Determining Mechanical, Plumbing, and Electrical Systems Flashcards

Question

What is a constant-volume single-duct system? - central unit? - independent control? - boiler/chiller or heat pump or refrigerant? - where it is most often used?

Answer 1

the simplest type of all-air system in which air is heated/cooled in a central furnace/air conditioner and is distributed through ductwork at a constant volume. - central unit - central thermostat = no independent control - boiler/chiller to heat/cool air - often used in residential and small commercial

Answer 2

Air is heated/cooled in a central plant and distributed through a single duct at a constant temperature. - central plant - individual zone control but not simultaneous H/C - boiler/chiller - efficient air conditioning large internal load dominated buildings. - Limited in extreme simultaneous heat/cooling demands

Answer 3

2 parallel ducts run to each space, one carrying hot air and the other cold air. The two streams of hot/cool air are joined in a mixing box in proportions to suit the temperature requirements of the space. - central distribution unit - individual zone controls = thermostat controls the mixing box for each space - boiler/chiller - best for buildings that need varying simultaneous heating/cooling requirements. 1. - inherently inefficient since both hot air and cold air are supplied at all times 2. - high velocity = higher energy for more powerful fans and higher noise with in ductwork 3. - high quantity of ductwork = higher cost

Answer 4

They both provide heating/cooling with boiler/chillers with individual zone control. VAV cannot provide large simultaneous differences in heating/cooling since it has a single duct, but high-velocity dual duct can. VAV is better for large internal load dominated buildings. high-velocity dual duct is better for buildings that need varying simultaneous heating/cooling requirements.

Answer 5

A single compressor and condenser unit is located outdoors and connects to multiple evaporators located in different zones/rooms. Reduces power consumption by operator compressor and evaporators at varying speeds to precisely meet the load in each zone. - individual zone control through individual evaporators - uses refrigerant. Can also be designed to use a heat pump or heat recovery to reduce power consumption. - best for buildings with varying heating/cooling loads and different zones: - office buildings - hotels - schools - multifamily residential

Answer 6

Supplies air to a central mixing unit where separate heating (coiler) and cooler (chiller) coils product separate hot/cold air streams. Hot/cold air streams are mixed with dampers controlled by zone thermostats and delivered to the zones. Best used for medium sized buildings that needs various heat/cooling in different zones, but where each floor is one with 1 central mixing unit/floor.

Answer 7

uses a fan coil (boiler/chiller) in each conditioned space to heat/cool water. - individual controls = thermostat in each room regulates how much water flows through the coils - most often used in dry/arid locations = It is an efficient way to transfer heat and is easily controlled, but cannot control humidity.

