Ballast: Chapter 17 - Mechanical, Electrical, and Plumbing Systems Flashcards
Net-Zero Structure
One that only consumes as much energy as it produces on site through renewable means.
Natural Gas - Pros + Cons
Pros -
Most efficient fossil fuel
Clean burning
Relatively low in cost
Cons-
Not available in rural or remote areas
Price fluctuates
Heating value 1050 Btu/ft3
Propane
A type of gas used where natural gas is not available - stored in pressurized tanks
Heating value 2500 Btu/ft3
Oil
- Cost and availability depend on world and local market conditions.
- Must be stored in or near the building
- Produced in 6 grades (lower numbers are more refined/expensive)
- No. 2 fuel for residential and light commercial (heat value 137,000 Btu/gal)
- No. 4 and No. 5 fuel for large commercial (heat value 152,000 Btu/gal)
Electricity
- Easy and inexpensive to install
- Easy to control/flexible in zoning
- Cost can be disadvantageous due to “peak use” pricing
- Ideal for radiant heating/hydronic radiant
- Heating value 3413 Btu/kW
Steam
- Not a basic fuel
- Available in urban areas/campuses as a by-product of electricity generation
- Not used directly for heating; used to heat water for water and air heating systems and to drive absortion chillers
Heat Pumps
A device that reverses the travel of heat from warmer locations to cooler ones. Can provide heat in the winter and cooling in the summer.
Heating efficiency decreases as outside air temperature decreases - sometimes used with a solar system for better efficiency.
How does a heat pump function as an air conditioner?
- Evaporator absorbs heat from the inside air
- Warmed refrigerant moves to condenser
- Releases heat in the condenser to the outside air
- Cooled air moves back to evaporator, etc.
Name 5 natural energy sources
- Solar (active or passive) - okay for residential and light commercial
- Photovoltaic (PV) - still expensive and limited use
- Geothermal
- Wind
- Tidal
Degree Days
A unit to measure how much heating or cooling is needed in a particular location over the course of a year.
Found by taking the difference between a baseline indoor temp of 65 deg. and the average outside temperature for the day. Total sum of all daily values to determine annual degree days.
Approximate Efficiency of Natural Gas
70-80%
Approximate Efficiency of Propane
70-90%
Approximate Efficiency of No. 2 Oil
65-85%
Approximate Efficiency of Anthracite Coal
65-75%
Approximate Efficiency of Electricity
95-100%
What is a furnace?
Device which converts fuel to heat by burning fuel inside a combustion chamber
What are the three types of forced air furnaces?
- Upflow - return air supplied at bottom of unit and heated air is delivered out the top of the furnace and distributed through ductwork
- Downflow - opposite of upflow. Used in cases where ductwork is located in a basement or crawl space and furnace is on first floor
- Horizontal - used where headspace is limited
What is a boiler?
A device which uses fuel to create hot water or steam
What are the two main types of refrigeration?
- Compressive refrigeration
2. Absorption
What is compressive refrigeration?
Based on transfer of heat during liquefaction and evaporation of a refrigerant .
Gas releases heat as liquefied
Liquid absorbs heat as it vaporizes
Problematic Refrigerants
- Freon - contained CFCs
- CFCs - deplete the ozone layer. Now banned
- HFCs - okay for ozone, bad for CO2 production
- Other more environmentally friendly substances tend to be toxic (ammonia, sulfur dioxide)
What are the primary components of a compressive refrigeration system?
Compressor, Condensor, Evaporator
Absorption
Produces chilled water through the loss of heat when water evaporates in a closed loop system using a saltwater solution
Evaporative cooling
Only works in hot-arid climate
HVAC System: Direct Expansion (incremental unit)
Self contained unit that passes non-ducted air over an evaporator. Ventilation comes from outside which is good for indoor air quality.
Can be through wall types, roof mounted, or packaged
HVAC System: Variable Air Volume (VAV)
All-air system where
- air is heated or cooled as needed in a central plant and distributed to the building at a constant temp through one duct.
