Building Electrical and Signal System

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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 1

BUILDING ELECTRICALAND SIGNAL SYSTEMS


Electricity – Background

• Electric charge was known to the ancient Greeks• Magnetism was known historically via observation• A link between electric and magnetic phenomena

was noted in the 1820s• Maxwell’s equations/physics in the late 1800s• The first use of electricity in buildings was also in

the late 1800s (Edison and Tesla played a role)• The impact of electricity was phenomenal – it

radically changed building design

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Residential BuildingTransformation

Pre-electric(and pre-mechanical) >>

Post-electric(and post-mechanical) >>


Office Building Transformation

Pre-electric Post-electric

(daylit and naturally ventilated) (electric lighting and HVAC)

predominantlyexterior space

predominantly interior space

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Static Electricity

• Involves a charge accumulation and subsequent discharge

• Intermittent current flow (as in lightning or static shock)

• Limited building applications

• Nature’s attempt to increaseentropy (disorder)

faculty.clintoncc.suny.edu

nimrod.phy.uc.edu


Dynamic Electricity

• Involves a consistent flow of electric current

• Limited examples in natural systems (galvanic action is one)

• Vast potential in human-made systems

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Electric Current

• Represents a flow of charge through an appropriate medium (a conductor)

• Moves at the speed of light (electricity is a form of electromagnetic radiation)

• DC = direct current (as with battery-driven devices, photovoltaics)

• AC = alternating current (as with public and private utilities)


Direct Current (dc)

involves a continuous andconsistent flow of current through a circuit

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Alternating Current (ac)

involves a cyclic flowof changing current through a circuit


Circuits

• Series circuit loads are an integral part of the network of conductors

• Parallel circuit there are multiple paths for current (flow can bypass any individual load)

parallel circuits predominate in building power distribution systems

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Circuits

www.berkeleypoint.com/

series

parallel


Electrical Circuit Properties

• Voltage analogous to water pressure, it represents the difference in “potential” between points on a circuit, voltage is the driving force for current flow

Volts (V)

• Amperage analogous to water flow rate, it represents the volume of electron flow; amperage is often used as a measure of circuit capacity

Amps (A) (1 amp = 6 x 1018 electrons/sec)

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• Resistance analogous to friction, it accounts for energy lost due to electron flow through an imperfect conductor (no free lunch, entropy); electrical resistance is proportional to flow

Ohms (Ω)

• Wattage represents the combined effect of voltage and amperage (wattage is a measure of the potential for work)

Watts (W) W = (V)(A)



• Frequency a measure of the cycling pattern in an alternating current circuit (North American frequency is 60 Hz; Europe is often 50 Hz)

Hertz (Hz) Hz = cycle per second

• Power factor represents the phase relationship between voltage and amperage in a circuit (high is good, low is bad … and low may incur penalty charges from a utility)

PF (a decimal value)

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Residential Voltage Standards

120 volt, 2 wire, 1 phase

120/240 volt, 3 wire, 1 phase

120 V is used for plug loads; 240 V for large appliances

from a physics perspective, voltage can be any value desired; from a practical perspectivedistribution voltage should match the operating voltage of connected appliances

only 120 V is available for loadshot

neutral


Non-Residential Distribution Voltage Standards



480 V is used for large motors; 277 V for some fixed lighting and/or motors

277

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Power Factor

resistive loads non-resistive loads(incandescent lamps, (fluorescent lamps,

electric heaters) motors)

www.pittjug.org/

e = voltage, i = current; p = power; note decrease in magnitude of power curveon the right (for the same voltage and current)


Energy and Power

• power = instantaneous work (now!)kilowatts (kW)

• energy = work integrated over timekilowatt-hours (kWh)

• utilities often charge for both of these via an energy charge (for kWh) and a demand charge (for peak kW)

• other “tariffs” include time-of-day pricing, sliding scale pricing, and interruptible service pricing

a tariff is a utility’s rate structure

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Energy and Power

Power

Energy


Matching Energy and Power (for PV)

Power

Energy

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Electricity and Building Design

• Electricity is a very high quality form of energy (it has low entropy) that has hundreds of uses (heating, cooling, computers, motors, toasters, TVs, …)

• Electrical safety caused the development of the first firecode (the National Electrical Code >> NFPA)

• Codes, standards, listings:

– NEC [typically enacted as a code]

• minimum system and equipment requirements

– ASHRAE 90.1 [a standard, often enacted as a code]

• a few electrical energy constraints

– UL [a “listing” incorporated into codes]

• product listings; everything must be listed


Building Electrical Systems

• Include service components– concerned with getting electricity “into” a building

safely and in a usable form (the local utility company and the design team make service decisions)

• Include distribution components– concerned with getting electricity safely where it is

needed within a building (the design team determines what is appropriate relative to distribution—within the constraints of the NEC)

• Include load components– the things that consume electricity (the owner and

design team determine loads)

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Electrical System Block Diagram

utility

PV?

tf = transformer; sg = switchgear; ep = emergency power; mcc = motor control center; lp = lighting panel; pp = power panel

Receptacles

Luminaires

service distribution loads

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Building Electrical System One-Line Schematic Diagram

some examples of service components follow >>

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Service Location Planning

plan for location andsize of electrical spacesapx. 1% of floor area for main electrical room

mechanical room

electrical room

shop

service

an example of goodspatial planning

large loads (mechanical and shop equipment) are adjacent to electrical room


Transformers

internal step-down

external, utility

external, building service

purpose: to change voltage (usually to reduce V)

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Switchgear

purpose: meter, control, monitor power flow


Emergency Power

dieselgenerator at ahospital; withundergroundfuel tank

architecturally …is this acceptable?is such equipment just“invisible”?

purpose: to provide power during an outage of the utility source

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some examples of distribution components follow >>


Distribution: Using “Open” Channels raised access floor

this links to UFAD

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Distribution: Using Closed Channels

conduit


Distribution: Using Closed Channels

cellular metal deck (used as “structure” and electrical channel)

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Distribution: Using Packaged Systems

surface raceway



some examples of load components follow >>

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Fixed Loads (Motors)

escalators, elevators, fans,pumps, chillers, cooling towers,air-handling units, fan-coil units, etc.

hard wired

fixed loads are essentially “bolted down” and aresized by the design team

HOBO datalogger


Plug Loads

conveniencereceptacles for movable stuff …. you name it

building lighting loads have been steadily reduced over the past 15 years, while plug loads have increased by like magnitude

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Building Signal Systems (they are numerous and diverse)

• telephone• data• fire alarm• energy and/or building management

– most larger buildings have EMS, BAS, or BMS: energy management system, building automation system, building management system (different terms for similar systems)

– “smart buildings” on the horizon?• security• sound (background, ambience, music)• master clock• closed circuit or cable TV ….


Signal System Characteristics

• usually involve dedicated (sole-use) distribution lines for each system

• systems are often proprietary (secret stuff, not specified in detail)

• systems are often low voltage (allowing for fairly flexible distribution)

• rapid change is often necessary (demanding easy access and flexibility)

• key design issues:– access, access, access (for maximum flexibility)– performance specifications will be involved if system is

proprietary– architectural coordination (with, for example, fire zones)

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Typical Signal System Schematic

service panel orcomputer devices

site boundary

information flow

“signal” systems typically involve communications and data


Typical Signal SystemBlock Diagram

sensor or interface device(smoke detector, motion detector, thermostat, photosensor, etc.)

panel or computer(for making “if … then”decisions)

activated device(fire alarm, fan control, VAV box, computer display, etc.)

Building Electrical and Signal System

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