Answer 8

``` two-pipe = one supply pipe for both hot and cold and one return pipe three-pipe = two supply pipes for hot and cold and one return four-pipe = one supply/return circuit for hot and another for cold ```

Answer 9

a central air system provides humidity control and ventilation air to spaces, with the majority of heating/cooling provided by fan coil units in each space for independent control. Supply air is 100% fresh and return air is completely exhausted to exterior. - often used when return air cannot return to the system due to potential contamination (like laboratories or hospitals)

Answer 10

1. air-water induction system = air is supplied to an induction unit (instead of coils) in a room/zone, where air is heated/cooled as needed 2. fan coil with supplementary air = fan coiled unit provides heating/cooling, but separate supplementary air supply provides humidity control and ventilation

Answer 11

most commonly a grid of wires in the ceiling of a room that provide radiant heating. Can also baseboard or floors. - individual room control - no space required for ductwork or piping

Answer 12

1. use profile of the building 2. building scale 3. control needs 4. fuels available 5. climatic zones 6. flexibility 7. integration with building systems 8 integration with alternate energy sources 9. economics 10. energy efficiency

Answer 13

An all-water system has smaller ductwork.

Answer 14

1. mechanical system components 2. heat transfer methods 3. building automation systems 4. building commissioning

Answer 15

A mechanical system component that can reduce reliance on HVAC. It uses outdoor air when it is cool enough to mix with recirculated indoor air to save energy for internal load buildings that need AC even in cool months. Useful at 60 deg F.

Answer 16

A mechanical system component that can reduce reliance on HVAC. It is a refrigeration equipment that uses two condensers instead of one (can also have two chillers): 1. heat recovery condenser = used when heat is needed 2. heat rejection condenser = used when heat is not needed It is efficient because the system can operate using the best condenser or chiller with the best size for the load.

Answer 17

A mechanical system component that can reduce reliance on HVAC. Absorption chillers are powered by gas instead of electricity or refrigerants. Not as efficiency as electric chillers, so best used in a place where electricity is expensive.

Answer 18

A mechanical system component that can reduce reliance on HVAC. Absorption chillers can be made more effective if powered by hot water from solar collectors.

Answer 19

A mechanical system component that can reduce reliance on HVAC. Uses desiccants to dehumidify and cool air by evaporative cooling.

Answer 20

A mechanical system component that can reduce reliance on HVAC. It passes hot gases directly through water to heat it. Very efficient but very costly. Best used when there is continuous demand for water (food processing, laundry, industrial).

Answer 21

A mechanical system component that can reduce reliance on HVAC. They recover the heat from flue gases that would be otherwise exhausted and use them to preheat water or air.

Answer 22

A mechanical system component that can reduce reliance on HVAC. An air distribution system where supply air is dispensed at the floor level and exhausts through the ceiling as it warms and rises naturally. Air does not need to be cooled so much. Required underfloor ductwork, so an extra 12" in floor-to-floor height. Best for new construction.

Answer 23

A mechanical system component that can reduce reliance on HVAC. A series of heat pumps in different zones in the building are all connected to a piping system of circulating water. When some zones are cooling others are heating, and heat is transferred between them. Only when all zones are operating at the same temperature does the water need to be heated or cooled. Most efficient when there are simultaneous heating/cooling needs. Not appropriate for buildings in small cooling loads.

Answer 24

A mechanical system component that can reduce reliance on HVAC. Uses water, ice, or rock beds to store extra heating or cooling until it's needed. Can reduce how much the building needs to be heated or cooled later.

Answer 25

Taking heat from where it's not wanted to where it is wanted.

Answer 26

An air-to-air heat exchanger that reclaims waste energy from the exhaust airstream and uses it to condition incoming fresh air. Most effective in very cold, hot, or humid climates where the temperature differential between outside/inside is high. Not as efficient in temperate climates. Most effective in buildings with continuous occupancy, like hospitals or hotels. Prohibited in hazardous exhaust systems.

Answer 27

1. exhaust and intake must be located as far away as possible 2. exhaust air containing excess moisture, grease, or other contaminated must be separated from the heat exchange air 3. in cold months, a defroster may be needed to keep exhaust air from freezing

Answer 28

1. flat-plate heat recovery units = a flat plate separating the incoming air and exhaust air facilitates the heat exchange of sensible heat only. No humidity control. 2. energy transfer wheels = a heat exchanger wheel with small openings filled with a desiccant absorbs moisture and transfers heat between intake/exhaust. Helps control humidity. 3. heat pipes = refrigerant and a condenser/evaporator exchange sensible heat between cool intake and hot exhaust air. Intake and exhaust can be adjacent.

Answer 29

Uses water or other liquid in coils to transfer heat between intake/exhaust. Main advantage = intake and exhaust do not need to be adjacent. Commonly used in large buildings

Answer 30

A type of heat exchange in which air circulates between a double pane insulated glass and another layer of glass on the interior side. In the winter, air warms the glass and in summer air cools the glass. It can eliminate the need for separate perimeter heating/cooling.

Answer 31

A ceiling mounted unit that uses water to provide heating and cooling.

Answer 32

1. passive chilled beam system = uses natural convection. Warm air rises, is cooled by the unit, then sinks back down. Separate ventilation ducts and humity controls are required. 2. active chilled beam system = heats or cools fresh air and then forces it into the room. 3. multi service chilled beam system = combines active chilled beam system with other building systems like sprinklers, lighting, data cabling, etc.

Answer 33

a computer-based integration system used to monitor and control building systems. They contain energy management systems (EMS) to help with energy conservation.

Answer 34

A conductor. Sizes range from: Smallest = AWG size 16 gage larger = AWG size 4/0 gage Even larger = MCM sizes = 250, 300, 400, 500