- Each zone has a thermostat which controls a damper to vary the flow of conditioned air to user’s needs
- Return air dampers regulate amount of fresh air intake (up to 100%)
- Not great for simultaneous heating and cooling loads
HVAC System: High Velocity Dual-Duct
- Two parallel ducts run to each space, one with hot air, one with cool air.
- Mixing box at each zone controlled by a thermostat
- Good for req’d simultaneous heating and cooling
- Inherently inefficient due to amount of ductwork and fans req’d
HVAC System: Reheat (Constant Volume)
Return air and fresh outdoor air are mixed for cooling and dehumidification
Reheating can be done with hot water or electricity
HVAC System: Multizone
Air is supplied to a central mixing unit with separate dampers to temper air being sent to different zones
HVAC System: All-Water
Uses a fan coil in each conditioned space. Fan coils are connected to water circuits or hot and chilled air. Efficient system
HVAC System: Air-Water
Central air system using local fan-coil units
Used where air cannot be recirculated bc of potential for contamination (such as hospitals and labs)
“Induction System”
HVAC System: Electric
Grid of wires to produce radiant heat is most common
Electric baseboard radiators are also common
Only economical where electricity is inexpensive
Direct Expansion Systems are used for:
Single Fam Residence
Constant Volume Single Duct systems are used for:
Auditoriums/Theaters Churches Hospitals Hotels/Motels Laboratories Single Fam Residence Shopping Centers
Variable Air Volume systems are used for:
Auditoriums/Theaters Churches Small commercial Laboratories Libraries Office Buildings Shopping Centers
Dual Duct High Velocity systems are used for:
Hospitals
Laboratories
Constant Volume Terminal Reheat systems are used for:
Hospitals
Laboratories
Multizone systems are used for:
Auditoriums/Theatres Churches Small Commercial Hospitals Libraries Office Buildings
All-Water systems are used for:
Small Commercial
Single Fam Residence
All-Water Induction systems are used for:
Hospitals
Office Buildings
Closed Loop Heat Pumps are used for:
Apartments
Hotels/Motels
Fan Coils are used for :
Apartments Hospitals Hotels/Motels Office Buildings Schools
Electric systems are used for:
Small commercial
Single Family Residence
What criteria do you use to select an appropriate HVAC system?
- Use profile of the building
- Outdoor air requirements
- Building Scale
- Control Needs
- Fuels Available
- Climatic Zone
- Flexibility
- Integration with the Building System (structural, etc)
- Economics
Name 5 of 12 systems that may require a dedicated exhaust system.
- Equipment/processes that throw off dust
- Equipment/processes that emit heat, odors, fumes, spray, gas, or smoke
- Hazardous mat’ls used in production
- Garages and car repair facilities
- Clothes dryers
- Domestic kitchen exhaust
- Commercial kitchen hoods
- Laboratories
- Dust + refuse conveying systems
- Sub-slab soil exhaust systems
- Smoke control systems
- Energy recovery ventilation
Define Nuisance
Legal term meaning that which is dangerous to human life or detrimental to health. Used in reference to exhaust air discharge locations
What percentage of the overall energy consumption of a building is HVAC?
40-60%
How are HVAC systems rated on energy efficiency?
- Annual fuel utilization efficiency
- Coefficient of performance
- Energy efficiency ratio
- Integrated part load value (IPLV)
- Seasonal energy efficiency ratio (SEER)
Economizer cycle
It is a mechanical system which uses outdoor air when it is cool enough to mix with recirculated indoor air
Dual Condenser Cooling
Refrigeration equipment with 2 condensers instead of one. If heat is needed, condenser A sends waste heat to fan coil units. If cooling is needed, condenser B sends heat to cooling towers.
