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170 Cards in this Set
- Front
- Back
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What is the primary objectives of the M&E systems? |
to maintain the necessary conditions of environmental comfort, health and safety for the occupants. |
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What are the Main M&E building systems and what they do, generally? |
HVAC - condition interior spaces for the environmental comfort of the occupants Potable Water - for consumption and sanitation Disposal of Waste - Maintain sanitary conditions within the building and surrounding area Fire protection Electrical Systems - furnish light, heat and power Vertical Transportation |
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When is thermal comfort achieved? |
When the human body is able to dissipate the heat and moisture it produces by metabolic action through: Conduction, Convection, Radiation and Evaporation. |
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Define: Conduction, Convection, Radiation and Evaporation |
Conduction - is the process by which heat energy is transmitted through collisions between neighbouring molecules. Eg. frying pan on gas stove. The heat causes molecules in the pan to vibrate faster, making it hotter. Accounts for a small portion of the total heat loss from the body Convection -is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. Convection above a hot surface occurs because hot air expands, becomes less dense, and rises. Radiation - is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Light colours reflect, dark colours absorb heat thus poor reflectors are good radiators. Radiant heat cannot travel around corners and is not affected by air motion. Cannot counteract cold downdrafts along exterior glass. Evaporation- is the process of a substance in a liquid state changing to a gaseous state due to an increase in temperature and/or pressure.heat loss increases with air motion. evaporative cooling is especially good when high air temps, humidity and activity levels exist. |
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What are the factors affecting human comfort, and which are of primary importance? |
Air temperature, Relative humidity, Mean radiant temperature, air motion, air purity, sound, vibration and light. |
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MRT |
Mean Radiant Temperature - important for comfort because the body transfers radiant heat with its surrounding surfaces. - if the surrounding surfaces have higher MRT the air temp should be maintained cooler -in cold weather the MRT of interior surfaces of exterior walls should be 9 deg celsius below the indoor air temp. |
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True or False: MRT has about 40% more effect on comfort than air temperature |
True |
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RH |
Relative Humidity - the higher the RH the lower the air temperature should be - it is more critical at higher temps than within the normal temp range |
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What are some undesirable effects of Low )<20%) Relative Humidity? |
Buildup of static electricity Drying out of wood Vice Versa, high RH can cause condensation problems. |
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Air Temperature VS Mean Radiant Temperature |
Air temperature is a measure of how hot or cold the air is. It is the most commonly measured weather parameter. Mean radiant temperature (MRT) is the sum of the temperatures of the surrounding walls, floors and ceiling of a room, weighted according to the solid angle subtended by each at the point of measurement. |
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Comfort Zone |
ASHRAE - refers to the combinations of air temperature, mean radiant temperature (tr), and humidity that are predicted to be an acceptable thermal environment at particular values of air speed, metabolic rate, and clothing insulation |
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What should the range of the velocity of air be? |
3-5 meters per minute mpm Higher velocities can cause drafty conditions. |
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Psychrometer |
is an instrument for measuring atmospheric humidity, consisting of two thermometers, the bulb of one being dry and the bulb of the other being kept moist and ventilated so that the cooling that results from evaporation makes it register a lower temperature than the dry one. the difference between the readings is the atmospheric humidity. |
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Psychometric chart |
is a chart that relates the wet-bulb and dry-bulb readings to relative humidity, absolute humidity and dew point. |
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Effective Temperature |
represents the combined effect of ambient temperature, relative humidity, and air motion on the sensation of warmth or cold felt by the human body |
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Evaporative Cooling |
is a drop in temperature occurring without the addition or removal of heat, as when moisture evaporates and the sensible heat of the liquid is converted to latent heat in the vapour. |
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Adiabatic Heating |
is a rise in temperature occurring without the addition or removal of heat, as when excess water vapour in the air condenses and the latent heat of vaporization of the water vapour is converted to sensible heat in the air (opposite of evaporative cooling) |
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What are the main types of heating generation equipment? |
Furnaces - heat air, burn gas or oil Boilers - heat water or produce steam. Require fuel and air supply for combustion. oil requires on site storage. Electric may be ok if electricity $ are low and eliminate need for chimney. not required if central plant steam/water is provided. Electric heaters - convert electric energy into heat. |
