HVAC Electrical Test

In the schematic, what voltage would be found across the condenser fan motor?

0 volts

In the schematic, what voltage would be found across the fuse in line #10?

0 volts

In the schematic, what voltage would be found from terminal Y to the input side of the coil on line #11

0 volts

In the schematic, what voltage would be found from terminal Y to the output side of the coil on line #11

0 volts

Which of the following is equal to 100 milliamps?

0.10 amperes

The synchronous speed of a four pole, 60 Hz single phase motor is;

1800 rpm

In the schematic, what voltage would be found from terminal R to terminal G on the thermostat?

24 volts

A transformer has 1,000 turns of wire in the primary coil and 2,000 turns in the secondary coil. If 120 volts are applied, the output voltage will be;

240 volts

which of the following is an acceptable temporary replacement for a run capacitor rated at 35MFD @ 440VAC;

37.5MFD @ 440VAC

What is generally considered to be the maximum allowable (plus or minus) supply voltage variation?

5%

A transformer has 1,000 turns of wire in the primary coil and 500 turns in the secondary coil. If 120 volts are applied, the output voltage will be;

60 volts

The symbol for a thermal overload is represented by diagram ______

A

The symbol for a transformer is represented by diagram ______

B

The symbol for a pressure switch is represented by diagram ______.

C

A _____________ is commonly used on a single phase fractional horse power compressor motor to disconnect the start winding after the motor starts

Current relay

Resistance can be calculated by

E divided by I (R = E/I)

Which of the following motors is most energy efficient?

ECM

A typical thermocouple used on a gas furncae can

Generate a smalll DC electrical current

the symbol for current is

I

A 240 volt, 3 wire circuit can be split into two 120 volt circuits.

TRUE

The terminals T1, T2, & T3 are located at the _______ of a contactor.

Top

Transformers are rated according to;

VA at the secondary

Any material that will readily release electrons is called

a conductor

An ohmmeter should never be connected to

a live circuit

When checking the windings of a three phase motor;

all three terminals should show the same resistance

To change direction of rotation of a three phase motor;

change the position of any two supply wires

When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance will;

decrease

Which of the following would be considered an inductive load?

electric motor

The capacitor start-capacitor run (CSCR) motor provides;

high starting and running torque

Capacitors are always connected __________ to the start winding

in series

When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance will;

increase

If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called;

inductive reactance

Single phase motor speed is determined by the;

number of stator poles

What type of meter uses its own battery?

ohmmeter

If contacts become badly pitted, it is acceptable to;

replace the contacts or control

Excessive can be caused by;

short circuit

Which of the following materials would best be suited for use as a semi-conductor

silicone

Current flow is

the flow of electrons in the circuit

in electrical wiring a black colored wire usually indicates

the hot conductor

A three phase load requires a minimum of;

three supply lines

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. When the fan switch at the thermostat is moved from the AUTO position to the FAN ON position, the blower runs. This could be caused by;

A faulty thermostat - AUTO/FAN ON switch

In a series circuit, the voltage drop across each resistance (load) will;

Add up to equal the source voltage

Two 120 volt incandescent light bulbs are wired in series, one is a 60 watt bulb, the other is a 4 watt bulb. The result would be;

Both bulbs light

Which of the following statements about current is true?

Current flow will increase when voltage increases.

A solenoid valve coil operates on the principle of;

Electromagnetism

The total resistance of a parallel circuit will be;

Less than the smallest resistance

Which of the following is the correct formula for determining wattage in an electrical circuit?

W = E times I (or V x I)

In the schematic, in the fuse in L2 is blown the;

blower motor will continue to operate

Which of the following is NOT a factor in determining impedance in an AC circuit?

frequency

A device with over load protection used to control a motor is a;

line starter

Circuit fuses and breakers are primarily used to protect;

loads

when current flows, a ______________ is produced around the conductor.

magnetic field

The thermal overload contacts on a line starter are usually __________ reset.

manual

A transducer can create a signal based on;

pressure

In the schematic, the coil on line #11 does NOT control;

the blower motor

A capacitor analyzer is designed to read;

the capacitance of a capacitor

To discharge a capacitor prior to ohmmeter testing;

use a 20,000 ohm, 2 to 5 watt resistor across the terminals.

A step up transformer increases;

voltage

The 300 ohm resistors are wired in parallel. The total resistance equals;

100 ohms

Which of the following is equal to 2.1KW?

2,100 Watts

The voltage to ground of a "high leg" on a three phase open Delta system will be approximately;

208

How many watts of power are used by a heater operating at 460 volts and drawing 5 amps?

2300 watts

In the schematic, what voltage would be found across L1 to L2?

240 volts

In the schematic, what voltage would be found across the contacts in line #8?

240 volts

In the schematic, what voltage would be found across the transformer primary?

240 volts

Utility companies usually supply residential homes with ___________ service.

240V, single phase, three wire

Relays are generally used to control inductive loads up to ______ amps.

25

Three defrost heaters; each 15 ohms are wired in parallel to a 120 volt power supply. How many watts of power will be used?

2880 watts

What is the minimum number of wires required between two Start/Stop push button controls?

3

A parallel circuit contains a 18 ohm and 9 ohm resistor. The total resistance equals;

6 ohms

How much resistance must be placed in a 120 volt circuit in order to limit the current to 2 amps?

60 ohms

A parallel circuit consists of three resistors R1=30 ohms R2=15 ohms R3=10ohms if the current through R2=4 amperes, what is the source voltage?

60 volts

One horsepower is equal to how many watts?

746 Watts

A diode is used to;

Control the direction of electron flow.

Voltage can be calculated by

I times R

Capacitors are rated in:

Microfarads & Volts

What is the term used to describe the output side of a transformer?

Secondary side

Technician #1 says that an OPEN transformer coil is indicated by a reading of infinity on an analog ohmmeter. Technician #2 says that a SHORTED transformer coil is indicated by a reading of infinity on an analog ohmmeter.

Technician #2 only

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan are not running. The blower motor is running. This could be caused by;

The HP, LP, overloads, or oil pressure switch are open (line #11).

When resistors are wired in parallel;

The voltage drop across each resistor will be the same as the applied source voltage.

Fuses are sized by

Volts & Amps

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. This could be caused by;

a faulty blower motor or blower relay.

when testing a motor with an ohmmeter, the run winding shows 1,000 ohms to the motor frame. This indicates;

a grounded condition

An electron has

a negative charge

the safety ground conductor is usually color coded

black (or bare or green & yellow stripe)

In the schematic the coil on line #12 controls the;

blower motor relay

Contactors are rated according to the maximum amperage through the;

contacts

When testing a capacitor with an analog ohmmeter, the needle on the meter should;

deflect towards zero then return to infinite reading.

with a motor running at full load, voltmeter leads are placed on L! and T1 terminals of the contactor. The voltmeter indicates no measurable voltage. This is an indication of;

good clean contacts

which meter is used to bench check a motor for shorts or open windings?

ohmmeter

impedance is

opposition to alternating current flow

resistance is

opposition to current flow

The __________ drawing illustrates where the components are located in small appliances.

pictoral

An electronically commutated motor (ECM) is Designed to

provide proper air flow under various conditions.

like charges

repel each other

In a single phase motor, which winding has the most resistance?

start

When testing the windings of a single phase motor,

the common to run terminals show the lowest resistance

Direction of rotation of a single phase induction motor is determined by;

the direction of current flow through the start winding.

The electric meter on a house measures the _______ passing through it.

wattage

In the schematic, the crank case heater will operate;

when the compressors is off