Electrical and Mechanical Components in HVAC: Key Concepts and Devices

What is the net charge when five electrons combine with three protons?

The net charge will be negative, as electrons have a negative charge and protons have a positive charge.

What device is attached to control ice build-up on a heat pump outdoor coil?

A diaphragm is attached to control ice build-up on a heat pump outdoor coil.

What is the easiest diagram to use to follow a circuit?

A ladder diagram is the easiest diagram to use to follow a circuit.

What is an example of a bimetal device?

An example of a bimetal device is a snap-disc.

Which overload device is not affected by ambient temperature?

A magnetic overload device is not affected by ambient temperature.

What happens to the magnetic field when a conductor carrying electrical current is formed into a coil?

The magnetic field around the wire will increase.

Why are explosion-proof motors not normally used on standard equipment?

They are too expensive.

What are modulating controls used for?

Modulating controls are used to vary the speed of the motor.

How is a capacitor safely discharged?

The recommended way to discharge a capacitor is to use a 20,000 ohm 5 watt resistor with insulated leads soldered to it.

What type of charge does an electron have?

An electron has a negative charge.

What is a slotted screw at the bottom of the bearing housing called?

It is called a purge screw.

What usually happens if a condenser fan motor grounds out?

It will usually trip a circuit breaker to shut off the unit.

What is the total capacitance acting on a CSCR motor when starting?

The total capacitance acting on the motor is 25 microfarads.

What happens when a connection becomes loose in wiring and connectors to a motor?

Oxidation occurs, which acts as electrical resistance and causes the connection to heat up.

How is the cold anticipator wired in a thermostat?

The cold anticipator is wired in series with the mercury bulb cooling contacts.

What device is used to check continuity through a heat relay?

An ohmmeter is used to check continuity through a heat relay.

What is the best method to repair a fractional horsepower motor with bad bearings?

The best method is to replace the bearings.

When is the heat anticipator in the thermostat control circuit active?

The heat anticipator is active when the heating contact is closed.

What type of device is a positive temperature coefficient resistor?

It is a type of switching device.

Why are grounding straps required on resilient mounted motors?

They are required to ground the motor in case of winding failure.

What is the total capacitance acting on a CSIR motor when running?

The total capacitance acting on the motor is 5 microfarads.

What does an open winding in an electric motor indicate?

It indicates that a wire in a winding is broken.

What happens to current draw if the voltage supplied to the motor is below the rated voltage?

The current draw will be higher than it should be.

What does the Bourdon tube do with an increase in vapor pressure?

The Bourdon tube tends to straighten out with an increase in vapor pressure.

How are transformers rated?

Transformers are rated using volt-amperes.

What is the recommended method to obtain an accurate reading of a fluid in a large pipe?

Use a permanently mounted thermometer in a well.

What type of sensing element do line voltage thermostats use?

Line voltage thermostats use bimetal sensing elements.

What type of motor should be used in a potentially wet area?

An explosion-proof motor should be used in a potentially wet area.

How is a direct-drive motor usually connected to a load?

A direct-drive motor is usually connected to a load with a coupling.

What does the term 'detent' refer to?

Detent refers to the slow motion of a contact to ensure good electrical contact.

What is an ampere?

An ampere is a measure of the quantity of electrons flowing past a point in an electrical circuit in a given time.

What are typical insulators?

Typical insulators include glass, rubber, and plastic.

What happens if the resistance of the run winding decreases?

The motor will draw too much current while it is running.

What is a control required to control space or product temperature called?

It is called a thermostat.

What starting device is usually used on single phase, fractional horsepower motors requiring low starting torque?

The starting device usually used is the centrifugal switch.

What is the difference between system overshoot and system lag called?

It is called temperature swing.

When should the alignment of a motor and the driven mechanism be done?

It should be done at room temperature and again after several days of operation.

What type of capacitor does a permanent split-capacitor motor have?

A permanent split-capacitor motor has a run capacitor only.

What is the voltage tolerance of a standard electric motor?

The voltage tolerance of a standard electric motor is +10%-10%.