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What are the primary sources of heat loss in cold weather? |
Convection, radiation, conduction of heat through exterior assemblies and through floors over unheated spaces. Infiltration of air through cracks in the exterior |
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What are some energy conscious design strategies to reduce heat loss/ heat gain? |
Siting, layout, orientation, using thermal insulation and thermal mass to control transmission of heat, selection of energy efficient systems/appliances/lighting, and employing "smart" systems to control thermal conditions and lighting |
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Heating Load |
is the hourly rate of net heat loss in an enclosed space, expressed in Btu per hour and used as the basis for selecting a heating unit or system. |
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Degree-day |
is a unit that represents 1 degree of departure in the mean daily outdoor temperature from a given standard temperature. It is used to compute heating and cooling loads, size HVAC systems and calculate yearly fuel consumption. |
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Heating Degree-day |
is one degree-day below the standard temperature of 19 deg celsius , used in estimating fuel or power consumption by a heating system. |
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Cooling Load |
is the hourly rate of heat gain in an enclosed space, expressed in Btu per hour and used as the basis for selecting an air-conditioning unit or cooling system. |
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Cooling Degree-day |
is one degree-day above the standard temperature of 24 deg celsius, used in estimating energy requirements for air-conditioning and refrigeration. |
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Energy Efficiency Rating |
is an index of the efficiency of a refrigerating unit, expressing the Btu removed per watt of electrical energy input. |
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What are the sources of Heat Gain in warm or hot weather? |
Convection Radiation and conduction through exterior envelope (varies with the time of day, solar orientation and thermal lag) Solar radiation on glazing Building occupants and activities Lighting and other heat-producing equipment Ventilation of spaces Latent heat, requiring energy to condense the moisture in warm air so that the RH in a space will not be high. |
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What is the most versatile and widely used heating system for houses and small buildings? |
Forced-Air Heating |
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What are the characteristics of a forced-air heating system? |
Furnace - oil/gas with vent, electric no vent Filtering, humidity control can be incorporated Fresh air usually by natural means Cooling unit can use same ductwork. |
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What are the main components of a forced-air heating system? |
Bonnet or Plenum - chamber at the top of the furnace from which ducts emerge Leaders - ducts that convey air from furnace to stack or branch duct Stacks - convey air from leader vertically to register on upper floors |
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Gathering |
refers to a tapered section of a dcut forming a transition between two sections, one of which has a greater area than the other |
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Boot |
is a duct fitting forming a transition between two sections that vary in cross-sectional shape |
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Manifold |
is a duct that has several outlets for making multiple connections |
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Extended Plenum System |
is a perimeter heating system in which a main duct conveys warm air to a number of branch ducts, each serving a single floor register. |
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What are the two types of forced-air perimeter heating? |
Perimeter heating distributes air to registers placed in or near the floor along exterior walls Perimeter Loop - a loop of ductwork, usually embedded in the slab Perimeter Radial - uses a leader from a centrally located plenum to carry air directly to each floor register |
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Furnaces are commonly placed in basement spaces, where are some other locations specialized types of furnaces can be located? |
Horizontal furnaces designed for installation in a low attic or crawl space Wall furnaces can be recessed in or mounted on a wall. (no use of ducts) |
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What type of heating system uses water heated in a boiler and circulated by a pump through pipes to radiators or convectors? |
Hot-water or Hydronic Heating |
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What type of system would eliminate the need for an on-site boiler? |
Hot water or steam generated at a central boiler plant available via underground pipelines. |
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Boiler |
is a closed vessel or arrangement of vessels and tubes in which water is heated or steam is generated. Can be oil, gas or electric. |
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One-Pipe system |
is a hot-water heating system in which a single pipe supplies hot water from a boiler to each radiator or convector in sequence. |
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Two-Pipe System |
Is a hot-water heating system in which one pipe supplies hot water from a boiler to radiators/convectors and a second pipe returns the water to the boiler. |
