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72 THE ARCHITECTURE REFERENCE + SPECIFICATION BOOK
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Chapter 6: Mechanical Systems
A building’s mechanical systems involve control of heat, ventilation, air-conditioning,
refrigeration, plumbing, re protection, and noise reduction, all of which must be
integrated with the architectural, structural, and electrical design.
ENERGY DISTRIBUTION SYSTEMS
All-air Systems: Conditioned air is circulated to and from spaces by central fans that direct
it through runs of ductwork.
Air and Water Systems: Conditioned air is ducted to each space, and chilled and heated
water are piped to each space to modify the temperature of the air at each outlet.
All-water Systems: No ductwork is used, and air is circulated within each space, not from a
central source. Chilled and heated water are furnished to each space. Because water piping
is much smaller than ductwork for air, all-water systems are very compact.
Air duct: Pipe that carries warm and cold
air to rooms and back to a furnace or air-
conditioning system.
ASHRAE: American Society of Heating,
Refrigerating, and Air-Conditioning Engineers.
Cavity wall: Hollow wall formed with two lay-
ers of masonry, providing an insulating
air space between.
Chase wall: Cavity wall containing electrical
runs or plumbing pipes in its cavity.
Closed loop: Evaporator side of chiller
system, closed to the atmosphere.
Dry bulb: Ambient outside temperature.
Furnace: Device that generates heated air,
and is powered by natural gas, fuel oil, or
electricity. Most often used in small commer-
cial or residential applications.
Heat pump: A device that warms or cools by
transfering thermal energy from a heat source
to a heat sink.
HVAC: Heating, ventilating, and air-condition-
ing.
IAQ: Indoor Air Quality
Louver: Opening with horizontal slats that
permit passage of air, but not rain, sunlight, or
view, into a structure.
Plenum: Chamber that serves as a distribu-
tion area for heating or cooling systems,
usually found between a false ceiling and
the actual ceiling.
Open loop: Condenser/tower side of chiller
system; open to the atmosphere.
Radiant heat: Heating system that uses
coils of electricity, hot water, or steam
pipes embedded in oors, ceilings, or
walls to heat rooms.
Shaft: Enclosed vertical space (usually with
re-resistive walls) containing all vertical runs
of pipes, ducts, and elevators.
Variable air volume (VAV): Air-handling system
that conditions air to a constant temperature
and varies airow to ensure thermal comfort.
Wet bulb: Combination of outside air tem-
perature and relative humidity; higher relative
humidity makes it more difcult for a cooling
tower to evaporate water into the atmosphere.
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Job: 03-30364 Title: Rp-Architecture Reference & Specification
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Mechanical Systems 73
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Job: 03-30364 Title: Rp-Architecture Reference & Specification
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HVAC SYSTEMS
The systems for accomplishing heating, ventilation, and air conditioning of indoor spaces vary
considerably, based on factors including building type and program, cost, climate, and building
size. The basic principals and components of heating, cooling, and circulating are similar across
all systems.
Boiler: Tank where the
heat produced from the
combustion of fuels (natu-
ral gas, fuel oil, wood, or
coal) generates hot water or
steam for use in heating.
Chiller: Heat exchanger (evaporator, condenser,
and compressor system) that uses air, a refriger-
ant, water, and evaporation to transfer heat and
produce air-conditioning.
Cooling tower: Open recirculating
system where heat exchange occurs
by evaporation.
Air handling unit
(AHU): Equip-
ment including
a fan or blower,
heating and/or
cooling coils, reg-
ulator controls,
condensate
drain pans, and
air lters.
BOILER
CHILLER
AHU
COOLING TOWER
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MECHANICAL DISTRIBUTION TYPES
FAN COIL UNITS
Fan coil units (FCUs) contain cooling or heating coils and a fan. Typically, hot or chilled water is piped
to the unit from a central boiler and chiller. Air from the room is drawn into the unit (return air) and
blown over the coil by a fan. The air is then heated or cooled and discharged (supply air) to the
room. FCUs may be vertical or horizontal, mounted on walls, ceilings, or freestanding.
Horizontal Console
Floor-mounted, often
at exterior wall
Boiler
Chiller
Return air
Supply air
Fan Coil Unit
Piping
2-Pipe: System has one sup-
ply and one return pipe. Must
be changed over from hot to
cold with change in seasons.
4-Pipe: System has hot
supply, hot return, cold sup-
ply, and cold return pipes,
allowing the system to change
between heating and cooling
at any time.
Horizontal FCU
Ceiling-hung, may
be within soft or
exposed
Vertical Stack
May be concealed within wall
system, or freestanding
Vertical Stack — ducted
May be concealed within wall
system, or freestanding
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