowering the undertemp safety thermostat setting.
However, the cause of the problem must be determined and cor-
rected before normal operation under the main temperature con-
troller is resumed.
Humidify Switch and Indicator
(Figure 3-3)
The humidify switch controls the
power to the humidification system cir-
cuit. The humidity indicator light will
cycle as the controller toggles between humid-
ify and dehumidify.
Dehumidify Switch and Indicator (Figure
3-3)
The dehumidify switch will enable
the refrigeration system if the refrigera-
tion switch is currently off. When con-
trolling humidity, the dehumidification switch
should be in the ON position for most appli-
cations. The dehumidification light will cycle
on and off as the humidity controller toggles between humidify
and dehumidify. The dehumidify light will be de-energized
when the system is in Defrost mode.
Humidity is removed from the cabinet by the refrigeration
evaporator coil. Moisture accumulates on the coil and is collect-
ed into the evaporator pan. The accumulated moisture is then
plumbed to the back of the cabinet, which can be emptied to a
floor drain, or an evaporative device.
E F
I
J
G
Figure 3-3
H
3 -2
Figure 3-4
