Performed when the desired airflow is not achieved and the fault is suspected to be in the unit. To determine if there is a fault in the unit, the following measurements must be taken.
Switch off the supply voltage and check the unit internally before testing.
Run the unit at maximum capacity, 100 %.
Tests are carried out with filters that are as clean as possible; in the case of very dirty filters, double measurements are taken both with and without filters.
- Measure air flow in supply air.
- Measure air flow in exhaust air.
- If possible, measure the air flow in the duct as close to the unit as possible to rule out leaks.
- Measure duct pressure in all duct connections directly at the connection to the unit before dimensional changes, bends and any duct components.
Pressure is measured in the duct connection directly at the unit with a measuring probe (hose) directly inside the duct wall, do not insert the probe (hose) into the duct. Otherwise the static pressure will not be measured correctly. However, the probe (hose) must close tightly against the hole in the duct.
The illustration above shows a side-connected unit, but the same method is used for all units, including top-connected units.
Note the measurements below:
| Parameter | With filter | Without filters (if filters are very dirty) |
|---|---|---|
| Supply air flow rate | _____ l/s | _____ l/s |
| Exhaust air flow rate | _____ l/s | _____ l/s |
| Static pressure supply air | _____ Pa | _____ Pa |
| Static pressure of exhaust air | _____ Pa | _____ Pa |
| Static pressure outdoor air | _____ Pa | _____ Pa |
| Static pressure of exhaust air | _____ Pa | _____ Pa |
Using these measurements, we can determine whether the fault is in the unit or in the ductwork.