HVAC 140 FINAL REVIEW

What is the most common source of the electric energy used in the electric circuits of a heating, cooling, or refrigeration system?

Alternating current power supply.

What are the loads in the commercial freezer?

Compressor, condenser fan motor, evaporator fan motor, defrost heater, and defrost timer motor

What are the electrical components of a walk-in cooler?

Evaporator fan motor, compressor, condenser fan motor, electrical controls

A packaged air-conditioning unit is manufactured in one piece with all components including the thermostat.

False

A solenoid is not considered to be a load because it consumes very little electricity.

False

If the control system is set for heating and the temperature in the structure drops below the set point, the first stage of the heating thermostat opens.

False

Normally open contacts open and normally closed contacts close when the relay or contactor is energized.

False

The parallel circuit has only one path for the electron flow.

False

The schematic wiring diagram uses photos to represent electrical components in the system.

False

The total current draw of the entire parallel circuit can not be determined.

False

The voltage in a series circuit is the same for each device.

False

Thermal overload devices operate by magnetism.

False

__________ are loads found in many systems and wiring diagrams that take electric energy and convert it to heat.

Heaters

List the electrical components of a dehumidifier

Humidistat, compressor, fan motor

What is the function of a transformer?

Increase or decrease incoming voltage to a desired voltage.

How does a pressure switch's purpose affect its operation?

It determines whether it opens or closes on a rise or fall in pressure.

Why is a circuit-by-circuit arrangement used on schematic diagrams?

It is easier to focus on one small section of the diagram rather than the entire diagram.

__________ are electrical devices that consume electricity to do useful work.

Loads

What is the most important part of a heating, cooling, or refrigeration system? Why?

Loads because they do the work in the system.

What is the formal for finding the total resistance of a parallel circuit with two resistances?

Rt=(R1xR2)/(R1+R2)

What is the formula for finding the total resistance in a series circuit?

Rt=R1+R2+R3...

Why are thermostats said to be mechanically operated?

The temperature sensing element moves a set of contacts by a mechanical linkage.

How are the electrical loads that require electrical power for operation usually connected? Why?

They are connected in parallel because it allows them to receive full supply voltage.

How are the switches on electrical circuits that control parallel loads connected? If the switch opens, what happens to the circuit?

They are connected in series and the circuit would break

What is the purpose of a humidistat?

To open and close a switch in reference to a set humidity.

What is the purpose of a signal light?

To show a piece of equipment that is operating or operating at an unsafe condition.

A heat pump is an air-conditioning system that uses a reversing valve to reverse the refrigeration cycle in order to provide heating.

True

A parallel circuit is designed to supply more than one load in the system.

True

A series circuit is usually used for devices that are connected in the circuit for safety or control.

True

All electric circuits must have a complete path for electrons to flow through, a source of electrons, and some electric device (load) that requires electric energy for its operation.

True

An electric circuit is the complete path of an electric current, along with any necessary elements such as a power source and a load.

True

An electric circuit is the complete path of an electric current, along with necessary elements, such as a power source and a load.

True

Loads are devices such as motors, solenoids, resistance heaters, and other current-consuming devices.

True

Motors are used in the industry to rotate devices such as compressors, condenser fan motors, pumps, and other devices that require rotating movement.

True

The current draw in a parallel circuit is determined for each part of the circuit, depending on the resistance of that portion of the circuit.

True

The electrical source refers to the electrical energy being supplied to equipment.

True

The most common device supplied with energy is an electric motor.

True

The schematic diagram is the most useful and easiest to follow of any electric diagram.

True

The schematic diagram resembles a ladder in that it is made up of two vertical lines representing the incoming electrical sources.

True

The term normally refers to the position of a set of contacts when the device is de-energized.

True

The efficiency of a heat pump decreases as the outdoor temperature drops, and at a certain point, called the __________, the heat pump can no longer supply enough heat to properly condition the structure.

balance point

When an electric circuit is complete so that the current can flow, it is termed ____________.

closed

The ________________ is the section of the furnace that encloses the gas flame.

combustion chamber

A(n) ________________ is a refrigeration system that is designed to maintain a temperature lower than 32*F in the refrigerated case.

commercial freezer

A(n) _____________ is an electric circuit that controls some major load in the system.

control circuit

The _____________ is a cycle of operation of a heat pump that is designed to defrost the outside coil during the heating operation.

defrost cycle

A(n) _____________ takes the humidity out of air in a specific area.

dehumidifier

The _______________, used to help the installation electrician to ire the unit properly, give specific information about terminals, wire sizes, color coding, and breaker or fuse sizes.

installation diagram

A(n) _____________ system is a control system that is operated by less voltage than that applied to the equipment.

low voltage control

A(n) _______________ is the same type of device as a contactor in terms of the ampere rating of the device, but is has a means of overload protection in it.

magnetic starter

A(n) ___________ is an electrical device that consumes electric energy to rotate a device in an electric system.

motor

When the path of the current flow is interrupted, the circuit is termed __________ or broker.

open

The _______________, also referred to as a label or line diagram, is intended to show the actual internal wiring of the unit.

pictorial diagram

The _________ diagram not only identifies the electrical components that re in the unit, but also illustrates how the unit works and electrical connections that need to be made.

schematic

The ____________ circuit allows only one path of current flow through the circuit.

series

A(n) _______________ circuit is a combination circuit made up of series and parallel circuits and is used only sparingly in the industry.

series parallel

The _____________ of a control is the point at which the contacts open or close, depending on the function of the control.

set point

A(n) ______________ is a light that is illuminated to denote a certain condition in a system.

signal light

The _________ is a device that creates a magnetic field when energized and causes some action to an electric component such as a relay or valve.

solenoid

A(n) _____________ is a refrigerated area that is conditioned by a mechanical refrigeration system.

walk in cooler