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What are the three types of Two-Pipe Systems? |
Direct Return - return is the shortest route Reverse Return- lengths of the supply and return are nearly equal Dry Return - steam heating , carries both air and water of condensation. |
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What is the difference between radiators and convectors? |
Radiators have heated pipes (steam or water) that warm a space by radiation Convectors heat air by air contact with a radiator or a fin-tube though convection. |
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What is a direct means of heating with Electric heating aka electric-resistance heating? |
housing the resistance wires or coils in space-heating unites. Compact and versatile but have no provision for controlling humidity and air quality. |
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What are some types of Electric-resistance heating elements? |
Electric unit heaters Toespace unit heaters Wall unit heaters Fully recessed floor unit heaters Industrial unit heaters. Are often equipped with internal fans. |
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What are the 5 general types of Heating? |
Forced-Air Hot-water/Steam Electric Radiant Solar |
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What are some general characteristics of Radiant Heating systems |
Use heated, ceilings, floors and sometimes walls as radiating surfaces May use pipes, tubing or electric cables embedded in floor/wall/ceilings Radiation raises the MRT as well as the ambient temp in the space. |
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True or False Floor installations of radiant heating systems are effective in warming concrete slabs and are the preferred method for radiant heating. |
False, Ceiling installations are preferred because ceiling constructions have less thermal capacity and can respond faster. Also, panels can be heated to a higher surface temperature. |
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Liquid radiant heating systems circulate warm water through metal or plastic pipes either encased in concrete or secured to the underside of sub-flooring with conductive heat places. In applications encased in concrete what is the typical spacing of the pipes/tubing? |
150 - 455 o.c. Closer spacings are used where more warmth is required. |
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What are the typical components of active solar energy systems? |
Solar collector panels - collector surface area depends on the heat transfer medium and heating/cooling loads. Current recommendations range from 1/3 to 1/2 of the net floor area of the building. Circulation and distribution system for the heat transfer medium - carries collected heat energy from solar panels to the heat exchange equipment or storage Heat exchanger and storage facility - heat distribution may be similar to conventional systems, for cooling a heat pump or absorption cooling unit is required, backup heating system is recommended |
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How many degrees of true south should solar collector panels be oriented? |
within 20 degrees |
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What are some types of heat transfer mediums in solar energy systems? |
Air, water, other liquid |
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What is an important characteristic of the building for the active solar energy system to be efficient? |
The building itself must be thermally efficient and well insulated...also siting orientation and windows should take advantage of the seasonal solar radiation. |
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Compressive Refrigeration |
is a process in which cooling is effected by the vaporization and expansion of a liquid refrigerant |
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Heat Pumps |
are electrically powered heating and cooling units. for cooling the normal compressive refrigeration cycle is used to absorb and transfer excess heat to the outdoors for heating, heat energy is drawn from the outdoor air by reversing the cooling cycle and switching the heat exchange functions of the condenser and evaporator. |
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Absorption Refrigeration |
Uses an absorber and a generator instead of a compressor to transfer heat and produce cooling. |
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HVAC systems simultaneously control what conditions of the interior environment? |
Temperature of the air Humidity of the air Purity of the air Distribution of the air Motion of the air |
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Cooling Tower |
is a structure, usually on the roof of a building in which heat is extracted from water that has been used for cooling. Size and number depends on the Cooling load. They should be acoustically isolated from the structural frame of the building |
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Chilled Water Plant |
powered by electricity, steam or gas, delivers chilled water to the air handling equipment for cooling, and pumps condenser water to the cooling dower for the disposal of heat. |
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What are the components of Air Handling Units that are necessary to treat and distribute conditioned air? |
fans filters and other components. |
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True or False: Over 1/2 of indoor air quality problems result from inadequate ventilation and filtration |
True, codes specify the amount of ventilation required for certain uses and occupancies in air changes per hour or in cubic feet per minute |
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What is the ASHRAE recommendation for cubic feet of air per minute per person? |
0.42- 0.57 m3/min per person (15-20 cfm - cubic feet per min) |
