Pid Control Loops; Pid Control Loops; Airflow Set Points Sequence; Airflow Set Points Sequence - Nailor 35SW Manual

Unoccupied set point — A temperature set point entered by the controls technician during controller setup and system
commissioning. This is the set point used when the system is unoccupied .
Standby set point — The standby set point is used when the controller is in the standby state. It is a value calculated from the
occupied set point and the value of Standby Offset. The standby offset value is entered by the controls technician during controller
setup and system commissioning. See the topic Occupancy sequence on page 35.
Set Point Limits
The programming in the EZvav controller limits the set point entry so that no heating set point is set higher than its corresponding
cooling set point.
If a user is adjusting a set point and it falls within the range set by the value of Minimum Set point Differential, the corresponding
set point will be changed to maintain the differential. For example, the Minimum Set point Differential is 4° F (-15.56° C) and the
Occupied Heating set point is 70° F (21.11° C). If the user lowers the Occupied Cooling set point to 71° F (21° C), the controller
recalculates the Occupied Heating set point and changes it to 67° F (19.44° C).
PID Control Loops
A PID control loop calculates an error value from the difference between the measured room temperature and the active set point.
The error value is expressed as a percentage and is typically used in a BAS controller to control the state of an output. When the
difference between the set point and room temperature is large, the error is large. As the system reduces the difference between
the set point and space temperature, the error becomes smaller.
The EZvav controllers use up to three PID loops.
• The heating PID loop.
• The cooling PID loop.
• The discharge air temperature (DAT) loop.
For EZvav controllers, the output of either the cooling and heating PID loop is used to calculate the position of the damper. If
present, the DAT input and DAT loop controls the Reheat loop.
The PID loops in the EZvav controllers are standard BACnet objects and are described in the topic BACnet objects on page 44.
Airflow Set Points Sequence
Airflow Set point is calculated based on the demand for cooling or heating depending on whether the Cooling loop or Heating loop
is greater than zero.
If no room sensor is connected to the controller, the controller uses the Minimum Cooling Airflow set point to maintain airflow.
Cool Air Sequence
As the Cooling loop increases from 0% to 100%, Primary Airflow Set point is proportionally calculated between Minimum Cooling
Airflow and Maximum Cooling Airflow.
If there is a call for reheat to maintain room temperature, the primary airflow is set to the value of Auxiliary Flow.
Tip: Auxiliary Flow is only for unit with reheat. Set to Minimum Cooling Airflow unless alternate airflow is desired.
Warm Air Available
In the heating mode, as the Heating Loop increases from 0% to 100%, Primary Airflow Set point is proportionally calculated
between Minimum Heating Airflow and Maximum Heating Airflow.
See also the topics, Changeover on page 36 and Input sources on page 34.

Changeover

The Discharge Air Temperature input is used by the controller to determine the type of air that is being supplied by the AHU. The
sensor is required for applications that require automatic change over between cooling and heating.
When the Heating loop is inactive, the Discharge Air Temperature input is compared to the SAT Changeover Temp. If the
Discharge Air Temperature is below the SAT Changeover Temp minus 2° Fahrenheit (-16.67 Celsius), the SAT Changeover Mode
is set to Cool. If the Discharge Air Temperature is above the SAT Changeover Temp plus 2° Fahrenheit (+16.67 Celsius), the SAT
Changeover Mode is set to Heat. The default changeover temperature is 74° Fahrenheit (23.33 Celsius).
See the topic Discharge Air Temperature (DAT) limiting on page 37 and Input sources on page 34.
Date: 10-2016 Supersedes: 7-2016
Nailor reserves the right to change any information concerning product or specification without notice or obligation.
Installation and Operation Manual
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EZvav Digital Controls
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EZVAVINST