Gas Fired Absorption Chillers
Does not rely on electricity or refrigerants. Not as efficient, and not necessarily cost effective
Solar Power Absorption Chillers
Efficient and sustainable - powered by hot water from solar collectors
Solar Powered Desiccant Chillers
Passes air over a desiccant which cools and dehumidifies the air
Direct Contact Water Heaters
Passes hot gases directly through water to heat it
Recuperative Gas Boilers
Recovers the heat in flue gases that would normally be discharged. Cools the flue gas enough to condensate, recovering both latent and sensible heat
Displacement Ventilation
Air distribution system in which supply air is dispensed at floor level and rises to return air grilles in the ceiling as it warms. Bc it is delivered closer to users, it doesn’t need to be cooled as much
Water-Loop Heat Pumps
Uses a series of heat pumps for different zones of a building. All pumps are part of the same piping system. When some zones are cooling, they dump heat into the system which helps with the heating zones and vice versa
Thermal Energy Storage
Uses water, ice, or rock beds to store excess heat or coolness for use at a later time.
Energy Recovery Ventilators (or Air to Air Heat Exchangers)
Reclaim waste energy from the exhaust air stream and use it to condition incoming fresh air.
Can reduce energy needed to condition incoming air by 60-70%
Best in cold, hot, or humid climates and in bldgs with continuous occupancy, such as hotels and hospitals
What 3 conditions should be met when using Energy Recovery Ventilators?
- Fresh air intake should be as far from exhaust outlet as possible to avoid reusing exhaust air
- Exhaust air that contains excessive moisture, grease, or contaminants should be separated from the ERV
- In cold winter conditions, a defroster may be req’d
Flat Plate Heat Recovery Units
Part of an air to air heat exchanger - uses two separate ducts (incoming vs exhaust) separated by a thin wall for heat transfer
Energy Transfer Wheels
Part of an air to air heat exchanger - transfers heat between incoming and exhaust through small filtered holes in a connective wheel
Heat Pipe
Part of an air to air heat exchanger - self contained device that transfers sensible heat energy from hot exhaust air to cool incoming air by passing hot air over a vaporizing refrigerant which then moves to the cool area and condenses, releasing heat.
Water-to-Water Heat Exchangers (or Runaround Coils)
Use water or a liquid as a medium to exchange heat - eases burden of locating incoming and exhaust air adjacently
Extract Air Windows
Uses a double paned insulated glass unit over which another pane of glass is placed on the inside of the building. Air is drawn up through the window unit to the return air system (warms glass in winter, cools it in summer)
Ground-Coupled Heat Exchangers
Heat or cool outside air by circulating it in pipes buried in the ground. Typically only appropriate for low rise bldgs
Passive Chilled Beams
Ceiling mounted units that uses water. Relies on natural convection and can only provide cooling. Cold water passes through piping attached to aluminum fins which cool rising warm air
Active Chilled Beams
Integrated into the ventilation system and can provide both heating and cooling. Fresh air is drawn into the unit, heated or cooled by the water, forced out of the unit and into the air.
Variable Refrigerant Flow (VRF) system
Uses a single compressor condenser outside connected to multiple interior evaporators in different building zones
Good for office bldgs, schools, multi family, etc
Building Automation System
Computer based integration system used to monitor and control bldg systems such as HVAC, energy mgmt, lighting, life safety, and security
Ampere
“Amp”; abbrev. A
Unit flow of electrons in a conductor
Energy
The product of power and time, also called “work”
Impedance
The resistance of an alternating current (AC) circuit, measured in ohms
Ohm
Ω; Unit of resistance in electrical circuit
Power factor
Phase difference btwn voltage and current in an AC circuit
Reactance
Part of the electrical resistance in an AC circuit, caused by inductance and capacitance
Volt
V; Unit of electromotive force or potential difference. 1 V is the amount of force or potential difference that will cause a current of 1A to flow through a conductor whose resistance is 1Ω
Watt
W; unit of electrical power
What does a basic circuit consist of?
A conductor, the actual flow of electrons (current), an electric potential difference to cause the electrons to move (voltage), and some type of resistance to the electrons.
Ohm’s Law for DC ciruits
The current in a circuit is directly proportional to the voltage and inversely proportional to the resistance.
I = V/R
Power
The rate at which work is done or the rate at which energy is used (expressed in watts)
Calculate Wattage
P=VI
Wattage is the product of voltage and current
“PIE” power (P) equals current (I) times electromotive force (E) [another term for voltage]
Alternating Current (AC)
Operate according to the principle of electromagnetic induction, discovered by Michael Faraday in 1831. Typically represented in a sine curve
When a conductor is moved in a magnetic field, a voltage is induced. The direction of the movement determined the polarity.
