Refrigeration Machine Operator Course - Turner

Vacuum Gauge

0hg - 30hg below atmospheric pressure (inches of mercury)

ANSI/ASHRAE 34

1 Purpose - This standard is intended to establish a simple means of referring to common refrigerants instead of using the chemical name, formula, or trade name. It also establishes a uniform system for assigning reference numbers and safety classifications to refrigerants.

Refrigerant stored in a machinery room

1. Shall not be more than 20 percent of the normal refrigerant charged. 2. Not more than 300 pounds of the refrigerant, in addition to the charge of the system and the refrigerant stored in a permanently attached receiver. 3. And then only in inter-state commerce commission approved storage containers.

288,000 BTUs (day) /24 hrs (day)

12,000 BTUs hr

29.92 converted to "pounds per square inch"

14.7 psi

ANSI/ASHRAE 34

2 Scope - This standard provides an unambiguous system for numbering refrigerants and assigning composition-designating prefixes for refrigerants. Safety classifications based on toxicity and flammability data are included.

12,000 BTUs (hour)/ 60 (minutes per hour)

200 BTUs minute

One Ton

2000lbs

2000 lbs x 144 btu/lbs

288,000 BTUs

Refrigerants should be non-poisonous and nonirritating (non-toxic).

A poisonous or highly irritating refrigerant could create a hazard in case of leakage from the system.

Freezing Temperature

A refrigerant can't be used for applications that require the evaporator temperature be lower than their freezing point.

It's freezing point should be well below the evaporator temperature.

A refrigerant that freezes in the evaporator would prevent consistent flow and could not be used.

Boiling Point

A refrigerant with a low boiling point can achieve low evaporator temperature without having to be in a vacuum.

Refrigerants should have an evaporating pressure suitable for the type of compressor used.

A systems compressor and metering device must maintain the pressure inside of the evaporator. This pressure determines the boiling point of the refrigerant in the evaporator.

ASHRAE Refrigeration Code - Low Toxicity

A1, A2, A3

ASHRAE Refrigeration Code - No Flammability

A1, B1

ASHRAE Refrigeration Code - Low Flammability

A2, B2

ASHRAE Refrigeration Code - High Flammability

A3, B3

Ultrasonic Leak Detector

Allows you to hear minute sounds such as leaks inside of shell and tube type heat exchangers.

The refrigeration process is made possible by

Boiling a refrigerant

Group 1 Refrigerants - Non Toxic, Non Flammable

CO2 (Carbon Dioxide), R-11, R-12, R-21, R-22

Conduction

Conduction is heat transfer by contact.

Convection

Convection is heat transfer by the movement of a fluid, usually water or air.

Dalton's Law of partial pressures

Dalton's law states that more than one gas placed in a container will exert a pressure that is an accumulation of the pressures that each gas exerts.

ANSI/ASHRAE 34

Designation and Safety Classification of Refrigerants.

A minimum of power should be required to compress it.

Different refrigerants require different amounts of power to compress them. The less the power required, the cheaper the operating costs of the refrigeration plant.

It should be easy to find leaks.

Due to cost and threat to safety determining if and locating leaks should require as little effort as possible.

Desirable properties of refrigerants

Each refrigerant has desirable properties that distinguish it from all others.

Fahrenheit to Centigrade

F = (1.8 x C) +32

Gauge Size

Generally, the more accurate gauges are larger and more costly.

Latent heat of vaporization

Heat energy added to change the state of a substance without a change in temperature from a liquid to a vapor, or in the case of water, from a liquid to steam (vapor). In the case of refrigerants, it is a change from liquid to gas (in the evaporator).

Latent heat of fusion

Heat energy needed to change the state of a substance without a change in temperature from a liquid to a solid or a solid to a liquid. In the case of water, from a solid, ice to water or vice-versa.

Latent Heat

Heat which is associated with a change in state.

Sensible Heat

Heat which is associated with a change in temperature

Horsepower per ton of refrigeration.

Horsepower required to produce one ton of refrigeration at standard ton conditions. This is the power required to compress the refrigerant vapor without including any efficiency losses.

HG

Inches of Mercury

Pressure Gauge - PSIG

Indicates values of pressure above atmospheric pressure. Value starts at 0.

