CITY OF OMAHA STATIONARY ENGINEER
FIRST GRADE 2026 FINAL PAPER
QUESTIONS AND ANSWERS DETAILED
PREP RESOURCE GRADED A+
⩥ boiler.
Answer: equipment that provides hot water or steam for various uses
⩥ PRV.
Answer: PRESSURE RELIEVE VALVE
⩥ NOWL.
Answer: Normal operating water level
⩥ BTU.
Answer: British Thermal Unit
⩥ absolute pressure.
Answer: gauge pressure (psi) + atmospheric pressure (14.7 psi) at sea
level
⩥ air changes per hour.
,Answer: The hourly ventilation rate divided by the volume of a space.
For perfectly mixed air or laminar flow spaces, this is equal to the
number of times per hour that the volume the space is exchanged by
mechanical and natural ventilation.
⩥ Air conditioner.
Answer: An appliance, system, or mechanism designed to dehumidify
and extract heat from an area.
⩥ Chiller.
Answer: A device that removes heat from a liquid via a vapor-
compression or absorption refrigeration cycle. This cooled liquid flows
through pipes in a building and passes through coils in air handlers, fan-
coil units, or other systems, cooling and usually dehumidifying the air in
the building. Chillers are of two types; air-cooled or water-cooled. Air-
cooled chillers are usually outside and consist of condenser coils cooled
by fan-driven air. Water-cooled chillers are usually inside a building, and
heat from these chillers is carried by recirculating water to a heat sink
such as an outdoor cooling tower.
⩥ Condenser.
Answer: A component in the basic refrigeration cycle that ejects or
removes heat from the system. The condenser is the hot side of an air
conditioner or heat pump.
⩥ Controller.
, Answer: A device that controls the operation of part or all of a system.
⩥ Dry Bulb Thermometer.
Answer: Dry bulb temperature is the temperature of air measured by a
thermometer which is freely exposed to the air while it is shielded from
radiation and moisture. It is usually thought of as air temperature, and it
is the true thermodynamic temperature. It is a measurement of heat
intensity independently of humidity and a dry bulb thermometer is used
to measure it.
⩥ Economizer.
Answer: An HVAC component that uses outside air, under suitable
climate conditions, to reduce required mechanical cooling. When the
outside air's enthalpy is less than the required supply air during a call for
cooling, an economizer allows a building's mechanical ventilation
system to use up to the maximum amount of outside
⩥ Enthalpy.
Answer: For a given sample of air, a measure of the total heat content
(the sum of the heat energy of the dry air and heat energy of the water
vapor within it). It is typically used to determine the amount of fresh
outside air that can be added to recirculated air for the lowest cooling
cost.
⩥ psychrometric.
FIRST GRADE 2026 FINAL PAPER
QUESTIONS AND ANSWERS DETAILED
PREP RESOURCE GRADED A+
⩥ boiler.
Answer: equipment that provides hot water or steam for various uses
⩥ PRV.
Answer: PRESSURE RELIEVE VALVE
⩥ NOWL.
Answer: Normal operating water level
⩥ BTU.
Answer: British Thermal Unit
⩥ absolute pressure.
Answer: gauge pressure (psi) + atmospheric pressure (14.7 psi) at sea
level
⩥ air changes per hour.
,Answer: The hourly ventilation rate divided by the volume of a space.
For perfectly mixed air or laminar flow spaces, this is equal to the
number of times per hour that the volume the space is exchanged by
mechanical and natural ventilation.
⩥ Air conditioner.
Answer: An appliance, system, or mechanism designed to dehumidify
and extract heat from an area.
⩥ Chiller.
Answer: A device that removes heat from a liquid via a vapor-
compression or absorption refrigeration cycle. This cooled liquid flows
through pipes in a building and passes through coils in air handlers, fan-
coil units, or other systems, cooling and usually dehumidifying the air in
the building. Chillers are of two types; air-cooled or water-cooled. Air-
cooled chillers are usually outside and consist of condenser coils cooled
by fan-driven air. Water-cooled chillers are usually inside a building, and
heat from these chillers is carried by recirculating water to a heat sink
such as an outdoor cooling tower.
⩥ Condenser.
Answer: A component in the basic refrigeration cycle that ejects or
removes heat from the system. The condenser is the hot side of an air
conditioner or heat pump.
⩥ Controller.
, Answer: A device that controls the operation of part or all of a system.
⩥ Dry Bulb Thermometer.
Answer: Dry bulb temperature is the temperature of air measured by a
thermometer which is freely exposed to the air while it is shielded from
radiation and moisture. It is usually thought of as air temperature, and it
is the true thermodynamic temperature. It is a measurement of heat
intensity independently of humidity and a dry bulb thermometer is used
to measure it.
⩥ Economizer.
Answer: An HVAC component that uses outside air, under suitable
climate conditions, to reduce required mechanical cooling. When the
outside air's enthalpy is less than the required supply air during a call for
cooling, an economizer allows a building's mechanical ventilation
system to use up to the maximum amount of outside
⩥ Enthalpy.
Answer: For a given sample of air, a measure of the total heat content
(the sum of the heat energy of the dry air and heat energy of the water
vapor within it). It is typically used to determine the amount of fresh
outside air that can be added to recirculated air for the lowest cooling
cost.
⩥ psychrometric.