Answer 35

conductors no. 8 AWA and smaller a single insulated conductor no. 6 AWA or larger OR several conductors assembled in a single unit

Answer 36

1. copper = more cost effective in small and medium-size wire and cable 2. aluminum = requires special care so limited to primary circuits installed by skilled workers

Answer 37

for commercial or large residential construction

Answer 38

1. AC (alternating current) = most common | 2. DC (direct current) = used in some types of elevator motors and for low-voltage applications

Answer 39

1. 120/240 V single-phase, three-wire system = common for SFR and small buildings 2. 120/208 V, three phase, four-wire system = common for larger buildings 3. 277/480 V, three-phase, four wire system = same as 120/208 system, except with higher voltage 4. 2400/4160 V, three-phase, four-wire system = used by very large commercial buildings and factor with a lot of machinery

Answer 40

at 120/280 V or higher. At 120/240 it is provided by the utility company.

Answer 41

Metering is provided at a building's service entrance to allow the utility company to charge for energy use.

Answer 42

a central electrical distribution center required in large buildings to distribute power to individual panel boards and then to individual branch circuits for lighting, power, motor, etc.

Answer 43

1. grounding = 2. ground-fault circuit interrupter (GFCI) 3. arc-fault circuit interrupter (AFCI)

Answer 44

= protects from small leaks unnoticed by the circuit breaker by disconnecting from power if there is a leak. Required in bathrooms, kitchens, laundry rooms, and outside .

Answer 45

de-energizes unit when an arc fault is detected. required in dining rooms, living rooms, libraries, dens, hallways, etc .

Answer 46

1. time-of-day controller = turns of power at specific times 2. occupant sensor 3. daylight compensation control

Answer 47

emergency power is required for buildings where life safety is affected by lack of power. Powered by generators or batteries. Power/electrical system is totally separate from rest of building. standby power provides electricity for building functions the building owner needs to avoid interruption of business. Power/electrical system can be integrated with other building components.

Answer 48

1. groundwater = water seeps into ground and forms a water table that can be tapped into by drilling 2. surface water = rain and snow that run off into rivers and lakes

Answer 49

1. pretreatment = removes larger particles 2. filtration = removes smaller particles, bacteria, viruses 3. demineralization = removes dissolved liquids/minerals that cause hard water 4. disinfection = destroyed microorganisms that cause disease in humans 5. distillation = often used on seawater. Water is boiled down and vapors are captured, resulting in very clean water. 6. oxidation/aeration = improves color or taste

Answer 50

1. coagulation/flocculation 2. filtered and treated with chlorine/sim 3. aerated 4. treatments to adjust pH level then piped through water mains at 50 psi

Answer 51

Determine the location of the public water main, its size, its pressure, and the cost for tapping it. Get this info from the local water company. Costs of extending water mains can be significant, so need to know early.

Answer 52

= water used in the building is the same water that is heated in the solar collectors Simple and highly efficient, but subject to freezing so must use some type of drainage system

Answer 53

= a separate fluid is used to collect heat, which is then transferred to the domestic hot water Easier to protect from freezing since fluid contains anti-freeze Requires a heat exchanger, which reduces efficiency Fluid can either be pumped passively (gravity) or actively (pumps)

Answer 54

= a passive direct/open-loop solar heating system where water is heated directly in a black-painted tank inside a glazed box. Simple but subject to freezing and nighttime heat loss

Answer 55

= passive open-loop solar heating system that relies on the natural movement of heated water Storage tanks located above the collectors Keep piping simple to avoid pipe friction Subject to freezing Can use a variation of this system that is a passive closed-loop system with antifreeze fluid

Answer 56

= solar heating in which liquid with antifreeze is circulated by pumps through solar collects and uses a heat exchanger to heat domestic water Loss of energy due to heat exchanger One of the most common types for residential and commercial Flexible and provides control

Answer 57

= a direct, open loop active solar heating system that automatically drains water from collectors when outside temperature is near freezing Best for climates with mild winters so draining does not happen frequently

Answer 58

= closed loop, indirect active solar heating system that uses water as the heat-collector fluid. Heated water is pumped to a heat exchange where a coil of domestic water is heated. When the pump is off, the heat collector fluid drains out of the properly sloped collectors and pipe, leaving them empty and protected from freezing.

Answer 59

= a solar heating system that uses phase change materials as the collector fluid. Phase change materials store large amounts of both latent and sensible heat.

Answer 60

depth (the taller the column of water, the more pressure it exerts)

Answer 61

1. Upfeed system = uses pressure in the water main to directly supply the fixtures Limited in height to 40 ft to 60 ft 2. Downfeed system = water from the main is pumped to storage tanks near the top of the building and flows to the fixtures by gravity The pressure at any fixture can be determined by its vertical distance from the storage tank (4.33 psi/1ft of height) Tank location may be driven by pressure needed and therefore vertical distance required) by fixtures near the top of the building Limited in height to 138 ft. Taller structures require pressure-reducing valves Choosing between the 2 is determined by a building’s height and its fixture pressure needs

Answer 62

= after the pressure losses are deducted from the available pressure at the water main, there must still be adequate pressure at the most remote fixture. You get total pressure at water main from the local water company Calculate pressure loss from rises in elevation by multiplying total rise in feet by 0.433 psi/ftt Include pressure losses through piping and water meter (trial and error) Pressure loss in pipes depends on diameter of the pipe and flow rate and is due to friction in the pipe.

Answer 63

= maximum possible flow = flow rate that would be needed if every fixture in the system were used at the same time Can be found by adding up all the load values for every fixture