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What are the four general types of HVAC systems? |
All-Air - duct system delivers air to served spaces All-Water - pipes (less installation space to ducts) deliver water to fain-coil units in serviced spaces Air-Water - use high-velocity ducts (normally from a central plant) mixed with room air which is further heated/cooled by induction units Packaged - are self contained, weatherproof units incorporating all components. powered by electricity or by combo of electricity and gas. |
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CAV system |
Constant-Air-Volume system Delivers conditioned air at a constant temperature through low-velocity duct system. Typically used in large open areas with few windows and uniform loads eg, lobbies, theatres, department stores. Pros: high degree of control of air quality, simple and easy to maintain Cons: Entire system served by a single-zone, no individual temperature control. |
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What are the benefits of an All-Air system? |
Excellent control of interior air quality Central AHU's can be designed for precise control of fresh air, filtration, de/humidification, heating and cooling Economizer cycle allows the circulation of maximum amounts of outdoor air. Maintenance activities are concentrated to unoccupied areas (there are no pipes, condensate drains, valves, fans or filters outside the mechanical room) |
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When would an Air-water system be more appropriate than an All-Air system? |
When space for mechanical infrastructure is limited. Air-water systems circulate less air than all-air systems which makes them more compact and easier to house in a building. If space is VERY limited All-water systems are best because they are the most compact. |
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VAV |
Variable-Air-Volume Systems use dampers at terminal outlets to control the flow of conditioned air according to the temperature requirements of each zone or space. Is most versatile and widely used system for heating and cooling large buildings |
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What are the advantages and disadvantages of All-Water systems |
Saves space and offers better individual control of temperature than some all-air systems Are more complicated Most maintenance must take place in occupied spaces Requires separate system for ventilation |
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What are the advantages and disadvantages of VAV systems |
High degree of local temperature control Moderate cost/ economical Virtually self-balancing Limited in range of heating and cooling demand (cool O.R. aside a warm nursery) |
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What are some types of Packaged systems and their defining characteristics? |
Single-packaged system - incorporates all central components in a single metal box. Split-packaged system - a compressor and condensing unit is contained in an outdoor box and an air handling unit is contained in an inside box. Small Terminal Units- may be mounted directly below a window or in an opening, usually for retrofitting (window AC) Multiple-packaged systems are used to serve long buildings |
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What are some of the factors to consider in the selection, design and installation of a HVAC system? |
Performance - initial and life Fuel, power, air and water requirements (delivery/supply and storage) Flexibility of the system- Zones, decentralized vs centralized Type and layout Space requirements for equipment and distribution Access required for services and maintenance Construction requirements for enclosure - fire rating, noise and vibration control Structural Requirements Visibility - concealed or exposed |
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What are the key differences between decentralized vs centralized systems ? |
Decentralized - economical to install, short distribution runs, all ow individual zone/space temperature control Centralized - more energy-efficient, easier to services and offer better air quality control. |
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What can be done to minimize friction loss in an HVAC distribution system? |
ductwork and piping should have short, direct runs with a minimum of turns and offsets. |
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What is the typical % of the total building area designated to HVAC equipment? |
10-15% |
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What is housed in the services core or cores of a building? |
vertical distribution of mechanical and electrical services, elevator shafts and exist stairs. |
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What are some general arrangements of the services cores of a building and their benefits/disadvantages? |
Single Core - High rises, large unobstructed area, core is usually centrally located for short and efficient distribution runs/patterns Detached core - max unobstructed area but long services runs and no dual function for lateral bracing Two Cores - symmetrically placed reduces service runs and acts as lateral bracing, reduction in flexibility of layout, area and use. Multiple cores - broad low-rises to avoid long horizontal runs, cores dispersed to better serve unique (demands and loads) spaces or zones |
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What should be considered when choosing registers and diffusers? |
air flow capacity and velocity, pressure drop, noise factor, and appearance |
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Throw |
is the distance a projected airstream travels from an outlet to a point where its velocity is reduced to a specified value. It should extend at least 3/4 into the depth of the space.
