Sensors & controls
What sensor measures outdoor air temperature for economizer operation?
Outdoor air temperature sensor
Which damper brings in outdoor air?
Outside air damper
When does an economizer provide free cooling?
When outdoor air is suitable (cool/dry)
Economizer stuck closed is a likely cause of what?
Failed actuator or control signal
How can you verify damper rotation is correct?
Measure position with a gauge or visually inspected linkages
What does an enthalpy sensor measure?
Total heat (temp+humidity) in the air
Purpose of the minimum position setting?
Maintains ventilation airflow
If outdoor temp is higher than return temp, what happens?
Dampers close, mechanical cooling runs.
Economizer stuck open on a hot day is likely a cause of what?
How often should economizer sensors be cleaned?
At least annually or per manufacturer recommendation
A CO2 sensor can be tied in an economizer
TRUE
If an actuator fails, what damper position is safe?
Closed or minimum position
What’s mixed air temperature supposed to be maintained at?
Around 55 degree F supply air
If mixed air is too hot, what might be wrong?
Outside damper is stuck open? Possibly parameter setting.
What tool can check if the actuator torque is sufficient?
Torque meter or manufacturer specified wrench.
Which controller decides if the economizer opens or mechanical cooling starts?
Economizer control module
Two types of damper actuators?
What’s the “high limit“ control in economizers?
Temp/enthalpy limit where outdoor air is no longer efficient
CO2 levels stay high- economizer not helping, what can be the cause?
Minimum position not set, damper, not opening
Why inspect damper linkages?
To ensure smooth operation and avoid sticking or binding
Difference between dry bulb and enthalpy economizer control?
Dry bulb= temperature only
Enthalpy= temp+humidity
Effect of misadjusted linkage?
Dampers don’t fully open/close, poor control.
Why is economizer lockout needed?
Prevents economizer use in extreme hot/cold or humidity conditions?
Damper keeps hunting open close rapidly what are the likely causes?
Faulty sensor or control calibration
How do you verify an entropy sensor is reading correctly?
Compare sensor reading to non-outdoor temp and humidity or calibrated psychrometer