TENNEY ENVIRONMENTAL
Tenney Junior Test Chambers: Models TJR and TUJR, W942, or WF4
Page 29
As an option, your chamber may be equipped with the boost heat feature, which includes extra heaters to
provide rapid increases in temperature. This feature is available in either a 500 W, or 1000 W version. The
boost heat will automatically turn on if a preset time delay relay times out, indicating that the desired
temperature has not been achieved.
As the heat output of the main controller energizes the main heater bank, it will at the same time energize
time delay relay TC, which is set for three minutes. When this relay times out it will energize mercury relay
MR, which provides power to the boost heaters.
With this option the Heat Limiter fuse is not used. In its place, a Watlow 147 Limit Controller 1TS is used
to monitor and protect the chamber against an overtemperature condition. This controller is an open board
type with an adjustable dial and a calibrated scale for selecting the high limit temperature setpoint. It is
installed inside the main control panel. A red LED on the Watlow 147 will illuminate in an alarm condition. A
Type T thermocouple is used for temperature measurement. Note: The high limit is preset at the factory and
should never be changed.
When the temperature is below the preset limit, 1TS contacts will be closed to energize contactor BHCON.
Separate contacts of BHCON are wired in series with both the existing heater elements and the boost heater
elements. When the Watlow 147 detects an overtemperature condition, 1TS will open to deenergize BHCON
and all heaters.
Reference the Boost Heat Electrical Schematic for more details.
12.0 BOOST HEAT (Optional)
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