Transcript File

Chapter 12
Mechanical Systems
I.
Mechanical Systems – HVAC – Heating, Ventilating
and Air Conditioning. Plumbing – Complicated 1/5th
Construction Costs
A.
Fresh & conditioned air
B.
Hot/Cold, potable water
C.
Waste water, venting
II.
Drawings – Typically Segregated into
Mechanical/Plumbing Sheets
III.
Basic System of Treating Air Requirements – Control
of Ambient Air, Relative Humidity, Air Movement,
Mean Radiant Temperature
A.
Heat generation – Hot water, steam, warm air systems by
natural gas, fuel oil, coal, electricity or combination there
of – distribution system
B.
Cooling – Typically by a gas cycled through a compressor
condenser and evaporator – gas to liquid – transfer of –
heat/cooled air circulated by distribution system – ducts
C.
Controls – Low voltage – thermostat/computer
chips/mechanical/electrical responsibilities
D.
Fire safety – Both HVAC, plumbing require alarm
circuitry required by fire code
IV.
System Types – Most Systems in Buildings are Air or
Water or Combination
A.
Air systems
(1)
Single zone system – uses single air handler)
filtered – heated/cooled –
humidified/dehumidified and distributed
throughout buildings – typical for residential
(2)
Multi-zone system – produce heat/cool air
simultaneously and distribute to various rooms
through ducts
IV.A.(3)
Reheat systems – utilize advantage of single and multizone systems by producing conditioned air at lowest
required temperature then adjusting temperature by
treating air as it travels to zones. Used in buildings where
temperature variations required.
Variable air volume (VAV) – constant temperature
systems that adjust temperature in a room by mixing cool
and warm air. Typically used in office building and
where humidity not a critical issue.
(4)
(5)
Dual duct systems – conditioned air is simultaneously
heated/cooled in air-handling equipment – distributed to
spaces in separate ducts - expensive
IV.
B.
Return air – Air must be returned to system (return air
system) – strategically located
C.
Hydronic systems – Rely on hot/cold water distributed to
coils in duct systems across which air is blown
D.
Air purity – By filter system of simple fabric filters to
ionizing filters to remove dust and allergens.
E.
System maintenance – Important that equipment design
allows for safe and ease of maintenance
F.
Controls – Air speed, volume and temperature.
Mechanical contractors are responsible for start-up and
testing of equipment. System controls often installed by
specialists.
V.
Analysis of Drawings – Complicated for Mechanical
Contractor: Major Considerations
A.
Type of system
B.
Location of equipment (i.e. roof)
C.
Energy – who supplies/supply connect
D.
Distribution system
E.
Focus on high cost items
F.
Conflicts of distribution system with other components –
structures, fire separation, floors, walls
VI.
Plumbing Systems – Basic Buildings Simple, Special
Projects – Hospitals, Etc.
A.
Piping – Type of fluid or gas piped determines material
used and coupling method.
-
Steel – steam, hot water, chilled water,
compressed gas or air and oil
-
Verified clay pipe – underground sewage
-
Cast iron – commercial drains
-
ABS/PVC – residential drains
VI.
B.
Pipe thickness – Size/pressure
C.
Fittings – Join sections, change direction, reduce/increase
size; split or terminate. Most of same material
-
Threaded and coupled
Flanged – steel pipe
Grip type – fire protection systems
No HUB – stainless steel
Fused – welded, soldered, glued
Bell and spigot – clay lines
Compression – refrigeration lines
VI.
D.
Valves – Control flow, volume, level, temperature of
liquids to regulate pressure – cast iron bronze, copper,
plastic and attached to pipes by those listed in B. Types
-
Gate – used as shut off
Globe – reduces flow
Angle – less restrictive than globe
Ball
Swing check – allow flow in one direction
Lift check valve – like swing
Butterfly – control volume
E.
Water sources – Most often by city/county sources
F.
Fire service lines – Initial planning stage of project
VI.
G.
Fire sprinkler systems – Guidelines by NFPA National
Fire Protection Association
(1)
Wet pipe system – most common – connected to
water supply systems – under constant pressure –
heat triggers system
(2)
Dry sprinkler system – used in environments
subject to freezing – more expensive – slower to
respond
(3)
Fire cyclone system – water damage must be kept
to a minimum – stop and start type system
(4)
Preaction system – use sensitive system – water
enters system in heat – releases water on specific
heat requirement
(5)
Deluge system – nozzles instead of sprinkler
VI.
H.
Drain, waste, venting
(1)
Drain pipes called soil piping
(2)
Vents – allows lines to function to allow air to
replace liquid leaving system – drains dependent
on gravity to work properly 1/4 - 1/8 per foot on
buildings
VI.
I.
Fixtures – Devices used by occupants – sinks, fountains,
toilets, etc. installed late in construction process
J.
Pipe supports systems – Hangers for support when pipes
move/expand
-
Carriers – structural support of fixtures
-
Expansion joints – allow for thermal expansion in
pipes
-
Water hammer – a shock to system
VI.
K.
Insulation – By specialize contractors often both pipes
and mechanical equipment – refrigeration pipes and
equipment in HVAC
L.
Maintenance, service of system – part of system are
components that allow for maintenance and service
-
Clean outs
Shut off valves
Water hammer arrestors
VII.
Mechanical Drawings – General to Specific – First
Pages Consist of Equipment Schedules and Legend
and Move to More Detailed Drawings
A.
Supply and return super imposed on over architectural
floor plan, floor by floor
B.
Plumbing drawings – Usually by enlarged-scale to show
all plumbing
Fire systems – Usually drawn by specialist – someone
besides architect or mechanical contractor
VIII.
Summary – Mechanical Engineers Provide Information:
-
General requirements of mechanical systems within
parameters of architectural program – code – budget
-
Provide compatible system of HVAC/plumbing
-
Consideration of fuel type
-
Source of water/and disposal of waste
-
Conditioned air supply/heat
-
Fixtures
-
Controls
-
How all components correlate