HVAC ELECTRICAL MAIN TEST

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

0 Volts

in the schematic, what voltage would be found from terminal G to the load side of the transformer

0 Volts

In the schematic, What voltage would be found across the fuse in the line #10 with the thermostat closed?

0 volts

which of the following is equal to 100 milliamps?

0.10 Amperes

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

100 ohms

In the schematic, if the fuse in L2 is blown the:

Blower motor will continue to operate

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

0 Volts

How many Watts of power are used by a heater operating at 240 Volts and drawing 5 amps?

1200 watts

The synchronist speed of 4 Pole, 60 Hz single phase motor is;

1800 RPM

Which of the following is equal to 2.1 KW

2,100 Watts

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

208

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

24 Volts

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

240

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

240

Utility companies usually supply residential homes with ___________ service.

240V, single phase, three wire

Relay's 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

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

37.5MFD @ 440VAC

Which of the following is generally considered to be within the maximum allowable (plus or minus) supply voltage variation?

5%

A parallel circuit contains 18 ohms and a 9 ohms 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 = 10 ohms if the current through R2 = 4 amperes, what is the source voltage?

60 Volts

A transformer has a 1000 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

One horsepower is equal to ________________ Watts

746 Watts

An ohmmeter should never be connected to;

A charged capacitor until it has been discharged

Any material that will readily release electrons is called

A conductor

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

A faulty blower motor or blower relay

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.

When checking the windings of a 3 phase motor

All 3 terminals should show the same resistance

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

Blower Motor Relay

To change direction of rotation of a three phase motor;

Change the position of any two supply wires.

The starting device usually used on a single phase, fractional horsepower motors requiring low starting torque is the

Current Relay

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

Decrease

Resistance can be calculated by

E divided by I

Which of the following motors is most energy efficient

ECM ( Electronically Commutated Motors )

Which of the following would be considered an inductive load?

Electric Motor

A solenoid valve coil operates on the principal of;

Electromagnetism

Direct Digital Control (DDC) is

Electronic controls use for equipment operation and monitor

A typical thermocouple used on a gas furnace can;

Generate a small DC electrical current

With a motor running at full load, voltmeter leads are placed on L1. and T1 terminals of the contactor. The voltmeter indicates no measurable voltage. This is an indication of;

Good clean contacts

The safety ground conductor is usually color coded

Green and bare.

An Electron has

Has a negative charge

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

High starting and running torque.

The symbol for Current is

I

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

Increase

The total resistance of a parallel circuit will be;

Less than the smallest resistance

A device with overload protection used to control motor is a;

Line starter

What connects to the terminals T1, T2, & T3 on a contactor or motor starter?

Load connections

When testing a capacitor with an analog or digital ohmmeter, the meter should;

Measure low resistance then return to high reading

Capacitors are rated in?

Microfarards & Volts

Single phase motor speed is determined by the;

Number of stater Poles

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

Ohmmeter

Which of the following meters must use its internal power to check a load or circuit

Ohmmeter

what would be the result, if a 24 volts , 20-ohm low voltage contactor coil were wired in series with a 24 volt, 200-Ohm control relay coil?

Only the control relay would operate.

Impedance is?

Opposition to alternating currentflow.

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

Pictorial

A transducer can create a signal based on;

Pressure

An electronically commutated motor (ECM) is designed to ;

Provide proper air flow under various conditions.

Voltage can be calculated by

R divided by I

Like Charges?

Repel each other

If contacts become badly pitted, it is acceptable to;

Replace the contacts or control

On a good single-phase compressor motor, which winding terminals have the highest resistance?

Run to start.

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

Secondary side

Excessive current can be caused by;

Short circuit

Which of the following material would be best suited for use as a semiconductor?

Silicone

When troubleshooting the AC system in the schematic, the following conditions are found. The authorities that 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).

In the schematic, the coil on line #11 does not control

The blower motor

When testing the winnings 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

current flow is?

The flow of electrons in the circuit.

When resistors are wired in Parallel

The voltage drop across each resistor Will depend on the value of each resistor

A three phase load requires a minimum of;

Three supply lines

On an electronic oil safety switch what changes the pressure signal to electrical signal?

Transducer

Is True or False; Current flow will decrease when voltage increases

True

To discharge a capacitor prior to ohmmeter testing;

Use a 15,000 or 20,000 ohm, 2 to 5 watt resistor across the terminals

Transformers are rated according to

VA at the secondary

A step up transformer increases

Voltage

Fuses are sized by:

Volts & Amps

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

W = E x I

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

Wattage

In the schematic, the crank case heater will operate;

When the compressor is off.

Which of the following is the symbol for impedance in an AC circuit?

Z

When current flows in a 2 wire circuit (such as 120 Volts) if a clamp on amp meter is clamped around both wires. What measurement would you expect?

Zero amps due to cancelation of the two fields.

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

add up to equal the source voltage.

Contactors are rated according to the maximum amperage through the;

contacts

A diode is used to

control the direction of electron flow

When testing a motor with an ohmmeter, the following measurements are recorded, common to run 4 ohms, common to start 6.2 ohms, run to start 10.2 ohms, and common to ground 20.4; this indicates a/an;

grounded condition

Capacitors are always connected to the start winding

in series

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

The thermal overload contacts on A-line starter are usually _____________ reset

manual

Resistance is

opposition to current flow

Circuit breakers & fuses are primarily used to provide;

protection from an overload of current

A capacitor analyzer is designed to read;

the capacitance of a capacitor

In an electrical wiring, a black colored wire in an alternating current circuit usually indicates;

the hot conductor