Vacuum Gauge - HG

Indicates values of pressure below atmospheric pressure. The values of pressure on a vacuum gauge descend down to 29.92Hg, indicating that virtually no pressure is exerted (perfect vacuum)

Dye Method

Indirect systems which use water or brine as secondary refrigerants have to be monitored for refrigerant leaks in the brine. Dyes like Bromothymol Blue or Nessler's Solution are added to a brine sample. If refrigerant is present in the brine the dye will change color. Bromothymol Blue turns yellow if C02 is present. Nessler's Solution turns yellow if ammonia is present. Litmus paper is a dye coated paper which is dipped in the brine sample. Red litmus paper turns blue if ammonia is present.

Leak Detection - Halide Torch

Inexpensive, fast, reliable. Air is drawn in over a heated copper element, which changes color in the presence of freons such as R-11, R-12 and R-22. Can detect chlorinated refrigerants. Can be dangerous because of open flame.

Pressure Gauge - 0 Psig-300Psig above atm

Installed on the discharge side of a compressor

Pressure Testing

Leaks in systems that operate below atmospheric pressure cannot be discovered by a halide torch or electronic detector. By raising the pressure above atmospheric a halide torch or electronic detector may be used. Empty systems or isolated components can be pressurized with nitrogen to see if the pressure changes over time. A halide torch or electronic detector may be used if trace of R-22 is added.

Gauge Manifold

Makes it possible for a service mechanic or operating engineer to determine both the high and low side operating pressures in a system that is not equipped with permanently installed pressure gauges. Used while adding or removing refrigerant from a system.

Halide Torch Colors

Pale Blue - No Leak Green - Small Leak Dark Blue - Big Leak Yellow - Restriction in Line

PSIA

Pounds per square inch absolute - Absolute pressure values are based on a perfect vacuum.

PSIG

Pounds per square inch gauge.

p=f/a

Pressure

Group 3 - Flammable Refrigerants (explosive hydro carbons)

Propane, Butane, Isobutene, Ethane, Ethylene

Barometric Pressure to Psia

Psia - = Hg x .491

Vacuum pressure to Psia

Psia = (30-Hg)/2

Psig to psia

Psia = psig + 14.7

Psia to Psig

Psig = psia - 14.7

Electric Leak Detector

Quickest way to find leaks. Measures the resistance of refrigerant vapor. Designed to detect certain types of refrigerant (cfc, hfc, hfcf, etc). Should not be used near flammable vapor due to high temperature internal sensor.

Radiation

Radiation is heat movement through space by shining, just as light is radiated. Ex: The sun.

Refrigerants should be stable.

Refrigerants are made up of chemical mixtures. Above a certain temperature, they will separate into the elements. It is necessary that refrigerants breakdown temperatures be well above the operating temperatures of the system.

Refrigerants should have no effect on metal.

Refrigerants must not corrode or react with the metals used in the refrigeration system.

What is refrigeration

Refrigeration is the removing of heat from an object or mass and then dissipating that same heat in a place where it's presence will not be objectionable. "Refrigeration systems move heat"

Specific Gravity (liquid) at 5 degrees F

Specific gravity of the liquid at 5 F compared to water, that is, the ratio of its weight to the weight of the same volume of water.

Specific Gravity (Vapor) at Atmospheric Pressure

Specific gravity of the refrigerant vapor at atmospheric pressure compared to the weight of air.

Gauge Case and Housing

Stainless steel, black, ABS, painted steel, brass and fiberglass reinforced thermoplastic are standard case materials. Stainless, brass or ABS cases are recommended for outdoor service.

Sublimation

Sublimation is a process whereby a substance changes from a solid to a vapor without passing through the liquid state. Ex: Dry ice.

Superheat

Superheat is heat added to steam or refrigerant gas (vapor), to raise the temperature above its boiling point. Each additional degree above the boiling temperature is a degree of superheat.

Vacuum Testing

System components can be isolated and placed in a vacuum state. If there is a leak, air will be sucked into the system. This method is extremely time consuming.

Temperature

Temperature is the intensity of heat.

Specific Heat (Liquid) at 86 F

The amount of btu's needed to cause a 1 degree F temperature change.

Specific Heat (Vapor) at 5 F

The amount of btu's needed to cause a 1 degree F temperature change.

Latent Heat @ 5 degrees F.

The amount of btu's that must be absorbed in order to vaporize one pound of the refrigerant.

Pressure

The force exerted by a fluid (liquid or vapor) which has been uniformly distributed over a surface and is measured per unit area.

Discharge Pressure @ 86 degrees F.

The pressure at which the refrigerant in the condenser must be maintained in order for it to condense at 86 degrees F.

Suction Pressure @ 5 degrees F.

