Issue
MP-V Air Flow is reading zero flow despite the Velocity Pressure having a positive value.
Product Line
EcoStruxure Building Operation
Environment
- MP-V-7A, MP-V-9A, RP-V-4A, RP-V-5A
- Variable Air Volume Data
Cause
The Air Flow value is an internally calculated value based on the Velocity Pressure. There are a number of values involved in that calculation that could result in no flow.
Resolution
- Validate Variable Air Volume Data > Flow Balance Data > Rated box flow. The rated box flow defaults to 0 ft³/min in a new controller and must be replaced with the rated flow at 1.0inH₂O (provided by the box manufacturer).
- Compare Variable Air Volume Data > Velocity Pressure > Value to the Zero flow threshold. Any Velocity Pressure below the threshold will result in no flow. This threshold defaults to 0.008inH₂O.
Check Variable Air Volume Data > Properties > Balanced k-factor and Balanced flow correction factor. If either of these values are at 0, there will be no flow. These values cannot be directly written to and are only the result of a flow balance calculation. To get them to update:
- Go to Variable Air Volume Data > Flow Balance Data and record all balancing data (you will need to manually re-enter it later).
- Set all 7 balancing values to 0 - Rated box flow, Box/Hood measured maximum/intermediate/minimum
- Right-click on Variable Air Volume Data and Download
- Re-enter the valid balancing data. The balanced k-factor should now show a value close to the rated box flow and the balanced flow correction factor should show a multiplier ideally between 0.5 and 2.
If the box has not been balanced and no valid balancing data is available, leave the minimum flow readings at 0 and enter the same value into both the hood and box maximums (for example, 1000 and 1000). This will result in a balanced k-factor equal to the rated box flow and a balanced flow correction factor of 1.
