OBJ 3.1

Question 1

PEX

Answer 1

A type of plastic tubing used for plumbing or hydronic piping.

Question 2

PTAC

Answer 2

Packaged terminal air conditioner. A self-contained thru-the-wall HVAC unit commonly found in hotels, hospitals, and condos.

Question 3

Degree-day

Answer 3

Degree-day is a way of summarizing the heating (or cooling, in the case of cooling degree-days) requirements in a particular climate over the course of a year. It is used to calculate heating and cooling demand. Degree-days are defined against a base temperature, which is the approximate lowest outside temperature at which a building would not need heating in order to be comfortable. The difference between the base temperature and the mean ambient temperature for the day is a degree-day. For example, on a day in January in New York City, if the base temperature is 65 degrees F, and the average temperature for the day is 40 degrees F, there are 25 heating degree-days. If there is a whole month with 25-degree days, the month has 775 degree-days. The city of New York has 5,050 HDD annually.

Question 4

ASHRAE

Answer 4

American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

Question 5

Upfeed system

Answer 5

Plumbing system in which water is supplied and pumped upward, using pressure from the water main, to the highest point of the system and directly to the fixtures. The building height limit is 40 feet to 60 feet due to the friction of the upward lift.

Question 6

Downfeed system

Answer 6

Plumbing system used in buildings too tall for an upfeed system, in which water is supplied from the main and pumped to storage tanks at the top of a building or zone. Water then flows by gravity to fixtures. The height of zones being served is determined by the allowable pressure on the fixture at the bottom of the zone.

Question 7

Direct expansion (DX) system

Answer 7

Type of HVAC system that uses a refrigerant vapor expansion/compression cycle to remove sensible/latent heat from the air. Air passes over the evaporator to cool it, and it is then ducted into rooms. DX systems can be packaged or split systems. They typically take up less space and can be used in zones.

Question 8

Variable air volume (VAV) system

Answer 8

TA type of Heating, Ventilating, and/or Air-Conditioning (HVAC) system that provides a varying rate of airflow through diffusers in each zone under the control of zone thermostats.

Question 9

Economizer cycle

Answer 9

Energy-efficient HVAC method that brings in outdoor air when it’s cool enough (around 60°F) and ducts out warm air. This method reduces the energy required to cool air mechanically.

Question 10

Electrical HVAC systems

Answer 10

System in which radiant heat is run through panels or wires into rooms and convection is used to heat spaces. It is the simplest system, with low initial costs, yet it has expensive life cycle costs.

Question 11

Chiller

Answer 11

A machine that removes heat from a liquid via a refrigeration cycle. In many commercial facilities that require air conditioning, chillers are a major energy user. Thus, it is important to select a chiller that costs as little as possible to operate for the specific application.

Question 12

Furnace vs. boiler system

Answer 12

A furnace is fired by gas or oil and used to heat air. A boiler heats water or some other fluid that is used to heat various heating systems. Both are about 80 percent efficient.

Question 13

Forced air systems

Answer 13

HVAC system which uses air as a heat transfer medium. Air is tempered as it is blown by a fan across a heat exchanger, and distributed throughout a building by a network of ducts and plenums.

Question 14

Active solar heat gain

Answer 14

Mechanical equipment is used to collect/store solar energy, and it often requires a backup system. System examples include flat-plate collectors, concentrating collectors, evacuated tube collectors, and air-based systems.

Question 15

Passive cooling system

Answer 15

Solar collection and storage is integrated into building elements (walls, floors, ceilings, etc.) and does not rely on mechanical systems. Most effective when outdoor air temperature is below 85°F.

Question 16

Low-E glazing

Answer 16

Double glazing with a thin film in the glazing cavity. Applied to the inside pane of glass in cold climates and outside glass in warm climates. Allows infrared to be transmitted and prevents loss of heat in the winter and excessive heat in the summer.

Question 17

Thermal bridging

Answer 17

Transfer of heat through materials, usually from outside to inside the envelope, or vice versa. Occurs when poor insulation materials come in contact with each other, allowing heat to pass between them with little resistance. Separating materials or wrapping with insulation is the most effective way to mitigate bridging.

Question 18

How much will one PSI of water pressure raise a column of water?

Answer 18

2.31 feet.

Question 19

Static head

Answer 19

Also called pressure head. It denotes the static pressure in a pipe, channel, or ductflow.

Question 20

SMACNA

Answer 20

Sheet Metal and Air-Conditioning Contractors National Association.

Question 21

Ohm’s Law

Answer 21

V = I*R, where V = voltage in volts, I = current in amps, and R = resistance in ohms.

Question 22

Watts

Answer 22

The SI unit of power, equal to one joule per second. Electrical wattage can be calculated by the following formula:
W = I*V, where W = wattage in watts, I = current in amps, and V = voltage in volts.