The pressure at which the refrigerant in the evaporator must be maintained in order for it to evaporate at 5 degrees F.

Using the PT chart.

The pressure temperature chart is a tool that is used by service personnel and Operating Engineers alike. PT Charts list the relationships between pressure and temperature for specific refrigerants.

Refrigerants should have no effect on oil.

The refrigerant must have no harmful effect on the selected lubricating oils. Besides possible sludge formation there is also the danger of refrigerants mixing with and thinning the oil.

Changes of state are accompanied by

The removal of heat

Specific Heat

The specific heat of a substance is the number of BTU's required to raise the temperature of one pound of that substance 1 degree Fahrenheit.

Critical Temperature.

The temperature above which it is impossible to condense a vapor, regardless of the pressure applied.

Compressor discharge temperature.

The temperature of the refrigerant as it is discharged by the compressor. High temperatures may cause lubrication problems due to oil breakdown.

Refrigerants should be available at reasonable prices.

There has recently ben an attempt to regulate refrigerants that are threats to the environment. Operators of systems that use CFCs must take great care in handling these refrigerants since replacing it would be difficult and expensive.

Charles Law

There is a direct relationship between the pressure, temperature and volume of a vapor or gas.

Favorable properties of refrigerants

There is no one refrigerant that demonstrates only favorable properties.

Test Pressures.

These are the pressures at which the high and low side of the system must be tested at prior to being charged with refrigerant and after servicing. These pressures are above the normal operating pressures in the machine to ensure that the system components will not leak during operation.

Refrigerant #

To limit confusion that arose from manufacturers differing brand name (Freon is a brand name from Dupont) refrigerants are identified the letter R followed by numbers.

Soap and Bubbles

Used when approximate area of leak is known. Simplest and least expensive method. Applied with brush or spray. Can only be used on high pressure systems.

One ton of refrigeration

based on the cooling capacity produced by a 2000 block of ice.

One Ton of refrigeration

capable of moving 288,000 BTUs/Day (24hrs)

Latent heat of condensation

heat energy removed to change the state of a substance without a change in temperature from a vapor to a liquid.

144 BTUs

must be removed from one lb of water (at 32F) to form one lb of ice.

Compound Gauge - 30 hg - 100 psig

psig above atm & vacuum below atm, Installed on the suction side of a compressor.

ASHRAE Refrigeration Code - High Toxicity

B1, B2, B3

BTU "British Thermal Unit"

A BTU is the quantity of heat needed to raise one pound of water one degree Fahrenheit.

Refrigerants should produce maximum refrigeration per cubic foot of vapor pumped.

A compressor, depending on it's size can only pump a given amount of refrigerant vapor. The refrigerant used should absorb the greatest amount of btu's allowed for that particular size.

Barometer

A device for predicting weather changes.

Refrigerants should be non-flammable.

A flammable refrigerant could create an even greater danger in case of leakage, due to the possibility of fire or explosion.

ASHRAE

American Society of Heating, Refrigeration and Air-Conditioning Engineers is an international membership organization founded to advance the arts and sciences of heating, ventilation, air conditioning, refrigeration and related issues.

Group 2 Refrigerants - Toxic, irritant

Ammonia, Sulphur Dioxide, Dichlorethylene, Methyl Chloride, Ethyl Chloride, Methyl Formate.

Refrigerants

Are the working fluid used to transfer heat through refrigeration systems.

Refrigerating Effect.

As liquid refrigerant passes through the metering device a percentage of the liquid vaporizes, or flashes. This "flash gas" lowers the temperature of the remaining liquid from the condenser temperature (86 degrees F) to the evaporator temperature (5 degrees F). The remaining percentage of latent heat that can be absorbed in the evaporator is the "Refrigerating Effect"

Pounds Per Minute Ton

The amount of vapor that must be pumped per minute to produce one ton of refrigeration (200 btu per minute). Looking at the refrigerating effect of ammonia (B6) we know that we only have to pump less than half a pound of vapor to produce 1 ton of cooling. Therefore the "Pounds per minute per ton" of ammonia is .5. By comparison we would have to pump almost 4 "Pounds per minute per ton" of R-12, because it's refrigerating effect is only 50 btu's.

Refrigerants should have condensing pressure suitable for the type of compressor used.

The compressor raises the pressure of a vapor to increase the temperature it can be condensed into a liquid at.

Refrigerants critical temperature should be well above the condensing temperature.

The critical temperature is the temperature above which it is impossible to condense a vapor regardless of the pressure applied.

29.92

The earth's pressure at sea level.