Chapter 50 Review Questions
In a chilled-water system, a 50/50 mix of water and ethylene glycol will have a freezing temperature in the range from
-36°F to -30°F
An 18-in. square air duct can deliver the same amount of cooling Btus as a
1-in. water pipe.
Which of the following sets of terms best describes a rooftop package unit?
Factory-assembled, factory-charged, self-contained
Which process would best represent the opposite of exhausting air from a system?
Ventilating
A fixed-type economizer control compares
a sensed/measured value to a constant value.
Ultimately, the speed of the blower on a VAV system is controlled by
a variable frequency drive (VFD).
A bonded roof is one that has
a written warranty or insurance policy.
The portion of the crane that extends and retracts is called the
boom.
The pump on a dry cooler can direct water to either the tube-in-tube heat exchanger or the cooling coil with the aid of a
three-way valve.
The acronym VRF stands for
variable refrigerant flow.
The main purpose of a reheat coil on VAV systems is to
temper the air as needed when cooling or ventilation is called for.
The most efficient way to establish the best possible economizer position is to measure
the enthalpy of both the return air and the outside air.
The chiller on a water-cooled, chilled-water system will have
two condenser water lines and two chilled water lines.
If, while communicating with the crane operator, a team member taps his elbow with one hand, the crane operator should
use the auxiliary hoist (whip line).
In a VAV system, the amount of air supplied to an occupied space
varies in response to the needs of the space.
Passive chilled beams can remove
200 Btuh to 650 Btuh of sensible heat per linear foot.
When rigging a unit to the roof, what minimum number of installation crew members should be on hand, not including the crane operator?
3
A demand control ventilation strategy monitors what substance in air?
Carbon dioxide
Which of the following is typically true regarding the fans and blowers on rooftop package units?
Centrifugal blowers are used to move air to and from the occupied space.
VRF systems rely on what technology to perform as intended?
Inverter-controlled motors
The heat exchangers in a rooftop package unit are exposed to which two airstreams?
Mixed air and supply air
Which of the following is true regarding the refrigerant piping on a rooftop package unit?
No refrigerant lines are field installed.
Which of the following statements is true regarding a heat-recovery VRF system?
Simultaneous heating and cooling can be achieved at different indoor units.
Which of the following is true regarding a reheat water circuit that utilizes three-way modulating valves?
The water is always circulating and is not prone to coil freeze-up.
Which of the following is true regarding a reheat water circuit that utilizes two-way modulating valves?
The water pump must be able to vary its flow.
What is the benefit of having two refrigerant circuits, each with a different capacity on a rooftop package unit?
There will be an additional capacity "step" to better match the needs of the structure.
All of the following should be taken into account when selecting the location and position of a rooftop package unit except
electrical power availability.
Free-cooling can be accomplished if the
enthalpy of the outside air is lower than the enthalpy of the return air.
What is the acceptable method for communicating with the crane operator while rigging a unit to the roof?
hand signals
All of the following are common VAV box types except
heating only.
The economizer mode of operation that uses the system compressor(s) and has the outside air dampers fully open is called
integrated mode.
In a CAV system, the amount of air supplied to an occupied space
is always constant when the system is calling for blower operation.
Properly installed roof curbs will reduce the chances of
leaks and noise.
When penetrating a roof for the installation of a rooftop package unit,
measure, layout, and check penetration locations at least twice and cut once.
The economizer mode of operation that uses the system compressor(s) and has the outside air dampers at their minimum position is called the
mechanical mode.
A demand control ventilation strategy varies the ventilation rate based on the
occupancy level.
Economizers have a return-air damper that
opens when the outside air damper closes.
On chilled-water VAV systems, a freezestat is used to
prevent the chilled water coil from freezing.
Economizers are intended to
provide ventilation and reduce cooling costs.
During low ambient conditions, the dry cooler provides space cooling by
pumping water to a cooling coil located in the airstream.
If, while communicating with the crane operator, a team member extends his arm with his thumb pointing up, the crane operator should
raise the boom.
The three field-installed refrigerant lines on a 3-pipe VRF system carry
refrigerant in different states depending on the mode of system operation.
A cooling-only VAV box has all of the following except a(n)
reheat coil.
Mixed air is best described as the combination of
return air and outside air.
All of the following are typically required to install a rooftop package unit except
system evacuation and charging.
VRF systems the optimal amount of refrigerant to circulate based primarily on the
system's operating temperatures and pressures.
In a building that utilizes active chilled beams, the primary air system
will handle the latent cooling load and the space ventilation requirements.
