Commercial Air-Conditioning Systems Flashcards
In a commercial HVAC system in cooling mode, a thermostat’s switch may directly control a ____.
liquid line solenoid valve
The purpose of sequential controls in commercial air conditioning is ____.
adjusting equipment operation to meet demand
During installation of an RTU, be sure to properly install the ____ to prevent leaks into the building.
resilient gasket
When using a portable ladder to work on a rooftop unit be sure to ____.
lean the ladder against the building at an angle so that the base is 1’ away from the building for every 4’ of vertical rise.
extend the top of the ladder 3’ above the edge of the roof.
use both hands on the ladder while climbing or descending.
To avoid excessive pressure drop, VRF systems should pump refrigerant vertically no more than ____ feet.
150
A chiller provides cooling using ____.
a chilled water loop
Modern compression chiller systems typically use ____ as a secondary refrigerant.
water, brine, or glycol solutions
When a chiller uses a water-cooled condenser, ____.
the two water circuits are kept separate and do not mix
Fans are used in cooling towers to ____.
aid in evaporation
chill the chiller water
circulate the refrigerant
Chiller efficiency is primarily based on ____.
the temperatures of water entering and water leaving the chiller
AHRI recommends that chillers operate at ____.
44 F
Purge units are designed to remove noncondensables from a(n) ____.
low-pressure chiller’s primary refrigerant circuit
Cylinder unloading is used on ____ compressors.
reciprocating
The capacity of screw compressors is controlled with ____.
slide valves
A centrifugal compressor creates a pressure difference in the refrigerant circuit using ____.
impeller
The purpose of a compression chiller economizer is to improve system efficiency by ____.
subcooling the high-side refrigerant
lubrication for a centrifugal compressor is provided by ____.
a separate motor used only for the oil pump
A centrifugal compressor’s capacity control is provided by ____.
inlet guide vanes or guide vanes
A cooling tower is a structure that removes heat directly from ____.
an HVACR system’s cooling water
The main method by which a cooling tower removes heat from water in warm weather is through ____.
evaporation
The purpose of a wet deck in a cooling tower is to ____.
increase contact between air and water
A cooling tower the distributes water out of spray nozzles uses a ___.
pressured water system
A cooling tower that distributes water passively out of precision holes uses a _____.
gravity flow basin
Pressure water valves have bellows that primarily react to ____ pressure.
high-side
A thermostatic water valve reacts to heat in ____.
condenser outlet water
