HVAC review

Find the outside design temperature for Spokane, WA. This is the heating dry bulb for 99%.

7-13

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.

Identify the specified parts of the system below.

A return air intake B feeder ducts C perimeter ducts D register E concrete floor slab (refer MC30 q6)

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.

Define what constitutes a ton of refrigeration.

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

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

Boiler.

What is CLTD?

Cooling Load Temperature Difference (theoretical temperature difference)

Select the reason why oversizing 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 temperatuere (if insulation is insuffficient or warm building air enters the attic) Melting snow or ice on the roof sufrace backs up at the roof overhang and seeps through the shingles into the roof, damaging materials.

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

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 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.

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

Series loop

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.

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

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

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

The outside design temperature is determined using weather records.

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

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.

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.

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.

evaporator, condenser

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

it stops the infiltration of outside air or exfiltration of comfortable conditioned inside air by way of convection currents.

What methods may be used to dispose of the water from roofs, courtyards, and parking lots? Select all the answers that apply.

private storm sewer drywell community storm sewer creek, stream, lake, or pond

What methods are commonly used for roof drainage? Select all the answers that apply.

roof drains gutters downspouts or conductors

When the roof drainage water is run into roof drains or gutters, what solutions may be used to disperse the water at the end of the downspout?

splash block

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

temperatures and pressures

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

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.

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.

Select the items that correctly describe a two-pipe system, how it works and its advantages and disadvantages.

Appropriate for large installations. The supply of hot water is kept separate from water that has been cooled by passing through a convector. One pipe is used to supply the hot water, which then empties into another pipe used for return.

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.

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

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 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 factors determine where the supplies and returns are located? Select all the answers that apply.

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.

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

Heat loss through the building envelope (building assembly).

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.

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

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.

Under what conditions should a combined sewer be used?

It should be done only if no other solution is available and if the city allows storm lines to be tied into its sewage lines.

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 is infiltration heat loss, and where does it occur in a building? Select all the correct answers.

Leakage of heated air to the outside. Energy required to heat unheated air that leaks into the inside. Infiltration happens mostly around doors and windows.

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.

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.

Select all the types of material that are satifactory for ductwork in a warm air perimeter system.

Sheet metal. Vitrified tile. Concrete pipe Plastic pipe.

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

Smoke particles Dust Bacteria Fungus Mold spores Chemical vapors

What is a combined sewer?

Storm sewer added to sanitary sewer line.

What methods are commonly used for subsurface drainage? Select all the answers that apply.

Sump pump French drain Perimeter drain Interceptor drain

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 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.

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.

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.

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 Effects are associated with occupancy, operation, outdoor environment Intended to understand and prevent problems related to building design, construction, and operation.

Identify the true statement regarding the degree day and how it will affect the amount of fuel used each year.

The sum of the number of degrees that the outside air temperature is below 65 degrees for each day of the year. Higher degree day means more fuel used.

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

True

How can moisture problems associated with water intrusion be reduced?

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

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.

Refer to the illustration. Name the device represented by the drawing.

air exchanger (MC 30 q10)

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

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

every two to three hours

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

extract process refine fabricate transport install

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

the building has zone heating