Throw distance and spread/diffusion pattern of the supply outlet should be carefully considered along with any obstructions that might interfere with the air distribution. |
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Spread |
is the extent to which a projected air stream diffuses at the end of the throw. Spacing should be almost = to the extent of the outlets spread. |
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What are the principle uses for water in a building? |
Occupants use - drinking, washing etc HVAC systems - heating cooling and humidity Fire protection systems - store water for extinguishing fires |
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What are the important characteristics of water supply to a building to satisfy the principles uses? |
Quantity, flow rate, pressure and temperature. |
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What are the main requirements for drinking water? |
Free from harmful bacteria (potable)and palatable. |
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What are some forms of water supply? |
Municipal or public system Wells Rainwater collection/storage |
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If a public water system is not available and a well is the preferred method of water supply how far should the well be located from building sewers, septic tanks and sewage disposal fields? |
100' - 30m |
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What is the main function of a pressure tank? |
It maintains service pressure of water. Requires electrical power and a fused disconnect switch. Total operating head = service pressure minus friction head loss |
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What are the main components of a public water supply system? |
Water main - conduit through which public/community water system conveys water to all services connections Corporation stop - valve controlling the low of water from a main to a service pipe Curb Box - provides access to water meer and records quantity of water that passes through. also houses the control valve for shutting of water supply to a building in an emergency. Service Pipe - connects water main to a building, usually installed by public utility Building shutoff valve Upfeed system - distributes water from a water main or an enclosed tank under pressure from compressed air. |
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What is the typical water pressure of a public water supply system? |
345 kPa (50 psi) At this pressure upfeed is feasible for low-rise buildings up to 6 stories. Is also the upper limit for most private wells. |
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What is a common practice for tall buildings where the water service pressure is insufficient to maintain proper fixture services? |
Water is pumped up to an elevated or rooftop storage tank for gravity downfeed. (often doubles for fire protection) |
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What is the typical pressure range for fixtures to ensure satisfactory operation? |
35 - 207 kPa (5 - 30 psi) |
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What are the typical components of a water supply system inside a building? |
Water supply - Branch lines, risers Water heaters Hot-water storage tanks Water softener Exterior Hose bibs |
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What is the benefit of employing a water softener? |
it removes calcium and magnesium salts from hard water by ion exchange; hard water can clog pipes, corrode boilers and inhibit sudsing aciton of soap. |
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What is the typical temperature of water in a Water heater or Hot-Water storage tank? |
50-60 deg celsius |
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What are the benefits of an On-demand water-heating system? |
Energy-efficient and require no space for a storage tank,
Cons - require an exhaust vent and are $$ |
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What are some factors influencing pressure loss due to hydraulic friction in a water supply pipe run? |
Diameter of the pipe, distance of water flow, number of valves, number of tees, number of elbow fittings. Runs should be short, straight and as direct as possible to reduce hydraulic friction. |
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What are some types of water supply lines and their unique characteristics? |
Copper - corrosion resistance, strong, low friction loss and small outside diameter, costly Plastic - light, easily joined, low friction, do not corrode, not all suitable for potable water Galvanized Steel |
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True or False The total demand for water supply systems is directly proportional to the total load in the fixture units. |
False, It is assumed that not all fixtures will be used at the same time so total demand is not directly proportional to the total load. Pipes are sized according to the number and types of fixtures served and pressure losses due to hydraulic friction and static head. Each type of fixture is assigned a number of fixture units. Based on the total number of fixture units for a building, an equivalent demand in gallons per minute is estimated. |
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Static Head |
The static head of a pump is the maximum height (pressure) it can deliver. |
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True or False: Both Cold and Hot water pipes should be insulated. |
True, Cold should be insulated to prevent heat flow into the water from the warmer surrounding air. Hot should be insulated against heat loss and should be no closer than 150mm to parallel cold water pipes. ALL pipes in cold climates should have drainage to a low point in the system where a drainage faucet is located. If supply must be located in an exterior wall (cold climate) it should be placed on the warm side of the wall insulation. |
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Water Hammer |
is the concussion and banging noise that can occur when a volume of water moving in a pipe is shut off abruptly. |
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What can be installed to prevent water hammer? |
Air chambers installed at fixture branches. the trapped air elastically compresses and expands to equalize the pressure and flow of water in the system. |
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What are the characteristics of fire sprinkler system? |
Pipes located in or below ceilings, connected to a suitable water supply and supplied with valves or sprinkler heads made to open automatically at a certain temperature. |
