Heating final

When testing for voltage across a switch located in a 120-volt circuit, what reading would be obtained if the switch we in the closed position?

0 volts

All AC equipment is designed to operate at voltages within what percent of its rated power?

10

When replacing motor capacitors technicians should be sure the new capacitor is rated within what percentage of the original?

10%

What is the maximum run for a #12 wire carrying 10 amps based on a voltage drop of 3% at 120 V?

109 feet

Line voltage thermostats are designed to switch circuits that operate on the line voltage supplied to the unit, such as

120 VAC or 240 VAC

When testing for voltage across a switch located in a 120-volt circuit, what reading would be obtained if the switch were in the open position?

120 volts

What is the maximum run for a #8 wire carrying 30 amps based on a voltage drop of 3% at 240 V?

182 feet

Low voltage thermostats operate on:

24 VAC and switch less than 2 amps.

HVACR equipment typically uses control voltage of:

24 volts AC

Hot Surface Ignition System (HSI) controls lockout after how many unsuccessful attempts?

3 or more attempts

Newer-style gun burners with special air-handling parts should be set in what range of CO2 percentage?

9 - 11%

What is the maximum level of the normal CO range?

9 ppm

When there is voltage at the primary side of a transformer and no voltage at the secondary, what could be the problem with the transformer?

A bad secondary or primary winding

What component uses magnetism for operation?

A motor

How do two-stage thermostats control modulation?

A two-stage thermostat operates at a higher capacity in the second stage of operation.

_________________ are available for integration in communicating control systems.

A) Zoning boards B) Humidifiers C) Air cleaners D) All of the above

When measuring voltage to a load, the voltmeter must:

Always be placed in parallel with the load.

The meter used to measure the electrical current in a circuitis the:

Ammeter

When measuring an open secondary winding of a transformer, what measurement will be obtained? end 34

An infinite resistance

When using a digital meter that has the capability of displaying the proper scale to be used, this is called:

Autoranging

The availability of "standard" communicating components and an open protocol means that more manufacturers can use communicating controls, opening the market up. This was demonstrated at the 1996 ASHRAE show in Atlanta, when multiple controllers from several major manufacturers were up and operating, all connected to the same _____________ system.

BACnet

How is the magnetic field intensified in an electrical circuit?

By adding more turns to the conductor

Communicating systems ______ communicate with devices and networks outside of the HVACR network.

Can

An electrical component that stores energy when an electric charge is forced onto its plates is called a:

Capacitor

Available ________________ controls include thermostats, furnace control boards, air-conditioning and heat pump control boards, and variable-speed brushless DC motors.

ClimateTalk

The system __________________ can communicate with each other and adjust system operation to match the heat load and operating conditions.

Components

Poor ____________________ are the most common cause of communication errors.

Connections

A relay that is designed to handle more than 15 amps of current is referred to as a: end 36

Contactor

This electrical component allows current to flow in only one direction, and operates similar to a check valve:

Diode

The first operation in testing a capacitor is to:

Discharge it.

Because motors draw four to five times their normal operating current when they start,:

Dual-element time-delay fuses must be used.

Communicating variable-refrigerant-velocity mini-split systems can save energy by matching the ___________ capacity to the demand.

Equipment

In most 24V AC low voltage systems the red wire is hot, the yellow wire is the cooling circuit, and the green wire controls:

Fan Circuit

Communicating systems record the system ___________ history, allowing service technicians to view the problems that have occurred in each of the system components. end 40

Fault

Flow switches open or close based on the movement of:

Fluid

What is known as magnetic lines of force?

Flux

Most residential communicating systems use _______ wires between all components.

Four

The increasing popularity of communicating systems lies in their ability to ________ overall system efficiency and comfort.

Improve

The _____________ popularity of communicating systems lies in their ability to _______ overall system efficiency and comfort by matching the system capacity to the heat load.

Increasing; improve

Which of the following statements accurately describes silicon carbide?

It is brittle and will break easily

What safety function does the limit switch perform?

It prevents the furnace from overheating.

What is the purpose of a flame-proving device in a system with a standing pilot?

It shuts off the gas flow in case the pilot goes out.

When current flows through the conductor in a solenoid coil, what happens to the iron core

It tries to center itself in the magnetic field.

This type of diagram provides the technician with the unit's sequence of operations:

Ladder

To view the Advanced Installer menu on Rheem and the Ruud Comfort Control System, press the _______________ simultaneously for three seconds.

Left and right

To access the Lennox Installer menu, press the ____________________ in the bottom right corner of the screen for five seconds.

