4 Minute Read
| How it Works
75F VAV profiles operate by ASHRAE GPC36. To read a full description please read GPC36 in its entirety. Below you will find a highly summarized description of how this VAV application will operate. The description below does not cover all details of GPC36 but is meant to be used as a quick and dirty field-level understanding of the VAV box operation.
Cooling Mode - If the system is supplying cool air and the zone requires cooling, the damper actuator will modulate towards its maximum cooling position until the airflow setpoint is achieved. If the system is supplying cool air but the zone requires heating, the damper will be maintaining its minimum heating airflow setpoint and will first stage on the parallel fan to try to meet the DAT setpoint. If the plenum air is not enough to raise the DAT setpoint then the reheat will be engaged to raise the DAT. As the DAT rises past the DAT setpoint then the damper actuator will begin to modulate open to its max heating airflow setpoint to mix the air back down to its DAT setpoint.
Heating Mode - If the system is supplying warm air and the zone needs cooling then the damper actuator will modulate down to its minimum heating airflow setpoint. If the system is supplying warm air and the zone needs heating then the damper actuator will modulate open to its maximum damper position.
Recirculate -If the zone is satisfied the damper actuator will modulate near closed to maintain its minimum airflow setpoint.
|VAV Reheat - Parallel Fan - Staged Electric RH
|TH1||X||Discharge Air Temp||10k Type II or DI|
|TH2||X||Entering Air Temp||10k Type II or DI|
|R1||X||Reheat Stage 1||Dry contact|
|R2||X||Parallel Fan||Dry contact|
|Damper 1||8 Pin RJ45||Primary Smart Damper|
|Damper 2||8 Pin RJ45||Secondary Smart Damper|
|RTS||3 Pin Molex Sensor Bus||Temperature/ Humidity/ Duct Pressure||3 pin cable connector (No local interface option)|
|RS485||4 Pin Molex Sensor Bus||Temperature/ Humidity Local control||4 pin cable connector (Local Interface option)|
Once you've paired the Smart Node as a VAV profile, the sequences for VAV applications in GPC36 will be followed. What you will need to do is select a few specific configuration parameters that define the physical characteristics of your box.
Damper Type - Select the type of damper actuator. The most common is a 2-10 Vdc actuator but other types exist. For example, if you are using Smart Dampers, you will select Smart Damper as the damper type.
Size - Tells the system the size of the duct. This helps the system accurately calculate the CFM.
Shape -Also helps the system calculate the CFM.
Reheat Type - Tells the system which output to use as the reheat. Staged and modulating options both exist.
Damper Min/ Max Positions -Sets the hard limit for damper actuator minimum and maximum positions.
Enable Occupancy Control - Only used if an occupancy sensor exists and is not a standard option. If you have the option and you enable this feature the occupancy sensor will set the zone to occupied during unoccupied hours if occupancy is detected.
Enable IAQ Control -Only used if an IAQ sensor exists and is not a standard option. This will enable the trim and respond logic from this controller for IAQ.
Enable CO2 Control -Only used if a CO2 sensor exists and is not a standard option. This will enable the trim and respond logic from this controller for DCV.
Enable CFM- To enable operation based on the Airflow in cubic feet per minute calculation. For more information refer to True CFM (Cubic Feet per Minute)
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