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What are the two major types of sprinkler systems? |
Wet-pipe - contain water at sufficient pressure to provide an immediate, continuous discharge through heads that open automatically. Pressure is maintained by a fire pump (also provides pressure for standpipes) when pressure drops below required value. Dry-pipe - contain pressurized air that is released in a fire allowing water to flow through the piping and out the opening. Usually used where piping is subject to freezing. |
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Preaction sprinkler system |
dry-pipe systems through which water flow is controlled by a valve operated by fire-detection devices more sensitive than in sprinkler heads. often used in locations where accidental discharge would damage valued materials. |
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Deluge sprinkler system |
have sprinkler heads open at all times, water flow is controlled by a valve operated by heat,smoke or flame sensing devices. |
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StandPipe |
is a water pipe extending vertically through a building to supply fire hoses throughout the building. can be wet or dry. |
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Siamese Pipe Fitting |
is installed close to the ground on the exterior, providing two or more connections through which the fire department can pump water to a standpipe or sprinkler system. |
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Air Gap |
is the clear vertical distance between the spout of a faucet or other outlet of a supply pipe and the flood level of a receptacle. They are required to prevent back-siphonage or backflow from a fixture into a pipe supplying potable water |
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What is an essential and required feature of the sanitary drains from all plumbing fixtures? |
A trap, U-shaped or s-shaped section of drainpipe in which waste water remains. it forms a seal that prevents the passage of sewer gas without affecting the normal flow of waste water or sewage through it. |
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What is the primary objective of the sanitary drainage system? |
to dispose of fluid waste and organic matter as quickly as possible. |
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What force does the sanitary drainage system rely on for its discharge? |
Gravity, which is why the pipes are much larger than supply as supply systems are under pressure. |
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What are the typical materials used for Drainage lines? |
Cast Iron Plastic (PVC polyvinyl chloride, ABS acrylonitrile-butadiene-styrene) |
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What is the main difference between general Tees and Sanitary Tees? |
Sanitary tees have a slight curve in the 90 deg transition. |
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Bell-and-spigot pipe joints |
are made by fitting the end (spigot) of one pipe into the enlarged end (bell) of another pipe and sealing with a caulking compound or compressible ring. |
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What are some types of pipe fittings? |
Elbows, Drop elbows, Closet bend, Tees, Drop tees, Sanitary tees, Wyes, Nipples, Couplings, Increaser, Reducer, Unions, Plugs, Caps, Bell-and-spigot joints. See 11.25 for plumbing fittings. |
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What should be done to prevent the deposits of solids and clogging in a sanitary drainage system? |
Ensure the layout is as direct and straightforward as possible and locate clean-outs for easy cleaning if they do clog. |
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Stack Vent VS Vent Stack |
Stack Vent - a pipe placed vertically or nearly so and connected to the traps of plumbing fixtures in such a manner as to ventilate them and prevent the water seal from being siphoned out of them. is an extension of a soil or waste stack above the highest horizontal drain connected to the stack (usually 305mm above roof surface) Vent Stack - a pipe placed vertically or nearly so and connected to the traps of plumbing fixtures in such a manner as to ventilate them and prevent the water seal from being siphoned out of them. |
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What is the typical slope for horizontal sanitary drain lines? |
1:100 for 75 diameter pipes and 1:50 for pipes larger than 75mm diameter |
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Waste Stack vs Soil stack |
Waste stack - carries discharge from fixtures other than water closets or urinals Soil stack - carries discharge from water closets or urinals to building drain or building sewer |
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Where should the fresh-air inlet be located on the drainage system of a building? |
at or before the building trap. Building trap - is a trap to prevent the passage of sewer gases from the building sewer to the drainage system of a building |
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What are some types of Vents and their unique purposes? |
Relief Vent - provides circulation air between drainage and venting system by connecting a vent stack to a branch drain. Loop Vent - loops back and connects with a stack vent instead of a vent stack. Common Vent - serves two fixture drains connected at the same level Vent Stack - vertical vent to provide circulation of air Branch Vent - connects one or more individual vents with a vent stack or stack vent Continuous vent - formed by a continuation of the drain line to which it connects Back Vent - is installed on the sewer side of a trap Circuit Vent - serves two or more traps and extends from infront of the last fixture connection to the vent stack Wet Vent - oversized pipe functioning both as a soil or waste pipe and vent. |
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Greywater |
is the wastewater from sinks, baths, showers and dishwashers which can be treated and recycled for uses in toilets and irrigation. |
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Sanitary VS Storm sewers |
Sanitary Sewers - convey only the sewage rom plumbing fixtures and exclude storm water Storm Sewers - convey rainfall drained from roofs and paved surfaces Combined sewers carry both. |
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What does a septic tank do? |
it receives the discharge from a building sewer, separates out the solid organic matter, which is decomposed and purified by anaerobic bacteria and allows the clarified liquid to discharge for final disposal. |
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What are the general distances for locating a septic tank near a well, stream or building? |
