HVAC EXAM

What is an air-handling unit? Select all the answers that apply.

-AHU -Consists of a fan and fan drive (motor), a cooling and/or heating coil, and a filter contained within a cabinet. -Moves warm or cold air to different parts of the building.

In an air cooling system, there are two coils through which refrigerant is circulated. One, called a ___(1)___ , absorbs heat from the warm air passing over it. The heated refrigerant is then pumped through another coil called a ___(2)___, where the refrigerant passes its collected heat to the atmosphere.

1. evaporator 2. condenser

Even the best windows create conduction losses more than ____ times higher than walls.

10

Define what constitutes a ton of refrigeration.

Based on the cooling effect of one ton of ice at 32 degrees F.

It is both illegal and unwise to conceal ductwork in a bulkhead or chase.

False

What is transmission heat loss, and where does it occur in a building?

Heat loss through the building envelope (building assembly).

Which of the following is (are) included in heating calculations?

Heat transferred through walls Heat transferred through windows Heat transferred through doors Heat transferred through ceilings Heat transferred through foundation

What type of system is most commonly used in a residence?

Series loop

Select all the types of material that are satisfactory for duct work in a warm air perimeter system

Sheet Metal Vitrified tile concrete pipe plastic pipe

What is the preferred material for supply ducts in conditioned spaces?

Sheet metal

Select the answers that are types of indoor air pollutants. Select all that apply.

Smoke particles Dust Bacteria Fungus Mold spores Chemical vapors

Select the true statement about registers.

Supply registers control the direction and throw of air into a room.

Why is limiting of window areas important in keeping heat loss low?

The R-value of windows is typically less than the R-value of the rest of the wall.

What is insolation?

The amount of solar radiation (all wavelengths) that strikes the earth.

How does the orientation of the windows in the building affect the heat gain?

The more south-facing windows, the greater the heat gain.

With respect to radiation heat transfer, select the correct definition of the term emissivity.

The ratio of radiant energy emitted by a surface and radiant energy emitted by a black body at the same temperature.

Multiple heating zones are often used for more even heating whereby each zone is controlled by its own individual thermostat.

True

The two basic types of heat transfer mediums on active solar systems are liquid and _____.

air

Testing has shown that in a modern home, indoor air should be exchanged with fresh outdoor air...

every two to three hours

Today, most residential cooling is supplied by a "_________" which consists of an outdoor condensing coil and compressor connected to an indoor evaporative coil with refrigerant tubing.

split system

The common term for cooling capacity is the _____. One of these is equal to 12,000 Btu.hr.

ton

Describe the psychometric variables.

x = dry bulb, y = humidity ratio, curve = relative humidity, increased temperature increases the amount of water that can be suspended in air

Select the items that are advantages of an electric heating system. Select all that apply.

-Low installation cost. -Individual room control. -Quiet operation. -Cleanliness. -No exposed heating units.

_______-room returns generally run more quietly and afford more privacy.

Multiple

Why must the number of occupants and the type of activity be considered in a heat gain calculation?

Occupants release sensible and latent heat to the conditioned space.

What is the one variable which affects the amount of heat given out by a finned-tube convector?

The amount of surface area of the finned tube.

In what ways does the surrounding air temperature affect the amount of body heat given off?

The greater the difference in temperature between the room and the body, the greater the heat transfer.

The outside design temperature is determined using weather records.

True

Although heat pumps cost a few hundred dollars more than a standard air conditioner, they can save money when used in ______ climates.

temperate

Which of the following statements are true regarding the natural processes by which body heat is transferred and the effect they have on comfort. Select all that apply.

-Activity level affects body heat. As activity increases, additional body heat is generated due to an increase in metabolic rate. This also includes shivering. -Clothing level affects body heat by providing insulation. Insulation slows heat transfer by radiation. -Clothing can also affect heat loss by convection. -The color of clothing can affect heat gain. -Drinking a cold liquid on a hot day is an effective method of cooling because of convection. -The body perspires to cool itself. Liquid is expressed onto the skin. The water molecules leave the skin (evaporate) and take thermal energy with them. This cools the body by convection. This is why you feel cooler when there is a breeze.

