HVAC MT 2 Ch. 36, 37, 39

To reduce or eliminate electrical arcing in an electrical control, use a ___

long bimetal strip coiled tightly, magnets to pull in electrical contacts, and a mercury switch

Miscellaneous heat loads include heat from:

the sun, appliances, lights and building's occupants

Heat loss or gain due to infiltration and exfiltration is dependent on: a. The tightness of a building's construction b. The amount of wall are exposed to outdoor conditions c. The temperature difference between the indoor and outdoor air d. All of the Above

d. All of the above

The release of dissolved gasses from water in a hydronic system is known as ___

Deaeration

In a forced-air zoned system, a ___ opens when temperature right above the evaporator coil drops to around 33degF

Freezestat

Line-voltage thermostats typically operate at ___

120 or 240 VAC

Low-voltage thermostats typically operate at ___

24-30 VAC

When outdoor air is low in temperature and humidity, a forced-air system can provide free cooling by using the following components ___

A barometric damper for exhaust air, duct dampers, and indoor blower

The basic components of a hydronic system include:

A boiler, circ pump, expansion tank, terminal units, and air removal components

Total heat load is calculated by ___

Adding together the individual heat loads

In a zoned hydronic system, each zone has its own ___ a. Room thermostat b. Terminal units c. Zone valve d. All of the above

All of the above

The purpose of an expansion tank is to ___ a. Provide space for water to expand as the system heats up b. Return water to the system as the system cools down c. Maintain a stable system pressure under varying conditions d. All of the Above

All of the above

The rate at which heat is transferred through a wall by conduction is dependent on the materials the wall is made of, the area of the wall, and: a. The pressure on each side of the wall b. The volume of the space enclosed by the wall c. The temperature difference between sides of the wall d. All of the above

All of the above

Why is a reverse return hydronic system the design that is the easiest to balance?

All supply and return branches are approximately the same length

To prevent indoor temperature from moving too far from set point, thermostats use ___

Anticipators

An ___ maintains proper water temperature in the boiler, while a room thermostat controls the temperature in the conditioned space

Aquastat

Which type oh hydronic system valve helps to distribute heat equally throughout the system?

Balancing valve

A common temperature-sensing component that reacts to temperature change by changing shape to actuate a reed switch or mercury switch is a ___

Bimetal strip

Venting problems affect ___ and may cause the system's rollout switch or blocked-vent switch to shut down the boiler

Boiler combustion

Combined heating and cooling hydronic systems have both ___ and ___

Boilers, chillers

In a forced-air zone system, what device operates to regulate airflow and compensate for when one of several zone dampers closes?

Bypass damper

A material's thermal conductance, ___, is similar to K-value but NOT dependent on the thickness of the material

C-Value

After speaking with the customer, begin a service call for troubleshooting a forced-air zoned system by ___

Checking overall airflow in the different zones

Boiler heat exchanges are typically made out of ___

Cast iron, steel or copper

When taking measurements on an energized circuit for low-voltage thermostat diagnostics, a 0V reading indicates ___

Closed switch

The devices used by mechanical cooling thermostats to turn off early enough to prevent system overshoot or temperature below the thermostat set point are called ___

Cooling anticipators

People, lights, and appliances all release heat into a conditioned space. In the case of people and animals, both sensible and latent heat are released. These miscellaneous heat loads must be included in ___

Cooling load calculations

The heat added by the sun load must be included in calculating ___, but is NOT included in calculating ___

Cooling load, heating load

Impurities in boiler water can cause ___ in a hydronic system

Corrosion and embrittlement

Which of the following types of water treatment forms a protective coating on the surfaces of a hydronic system?

Corrosion inhibiters

When installing a thermostat's subbase, some system setting may need to be managed using ___ switches

DIP

In a forced-air system, zone controls prominently use ___ to regulate the temperatures of the different zones

Duct dampers

Most hydronic system problems fall into one of three categories:

Electrical, venting, or water circulation

The relative ability of a surface to allow light rays to pass through describes ___

Emissivity

___ refers to air leaving a building through gaps in the construction

Exfiltration

Because a vented crawl space is exposed to outdoor air, heat loss through a floor over a crawl space is calculated the same that of an ___

Exterior wall

Which type of hydronic system valve prevents hot water from migrating to higher points in the system when the circulating pumps quits operating?

