TE Technology TC-720 - Manual (Page 53)

The “PROGRAM” OK button saves the temperatures to the controller. The “READ SETTINGS” OK button displays the
temperatures are currently stored on EEPROM.
Controlling fans when using PROPORTIONAL + DEADBAND MODE CONFIGURATION: It may be desirable for the user to
de-energize a fan when using this mode. For example, it may not be necessary or desirable for the fan on the outside of the
enclosure to always be energized, even when the when an enclosure is being heated. In this case you may wish to use
ALARM 2 to energize and de-energize the fan. To accomplish this, the following steps would be taken:
1. The negative terminal of the external fan would be connected to the ALARM 2 terminal, JP2-10. If using a TE
Technology standard cooling assembly, be sure to remove the electrical jumper in the terminal block which
connects the negative terminal of this fan to the negative terminal of the internal fan.
2. The ALARM 2 FUNCTION is set to KEEP OUTPUT ON
3. ALARM 2 SENSOR is set to INPUT 1 (the internal temperature)
4. The HIGH ALARM 2 SETTING is set to the temperature at which the fan is to be turned on. For the example screen
above this could be 25 °C.
5. The LOW ALARM 2 setting is turned off
6. The ALARM 2 DEADBAND is set to some non-zero number, for this example assume it is set to 2 °C. This
deadband keeps the external fan from turning on and off due to slight fluctuations in the internal temperature.
Be careful to set the HIGH ALARM 2 SETTING and ALARM 2 DEAD BAND so that the external fan is always
energized whenever cooling power is being applied to the thermoelectric modules.
7. The internal fan is wired to always be operating. That helps maintain a uniform internal enclosure temperature,
and when the controller applies heating power to the thermoelectric modules the internal fan distributes the
heat from the fins and keeps the thermoelectric modules from overheating.
Thus, for the screen example and fan control description above, the external fan would be energized whenever there is a
high alarm, in this case when the internal temperature increases to 25 C. When the internal temperature decreases to
23 °C the temperature the high alarm will turn off and the fan will be de-energized. This is the 25 °C HIGH ALARM 2
SETTING minus the 2 °C ALARM 2 DEADBAND temperature. The internal temperature will then need to rise to 25 °C before
the external fan will be energized again.
Referring again to the screen example above, the controller would start cooling when the internal temperature is at 30 °C,
and increase to full cooling when the temperature is above 40 °C. If the internal temperature drops to 20 °C the controller
will start applying heating power, and the controller will be applying full heating power when the internal temperature has
decreased to 10 °C.
This method of energizing and de-energizing the fan is useful in that it allows a defined temperature range when both the
internal and external fans are to be energized while and the thermoelectric are not energized. This is an energy-saving
feature because the thermoelectric assembly can be used to passively conduct heat through the thermoelectric modules to
outside of the enclosure while only powering the fans.
An alternative method is control the fan using the FAN CONTROL mode in conjunction with the ALARM 1 SIGNAL. However,
using this mode the fan will not be de-energized until heating power is being applied to the thermoelectric modules, in this
example at 20 °C. Then, the fan would not be re-energized until cooling power is being applied, in this example 30 °C.
For more information on configuring the alarms, see the ALARMS BOX section of the manual.
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