What is a warm-air furnace and what does it produce? Select all the truthful answers that apply.

-Appliance with an enclosed chamber where fuel is burned or electric resistance heating is used to heat air directly. -Operates by drawing air into a heat exchanger, where the air is warmed with a flame of gas or oil or with heated electric coils.

Select the answers that are common types of electric heat installations. Select all that apply.

-Baseboard -Resistance cable -Panels -Unit heaters

Select the following true statements regarding thermal comfort.

-Combined effects of environmental and individual factors. -Combination of temperature and humidity where people report comfort. -Seasonal relationship between indoor and outdoor temperatures. -Women, older people and people who live in southern climates prefer higher temperatures. -Suggested inside winter dry-bulb temperature -Inactive people require higher temperatures

Select the reason why over-sizing of cooling equipment is a problem.

-Could lead to short cycling. -Higher initial costs and higher operating costs. -Premature wear.

Select the items that are true statement regarding ice dams. Select all that apply.

-Created by melting snow -Can be avoided by venting the attic or space directly below the roof but above the conditioned space. -Develop in conditions when air in the attic space is at above-freezing temperature (if insulation is insufficient or warm building air enters the attic) -Melting snow or ice on the roof surface backs up at the roof overhang and seeps through the shingles into the roof, damaging materials.

Correctly identify the types of coatings and surfaces used on buildings that intentionally affect radiant heat transfer. Select all the true statements that apply.

-Dark colors absorb more sunlight than light colors because a large portion of the radiative energy of sunlight is in the visible light band. -Surface color is a poor indicator of the ability to absorb infrared radiation. -Selective surfaces/coatings (e.g., black chrome, black nickel, or black crystal) are specially designed surface coatings that have a high absorptivity and high emissivity for visible light and short wavelength infrared radiation, and a low absorptivity and low emissivity for long wavelength infrared radiation. -Unlike flat black painted surfaces, selective coatings can restrict long wavelength radiative evergy loss from surfaces at or near room temperature.

Identify methods used to improve indoor air quality.

-Eliminate the source of indoor air contamination -Provide more fresh air to the space -Maintain the HVAC system

Identify the methods of controlling moisture in a building. Select all the answers that apply.

-Eliminating water intrusion -Retarding vapor intrusion -Keep the air constantly circulating so there are no areas of stagnant air

What types of materials are currently most commonly used for forced air ducts? Select all that apply.

-Galvanized steel -Aluminum -Glass fiber molded duct board

What type of equipment may be used when both heating and air conditioning are required? Select the items that are used for both heating and cooling.

-Heat Pump -Ductwork -Thermostat

What factors determine where the supplies and returns are located?

-Heat load of each room. -Heat gain of each room. -Depends upon the climate. If heat is of prime importance, air returns should be located below a window. When cooling is of prime importance, registers should be located in ceilings and high on walls. -Depends on unit, size of space, type of unit, distance from combustion appliances and exhaust fans.

With respect to buildings, identify the factors and descriptions that contribute to heat loss in a building.

-Heat passing through a material in the building envelope. -Air leakage through the building envelope and the energy required to heat unconditioned air that has leaked into the structure. -The intentional introduction of outdoor air into the building or parts of the building with the intent to maintain or improve indoor air quality. -Convection of conditioned air to the outdoors and vice versa due to the opening of doors for human ingress and egress.

Select the effective methods in controlling the heat loss from a building. Select all the correct answers.

-In unfinished attic spaces, insulate between the ceiling joists to seal off the living spaces below. -In finished attic rooms with or without dormers, insulate between the studs of knee walls and exterior walls. -In finished attic rooms with or without dormers, insulate ceiling, leaving a cold spaces above the insulation. -In all exterior walls, insulate wall between living spaces and unheated garages or storage spaces. -At crawl spaces, insulate foundation walls above grade level. -Insulate foundation walls in heated basements. -Insulate floors above cold spaces, such as vented crawl spaces and unheated garages. -Insulate an portion of the floor in a room that is cantilevered beyond the exterior wall below. -Insulate slab floors built directly on the ground.

Select the accurate statement regarding operative temperature (in relation to comfort).