It should be located at leas 30m from wells, 15m from streams and 3m from buildings and property lines. |
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Once the liquid effluent is approximately 70% purified it may be discharged for final disposal. What are the types of systems this liquid effluent may flow into? |
Drainfield - open areas with an arrangement of absorption trenches through which effluent may seep or leach into the surrounding soil Seepage Pit - absorbent soil, pit lined with perforated masonry/concrete walls. highest level of water table must be 610mm below the bottom of the pit Subsurface sand filter - distribution pipes surrounded by graded gravel, layer of clean coarse sand and a system of underdrains to carry off the filtered effluent. only used of no other system is viable. |
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All electrical equipment should meet what standards? |
UL standards |
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The electrical system of a building supplies power for what? |
Lighting, Heating, Operation of equipment & appliances, security, communications etc. |
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Power is usually supplied to a building by the electric utility company. What are the typical voltage systems that may be supplied by the utility company to provide power for the varying load requirements of a building? |
120 V single phase two wire 120/208 V single phase three wire 120/240 V single phase three wire (common for residences) 120/208V three phase four wire (used by all but the largest installations |
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When should the public utility company be notified of the estimated electrical load requirements for a building? |
During the planning phase to confirm service availability and coordinate location of service connection and meter. |
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Service connections may be overhead or underground; what are the benefits or disadvantages of each? |
Overhead - less $, easily accessible and can carry high voltages over long runs Underground - more $ but used in high-load density situations eg. urban areas |
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When is a transformer used? |
usually by medium-sized and large buildings to step down power from a high supply voltage to the services voltage
Outdoor - cheeper, easier maintenance, less noise & heat inside Indoor - requires ventilation, fire rated vault with two exits |
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What are the main components of the electrical system? |
Service Entrance conductor Watt-Hour Meter - measures and records the quantity of electric power consumed with respect to time. (may have multiple for units) Grounding Rod (transformer - optional) Service Switch - main disconnect for entire electrical system of a building (accept for emergency systems) Main Switchboard - switches, overcurrent devices, metering instruments and busbars for controlling distributing and protecting electric circuits. Conduit system to to Panel Boards Panel Boards - control distribute and protect a number of similar branch circuits, electrical closets Low Voltage circuits Branch Circuits - supply current to outlets include: General purpose Circuits - general outlets Appliance circuits - specifically intended for appliances Individual Circuits - single piece of electrical equipment
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To avoid excessive drop in voltage a branch circuit should not exceed what length? |
30m |
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GFI |
Ground Fault interrupter Senses currents caused by ground faults and instantaneously shuts off power before damage or injury occurs. Receptacles in wet locations should be protected by GFIs |
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Circuit Breakers |
are switches that automatically interrupt an electric circuit to prevent excess current from damaging apparatus in the circuit or from causing a fire. |
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What is the voltage carried by Low-voltage circuits and what are their common uses? |
below 50 V and basically used when a central control point is desired from which all switching may take place. the switches control relays that do the switching at the service outlets. used to control doorbells, intercoms, heating and cooling systems, remote lighting fixtures etc |
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Wire, cable and busbars are sized according to their safe current carrying capacity and the maximum operating temperature of their insulation. What is provided on conductors to identify the above? |
Voltage class number and size of contuctors type of insulation |
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What are some components of the electrical wiring system? |
Conductor - covered with insulation Conduit - support and protection for wires and cables Raceway Junction boxes
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What are some types of buildings that typically use access flooring? |
Office spaces, Hospitals, laboratories, computer rooms, TV and communication centres. They provide accessibility and flexibility in the placement of furniture and equipment. |
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How can an access flooring system reduce energy consumption? |
Separating cool supply air from the warmer return air by using the space in the access flooring to be used as a plenum to distribute the supply air of the HVAC system allowing the ceiling to be used only for return air. |
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What are the typical heights for the installation of wall switches and outlets? |
Switches - 1220 mm AFF maximum for accessibility Outlets - 305mm typ. 455 min AFF for accessibility |
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What are the typical outlet spacings for residences and offices? |
Residences: Walls - one every 3660mm Counters - one every 1220 Offices: Walls - one every 3050mm or one for every 3.7 square meters for the first 37 square meters and one for every 9.3 square meters thereafter. |
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Candela |
is the basic SI unit of luminous intensity, equal to the luminous intensity of a source that emits monochromatic radiation of frequency 40 x 1012 hertz and that has a radiant intensity of 1/683 watt per steradian |
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Luminous flux |
is the rate of flow of visible light per unit time, expressed in lumens. |
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Inverse Square Law |
