TENNEY ENVIRONMENTAL
Tenney Junior Test Chambers: Models TJR and TUJR, W942, or WF4
Page 27
11.3 Circuit Operation
When chamber temperature is within the selected setpoints, the white NORMAL light 2LT is illuminated and
Master Contactor CON is energized. The contacts of CON provide power to the conditioning control circuitry.
Note: A spare set of CON contacts is provided for the customer’s closure. It is recommended that these
contacts be used to energize an active heat load if utilized.
When a preset temperature limit is reached within the Watlow 93, the alarm contacts TG will open and
deenergize CON, which causes the following to occur.
♦ Power is removed from the main temperature controller and conditioning circuitry.
♦ Alarm buzzer sounds.
♦ Alarm and Chamber Overtemp lights on the TempGard IV panel will illuminate. The lower display of the
Watlow 93 will blink with the corresponding alarm message, e.g., AHI and HI, or ALO & LO.
WARNING! When Master Contactor CON is deenergized due to an alarm condition, power is
only removed from the chamber circuitry. The instrumentation and alarm circuitry in the TempGard
IV control box will still be energized!
A Silence switch 4SS is provided to disable the alarm buzzer while corrective action is taken. When 4SS is
activated, the white Silence light 5LT will illuminate. When conditions are corrected, you must reset the
chamber power system.
RESET:
To reset the alarm circuitry and the main controller control circuitry, press the Chamber Power
switch on the TempGard IV panel. (The Power switch also serves as a Reset switch.)
Important: If the alarm buzzer was disabled and the system was successfully reset with the Power switch
2SS, the alarm buzzer will now sound to alert the operator to place the Silence switch 4SS in it’s off position.
A 1.5 second timer TC is included in the reset circuit to provide for automatic start when power is applied to
the system. This avoids the need for a manual reset each time that power is removed and reapplied.
The configuration for the TempGard IV option is detailed in the section entitled “TempGard IV Alarm Setpoint
Entry”, which follows. Reference the Watlow 93 user manual for complete details of the controller.
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