AC/Core NATE Certification

What type of copper are spring type tubing benders used on?

Soft Copper Tubing

What is the purpose of applying flux to copper tubing when silver soldering?

To keep the copper clean during the soldering process

Which of the following torches operate at a higher temperature oxy-acetylene or air-acetylene?

Oxy-acetylene

What type of process is combustion?

Chemical

When leak testing an AC system the system may be pressurized with ___________

Nitrogen

Refrigerant boils in the ____________ in an AC system

Evaporator

Name the basic components in a split system air conditioner

Condensing unit (compressor & condenser)

Line set

A-coil (evaporator)

Air handler

Ductwork

What component is used to store liquid refrigerant that is located after the condenser?

Receiver

What type of metering device maintains a constant superheat?

TXV

Where must the TXV sensing bulb be located on a 1" suction line?

At the 4 O'clock or 8 O'clock position

What system component is used to raise the RH of a home?

Humidifier

During winter months the humidifier bypass damper must be (open or closed)?

Open

How will a dirty air filter affect the temperature drop across an evaporator?

It will increase it

What does SEER stand for?

Seasonal Energy Efficiency Ratio

What is a common size for a drain line that connects to the evaporator coil of an AC system?

3/4” PVC

Name three factors that should be taken into consideration when installing a condensing unit at a residence

Clearance

Standing ground water

Roof overhangs

What type of system is easier to install a split system AC or a package system AC?

A package system AC

Why are rooftop package units sometimes installed on an elevated frame?

To keep above minimum snow levels

A ceiling that slopes upward from the walls is considered a

Cathedral or vaulted ceiling

What type of construction uses flooring over a crawl space?

Pier and beam

Name all the factors that contribute to the total comfort of a building

Temperature

Humidity

Air cleanliness

Air motion

When a homeowner talks about comfort they
commonly refer to the homes _____________
temperature

Dry Bulb

What component will increase a home's IAQ?

An EAC or filtration system

Refrigerant cylinders must never exceed
____________

125 F

Shipping and labeling refrigerant tanks is the
authority of __________

DOT

What oil is most commonly used with R-22?

Alkylbenzene

Why must refrigerants never be used in
an unconfined space without ventilation?

A leak can cause suffocation

What problems could inhaling refrigerants cause?

Heart irregularities and unconsciousness

What does a differential pressure gauge measure?

Air pressure within a duct system

What does a sling psychrometer measure?

Dry-bulb Temperature

Wet-bulb Temperature

Relative Humidity

What types of thermometers are used in a sling
psychrometer?

Very accurate mercury or alcohol filled thermometers

What type of thermometer uses a cloth wick
on its sensing element?

A wet-bulb thermometer

Electronic leak detectors are accurate up to a
___ per year

½ oz

What is the purpose for the adjusting knob
located on an electronic leak detector?

It is used for calibration

List all the uses of a manifold gauge set

Measures suction and discharge pressures

Recovers refrigerant

Pressurizes system for leak testing

Charge system

Evacuate system

Add oil

What is the purpose for changing oil in a
vacuum pump?

The oil becomes contaminated with acids
and moisture and the vacuum capability
decreases

What type of maintenance is required
for hand tools?

Clean and wipe them regularly

What is an acceptable use for a
screwdriver?

Use a screwdriver for the specific screw type that it was designed for

How many CFM of air is required over a 3 ton
evaporator coil on an AC system?

400 CFM/ton x 3 Ton = 1200 CFM

To properly remove air an moisture from an AC system
the system must be evacuated down to
_____________ microns

500

What measurements must be known to calculate a
systems superheat?

Suction pressure (low side) converted to temperature and suction line temperature

What method must be used to properly
charge a TXV air conditioning system?

The subcool method

What is the definition of superheat?

To raise the temperature of a gas above its
boiling point

What is the definition of subcool?

Lowering the temperature of a liquid below its condensing point

At what AC component is superheat
measured?

Evaporator

When adding refrigerant to an AC system
what happens to the subcool measurement?

Increases

What is the affect of an excessive heat load
on superheat?

Increases

An AC system is pre-charged for a 25-foot line set
(3/8" L and 3/4" S) with 4 lbs and 12 oz of R-22. A
35' line set is required for the installation.
Specifications show that .5 oz is needed for every 1
ft of additional liquid line. What should be the total
charge of the system after the installation is
complete?

4lbs. 12 oz. = (16 oz. / 1lbs x 4lbs.) + 12oz. = 76
oz. + 5 oz. = 81 oz

What is a GFI receptacle?

A receptacle that protects against electrical
shock which could be caused by defective
electrical components.

How is voltage induced into a coil of wire?

Move the coil of wire through a magnetic field

State Ohm's Law

I=E/R

When comparing an electrical system to a to a fluid system.

