Delta Controls
Document Edition 4.2 Page 27 of 43
If the Heating and Cooling controllers are both zero the control logic is in deadband and the compressor
output is turned OFF.
If the Heating controller value exceeds 90% the control logic will switch to heating, and the reversing
valve is turned ON if isn’t on already. After the transition timer has expired the compressor output will
be turned ON. The transition timer will then be reset (to the value set in the Setup variable AV24).
If the Cooling controller value exceeds 90% the control logic will switch to cooling, and the reversing
valve is turned OFF if isn’t off already. After the transition timer has expired the compressor output will
be turned ON. The transition timer will then be reset.
The HPU algorithm may use a fan on Output 3, or have an auxiliary heating or cooling output of type
Binary or PWM or Timed Proportional.
When the fan type is ‘Intermittent’ the fan will start when the compressor starts. When the compressor
stops the fan will be turned off when the delay time has expired (Setpoint 28, Output 3 Binary Delay).
NOTE: The analog outputs on the DNT-T221 do not modulate, but provide a 0 or 10v
signal for the compressor and reversing valve, and require interface relays for
switching purposes.
5. FAN COIL UNIT (FCU) – [Application (AV12) = 4]
Function: Control of a simple Fan Coil Unit with fan.
DNT-T103 I/O (Outputs 1 to 3 are Triacs)
Tri-State
Heating (Close)
Tri-State
Cooling (Close)
DNT-T221 I/O (Outputs 1 & 2 are Analog, and Output 3 is a Triac)
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