Chapter 16 Mechanical and Electrical Systems Coordination

Question 1

Coordination

Answer 1

Although interior designers/architects are not responsible for designing building systems, coordination with consulting engineers concerning locations of plumbing fixtures, air diffusers, sprinklers, and other mechanical/electrical elements

Question 2

HVAC

Answer 2

• heating, ventilating, and air conditioning

- Includes all equipment for these purposes

Question 3

Type of HVAC Systems

Answer 3

All-air systems

All-water systems

Question 4

All air systems

Answer 4

• Cools/heats spaces by conditioned air alone. Air transported with supply/return ducts. Can also supply humidified/dehumidified air as needed
• Each type requires supply air ductwork registers, and return air grilles in all spaces
• Duct penetrations through fire rated partitions must have fire dampers that close automatically in case of fire

Question 5

All Water Systems

Answer 5

Use a convector in each space through which hot water (sometimes cold, too) is circulated; water heats/cools fins in convector unit, causing change in air temperature
- Air may be circulated by convection, or forced circulation by fan

Question 6

Combo systems

Answer 6

Combination systems use ductwork to supply fresh air, but use water to heat/cool air before introducing it into space – called terminal reheat systems equipment is located in plenum
- Other installations use all-water system for heating, separate duct system for ventilation & cooling

Question 7

chases

Answer 7

fully enclosed shafts dedicated to ducts/piping

Question 8

Mixing Boxes

Answer 8

adjust quantity/temperature of air going into space from main air supply; ensuring adequate clearances for units important coordination issue; terminal reheat systems have boxes with water coils inside, identified by air ducts & copper pipes leading into boxes

Question 9

Plenum Requirements

Answer 9

Commercial bldg. codes prohibit using wood, exposed wire in plenums used as return air space; some telephone/telecom wiring using teflon-coated wiring allowed, in place of running wire in steel conduit

Question 10

Access to HVAC

Answer 10

Building codes require access to mechanical/electrical system components, including valves, fire dampers, heating coils mechanical equipment, electrical junction boxes, communication junction boxes, etc.
If suspended acoustical ceiling, access by removing tile; gypsum board ceilings, etc. require access doors-can be rated if required

Question 11

Thermostats

Answer 11

Normally 48” A.F.F., but may need lowering for accessibility, coordination with light switching, etc.

Question 12

Registers and grilles

Answer 12

Air supply registers should be placed near windows & other sources of heat loss/gain; return air grilles should be placed away from supply points to provide good heat/air circulation throughout space

Question 13

HVAC and Window Coverings

Answer 13

Window coverings
Can affect heat/cooling loads, interfere with supply air diffusers/heating units near windows
Coordinate with mechanical engineer
2” between glass & window to avoid excessive heat buildup

Question 14

Acoustics and HVAC

Answer 14

HVAC & electrical systems often pose acoustic separation problems, especially where ducts, etc. run continuously at exterior, while partitions intersect exterior wall at regular intervals – special detailing may be required to seal floor, ceiling, above ceiling, perimeter walls

Question 15

Diffusers

Answer 15

several types are available

common ones are slot air and square

Question 16

Square Difussers

Answer 16

1-2ft square diffusers commonly used in suspended ceilings; also available for wallboard & plaster with trim flange to cover rough opening

Question 17

Slot Diffusers

Answer 17

Slot air diffusers used where minimal appearance/space require them; typically 2-8 slots, 3-8” overall width – box above slot fed by flexible duct attached to box side

Question 18

Power System Requirements

Answer 18

Electrical systems include power for lighting, convenience outlets, and fixed equipment
- Designers responsible for schematic layout of outlets/switches, where power required for built-in equipment, appearance of visible electrical devices

Question 19

Conductors

Answer 19

Extend from service entry to circuit breaker boxes to individual switches, outlets, lights

Question 20

Nonmetallic sheathed cable (‘Romex)

Answer 20

has two or more plastic insulated conductors & ground wire surrounded by moisture-resistant plastic jacket; can be used with wood studs & grommeted steel studs – protected by wallboard & ceiling materials

Question 21

Flexible metal-clad cable (armored cable or ‘BX’ cable)

Answer 21

– sim. to sheathed cable, except encased in spiral-wound steel tape; used in remodels because of ease of pulling through existing spaces, also used to connect commercial light fixtures to junction boxes, allowing easy relocation in suspended ceilings when needed

Question 22

Under-carpet wiring:

Answer 22

thin, flat, protected wire laid under carpet; usually connects pedestals in middle of room with outlets/telephone connections to junction boxes in nearby walls

Question 23

Junction Boxes

Answer 23

Outlets, switches, & other connections to power supply must be made in junction boxes
Single switches, duplex outlets use 2x4” boxes; larger boxes available for multiple outlets/switches. Most boxes 1-1/2” or 2-1/8” deep

Question 24

Who specifies minimum outlet spacing ?

