Construction Inspection
The field technician should check the following:
•All temperature and sensors have been calibrated and read accurately.
•All sensors are mounted in a location away from direct evaporator discharge air draft.
•All evaporator motors are operational and rotate in the correct direction.
•Fan speed control is operational and connected to evaporator fan motors.
•All speed controls are in “auto” mode.
•Records showing calibration was performed, what offsets or control system calibration values were used, and documentation of the instrumentation used for calibration.
Functional Testing
Step 1: Measure the current space temperature and program this temperature as the test temperature into the control system. Allow 5 minutes for system to normalize.
Verify whether the evaporator fans are controlled based on the space temperature. This step brings the temperature setpoint for the evaporator within range to the current conditions of the space.
Step 2: Using the control system, lower the test temperature setpoint in 1 degree increments below any control deadband range.
Verify:
•Evaporator fan controls modulate to increase fan motor speed, by observing control system readout or variable speed drive readout values.
•Evaporator fan motor speed increases in response to controls, by observation of fan speed or sound level.
Step 3: Using the control system, raise the test temperature setpoint in 1 degree increments above any control deadband range until fans go to minimum speed.
Verify:
•Evaporator fan controls modulate to decrease fan motor speed, by observing control system readout or variable frequency drive readout values.
•Evaporator fan motor speed decreases in response to controls, by observation of fan speed or sound level.
Document:
•Record the minimum fan motor control speed and how it was determined.
•Note: Control system parameters may utilize percent of full speed, frequency (Hz), or sometimes RPM. Variable Frequency Drive (VFD) readouts may also provide these values, and may not read the same as the control system. The control system programmer may be needed to explain readout values.
Step 4: Restore the control system to correct control setpoints.
Confirm that the control system is restored back to initial space temperature setpoint.