EXPERIENCE 01A

On the last days that I served in the Colombian Navy, I remember some incidents. The one related here was very important to me:

The U.S. Navy sent three Coast Guard vessels to serve in Hawaii. These ships sailed from Mobile, Alabama, and each ship was equipped with a twenty-five-ton air-conditioning system. Two of these systems did not work. The ships were taken to Coco Solo, Panama's shipyard, where they determined that the machines had refrigerant leaks, but these leaks could not be located. Because it was proximate, the vessel's captain communicated with the U.S. naval mission in Barranquilla, Colombia.

They could take the boats back to Mobile, Alabama, or they could take the boats to this city, which was much closer. In the naval mission, Lieutenant Johnson decided to call me to troubleshoot the problem. I remembered my old man always said, "A good soldier neither offers nor refuses." I decided to do my best and prepared some questions for him to ask the captains of both ships. From their response, I had an idea of what the problem was. I explained to him the procedure that could be carried out. Both the captains and Lieutenant Johnson agreed with my plan.

I had taken some training courses in the USA, and was thankful for my education; I saw this as my opportunity to give back something from that knowledge. They took me to the ships to carry out an inspection. As we were down to the lower decks of the ship, I remember bringing some leak-detection tools. I was introduced to both captains and both engine room chiefs, who showed me the two systems that were leaking.

Note. Since the two vessels were of the same type, and used the same R-12, the exact same leak testing procedure was to be performed in both of them.

Before starting any procedure, we also verified the "lead fingers" (four in total) located at the condenser's heads. These pieces of metal are used to minimize the corrosion effect caused on the condenser's metals by the galvanic currents induced by water friction when flowing through the condenser. They were found at about 85% of their efficiency.

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Questions

1. If you were called for a problem similar to this, what would your idea be as to where the refrigerant's leak is?

2. What question should you ask the captain or the engine room chief?

3. What would be the first procedure you should perform?

4. What tools do you need to carry out the procedure?

5. What should the test pressures be?

6. What should be the operating pressures in the system?

EXPERIENCE 02A

This experience was relevant in my life after leaving the Colombian Navy. In this experience, as in other experiences in the future, we should study the complaint or problem, and through the analysis and applying our knowledge, the system should be repaired.

Somebody in the naval base told me that in the cafeteria this particular beverage cooler (property of the Beverages Factory) used to promote its products and lend their customers these commercial refrigeration units, which weren't working well. In those days, the beverage company had a private refrigeration service company to take care of the maintenance and repair of those units.

According to the person in charge, for the last several days the device was not cooling properly. The mechanics they sent all had problems in repairing the unit. He enumerated to me what the mechanics did on the three visits:

1. The first mechanic's visit was due, of course, to a poor cooling of the device. He installed the gauges and "worked" in the equipment for a while. After about fifteen minutes he said the system was OK. And he left.

2. The equipment continued with the same problem. The following day he called the beverage company and another mechanic showed up. This time the mechanic worked a little bit longer and finally said the same as the other mechanic, then left.

3. On the third day, the equipment still failed to work properly. He called the beverage company again. And another mechanic was sent. This one connected the manifold gauges and said that he added some refrigerant and made some adjustments.

This time the cooler worked a little bit better, but it was not enough.

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The system had the following characteristics:

a. It used a 1/3-hp air-cooled hermetically sealed condensing unit, equipped with a packing gland suction service valve attached to the compressor.

b. It used a 1/9-hp condenser fan motor.

c. Low-pressure control. Actual settings = Cut-in. 35 psig; Differential = 25 psig (*)

d. Both motors (working), compressor and condenser fan, used the same electrical characteristics: 115 volts, single phase, 60 Hz.

e. The system used refrigerant 12.

f. It used a capillary tube as a liquid control.

g. Ambient temperature at the equipment location: 80°F.

h. The FLA, discharge, and suction operating pressures, as well as the suction line and the liquid line's temperatures, were a bit too high.

The beverages required a temperature of 40°F.

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Let's see what we can ?nd.