Pressure is the same as ____________

Voltage

When comparing an electrical system to a to a fluid system.

Fluid flow is the same as ____________

Current

What are lines of flux?

An invisible magnetic field that is produced by
magnetism

Name 4 basic components in an electrical circuit

Source - Power supply

Path - Wire or switches for electron flow

Load - Current consuming device

Switch - Control of electrons

T or F - The same current that leaves a power supply flows through the electrical circuit

True

What is the purpose of a diode?

It allows current to flow in one direction, like a check valve.

States Watts Law

P=EI or P=EI(Pf)

What is the wattage of a 115 V motor drawing 8 amps with a Pf of .85?

115 V x 8 amps x .85 Pf = 782 W

T or F Current flow through three parallel electric loads in the same circuit are additive

True

What is the most common voltage supplied to a
residential split system AC?

230 V Single Phase

What rating is used to size a condensing units
fuses?

The minimum circuit ampacity located on the
nameplate

What is the voltage range of an AC motor?

+ or - 10% of the motors power source

What is minimum and maximum operating
voltage of a 230 volt AC motor?

207-253 V

What determines the speed of a belt drive
blower?

The ratio between the motor and blower
pulley

Which motor would have a higher RPM a 2-
pole, 4-pole, or 6-pole motor?

A 2-pole motor

Which motor has the highest starting torque,
a Shaded pole, a PSC or a CS?

CS motor

How are the speeds of a multi-speed motor
changed?

By changing the electrical speed taps

A CSR motor has a run and a start
capacitor wired in (series or parallel) with
the start winding?

Series

A motor that is above 5-hp is commonly
a ________ type of motor

Three-phase motor using 208/230 or
460/480 Volts

Capacitor start motors are generally
required when an AC system uses a
_________ type of metering device

TXV type

Which motor will handle a higher load,
one that uses ball bearings, sleeve
bearings or bushings?

One that uses ball bearings

What is the maximum amperage of a 24 V 40 VA
transformer?

1.7 Amps

Name two ways to control the capacity in an AC
system

Multiple Compressors and 2-speed Compressors

During low ambient conditions what affect will
slowing or stopping the condenser fan have on
high side pressure?

Increase

When using a heating and cooling thermostat
that uses the 24-V power supply for its display
light what terminal must be added to the T-
stat?

C - Common

The cooling anticipator is wired in
_____________ with the thermostats switch
contacts to prevent system ____________

Parallel, Lag

What is the purpose of an outdoor thermostat
that is used on an electric furnace?

It energizes additional strip heaters during low
ambient conditions

Why is it important to install outdoor ambient
thermostats out of direct sunlight?

It will give the T-stat a false reading

What is the purpose of a high-pressure
control and where is it connected on an AC
system?

It shuts the compressor down if the
compressor discharge pressure is too high
and it is connected on the discharge line

What are three considerations that must be
taken when replacing a contactor of relay?

Coil voltage

Contact amperage rating

Switch configuration

What control operates the blower motor and
electric heating elements on an electric
furnace?

Sequencer

If a cooling thermostat is set for 75F what
temperature will the 1st stage energize?

77F

If a cooling thermostat is set for 75F what temperature will the 2nd stage energize?

79F

Many electronic control boards start the
compressor and condenser fan motor first
and the indoor blower delays for 15 to 30
seconds. What happens to a system that
does not incorporate a delay on the control
board?

Compressor

Condenser fan

Indoor blower start at the same time

What electrical component controls the
opening and closing of a damper motor?

Potentiometer

When a Heat/Cool thermostat is set for fan-on
what two terminals on the furnace terminal
board should read 24 V?

G & C

If a Heat/Cool thermostat is shorted between
the heating and cooling circuit what
resistance would be obtained at terminals W
and Y?

0 Ohms

What action would a good capacitor have on
an analog ohmmeter?

The needle will swing from infinite resistance
to 0 ohms then back towards infinite again

What speed will the fan-on switch at the
thermostat energize?

High speed

As poles are added in a motor the speed
increases or decreases?

Decreases

How is a fully loaded motors speed
changed?

By changing the motor speed taps

What do solid heavy lines represent in an
electrical diagram?

High voltage / factory wiring and broken heavy
lines are field wiring

What type of electrical diagram shows the
electrical components in their approximate
location?

A pictorial diagram

What diagram best helps a technician
troubleshoot an AC system?

Ladder diagram

What do the vertical lines of a ladder
diagram represent?

The low or line voltage power supplies

A voltmeter is connected in ____________ to
the load being tested

Parallel

Describe the term continuity?

A complete path (continuous), 0 or
measurable resistance

In an electrical circuit it is best to troubleshoot
switch contacts using a/an _________ meter

Volt

What is meant by the term auto-range?

The volt,ohm, or ammeter automatically adjusts when it
is used