Amplitude
In an AC circuit sine curve, represents the voltage
Cycle
In an AC circuit sine curve, one cycle is the distance between peaks
Hertz
In an AC circuit sine curve, the frequency or cycles per second
Ohm’s Law for AC circuits
I=V/Z
Calculate power in AC circuits
P=VI(pf)
Calculate energy used in a system
E=Pt
Power times Time - resulting in W-hr or kW-hr
Name the two types of electric circuits
Series and Parallel
Series Circuit
Loads are placed in a circuit one after another. Current, I, remains constant, but voltage drops after each load.
Series circuits are not used in bldg construction
Parallel Circuit
Loads are placed between the same two points. Voltage remains the same, but the current is different across each load.
Two basic types of conductors
Wire (16 gage to 0000 gage) and Cable (250, 300, 400, 500 MCM)
Nonmetallic Sheathed Cable
2+ plastic insulated conductors and a ground wire in a moisture resistant plastic jacket. Good for wood frame residential bldgs 3 stories or less. No conduit req’d
Flexible Metal Clad cable
2+ plastic insulated conductors encased in a continuous spiral wound strip of steel. No conduit req’d
Most common type of wire or cable:
Single conductor in plastic or rubber. Must be used in conduit or sim.
Busbar
rectangular bar of copper used when high currents are involved instead of large cables
Rigid Steel Conduit
heaviest type - connected to J boxes and other devices with threaded fittings
Intermediate Metal Conduit (IMC)
Thinner walls than rigid steel conduit, but same OD. Also uses threaded fittings
Electric Metallic Tubing (EMT)
Lightest conduit; too thin to thread. Req’s special pressure fittings. Can’t be used in hazardous areas, but easy and fast to install
Underfloor Ducts
Type of power distribution - proprietary steel raceways cast into a concrete floor at regular spacing. Carry power from electrical boxes to distribution ducts
Cellular Metal Floors
Type of power distribution - part of the structural floor. Essentially metal decking used as cable raceways
Name the 2 types of primary electrical service from the property line to the building
Underground (better for resisting weather) and Overhead
Common voltages supplied to buildings
120/240V single phase - residences + small bldgs
120/208V three phase - large bldgs
277/480V three phase - huge bldgs
Transformers
change AC voltages up or down. Rated on their capacity in units of kVa and are described by their type, phase, voltage, method of cooling, insulation, and noise level
Electrical Metering
Provided at a bldg’s entrance to allow the utility company to charge for energy used .
Typically the watt-hour meter
Switchgear
Central electrical distribution center used in large bldgs
Name the 3 types of protection for electric circuits
- Grounding - provides a path for a fault
- Ground Fault Circuit Interrupters - devices that detect small current leaks and disconnect the power to the circuit or appliance
- Arc Fault Circuit Interrupters - device that recognizes characteristics that are unique to arcing and de-energizing
Wiring Devices
Receptacles, Switches, Pilot Lights, etc.
Switching
Controls powers to lighting, receptacles, and other devices. Can be two-way, three-way, dimmers, low-voltage, etc
Automatic Lighting Controls
- Time of Day controller
- Occupant Sensor
- Daylight compensation control
Emergency Power
Required for electrical systems that relate to the safety of occupants or community needs, such as exit lighting, alarms, elevators, telephones, and fire pumps, and some medical equipment. Supplied by batteries or generators
Standby Power
Provides electricity for functions that the building owner needs to avoid an interruption in business
Potable Water
Drinkable
Nonpotable Water
Not drinkable but okay for toilets
Two most common sources of large water supplies for cities
Surface Water - rain and snow runoff into lakes and rivers
Groundwater - seeps into the ground until it hits an impervious layer of rock or soil
Aquifer
Large regions or subsurface water
pH level
measure of relative acidity or alkalinity
below 7: acid
above 7: base
Water Hardness
Caused by calcium and magnesium salts in water
Turbidity
Caused by suspended material in water such as silt, clay, and organic material
Biological contamination
Caused by bacteria, viruses, etc.