Flow control valves

A ___ shuts down the system or bypasses part of it when there is inadequate water circulation

Flow switch

A ___ hydronic system has separate supply and return pipes for hot and cold water

Four-pipe

___ is the use of an air-side economizer

Free cooling

Which of the following heat loads is not considered when calculating heating loads for a building?

Heat from appliances and occupants

In the summer, heat from outdoors entering a building is referred to as ___

Heat gain

___ refers to the time it takes for heat to be conducted through a substance. Because of ___, a wall that is heated by the sun can I continue to release heat into the conditioned 1 space after the sun has gone down

Heat lag

___ refers to heat conducted through walls, ceilings, and floors due to a temperature difference between indoor and outdoor air

Heat leakage

A combination thermostat is used to control a ___

Heating and cooling system

The devices used by mechanical heating thermostats to turn on early enough to prevent temperature from dropping below its cut-in set point are called ___

Heating anticipators

All boilers have a ___

High limit control that automatically shuts off the fuel supply if the water temperature or pressure gets too high

___ use conditioned water or steam to distribute heat

Hydronic systems

For heating load calculation, heat transfer through basement walls is only considered if the basement ___

IS used as a living space

___ have numerous features and options, including various power sources, different temperature-sensing and switching devices, display options and internet/ mobile device communication capabilities

Modern thermostats

Which hydronic system control monitors the cycle time required to satisfy a call for heat?

Indoor reset control

Adding weather-stripping to all doors and windows, using building wrap and plenty of insulation during construction, and using a fresh air intake for positive pressure in a building are effective methods or reducing ___

Infiltration

___ refers to outdoor air entering a building through gaps in the construction

Infiltration

Which of the following best describes the function of an air vent in a steam heating system?

It allows air to exit the system, but prevents steam from exiting

A material's ___ indicated how much heat will transfer through 1Ft^2 of the material 1" thick in 1hr when there is a 1degF temperature difference between the two sides of the material.

K-value

Which of the following are NOT an advantages of hydronic heating systems compared to forced-air heating systems? a. Do not introduce dust or allergens into the conditioned space b. Greater efficiency of heat transfer, and c. Less sensitive to neglect and require less maintenance d. Provide a more consistent temperature level

Less sensitive to neglect and require less maintenance

A ___ automatically shuts down a boiler if the water level gets too low

Low-water cutoff

If a hydronic system is operating with a reduced water level, the ___ may open the makeup water valve to add water to the system

Low-water cutoff

Most local building codes require that heat loads for residential buildings be performed in compliance with the ACCA ___

Manual J

Most local building codes require that heat loads for commercial buildings be performed in compliance with the ACCA ___

Manual N

A programmable thermostat uses a ___ that functions as a clock and controls indoor climate for different blocks of time

Microprocessor

A ___ can control the heating or cooling capacity of a system

Multistage thermostat

Which of the following heat loads would be considered only when cooling loads are being calculated? a. heat transferred by conduction through walls, doors, and windows b. Heat transferred due to infiltration and exfiltration c. Sun load d. None of the above

None of the above

A good location where a thermostat should be installed is ___

On an inner wall

A ___ hydronic system is similar to a series loop system, except that its terminal units are on branch circuits, called secondary loops

One-pipe

Radiant hydronic systems use ___ directly in contact with a floor, wall, or panel to heat a conditioned space. The water circulating through the tubing warms the surfaces adjacent to it by conduction

Plastic or composite tubing

Tapping into a fan, cooling, or heating terminal and drawing a small milliamp current to recharge its internal battery is a feature of a ___ thermostat

Power-stealing

Once the system is operating, balance the system by using a ___ to measure the rate of water flow through each balancing valve