-It is based on an arbitrary set of indexes that combine into a single number. -It considers the effects of dry bulb temperature -It considers the effects of radiant temperature -It considers the effects of air motion -It is equal to the temperature at which a specified hypothetical environment would support the same heat loss from an unclothed reclining human body as teh actual environment.

Identify problems associated with building-related illness. Select all the answers that apply.

-Lack of fresh air. -Inadequately maintained or operated ventilation systems. --Disruption of air circulation -Poorly regulated temperature or humidity levels

What is a chiller and what does it produce? Select all the truthful answers that apply.

-Large piece of cooling equipment -Produces chilled water -Removes heat from a building -Extracts heat from water and rejects it to either outdoor air or water.

What are the advantages of a forced air system as compared to hot water? Select all that apply.

-Less expensive to install. -Easier to install than hot water. -Leaks in the systems do not cause immediate water damage.

Select the statements that are true about a building air barrier. Select all that apply.

-Placed on the exterior of the building sheathing -Effective in controlling moisture from airborne water vapor infiltration by obstructing much of the air movement into a building envelope. -Allows water vapor that does collect in the cavity to diffuse back through the barrier material. -They have microscopic pores, small enough to resist flow of liquid water and air molecules, but large enough to allow smaller vapor molecules to pass through the barrier material.

What is a rooftop unit? Select all the truthful answers that apply.

-RTU -Type of PTAC (Packaged Terminal Air Conditioning) -A type of mechanical equipment mounted on the roof of a building. -Mechanical equipment that can be so large, heavy and powerful they require special consideration by the architect, structural engineer, mechanical engineer and electrical engineer.

Why is supplementary heat often required in solar heating systems?

-Solar heating may not provide enough energy to adequately meet the needs of temperature or power. -Solar heating varies throughout the day and year. Solar gain may not be adequate at times due to cloud cover. -A solar system may be sufficient for most of the year but during very cold times off year it may not be able to keep the indoor air temperature at a desired level.

With respect to a heating load, select the true statement about a pick-up allowance?

-The capacity of the heating system may be increased by 10%- 20% to allow for future added loads or unexpected loads that may arise as space usage changes. -When HVAC systems are operated intermittently, the system must be capable of heating up the inside temperature, which has been allowed to coast to temperatures below comfort ranges. -The need for pick-up of heating generally occurs during the early morning hours when the inside-outside temperature difference is at its greatest.

Select the most correct and comprehensive statement regarding building science.

-The study of building dynamics -The functional relationships between a building's components, equipment, and systems -Intended to understand and prevent problems related to building design, construction, and operation.

What may solar energy be used for in a building?

-To heat the building air. -To cool the building air. -To heat the hot water. -To create electricity

What is sick building syndrome?

-Typical complaints from occupants include lethargy, headache, dizziness, nausea, eye irritation, nasal congestion, and inability to concentrate. -Sickness associated with people's presence in a building. -It is caused by poor design, maintenance, and operation of a building's ventilation system.

What can be done to ensure that the system will be as quiet as possible? Select all that apply.

-Use round fiber ducts because they have great acoustic properties. -Ensure that the furnace and metal ducts are connected with a flexible fire-resistant fabric. -Ensure all electrical conduits and pipes should have flexible connections to the furnace. -Maintain adequate distance between return air duct and the furnace. -Maintain adequate distance between return air grille and fans.

Describe the purpose of ventilating a building.

-Ventilate the air just below the roof to reduce interior heat gain in the summer and to help cool the roof to help it last longer. -Ventilate the air just below the roof so that you don't have ice dams in the winter. -Ventilate kitchen, bath and laundry room areas to decrease moisture and odor.

When is insulation around the ductwork recommended?

-When ductwork runs through enclosed unheated spaces. -When ductwork runs through areas exposed to outside temperatures. -When sound attenuation is required due to unwanted noise.

What is a thermal bridge in a building envelope assembly, and how does it affect heat loss in a building?

A penetration of the insulation layer by a highly conductive or non-insulating material (e.g., concrete or steel). Those areas of the building envelope assembly with high thermal conductivity will increase heat flow.

What is the function of a storage medium in the solar energy system?

Additional energy needs to be stored to meet demands when solar energy is unavailable or insufficient.