Question 23

Foot-candle

Answer 23

The most common measurement used to measure lighting levels, a foot-candle is equal to the light intensity of a one-candela object casting light one foot away.

Question 24

Color temperature

Answer 24

Measured in degrees Kelvin, color temperature is a way to quantify the light appearance produced by a lamp. Lower values indicate warm lighting, whereas higher values correspond to cool lighting. A warm fixture has a typical temperature of 2700K; a cool white fixture is closer to 3500K–4000K.

Question 25

CRI

Answer 25

Color rendering index. Measured from 0 to 100, CRI is a quantitative measure of how well a light source renders colors in relation to natural daylight. The higher the CRI, the more accurately colors are rendered.

Question 26

Interlayment

Answer 26

A layer of felt or nonbituminous saturated felt not less than 18 inches (457 mm) wide, shingled between each course of a wood-shake roof covering.

Question 27

Design day

Answer 27

Used to design and size a heating system. Design day determines the day that is cooler than 98 percent of all days in the year experienced in a climate.

Question 28

Dry bulb temperature

Answer 28

Typically referred to as air temperature, it’s what people are referring to when they talk about the temperature. It’s an indicator of heat content and measured by a common thermometer; it is given in degrees Fahrenheit.

Question 29

Wet bulb temperature

Answer 29

The lowest temperature that can be reached under current ambient conditions by the evaporation of water only; it is given in degrees Fahrenheit.

Question 30

Dew point (T)

Answer 30

The temperature at which water vapor starts to condense out of the air. Above this temperature, the moisture will stay in the air; it is given in degrees Fahrenheit.

Question 31

Barometer

Answer 31

An instrument for measuring atmospheric pressure.

Question 32

Specific heat

Answer 32

Capacity of a material to store heat (BTU/lb).

Question 33

Insolation

Answer 33

Radiant heat gain from the sun.

Question 34

Declination

Answer 34

A 23.5 degree tilt of Earth’s axis relative to a line perpendicular to the plane of the Earth’s orbit.

Question 35

Stack effect

Answer 35

When air rises due to buoyancy in a structure, creating pressure differentials within. Differences in temperature and moisture content cause air to be more or less dense, which drives the stack effect. Also called the chimney effect.

Question 36

Zone

Answer 36

In HVAC design, zones are a way to divide areas of a building according to heating and cooling needs and allow for individual control within those areas.

Question 37

Raised access flooring

Answer 37

Composed of load-bearing floor panels supported on a grid of pedestals. Provides an underfloor area for distribution of services such as electric, data, and air.

Question 38

HVAC system types. What are the four traditional system classifications?

Answer 38

Direct refrigerant systems, all-air systems, air and water systems, and all-water systems.

Question 39

Direct refrigerant systems

Answer 39

These systems mostly eliminate the need for distribution trees of air or water, relying on a heating/cooling device(s) located in or adjacent to the space it is serving. They are typically used in buildings with a high perimeter-to-area ratio, tending toward smaller buildings.

Question 40

All-air systems

Answer 40

All-air systems are when air is the only transfer method used between the mechanical room and the areas served. The downfall of these types of systems is that air does not hold as much heat per volume as water, thus making the distribution tree large. A benefit is that all-air systems are the best systems for comfort; the air moving through the spaces are temperature and humidity controlled. Some all-air systems are single-zone systems; single-duct, variable air volume systems (VAV); fan-powered VAV systems; multi-zone systems; single-duct with reheat; and dual-duct, constant-volume systems.

Question 41

Air and water systems

Answer 41

Air and water systems are typically designed where the heating and cooling of each zone is accomplished with water running through the distribution tree. Because water holds more heat per volume than air, the distribution tree is thinner. For air changes, to control the quality of air in the space in regard to humidity and freshness, a centrally conditioned airstrip, equal to the total fresh air required, is provided. With this system, several distribution trees are typically required, but the space they need is typically less than that of an all-air system. Some air and water systems are induction systems, fan-coil with supplementary air, radiant panels with supplementary air, and water loop heat pumps.

Question 42

All-water systems

Answer 42

All-water systems only heat and cool, and the distribution tree is very thin. Air quality is handled either locally, through an infiltration system or windows, or by fresh air from an adjacent system, such as a ventilated interior corridor zone. A fan-coil terminal is typically used so that air motion still occurs. Because air is handled locally, the system has very little cross-contamination of air from one zone to another. This system is easy to retrofit into an existing building but requires substantial maintenance; fan-coils need filters changed, and drip pans can cause problems. All-water systems include two - and four-pipe systems.

Question 43

Multi-zone systems

Answer 43

An all-air mechanical system where each zone in a building has an individually centrally conditioned airstream. The central station for the overall building produces both warm and cold airstreams, which are mixed at a central location in each zone to meet the thermal needs of that specific zone. A single-return airstream collects air from all zones. This type of system is more likely to be found in medium to larger buildings, where each floor is a zone.

