Economizer Controls and Accessories

What is the term for the following definition? A type of motor that moves or controls a mechanism or system. The position of the actuator responds to the output signal of the controller, which is constantly comparing the supply air or mixed air temperature to a user-adjustable setpoint.

• actuator

• sensor

• thermostat

• compressor

What is the term for the following definition? An averaging sensor takes an average temperature across its sensing probe, which has a much more stable temperature reading than the probe type duct sensor.

• averaging sensor

• point sensor

• humidity sensor

• pressure sensor

What is the term for the following definition? The dual enthalpy control determines the availability for free cooling with the use of an outdoor and a return air enthalpy sensor.

• dual enthalpy control

• single enthalpy control

• static pressure control

• variable air volume control

What is the term for the following definition? The enthalpy controller is a component that measures if sensible heat and latent heat are low enough to allow for free cooling or economizer cooling. Free cooling is cooling from the outdoor ambient and without the use of a mechanical cooling device.

• enthalpy controller

• humidistat

• thermostatic expansion valve

• pressure switch

What is the term for the following definition? Floating control uses a fast acting sensor that moves the damper or valve slowly until the controller is satisfied. The actuator maintains that position until the controller senses a need to adjust the position of the valve or dampers.

• floating control

• proportional control

• on-off control

• modulating control

What is the term for the following definition? Mixing dampers are two sets of dampers: a return air damper (normally open) in the return air plenum and an outdoor air damper (normally closed) in the outdoor air intake duct, which controls the amount of outdoor air entering the AHU. The mixing dampers are positioned by the economizer motor to mix colder outdoor air with warm return air, producing the cool supply air that is supplied to the conditioned space.

• mixing dampers

• fire dampers

• volume control dampers

• backdraft dampers

What is the main objective of this section?

• To describe economizer controls and accessories

• To install economizer systems

• To repair air conditioning units

• To design new economizer components

The function of the 'Mixed Air Temperature Controller' in the economizer wiring diagram is:

• To regulate the temperature of the mixed air entering the system

• To control the speed of the supply fan

• To monitor outdoor humidity levels

• To operate the compressor during cooling mode

The mixing damper is driven from 100% open to 0% open to control the amount of outdoor air entering the air handling unit (AHU).

• True

• False

What is a relief damper?

• A damper that responds to increases in space pressure and releases excess air to the outside.

• A damper that mixes outdoor and return air.

• A damper that heats the air.

• A damper that cools the air.