The FAN OPERATION HEAT MODE determines how the fan will be powered when the TE device is in the heating mode
(main output% ≥ ~1%).
• FAN OFF turns off output power to the fan when the controller switches to the heating mode.
• HOLD AT MINIMUM % PWM applies the FAN PWM % MINIMUM OUTPUT level to the fan when the TE device is
being powered the heating mode.
If the FAN OPERATION MODE is set to FAN OFF, there will be a slight delay between when the when the controller
switches into the heating mode and the fan actually shuts off. Likewise, there will be a slight delay before the fan
restarts when the controller switches into the cooling mode. This helps prevent the fan from cycling on and off
frequently if the output is frequently switching between positive and negative values.
For tighter temperature control stability and to avoid having the fan constantly stopping and restarting under certain
conditions it is recommended that the FAN OPERATION MODE be set to HOLD AT MINIMUM % PWM.
FAN PWM FREQUENCY can be set to 42 Hz; 169 Hz; 675 Hz; 5400 Hz; or 43,200 Hz. Consult with the fan manufacturer to
determine which frequency works best with the particular fan.
FAN PWM % MAXIMUM OUTPUT and FAN PWM % MINIMUM OUTPUT levels are adjustable from 0% to 100%. These
determine the maximum and minimum % PWM duty cycle for the fan.
The INCREASE FAN SPEED STARTING AT box determines the main output% (to the TE device) at which the fan output should
begin proportionally increasing from FAN PWM % MINIMUM OUTPUT to FAN PWM % MAXIMUM OUTPUT. FAN PWM %
MAXIMUM OUTPUT is always reached when the main output% to the TE device is at -100%.
FAN DELAY--The fan speed control incorporates an initial period of operation at 100% duty cycle when the fan is first turned
on, before the fan speed is adjusted to the output level according to the main output%. This helps ensure the fan has been
given full voltage to start the fan blades spinning before power is decreased. It is useful because fan bearings age,
potentially requiring increased start-up voltages. The FAN DELAY box determines the maximum amount of time the fan
runs at 100% before being adjusted according to the main output%. This delay happens any time the fan transitions from
completely off to on. However, if the FAN OPERATION HEAT MODE is set to FAN OFF, and the main output% switches from
heating to cooling, the fan restarts at 100% duty cycle. If the controller then switches from cooling back to heating before
reaching the full time corresponding to the FAN DELAY, the fan will simply turn off before the total FAN DELAY time has
passed. The FAN DELAY is not actually a time in seconds, but it is proportional to the amount time in seconds. Each
increment in the FAN DELAY box increases the delay time by approximately 2 seconds.
If the COOL SIDE MULTIPLIER is set to zero, the FAN DELAY is set to zero, and the FAN OFF is set, the fan will turn on at the
level set by FAN PWM % MINIMUM OUTPUT as soon as the temperature overshoot begins dropping back down. The fan
will shut off as the temperature begins dropping below the set point.
EXAMPLE: As shown in “FAN CONTROL SETTINGS” screen view above, the PWM frequency for the fan is set to 43,200Hz.
The fan PWM% will be set to 50% while the main output% is between 0% and -70%. The fan PWM% will then increase from
50% to 100% as the main output% increases from -70% to -100%. The fan will be off when in heating mode (main output%
≥ ~1%). This can be seen in the graph below. If the controller switches from heating mode to cooling mode, there will be a
delay of approximately 10 seconds before the fan PWM% is adjusted according to the main output% level. During these 10
seconds the fan PWM % will be 100% (unless the controller switches back to the heating mode before the 10 seconds has
passed, in which case, the fan would again shut off).
Additional information and examples are shown in Appendix E– “Additional Notes on Fan Control”
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