Question 44

Single-duct with reheat

Answer 44

A mechanical system where a central station provides a single stream of cold air that must be cold enough to meet the maximum cooling demand of any one zone in the system. All other zones reheat this air as needed (i.e., Zone A needs air that is 60°F and Zone B needs air that is 72°F; the 60° air will be delivered to ALL the spaces, and Zone B will use a reheat box to get the air to the desired 75°). This provides a smaller tree distribution because, in each zone, the only object added is a reheat coil that is small in size. In cold weather, the minimum outdoor air temperature has to be 38°F to be used. The colder this central airstream, the less air needs to be circulated. This system typically has a lot of waste unless carefully engineered for the right climate.

Question 45

Dual-duct, constant-volume systems

Answer 45

This mechanical system requires two complete distribution trees—one system is devoted to cold air and the other to hot air. During peak summer months and in winter, the all-cooling system or the all-heating system, respectively, does all the work. The rest of the year, air from the two steams is mixed at each zone’s terminal to achieve the desired zone temperature. Both temperature and air volume can be controlled with this system, which offers increased comfort under reduced load conditions than a traditional single-duct VAV system does. This system has a high initial installation cost; the two distribution trees take up a significant portion of the building; and it consumes more energy than a single-duct VAV system.

Question 46

Induction system

Answer 46

A high velocity, high pressure, and constant volume of fresh air supply is brought to each terminal, typically located below a window, and forced through an opening, allowing the air within the room to be induced to join the new air. Very little centrally conditioned air is needed because the circulation is strong. To condition the air, it passes over finned tubes for heating or cooling. Thermostats control the unit’s output by controlling the water or the air.

Question 47

Fan-coil with supplementary air

Answer 47

A below-window unit that moves room air as it provides either heated or cooled air. Centrally conditioned, tempered fresh air is brought to the space in a constant-volume stream.

Question 48

Radiant panels with supplementary air

Answer 48

Typically, ceiling or wall panels contain heated or cooled water, relying on large surface areas for radiant heat exchange. Centrally conditioned, temperature-controlled fresh air is delivered to the spaces served by the system at a constant volume. The panels in the ceiling or the wall must be kept clear of obstructions.

Question 49

Water loop heat pumps

Answer 49

This system can be an all-water system but can also be configured with a central outdoor air supply, making it an air and water system. Heat pumps either draw heat from a water circulation loop in heating mode or discharge heat in cooling mode.

Question 50

Convenience outlet

Answer 50

Receptacle attached to a circuit to be used by devices such as appliances or lighting. Usually located 12 to 18 inches above the floor or above countertops.

Question 51

Circuit breaker

Answer 51

A safety device that will open or close a circuit by manual means and will open the circuit automatically upon overload of current.

Question 52

Service panel

Answer 52

The main electrical distribution box that receives electricity and distributes it to various points through branch circuits. Contains the main disconnect switch. Also called distribution panel.

Question 53

Service entry

Answer 53

The fittings and conductors that bring electricity into a building.

Question 54

Circuit

Answer 54

A path through which electricity flows from a source to one or more devices and then returns.

Question 55

Branch circuit

Answer 55

One of several individual circuits that route from the distribution panel and transfer power to devices.

Question 56

Hardwiring

Answer 56

In electrical wiring, hardwiring is when a device is directly wired into the circuit as opposed to being battery operated. Examples include smoke alarms.

Question 57

GFCI

Answer 57

Ground fault circuit interrupter, a safety device on an outlet that monitors the current going to the load and coming back again. As long as the two are equal, the electricity continues to flow. But if the return current is lower, the GFCI will “trip” or open, interrupting the circuit. It must be placed within 6 feet of sinks, throughout baths, in garages, outdoors, in unfinished basements, and in crawlspaces.

Question 58

Dedicated circuits

Answer 58

Some appliances have their own circuits, such as dishwashers, water heaters, washers, and attic fans.

Question 59

Whole-house fan

Answer 59

A type of exhaust fan that usually vents into a house’s attic space. It is designed to ventilate the whole house.

Question 60

Three-way and four-way switches

Answer 60

Three-way switches allow circuits to be turned on and off from two locations. Four-way switches allow three locations.

Question 61

What system is required by elevator codes in case of fire?

Answer 61

An automatic fire recall (capture) system immediately returns elevator passenger cars to a predetermined floor (typically the ground floor) to remain parked, with the doors open, to allow firefighters to confirm that no persons are trapped in a passenger car.

Question 62

How do you determine the minimum diameter of a plumbing vent?

Answer 62

The diameter of the plumbing vent should be no less than one half the the diameter of the vented drain and no smaller than 1.25 inches.

Question 63

List the direction(s) that thermal expansion affects pipes.

Answer 63

Length is greatly affected by thermal expansion, which is why long runs of pipe must be held by flexible hangers. Diameter is not affected by thermal expansion.