Lennox logo

A technician looking for the 24V coil of a contactor in a schematic diagram would find it in which power section? end 38

Low voltage

The meter that is able to read in the tens of millions of ohms is called a:

Megohmeter

Run capacitors are normally encased in:

Metal

A capacitance meter measures in: end 35

Microfarads

Which of the following is true of the fan switch? end 50

Modern fan switches cycle the fan based on time.

AC induction motor speed is determined by the current frequency (HZ) and the number of:

Motor poles

The meter used to measure the electrical resistance in a circuit is the:

Ohmmeter

A control malfunction that results from a system heating or cooling past its setpoint is called:

Overshoot

The actual location of various components in the system and their point to point wiring is shown in this particular diagram:

Pictorial

Start capacitors are usually encased in:

Plastic

Wattmeters read true power in a circuit, and this power factor can be expressed by what equation?

Power = amps x voltage

A safety switch commonly used on air conditioning systems is the:

Pressure switch

A technician has installed a new 3 phase motor but it is running in reverse. What should she do to correct the rotation?

Reverse two motor power supply leads

A heat pump condenser contains this unique control device that switches the flow of refrigerant depending on heating or cooling mode: end 39

Reversing valve

In a gas furnace which control would shut off power to the gas valve in the event burner flame was detected outside the burner box?

Rollout switch

The two principal parts of an AC induction motor are the:

Rotor and stator

An electromagnet is produced by:

Running current through a coiled wire

In a communicating control system, the system components communicate over a __________ network.

Serial

This type of AC motor is characterized by low starting torque and is suitable for light applications such as refrigerator evap motors. end 37

Shaded pole

A heat pump defrost control must do three things: Turn on auxiliary heat, turn off the condensor fan motor, and:

Shift the reversing valve from heat to cool

If a schematic diagrams shows a clear path from L1 to L2, without passing through any load, then what condition exists in the circuit?

Short circuit

What is the first step a technician should take when changing out a capacitor?

Short the terminals with a screwdriver or bleed resistor

Why do solenoid type valves pose a problem for some types of burners?

Solenoids open and close too quickly

A step down transformer is designed to:

Take a higher voltage and decrease it to a lower voltage

A technician checks the coil of a relay with his ohmmeter, and the reading on the scale is infinity. This indicates what condition of the coil?

The coil is open

What is wired in a series with the thermostat?

The solenoid valve is in a series with the thermostat

What happens if a technician comes into contact with the spark-ignition circuit while it is energized?

The technician will experience great discomfort

What is the first step in the operational sequence?

The thermostat calls for heat.

If pulsed DC current is not present in the flame rod, what is the effect on the gas valve in a direct spark-ignition system?

The valve will remain closed.

This power distribution system provides reduced line current and smaller, more efficient motors.

Three phase

The point in an electrical circuit schematic where high voltage is stepped down to low voltage is at what component?

Transformer

This component uses the properties of AC induction to step up or step down voltage for particular HVAC applications:

Transformer

Fuses are rated for both amperage and:

Voltage

The meter used to measure the electrical pressure in a circuit is the:

Voltmeter

The meter used to measure electrical power in a circuit is the:

Wattmeter

When during troubleshooting should the wiring diagram be referenced?

after checking the thermostat

This test instrument reads current in an electrical circuit

ammeter

How are transformers in the HVACR field rated?

by secondary power output

A technician uses an ohmmeter to check resistance and for a complete path in the electrical circuit, also known as:

continuity

What must be used to test the output of the ignition transformer?

high-voltage probe

If the technician does not know the voltage range he will be reading, then he should set the meter at what range?

highest

Why might a technician need to install a larger transformer in a heating system?

if cooling is added to an existing furnace

A transformer uses this electrical principle to increase or reduce voltage with no moving parts or contacts.

induction

If a conductor is coiled as in a relay coil, then passing current through it will _____________the magnetic field.

intensify

Capacitance readers measure the capacitance in a circuit or in a start capacitor, and this is measured in what unit?

microfarads

Hot-surface ignition units

operate for only a few minutes per day.

Technicians should remember that AC power can be converted to DC power through use of components called:

rectifiers

Some furnaces use two automatic shutoffs that are mechanically in series to provide additional safety. What type of valves are these?

redundant valves

How might the unit become de-energized while troubleshooting a problem?

removing a door

Which type of burner has the highest common operating percentage of CO2?

rotary wall flame burner

How can the safety lockout be reset? end 52

setting the thermostat below room temperature

When the room-temperature setting is reached, what components are opened?

thermostat and gas valve circuits

Why does the draft switch close?

to prove the draft

What is used to clean the surfaces of the heat exchanger?

wire brush