Questions

1. What do you think the problem was?

2. What are supposed to be the operating pressures?

3. What should we do?

EXPERIENCE 03-A

This experience took place sometime later than Experience 02. The lieutenant aggregate of the naval mission was transferred back to the United States. Thus, he had to get rid of some things, among them an 18,000 Btu Carrier air conditioner. He had the bad luck of the equipment failing to work when he gave it to the new owner.

A/C's characteristics:

a. It was a 1 1/2-hp sealed rotary-type compressor.

b. It used a 1/2-hp, three-speed, double-shaft fan motor.

c. Selector switch. Thermostat. Thermal overload.

d. Both motors, compressor and condenser fan, were of the PSC type. Both had the same electrical characteristics: 230 volts, single phase, 60 Hz.

e. Used refrigerant 22.

The lieutenant got in touch with me and told me the problem; he asked me if I could check the device. Thus:

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Questions

1. What do you think the problem was?

2. What test or tests should you carry out to verify this equipment?

3. What should you recommend?

EXPERIENCE 04-A

I continued working with the beverage factory (cited on Experience 02) without any problems. Being aware that I needed some spare replacement parts, I talked to the company's manager and suggested he buy several spare parts, which would be needed for stock instead of ordering one at each time. He did it, and stored them in the factory's warehouse.

On this occasion, I had one problem; when only two compressors were left in the warehouse, the person in charge suggested to me to remove them, and hold them in my shop. I accepted and took them with me. I used one of them immediately and later on (about two months), when I installed the other, and I went to start it, it did not work.

Motor's characteristics: 115 volts, single phase, 60 Hz.

Questions

1. What do you think the problem was?

2. What test or tests should you carry out to verify the problem?

3. What would you recommend?

EXPERIENCE 05A

While working for a "Colombian Technical" Company — —, one of the various works that I remember was in Santa Marta City, on a 10-ton A/C system that had been operating for several years in the Clinic of Social Insurances. According to the person in charge, the equipment had lost little by little its cooling efficiency. For a while now, it's getting to the point where the evaporator, regardless of what they did (*), it was "frozen" all the time.

(*) According to the building's service engineer, in a span of about four years, these are some of the works that they and outside service companies performed on this A/C equipment:

1. Cleaned the evaporator with steam on a monthly basis.

2. Changed air filters on a weekly basis.

3. Changed the fan-blower to increase airflow through the evaporator.

4. Changed the evaporator fan motor (direct drive) with one of a higher speed.

5. Changed the evaporator fan motor type for an indirect drive (belts-pulley-flywheel).

6. Remove the refrigerant from the system and perform a deep vacuum to "clean" the system internally. This last procedure was performed several times.

The system had the following characteristics:

a. A self-contained system with a 10-ton semi hermetic unit, equipped with suction-discharge packing gland service valves type, attached to the compressor.

b. Shell and tube water-cooled-type condenser.

Water from cooling tower, temperature 80°F.

c. Used a 5-hp cooling tower fan motor.

d. Controls: High and low pressure, water-regulating valve. Pump-down (thermostat — liquid line solenoid valve. Thermostat's sensing bulb located at the evaporator's return airflow).

e. The evaporator's fan motor was of 5 hp. All the motors and the compressor, cooling tower, and evaporator fan had the same electrical characteristics 440 volts, three phases, 60 Hz.

f. The system used refrigerant 22.

g. The thermostatic expansion valve was of the external equalizer type.

h. The sight glass in the liquid line was full.

The system's operation was observed and the following were all lower than normal:

1. The suction and discharge pressures.

2. The suction and liquid line temperatures.

3. The running amperage.

4. The condenser's water temperature difference.

After hearing the detailed explanation from the person in charge,

Questions

1. What do you think the problem may be? Keep in mind the system is old and money is not in abundance in this place.

2. What are supposed to be the operating pressures?

3. What are supposed to be the suction and liquid lines temperatures?

4. Why is the running amperage so low?

5. What should be our recommendations?

EXPERIENCE 06-A

At one time, I performed some refrigeration work for a man who was retired from the navy. He had a restaurant called "La Canada" (The Gorge). The work to be performed was in a freezer. This was a self-contained unit, located in the pantry with the refrigeration unit positioned at the end of the cabinet.