In a forced air heating system, a(n)... is a system of ducts that brings cold air back to the furnace from various rooms of the building

Air return

What is the piece of equipment with a tank where combustion heats the water to make hot water or steam?

Boiler

Which of the following items would not be a part of a gas furnace forced air perimeter heating system?

Boiler

Select the statement that most accurately describes how thermal insulation restricts the flow of heat.

By trapping gases in the insulation. This restricts flow of heat from travelling through the envelope because conduction does not happen as well through a gas.

Which of the following is (are) included in a package unit?

Compressor Blower Coils Heater

What is CLTD?

Cooling Load Temperature Difference (theoretical temperature difference)

Why is it important to have well-insulated construction when electric heat will be used?

Electric heat has a high cost of operation, so it is important for proper insulation to reduce the amount of heating necessary.

A voluntary labeling program called ______ Star offered marketing advantages to manufacturers while alerting consumers to what products could save them money in operating costs.

Energy

(BAH) The author recommends that you do which of the following.

Engage your HVAC subcontractor early in the design process. Make sure your design includes a central spot for the air-handling equipment Make sure there is plenty of room to run ducts.

Embodied energy is the sum of all energy used to _________ a product or material.

Extract Process Refine Fabricate Transport Install

It is sometimes desirable to have supplemental heat with a solar heating system because a solar heating system is always so expensive to install and maintain.

False

What is GLF?

Glass Load Factor. It accounts for the effects of solar radiation.

What effect does humidity have on the comfort of a body?

Higher humidity makes a person feel warmer.

Select the answer that best describes how a radiant hot water heating panel works.

Hot water is circulated through pipes located in the floor or ceiling of a building.

How can moisture problems associated with vapor diffusion be reduced?

In climates with cold winters, vapor diffusion retarder (VDR) on interior (warm) side of wall.

What is the purpose of putting dampers and vanes in the ductwork?

To better control the flow of air and regulate the amount of air going to each diffuser.

Effective temperature is an index to determine equivalent temperature sensation.

True

Heat is easily transferred through windows and chimneys and not easily through insulation

True

Heat loss is the amount of heat that a building or building space loses from heat transfer during cold weather. Heating load is the heat that the HVAC equipment must generate into the building to maintain comfortable conditions.

True

Humidity may be introduced to the forced air system when a humidifier is installed directly into the duct.

True

If radon levels in a building interior are recorded at 8 pCi/Lm, then the U.S. Environmental Protection Agency recommends that the house be fixed.

True

In Spokane, WA, there are hot summers and cold winters. Heating is a necessity and cooling is common.

True

Moisture problems associated with airborne water vapor infiltration can be reduced by sealing joints.

True

Returns can work either actively or passively

True

Typically, seasonal efficiency of the heating system is inversely proportional to heating costs? The higher the efficiency, the less heat is wasted and therefore the lower the cost.

True

When calculating infiltration heat gain, the formula includes the outside air temperature and the inside design temperature.

True

You don't need to provide extra humidity during winter months because improved air-sealing techniques preserve indoor humidity.

True

Selects the statements that are true about a horizontal furnace.

Used primarily for attic and crawl space applications A larger and more efficient unit is required to offset energy losses that come with placing your furnace in an unconditioned space.

How can moisture problems associated with water intrusion be reduced?

Vapor diffusion retarder (VDR) on exterior side of wall.

Why does bitumen-impregnated kraft paper work effectively as a vapor diffusion retarder?

Varying permeance, low under dry conditions, high when humid.

The _____ furnace costs more, but you can use one over a crawl space or where ducts run under the slab.

down-flow

With an inline damper, the damper is controlled by a dual outdoor thermostat and ______.

humidistat

Sealing up even small openings in a building conserves energy because...

it stops the infiltration of outside air or ex-filtration of comfortable conditioned inside air by way of convection currents

A _____ system has a spiderweb-like distribution network of supply ducts running straight from the furnace to each outlet. This provides a direct method of air delivery that maintains balanced pressure throughout the system.

radial

The study of psychometrics is the study of the thermodynamic properties of gas-water vapor mixtures under varying ______________.

temperatures and pressures

A manifold, found in many hydronic heating systems, is used only if...

the building has zoned heating