Answer 24

National Electrical Code (NEC), International Residential Code (IRC) and ICC Electrical Code

Question 25

Residential Code requires outlets where?

Answer 25

convenience outlets in every kitchen, family room, dining, living, library, den, sunroom, bedroom, rec. room, etc.
No point along floor line in any wall space can be more than 6’-0” from an outlet

Question 26

Walls how long unbroken require outlet?

Answer 26

Walls 2’-0” to 6’-0” long, unbroken by doorways, fireplaces, etc. must have an outlet

Question 27

Telephone&Communication System Requirements

Answer 27

Interior drawings usually show telephone & communication systems on same plan as power outlets
Designer responsible for indicating telephone, intercom, PA speakers, buzzers, computer terminals;
Actual circuits, locations appear on electrical engineer’s drawings
Telephone/comm. systems low-voltage; less stringent conduit & protection requirements
Usually run from junction boxes without conduit, with some exceptions
Plenum-rated cable available – more expensive than standard cable

Question 28

Light sources

Answer 28

Affect construction detailing due to weight, location, size, mounting method, heat output

Question 29

incadscent

Answer 29

Consists of tungsten filament placed within sealed bulb containing inert gas
Several types, shapes used in surface-mounted, recessed downlights, etc.
Housings can be large, requiring significant above-ceiling space for recessed downlights
- Incandescent lamps used for low cost, easy dimmability, repeat starting without decrease in life, warm color rendition, ease of output control with lenses & reflectors

Question 30

Reflector lamps (R, ER, PAR type)

Answer 30

require large clearances, combustible material separation due to heat output unless specially constructed, rated units used

Question 31

Tungsten halogen lamps

Answer 31

have halogen gas in addition to inert gas; when tungsten burns, halogen causes particles to redeposit on filament, greatly extending lamp life, uniform light color; bulb made from quartz, smaller than standard incandescent lamps, give hotter, whiter light. Due to high pressure/heat, can shatter explosively – always encased in glass/screens

Question 32

disadvantages of incandscents

Answer 32

Disadvantages: low efficacy (light output relative to energy used), short lamp life, high heat output

Question 33

Flourescent

Answer 33

Used where more efficient source than incandescent required, linear source needed
Larger than incandescents, so controlling output precisely more difficult
Usually used for general illumination
Compact fluorescents available to fit in reflector housings sim. to incandescents
Ideal for continuous lighting, downlighting used to uniformly wash partitions with light
T8 & T5 (1” & 5/8” diameter) most common due to higher efficacy, better color rendition than older, larger lights; smaller luminaires, higher-efficiency control available

All fluorescents have ballasts – device that supplies proper starting, operating voltage to lamp; can be mounted as part of luminaire, or remotely located

Question 34

High-Intensity Discharge (HID)

Answer 34

HID lamps produce light by passing electric current through gas or vapor under high pressure; include mercury vapor, metal halide, and high-pressure sodium (HPS) lamps
Mercury vapor lamps: electric arc passes through high-pressure mercury vapor, producing ultraviolet & blue-green light. Phosphors applied to inside of lamp to produce more yellow/red light. Long life, poor color rendition
- HID’s usually limited to gymnasiums, parking garages, industrial settings

Question 35

Metal halide lamps

Answer 35

: sim. to mercury vapor, except metal halides added, increasing efficacy, improves color rendition, shortens lamp life. Combine best features of HID lamps; good color rendering, high efficacy, relatively long life. Main disadvantage is large shift in apparent color temperature over life

Question 36

High-pressure sodium (HPS):

Answer 36

pass electric arc through hot sodium vapor. Tube must be ceramic material to resist hot sodium; very high efficacy, long life 10,000-24,000 hours. Standard types have very yellow light; some color correction versions can be used indoors

Question 37

Neon and Cold-Cathode

Answer 37

• Neon lamps can be formed into unlimited shapes, used for signs, accent lighting; by varying gases within glass tube, variety of colors produced
• Cold-cathode lamps similar, but have higher efficacy, slightly larger (1” dia.), can produce several shades of white as well as colors
• Both types require brackets to hold glass tubes, transformers

