Refrigerator compressor failure, basics of the refrigeration cycle

Refrigerator badge on freezer door

A week or two ago, our 10-year-old Maytag Performa PTB1753GRW apartment refrigerator's compressor started buzzing noticeably. The refrigerator still seems to cool/freeze. However, the compressor seems on its last legs. It also produces a rather irritating buzzing noise.

Model PTB1753GRW, Serial 15723408CC

Make & model label inside refrigerator freezer compartment

Examining the refrigerator shows these details.

A note taped to the back of the refrigerator:

Details of the most recent compressor service

It reads as follows, with my thoughts:

• 134a: 3.49 oz 
• 134a refers to refrigerant R-134a (1,1,1,2-Tetrafluoroethane), which manufacturers began using "in the early 1990s as a replacement for the more environmentally harmful R-12"
• OIL: 9.63 oz
• All compressors contain oil to lubricate the moving parts
• CHARGE # 1
• Presumably to document how many times technicians have serviced the compressor
• BOARD # 103
• Most likely refers to the board model used to control the internal refrigeration cycle
• 2 / 17 / 03 13:35:29
• Date and time of first charge...this represents 11 years, 8 months, 9 days ago, as of this writing

COMPRESSOR

Removing the refrigerator rear panel reveals the following compressor equipment:

Compressor manufacturer label

The compressor, left, and fan, right

The label on the compressor reads as follows, with my thoughts:

• Embraco EGZ 70HLP
• Embraco represents the manufacturer, headquartered in Brazil
• Wikipedia entry
• The word "embraco" seems to represent an acronym of the corporate name: EMpresa BRAsileira de COompressores S.A.
• EGZ 70HLP represents the model of the compressor...see page 27 of the Embraco 2003 product line catalog
• EG = Basic prefix for all models of the EG COMPRESSOR DENOMINATION (no further information to gain)
• Z = Efficiency level: Z = 5th generation
• The next number = "Compressor capacity in BTH/HR – 60Hz – ASHRAE check point divided by 10" : so 70 seems to indicate compressor capacity of 7 BTH/hour, or how much heat it can remove (?)
• The next letter indicates the refrigerant: H = "R-134a"
• The next letter indicates the Application: L = "LBP (-35ºC to -10ºC ( -31ºF to +14ºF ))"...that is, the evaporating temperature range...LBP = "Low Back Pressure" and applications = refrigerators, frozen food cabinets, frozen food display cases, display windows, etc.
• The final letter indicates the Electrical equipment: P = "P - PTC + Run Capacitor (optional)"...PTC seems to mean "Positive Temperature Coefficient" relay (details)
• THERMALLY PROTECTED
• It seems insulated (?)
• 10 LRA
• LRA = Locked Rotor Amps. The prefix 10 indicates the "amperage the motor will pull while trying to make the rotor spin inside the stator, if the rotor is locked up."
• R 134a 1 PH
• Refrigerant
• 115-127V 60Hz
• This seems to represent the electrical input tolerances
• JOINVILLE-SC MADE IN BRAZIL
• This seems to represent the factory location: Joinville, Santa Catarina, Brazil
• 513700109 FAB 1 18/DEC/02 KA2YKPU5
• Seems like internal serial number and manufacture date

BASICS OF THE REFRIGERATION CYCLE

OK, so I spent some time attempting to get my head wrapped around the basic concepts of the refrigeration cycle.

It seems to involve several primary variables of the refrigerant:

• Pressure
• Temperature
• State of matter (that is, liquid, gas, or mixtures of the two during transitions)

It seems to involve several key insights about how to manipulate these variables of the refrigerant to get desired effects:

• A change in refrigerant pressure changes the refrigerant temperature:
• High pressure to low pressure = cools the refrigerant state of matter
• Low pressure to high pressure = heats the refrigerant state of matter
• A change in refrigerant temperature changes the refrigerant state of matter:
• Decreasing the temperature = changes from gas to liquid (note: perhaps only partially)
• Increasing the temperature = changes from liquid to gas (note: perhaps only partially)
• States of matter grant different refrigerant temperature ranges:
• Gas state of matter allows for super-heating it well above ambient temperature of the environment
• Liquid state of matter allows for sub-cooling it well below ambient temperature of the environment
• During a state of matter transition, heat goes in or goes out
• Refrigeration cycle occurs when a system uses the above insights repetitively in two ways:
1. Sub-cool the refrigerant
2. Move the sub-cooled refrigerant through the desired area to cool

In a modern refrigerator, this seems to involve four components:

1. Condenser: 
• Changes high-pressure, super-heated gas into lower-pressure, lower-temperature liquid
• Super-heated means a temperature well above the ambient temperature
• This step occurs after the refrigerant exits the compressor
• This readies the refrigerant for the expansion device in step #2
2. Expansion device: 
• Changes lower-pressure, lower-temperature liquid into low-pressure, sub-cooled liquid 
• Sub-cooled means a temperature well below the ambient temperature
• This step occurs after the refrigerant exist the condenser
• This readies the refrigerant for the evaporator in step #3
3. Evaporator: 
• Changes low-pressure, sub-cooled liquid into higher-pressure, higher-temperature gas
• This step removes the heat from the area to cool
• The refrigerant's increase in pressure and temperature, and its change of state of matter from liquid to gas, occurs as it absorbs heat from the area to cool
• During this step, the refrigerant boils as it absorbs heat, changing it from a liquid into a gas
• This prepares the way for the compressor in step #4
4. Compressor: 
• Changes higher-pressure, higher-temperature gas into high-pressure, super-heated gas
• This returns the cycle to the starting point in step #1, above
• The compressor may only compress refrigerant while in exists as a gas state of matter

So, to recap:

1. Sub-cool the refrigerant -- steps #4, #1, and #3
2. Move the sub-cooled refrigerant through the desired area to cool -- step #2

There is something I do not quite understand, yet: saturated mix, gas & liquid refrigerant, condensing at the same temperature...when it becomes a liquid, it sub-cools lower than the condensing temperature...I believe the principle = during a state of matter transition, the temperature and pressure remains the same, but heat comes in or goes out, changing the state of matter.

Cycle overview

Condensers
1963 United States Air Force training video (oy, the sexism and stereotypes, but solid on the rest)