Water Pretreatment
Removes suspended matter and large particles before other types of treatment
- Sedimentation uses gravity and still water allowing particles to sink
- Coagulation gets particles to stick together by using an additive
- Flocculation is the step after coagulation where sedimentation takes place
Water Filtration
- Slow Sand Filtration allow water to filter through a fine sand slowly. Good for some bacteria, not good for turbidity
- Direct Filtration passes water under pressure through a filter medium. Uses coagulation and flocculation. Good for viruses
- Packaged Filtration is the same as direct filtration except it is directly hooked up to water supply
- Diatomaceous Earth Filtration uses a thin layer of that soft sedimentary rock. Good for cysts, algae, asbestos; Bad for bacteria and turbidity
- Membrane Filtration forces water at a high pressure through a thin membrane. Good for microorganisms
- Cartridge Filtration uses self-contained units - good for individual faucets
Demineralization
Removes dissolved solids and chemicals that caue hard water
Ion Exchange
Used for hard water treatment by removing cadmium, chromium, and other chemicals. Calcium ions are exchanged for sodium ions
Reverse Osmosis
Removes contaminants by using a semi-permeable membrane that allows only water to pass through and not dissolved ions
Electrodialysis
Places charged membranes at the inflow stream of water to attract counter-ions. Expensive and difficult.
Disinfection
Destroys harmful microorganisms
- Chlorination uses chlorine to kill organisms
- Chloramine is like chlorination but uses a weaker disinfectant such as ammonia. Usually a secondary system.
- Ozonation uses ozone to disinfect and oxidize. Typically requires a secondary disinfectant
- UV Light destroys a cell’s ability to reproduce and is effective against bacteria and viruses
- Nanofiltration uses a membrane with very small holes which can trap microorganisms
Distillation and Aeration
Distillation boils water and condenses the vapors. used for seawater.
Aeration improves taste and color. Exposes water to air through sprays, falls, and fountains.
Private Water Supplies
Wells, springs, and collected rainwater
What are the two most important considerations in drilling a well?
Depth: 25ft-100ft+
Yield: gallons per minute provided
Types of well pumps
Suction pumps (only for 25 ft or less) Jet pumps (deeper wells)
Municipal Water Supply
Treated and delivered to buildings at 40-80psi
Solar Heating Systems
- Batch System - heats water in a black tank inside a glazed box
- Thermosiphon System - relies on the natural movement of heated water to circulate the water in passive open loop system
- Closed-Loop Active System - Very common. Uses a separate nonfreezing liquid circulated by pumps through the solar collectors and into a heat exchanger with the domestic hot water
- Drain Down System - Direct, active system which automatically drains the water from collectors when outdoor temp is near freezing
- Drain Back System - indirect, active system that uses water as a heat-collector fluid which is pumped to a heat exchanger for the domestic hot water
Actuator
device in a bldg control system that receives commands from a controller and activates a system
Annual Fuel Utilization Efficiency (AFUE)
ratio of annual fuel output energy to annual input energy
Coefficient of Performance (COP)
unitless number that is a rating of the efficiency of heating or cooling equipment
Controller
a device that measures, analyzes, and initiates actions in a building control system
Deadband
in a building control system, the range of temperatures within which neither heating nor cooling is needed
Energy Efficiency Ratio (EER)
ratio of net cooling capacity in Btu/hr to the total rate of electrical input in watts
Energy Management System (EMS)
Computer-based system used to monitor and control facility energy use
Ground-Coupled Cooling
a method of cooling a building by direct contact with the earth or by circulating air through underground tunnels
Heating Seasonal Performance Factor (HSPF)
a measure of the performance of a heat pump operating in the heating cycle
Home Energy Rating System (HERS)
a standardized system for rating the energy efficiency of residential buildings. Scores are 0-100
Relative Solar Heat Gain (RSHG)
ratio of solar heat gain through a window, corrected for external shading, to the incident solar radiation
Solar Energy Efficiency Ratio (SEER)
total cooling outout of an air conditioning system in Btus per hour during its normal usage period for cooling divided by the total electrical input in watt-hours
