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