Question 38

LED

Answer 38

these very low energy light sources highly resistant to vibration, can be mixed to provide acceptable color rendition; mostly used for accent lighting, some desk lamps at this time. One manufacturer offers a neon replacement, called ‘plexineon,’ which is field-bendable, outdoor compatible, and has very long life

Question 39

Lighting Systems

Answer 39

• Recessed lighting
• Recessed fluorescent troffers
• recessed incandescent downlights
• Cove lighting

Question 40

Recessed lighting

Answer 40

requires sufficient clear space above ceiling to install fixtures

Question 41

Recessed fluorescent troffers

Answer 41

mounted in acoustical ceilings usually have no clearance issues

Question 42

Large, recessed incandescent downlights

Answer 42

may require HVAC ductwork, conduit, plumbing pipes to accommodate fixtures

Question 43

Cove lighting design

Answer 43

requires knowledge of luminaire dimensions, sightlines to conceal fixture, lamp photometrics, desired cove strip design

Question 44

Control Devices

Answer 44

Designer should decide how lights should be switched, based on lighting function, amount of individual control needed, best switch locations, energy conservation needs, and maximum electrical load requirements on any one circuit
Switches should be located at primary door entering space to enable easy control as people enter/leave; larger spaces often have 3- or 4-way switches, which allow control from 3 or 4 locations
Dimmers can be used on both incandescent and fluorescent lights, but fluorescent dimmers expensive, special fixtures required; fluorescents & incandescents should be on separate circuits

Question 45

Custom Detailing for Lighting

Answer 45

While most projects do not require custom fixtures, some projects require custom fixtures
Use UL-approved components to ensure approval by code officials, consultation with lighting designer recommended in many cases

Question 46

Plumbing

Answer 46

Two major components: water supply (hot & cold), drainage
Water is supplied under pressure to individual plumbing fixtures
Due to small size & pressurized lines, relatively easy to locate pipes in wall cavities, ceilings, etc.; closer to source = cheaper

Question 47

Drainage Systems

Answer 47

Drainage Systems
Systems more difficult; work by gravity, so must be sloped to drain. Require vent pipes; ref. fig. 16.7 for basic components
First drain component is the trap, which is located at every fixture except those with internal traps (like toilets); designed to hold small quantity of water to provide seal against sewage system gases entering building. Multiple sinks sometimes connected to single trap
Traps connect to vent pipes connected to system at multiple locations, open to outside air

Question 48

Vents

Answer 48

Vents allow sewage gases to escape, allow pressure in system to equalize so discharging waste does not siphon draining water out of traps

Question 49

Sewage travels…

Answer 49

waste does not siphon draining water out of traps
From traps, sewage travels to a vertical stack via fixture branch lines; stacks carrying toilet waste called soil stacks, other stacks called waste stacks

Question 50

Vents for fixtures connect two ways:

Answer 50

Vents from individual fixtures connect above fixtures in two ways; if vent connects to waste stack above highest fixture in system, portion above this point called a stack vent, which extends through roof. Multistory buildings use separate pipe for venting, called a vent stack, which either extends through the roof or connects with stack vent above highest fixture, per fig. 16.7

Question 51

Drain Slope

Answer 51

slope min. ¼”/ft. (1/8”/ft. in pipes larger than 3”)

Question 52

Plumbing Walls

Answer 52

Many buildings require thicker partitions or plumbing chases to accommodate pipes, such as between back-to-back toilet rooms. Ref. Fig. 16.3 for typical pipe sizes, Fig. 1.13 for chase wall construction

Question 53

Fire protection

Answer 53

Fire protection systems include detection devices (smoke & heat detectors), alarm, communication, annunciation equipment, and fire suppression systems

Question 54

Sprinkler Location

Answer 54

Light hazard occupancies require (1) sprinkler head per 200s.f. if system is not hydraulically designed, or 225s.f. if hydraulically designed
- Open wood joist ceilings require (1) sprinkler per 130s.f.
-Min. distance from partitions to sprinklers 4”
- Sprinklers near vertical obstructions (such as columns) 4”-24” wide must be located at a distance at least 3x max distance of obstruction; see fig. 16.9
- When beams, dropped ceilings, other obstructions project below main ceiling, sprinklers must be located certain distance away so water stream is not deflected
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