Pressure guage

A material's ___ is a measure of its thermal resistance. The higher the material's ___, the slower heat will transfer through the material

R-Value

Which of the following statements about radiant hydronic systems is NOT true? a. They typically use PEX, other plastics, or composite material for tubing b. System tubing is completely enclosed in walls or floors c. Radiant hydronic systems typically circulate water at a cooler temperature than hot-water hydronic systems do d. Radiant hydronic systems typically use radiators as terminal units

Radiant hydronic systems typically use radiators as terminal units

Which of the following statements about terminal units is NOT true? a. Fan convectors can extract heat from lower-temperature water than a radiator can b. Radiators are available in baseboard, column and panel styles c. Radiators can be used as terminal units in both steam and hot0water hydronic systems. d. Radiators provide the majority of their heating through a radiation rather than through convention.

Radiators provide the majority of their heating through a radiation rather than through convention.

Low-voltage thermostats often use ___ to operate switch and control high current, line-voltage devices, such as fans and compressors

Relays

Air vents are designed to ___ from a hydronic system

Release free air

Regarding heat loss due to infiltration, only ___ is considered for calculating heating loads

Sensible heat loss

When pressure from airflow is reduced, most barometric dampers close due to ___

Spring tension

Millivolt thermostats can be used to control ___ systems

Standing-pilot light heating

Which of the following statements comparing steam and hot-water hydronic systems is NOT true? a. Hot-water systems are more efficient than steam systems b. Hot-water systems are now more commonly used than steam systems c. Hot-water systems can adjust water temperature to meet heating demands, which is not possible with steam systems d. Steam systems can be more easily modified to provide chilled water for cooling

Steam systems can be more easily modified to provide chilled water for cooling

A two-pipe steam heating system has ___ that allow condensed water to return to the boiler, but prevent steam from passing

Steam traps

Electrical problems commonly affect ___

System controls

A condition in which a furnace turns on but the temperature of a room drops too low before the heating effects is felt is called ___

System lag

What is the conditioned called in which the residual heat blown through the ductwork raises the temperature of the conditioned space above the thermostat set point after a heating thermostat has shut off a furnace?

System overshoot

The total difference of the high and low temperature in a room, including values below the cut-in temperature and above the cut-off temperatures is called ___

Temperature swing

The ___ of a building component is a measure of its thermal transmittance

U-Value

Which of the following accounts for the insulating effect of boundary air films?

U-value

When taking measurements on an energized circuit for low-voltage thermostat diagnostics, set a multimeter to the ___

Vac

To calculate the amperage load that a low-voltage thermostat's step-down transformer can handle, perform the following calculation ___

Volt-amperes+volt (secondary side)

A building's heat load include heat transferred through ___

Walls, ceilings, floors and windows

Heat loss due to construction of a concrete slab on grade is calculated based on ___

The perimeter of the slab

The temperature-sensing component that reacts to temperature change by changing its electrical resistance is a ___

Thermistor

Common temperature-sensing devices used in thermostats include ___ and ___

Thermistors and bimetal coils

A millivolt thermostat generates its own electric current from heat applied to its ___

Thermocouple

A sensing device that reacts to temperature change is a ___

Thermostat

Underfloor radiant heating systems can be classified as ___, depending on the installation and use of concrete

Wet or dry

Being able to adjust conditioned space temperature remotely using a tablet PC, smartphone, or laptop is specifically an advantage of a ___ thermostat

Wireless

What is the reason that conventional boilers operate with water temperature above 140degF?

To prevent combustion gases from condensing

The term "heat loss" refers to a ___

Transfer of heat from inside a building to outside a building

In ___ systems, the boiler and chiller use the same pipes to supply water to the terminal units

Two-pipe

Which of the following hydronic system designs provides the most consistent heat at the terminal units?

Two-pipe

A gas furnace with a multistage thermostat uses a ___ to control its heat capacity

Two-stage or modulating valve

___ are designed to heat or cool different areas of a building to different comfort, humidity and ventilation standards

Zoned systems