ACR114-A Intro to HVAC Test 1

Unit 1 Chapter 1 (+extra intro stuff)

Refridgeration

The process of moving heat from a place not wanted, and to somewhere more suitable or where it makes little to no difference.

Control Volt. Wires and their respective functions

Red = Power
Blue = Neutral

White = Heat

Yellow = Cool

Green = Fan

(If heat pump) Orange = Reversing valve

The 4 major components in a system

(In order of refrigeration cycle)

1. Compressor

2. Condenser

3. Metering Device

4. Evaporator

Compressor

Vapor pump. Pumps refrigerant through system. (Low Pressure —> High Pressure)

Condenser

Rejects Heat

Metering Device

Meters refrigerant within system. (High Pressure —> Low Pressure)

Evaporator

Absorbs Heat.

The 4 Temperature Scales

1. Fahrenheit (F)

2. Celsius (C)

3. Kelvin

4. Rankine

The 2 absolute scales

Kelvin and Rankine

The absolute scale of fahrenheit

Rankine

The absolute scale of celsius

Kelvin

The 3 main temps to know

1. Boiling Point (212F) (100C)

2. Body Temp. (98.6F) (37C)

3. Freezing Point (32F) (0C)

Absolute Zero

The temperature where all molecular activity ceases to exist. (-460F) (-273C) (0K&R)

The 3 states of matter

1. Solid - exerts force in a downward direction

2. Liquid - exerts force in a downward and out direction

3. Gas/Vapor - Exerts force in all directions

The 2 system components where refrigerant changes states?

The condenser and evaporator

How does refrigerant change state in the condenser?

(Vapor —> Liquid) Vapor enters and is compressed 25F-30F above ambient to a liquid state.

How does refrigerant change state in the evaporator?

(Liquid —> Vapor) Liquid enters the bottom of the evap. as a 75% liquid / 25% vapor mix and boils off at 40F into a 100% vapor mix.

What is the standard condition for water to boil at 212F?

at sea level with a barometric pressure of 14.696 PSIA or 29.92 INHG

In. HG

Inches of Mercury

PSIA

Pounds per Square Inch Absolute

PSIG

Pounds per Square Inch Gauge

To get PSIA from PSIG?

PSIG + 15 = PSIA

(British Thermal Unit) BTU

The amount of heat energy required to raise 1 pound of water 1 degree.

Specific Heat

The amount of heat energy required to raise 1 pound of a substance 1 degree.

What can temperature be thought of

A description of the level of the heat, and also may be referred to as heat intensity.

Heat naturally travels from what to what

From a warmer substance to a cooler substance

What are the 3 types of heat transfer

1. Conduction

2. Convection

3. Radiation

Conduction

heat transfer by molecule to molecule

Convection

heat transfer that uses a fluid medium like water or air. Can either be used by forced or natural convection.

Forced convection

Using a pump/motor to push air

Natural Convection

The natural rise of heated air

Radiation

heat transfer by radiation that travels through space and vacuum and heats whatever it comes in contact with.

Sensible Heat

Heat that can be measured with a thermometer

Latent Heat (Hidden Heat)

Heat that cannot be measured with a thermometer, but changes the state of a substance.

What are the 2 types of barometers

1. Aneroid

2. Mercury

Bourdon Tube

The tube in pressure gauge manifolds used to measure pressure

How does a bourdon tube work

The tube is curled and under pressure straightens out, but returns to being curled once pressure is released.

Low-Side/Compound Gauge

Pressure gauge that can red above and below atmospheric pressure

High-Side Gauge

Pressure gauge that can only read above atmospheric pressure