Table 1 describes the attributes used by the Flow Calculation modules.
|
Name |
Type 1 |
Description |
Default Value |
|---|---|---|---|
|
Autocalibrate Now |
When True, causes the Flow Calculation module to re-calculate the Autocalibration Offset property to make the current flow zero. |
False |
|
|
Autocalibrate Offset |
V |
Correction added to Differential Pressure that determines the Effective dP is used to calculate the Airflow Rate. It is recalculated whenever Autocalibrate Now is set to True. |
Display Units: Pa, in. W.C. |
|
CD-AREA, DA-AREA, EA-AREA, HD-AREA, MOA-AREA, OA-AREA, RA-AREA, or RLF-AREA (Area) |
Contains the area at the location of the pitot tube (m2 or ft2).
Note: In VAV applications, this input receives its value from the Balancer Override module.
|
0.0 m2, 0.0 ft2 |
|
|
CD-KFACTOR, DA-KFACTOR, EA-KFACTOR, HD-KFACTOR, MOA-KFACTOR, OA-KFACTOR, RA-KFACTOR, or RLF-KFACTOR (Pickup Gain) |
Amplification provided by the pickup tube. For single point calibration, Pickup Gain 2 is set to zero and Pickup Gain is calculated using the equation in Pickup Gain Calculations (Flow Calculation).
Note: In VAV applications, this input receives its value from the Balancer Override module.
|
2.0 |
|
|
Differential Pressure |
Differential pressure measured across a square law device (normally a pitot tube). The differential pressure measurement is related in a non-linear way to the flow rate. |
0.0 Pa, 0.0 in. W.C. |
|
|
Effective dP |
V |
Contains the effective differential pressure used for calculating Airflow Rate. It is determined by adding the Autocalibrate Offset to the Differential Pressure input. This value is clamped at a minimum value of zero. |
Display Units: Pa, in. W.C. |
|
Elevation |
Distance above or below sea level. A negative value represents a distance below sea level (m or ft). |
0.0 m, 0.0 ft |
|
|
Flow Units |
C |
Defines the preferred flow units (l/s, cu meter/h, or cfm). |
l/s, cfm Set Name: Flow Calculation Units |
|
FLOW, CD-F, DA-F, EA-F, HD-F, MOA-F, OA-F, RA-F, RLF-F, or SA-F (Airflow Rate) |
G, V |
Contains the measured airflow rate (l/s, cu meter/h, or cfm). |
|
|
Full Range dP |
Contains a scaling factor used for calculating the Percent dP Offset. If the percent dP Offset is far from zero, it likely indicates the Flow Calculation was autocalibrated when the flow was not really zero. |
373.5 Pa, 1.5 in. W.C. |
|
|
Percent dP Offset |
V |
Value of the Autocalibration Offset as a percentage of the Full Range dP (that is, the value is 100 * Autocalibrate Offset/Full Range dP). |
Display Units: % |
|
Pickup Gain 2 |
Used for 2 point calibration so that the measured airflow rate can match the balancer at both minimum and maximum airflow rate setpoints. For single point calibration the value of this input is zero. |
0.0 |