states that the illumination produced on a surface by a point source various inversely as the square of the distance of the surface from the source |
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Illumination |
is the intensity of light falling at any given place on a lighted surface |
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Lux |
is the SI unit of illumination, equal to one lumen per square meter |
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Foot-candle |
is a unit of illumination on a surface that is everywhere one foot from a uniform point source of one candela and equal to one lumen incident per square foot |
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Reflectance vs Absorptance vs Transmittance |
Reflectance - is the ratio of the radiation reflected by a surface to the total incident on the surface Absorptance - is the ratio of the radiation absorbed by a surface to the total incident on the surface Transmittance - is the ratio of the radiation transmitted through and emerging from a body to the total incident on it, equivalent to one minus the absorptance. |
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When the contrast or brightness ration is too high what can result? |
Glare The sensation produced by any brightness within the visual field that is sufficiently greater than the luminance to which the eyes are adapted to cause annoyance, discomfort, or loss of visibility. |
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What are the two types of glare? |
Direct - results from a high brightness ratio or an insufficiently shielded light source in the visual field. to control/minimize use shielded luminaries to cut off direct view of lamps, as well as diffusers/lenses that lower brightness levels Reflected - (/indirect) results from the specular reflection of a light source within the visual field. Prevention includes: locating light source so that the incident light are reflected away from the viewer. |
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Efficacy |
is a measure of the effectiveness with which a lamp converts electric power into luminous flux. Expressed in lumens per watt. |
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Rated Life |
is the average life in hours of a given type of lamp, based on laboratory tests under controlled conditions. |
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What types of lamps are designed for reduced energy consumption and a life longer than average for its general class? |
Extended-service lamps |
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What are the main types of Lamps and their unique properties? |
Incandescent - good for point sources, have low efficacy, render colour well and are easy to dim with rheostats. yellow-whit light Fluorescent - linear sources of light, efficacy of 50-80 lumens per watt and ability to render colour varies. High-Intensity Discharge - LED - |
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Colour Rendering Index |
is a measure of the ability of an electric lamp to render colour accurately when compared with a reference light source of similar colour temperature. (100 = perfect) |
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Luminaire/ light fixture |
consists of one or more electric lamps with all of the necessary parts and wiring for positioning and protecting the lamps, connecting the lamps to a power supply and distributing the light |
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What are some devices that are used to manipulate the light from a lamp? |
Reflectors - control the distribution of light emitted by a lamp Baffles - are louvered devices for shielding a light source from view at certain angles Lens - focus, disperse or collimate the emitted light |
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Isochart |
is a chart which plots the pattern of illumination produced on a surface by a lamp or luminaire. |
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What is Luminaire efficiency ? |
it is the ratio of luminous flux emitted by a luminaire to the total flux emitted by the lamps in the luminaire. |
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True or False: Diffuse light minimizes contrast and shadows and can make reading of textures difficult. |
True, Diffuse light emanates from broad or multiples sources and reflecting surfaces producing a flat and fairly uniform illumination. directional light enhances our perception of shape, form and texture by producing shadows and brightness variations on the surfaces of the objects illuminated. |
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What are some typical distribution curves for luminaires? |
General Diffuse Direct - Indirect Semidirect Semi-Indirect Indirect Direct |
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What is the maximum recommended brightness ratio between the visual task area and its immediate background? |
3:1 |
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What is used to determine how far apart luminaires should be installed for uniform lighting of a surface or area and what is it based on? |
Spacing Criteria , and it is based on mounting height Spacing criteria = spacing/ mounting height |
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What method is used to determine the number and types of lamps, luminaires, or windows required to provide a uniform level of illumination on a work plane, taking into account both direct and reflected luminous flux? |
The Lumen method (aka Zonal cavity method) |
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What are some factors/figures which measure phenomenon that might effect the performance of a lamp/lumen over time? |
Lamp Lumen depreciation - decrease in luminous output during operating life of the lamp Luminaire Dirt Depreciation - decrease in luminous output from accumulation of dirt Room Surface Dirt Depreciation - decrease in reflected light from dirt on room's surfaces Nonrecoverable light loss factor - any of several permanent light loss factors that take into account the effects of temperature, voltage drops/ surges, ballast variations and partition heights. Recoverable light loss factors - may be recovered by maintenance or relamping |
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What is the recommended illumination level for public spaces? |
32 Lx |
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What is the recommended illumination level for Simple task lighting spaces? |
107.6 Lx |
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What is the recommended illumination level for Normal visual tasks? |
322-1076 |
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What is the recommended illumination level for critical visual tasks? |
3230 |
