HVAC BASICS for Contractors, 4th Edition

A series of 96 flashcards based on HVAC basics aimed at preparing for a contractors' exam.

Who is primarily responsible for your safety on a construction site?

Yourself

What color is commonly used for informational signs?

Blue

Where must the SDS for any chemical used at a job site be available?

At the job site

A barrier with yellow and purple markings indicates what type of hazard?

Radiation hazard

Positioning lanyards may only be used as what type of device?

Fall restraint devices

How far should the base of a straight ladder be from the wall?

One-fourth the distance from the ground to the point where the ladder touches the wall

A scaffold with a yellow tag means it is under what?

Assembly and cannot be used

Which activity is most likely to produce flying objects?

Using a chipping hammer

What type of soil is most likely to result in a trench cave-in?

Type C

The purpose of double insulating an electrically powered tool is to protect users from what?

Electrical shock

When performing a lockout, what should be done with the key to the lock?

Kept by the person who applied the tag

True or False: Personnel working near arc welding must wear eye protection with tinted lenses.

True

Drilling concrete requires the use of a respirator because it produces what?

Silica dust

What does PEL refer to in terms of worker safety?

Maximum exposure limit

What condition involves body temperature dropping below normal?

Cold stress

What are symptoms of a flash burn?

Swollen eyes and sandy feeling in the eyes

What are the three elements needed for a fire to start?

Fuel, combustible liquid, and oxygen

What is a confined space?

An enclosed space that has limited access

Which type of copper tubing has the thickest wall?

Type K

Common compression fitting joints are commonly used for what?

Refrigerant lines

True or False: Soft copper tubing may become softer after bending.

True

What happens when a flare on a piece of tubing is too long?

The flare nut may not be able to engage the fitting threads

Nitrogen tanks used for pressure testing are charged to a pressure in excess of what?

2,000 psig

The spacing between hangers for copper tubing is based primarily on what?

Tubing size

The schedule system for plastic pipe helps identify what?

The type of cement that should be used

True or False: Cement is applied first to the fitting, then to the pipe, then a second coat to the fitting.

True

Which measurement remains the same for all schedules of a pipe of a given nominal size?

Outside diameter

The number of perfect threads required for a threaded joint is dependent on what?

The type of fitting to be used

A close nipple is one that is threaded on how much of its length?

Almost its entire length

A pipe length measurement made by measuring the length of pipe plus twice the thread engagement is called what?

Face-to-face measurement

What is the tool used to cut pipe called?

Pipe cutter

A threading operation stops when what condition is met?

Two threads are visible beyond the die

What type of wrench is best for polished stainless steel or chrome-plated pipe?

Strap wrench

The two main categories of grooved fittings are what?

Rigid and flexible

True or False: Flanged fittings should be tightened without a torque wrench.

False

What color PTFE tape is typically approved for use on natural gas piping?

Yellow

Multiplying the cross-sectional area of a duct by the air velocity calculates what?

Air volume

Why are supply-air grilles in residential systems placed around the perimeter?

Where a great deal of heat gain or loss occurs

What is a manometer used to measure?

Pressure

What type of blower is commonly used in residential systems?

Forward-curved centrifugal

What type of fan is usually housed in a short venturi?

Vane-axial fan

If a blower speed slows, what is affected?

Air volume

What is the best location for adding air conditioning to an existing system?

Ceiling

What device directs air in a concentrated stream?

Damper

What type of duct system is typically used in residential settings?

Extended plenum

Which type of unit uses gas-fired heating?

YAC

True or False: Packaged DX air handling units can be configured for horizontal or vertical service.

False

The main function of an economizer is to provide what?

Free cooling

Bag filters are generally used in package units that have what capacity?

5 tons or more

What draws in burner primary air?

Negative pressure

What forms when complete combustion takes place?

Water vapor

People will experience symptoms of CO poisoning if atmospheric levels exceed what ppm?

70 ppm

How much gas does an 80,000 Btuh input furnace consume in an hour?

80 cu ft

A condensing furnace belongs to which vent system category?

Category IV

Type B vent systems can only be used with what?

Gas furnaces

A chimney will not establish a good draft if it is too what?

Short

What can happen if a furnace is oversized?

Poor vent draft due to short-cycling

What can occur by venting a condensing furnace under a deck?

Icing of the vent pipe

What are the goals of the HVAC design process?

Determine equipment capacity and calculate duct size

When should existing capacity be the sole basis for replacement equipment?

Never

What effect does radiant energy have on materials?

It warms dark objects more than light ones.

When calculating heating load, how are portions of the wall treated?

They are treated differently.

In a desert, how much is the indoor coil of a split-system cooling unit typically oversized?

12,000 Btuh

Which factor does not affect the selection of heating fuel?

Local customs

In a dual-fuel heat pump, when should the heat pump provide heat?

When the outdoor temperature is above the balance point.

When installing a condensate pump, what should the overflow switch connect to?

Y control circuit

The loss coefficient value (C-factor) calculates what?

Pressure loss through a specific type of fitting.

Where is a loop-perimeter duct system likely to be found?

A home with a basement in Ohio.

Why are low-velocity ducts recommended for comfort cooling?

Quieter operation.

The R-value for duct insulation in an attic is based on what?

Mode of operation with the greatest temperature difference.

Which statement is incorrect about commercial HVAC systems?

A commercial building load is consistent throughout the day.

During air blast freezing, what are typical coil air discharge temperatures?

-10°F to -30°F.

Cold storage conditions depend on what factor?

Type of food being stored.

Why are air-cooled condensers not usually used on container ships?

High ambient temperatures and difficulty controlling humidity.

What compressor types are used in refrigeration systems?

Reciprocating, rotary, scroll, and centrifugal.

The typical temperature difference used for low-temperature refrigeration is what?

5°F to 10°F.

What is the defrost process when the compressor shuts off?

Atmospheric defrosting.

What color in a sight glass indicates high moisture content?

Red.

Where are EPR valves installed?

In the suction line between a compressor and evaporator.

Off-cycle defrost generally occurs in evaporator coils operating at what temperature range?

16°F to 32°F.

What device starts an electric defrost period?

Time clock.

What is known as a thermal bank?

A tank of heat exchanging liquid used for hot-gas defrost.

What is the first sign of an ammonia leak?

Noticeable odor.

Non-mechanical ammonia systems are called what?

Absorption systems.