The equipment had these characteristics:

1. It was a 1/2-hp air-cooled sealed condensing unit, equipped with a packing gland service valve attached to the compressor's suction side.

2. It used a 1/8-hp shaded pole-type condenser fan motor.

3. Both motors, compressor and condenser fan, used the same electrical characteristics: 115 volts, single phase, 60 Hz.

4. The system used refrigerant 12.

5. The device had a capillary tube as a liquid control.

6. Temperature at the equipment's location was about 85°F.

7. The frozen products to be stored required a temperature of 10°F.

The freezer's compressor, although working, was not cooling, and if touched it "passed current." The equipment was de-energized, the entire electrical installation was reviewed and although the compressor worked, it was "grounded."

After installing the low side gauge, I found that the system did not have any refrigerant.

Questions

1. Up to this point, what do you think the problem was?

2. What tests should we recommend?

3. What do you think can be done?

4. What are supposed to be the operating pressures in this device?

EXPERIENCE 07-A

At this time, I had a call from a Panamanian ship's captain who said that he had heard of me and wanted me to inspect the refrigeration equipment on board his ship. He confided to me that he had gone to Panama's shipyards and the only thing that they had recommended was the purchase of a new compressor. That was a greater problem.

According to the captain, the compressor was of European origin. It was of the open "W" type, with 6 pistons and with a capacity of about 20 tons. Due to the compressor's age and origin, it was not easy to obtain.

Questions

1. What component parts should we recommend to be checked in this device?

2. What do you think can be done?

3. Any other suggestions to the captain?

4. Can we intent the compressor's repair?

EXPERIENCE 08A

One day a retired sergeant major of the Colombian marines whose last name was Arias it came to my shop. He told me that he got some R and A/C works and asked me for help (in some way) to carry them out. He didn't have any mechanical experience.

The first work that he got was in the City of Cartagena, to repair a commercial refrigeration (walk-in box) used to store and freeze seafood products. The owner of this equipment bought the product from the fishermen. He stored it, and later he supplied it to the restaurants throughout the city.

We went to the place and inspected the equipment:

The repair was similar to one that I did on the boat (Experience 07); the only difference was that this equipment was on land.

The characteristics and requirements of the equipment or walk-in storage room were:

1. The compressor was an open "in-line" alternative type with 6 pistons.

2. It had a capacity of 25 tons.

3. The electric motor working at 440 volts, three phases, and 60 Hz. Approximately 550 rpm.

4. The system was working with R-12.

5. Thermostatic (external equalizer) expansion valve.

6. Required storage temperature was -10°F (-23°C)

7. High and low, separated pressure controls.

8. Condenser water-cooled "shell-tube" type (seawater). Water temperature was regularly approximately 80°F.

While inspecting the equipment, we found out (through the owner) that a former student of mine had been there, trying to make the repair. The peculiar thing was, according to the client, he tried to make the repair with the book in hand. In addition, he did not show that much experience, and it made the owner apprehensive as to the type of repair to be done.

After the inspection of the entire system and of all the spare parts, we reached at the conclusion that the work can be performed.

Questions

1. What should be the operating pressures for this system?

2. What tests should we recommend to make sure about the equipment's condition?

3. Should we use some of the information on Experience 07?

EXPERIENCE 09-A

At this time, I met with my brother-in law (he was working for an A/C company), and I asked him what he was doing. He said that he was working with a mechanic in a bank and there, they had some problems. The compressor was repaired. Later, it began to present several compressor faults (rupture of connecting rods, internal valves, and valves' plates, etc.).

Since we were very near the bank, I decided to go there and look at the problem. When we arrived I met with the mechanic. After he answered my greeting, not happily (I didn't have a good relationship with him), I asked him about the problem and he told me that the same problem persisted, the refrigerant returning to the compressor in a liquid state.

He was frank and told me that he didn't understand why.