A discussion of the cycle of the refrigerant in the system could take weeks or even months for you to have a comprehensive understanding of it.
BUT! Don’t panic! We are going to take a basic look at it and hope it is enough for you to identify basic problems. Remember that we do not want to be technically correct or make you an expert. We want to “get you by” safely and effectively between visits from your professional person.
Everything contains HEAT:
You must understand that we are dealing with heat, the heat that is contained in everything air, water, Freon®*(refrigerant), concrete, etc. It is stated in technical circles as fact that ice is not cold but rather it contains less heat than our body does, so we call it cold. Technical thought states that it is holding less heat than our body is holding. So if you can see heat in things in this way you can better understand a measurable difference they have. There may be 68°F difference between the heat of our body temperature (98.6°F) and the amount of ice (32°F).
If you place some small piece of frozen “thingy” that is 200°F below zero in a vat of ice, then the ice is HOT to the “thingy”, and it will quickly absorb some of the heat from the ice and it will “thaw”. I hope you understand the importance of all this as we later explore the amount of heat in a refrigerant even though it is at a temperature of 45°F. It could not absorb much heat from 65°F air passing over it, but it could absorb a lot more if the air blown over it is 90°F.
Refrigerant TEMPERATURE and PRESSURE vary directly:
This means that if you keep a can of refrigerant-410A sealed and the temperature of the air around it is 95°F., then the pressure inside is going to be 296 pounds. At 40°F, it is only 118 pounds. As you warm it, the pressure increases and as you cool it the pressure decreases (if it remains sealed in a container). Also, if you pump it up in pressure then the temperature of the refrigerant will also increase. Look at the charts showing this pressure/temperature relationship.
Refrigerant looks like WATER:
- If you look through a “sight-glass” into a container of refrigerant, you will see a liquid or a liquid and some vapor that looks just like water-clear and fluid. Very different from water, though, if you open the container, the refrigerant will zip off into space as a vapor. It does this for two reasons:
- It is under considerable pressure.
- It boils at any temperature above MINUS 38°F unless it is kept in a sealed container; thus, it boils instantly and vaporizes as soon as it is not under pressure.
- Reducing the pressure of refrigerant will cause it to absorb a lot of heat:
- If you were to deliberately spill some refrigerant on the floor, it would immediately vaporize, but in doing so it would absorb a lot of heat from that spot in the floor and the surrounding air. The floor would become cold.
If you flow refrigerant through a small tube and then through an orifice into another tube, but much larger, then the refrigerant would vaporize (boil) and absorb a lot of heat (the tube would feel cold). Did you ever place your thumb over a water hose and try to seal off the end from the flowing water? Didn’t you get a fine mist that sprayed into the air? Remember how cold it felt and how little of it hit the ground. It vaporized and as it did. It absorbed heat from the surrounding air as it vaporized. This is what refrigerants do inside the tubing of the evaporator coils as air blows over it.
If the compressor pumps the refrigerant to a higher pressure, the refrigerant gets HOT:
If pressure increases, temperature increases. If your compressor raises the pressure of the refrigerant to 375 pounds inside the condenser coils, the tubing will get HOT because the temperature of the refrigerant rises with pressure. The compressor as well adds a lot of heat because it uses a motor and mechanical pressure to make the refrigerant pressurize, however, we have to pressurize it to get it to flow through the tubing at a great pressure, so we can orifice it and reduce the pressure in the evaporator to get the “cooling effect”. Then it absorbs a lot of heat from inside the room and the compressor “sucks” it back to start the cycle again.
As refrigerant absorbs heat, it increases in pressure inside the EVAPORATOR:
The high-pressure refrigerant goes through the orifice (flow control device), vaporizes and rises is pressure again. The system is designed to keep that pressure just right, though, so that the temperature of the vaporizing (boiling) refrigerant will remain above 32°F and somewhere below 55°F. That is “cold” enough to absorb a lot of heat from an 80°F room air flowing over the evaporator. If it were below 32°F, then any moisture that it causes to condense on the tubing would freeze on the tube, and that would be detrimental.
A lot of it would even restrict the air flow through the evaporator and would insulate the tubing so that it slowed the boiling of the refrigerant on the inside of the tube. So the equipment manufacturer designs it to be above 32°F., it will blow just enough air over it, with just enough cooling coil surface, with just the right size of flow restrictor (orifice) to drop the temperature of the air going past it about 20°F. If an 80°F room air passes through the evaporator, then it comes out the supply grills at about 60°F.
It is designed so well that a lot of “the cooling effect” is still left in the refrigerant as it returns back into the compressor and this cools off the hot motor windings and mechanical parts just before it gets compressed again to start the new cycle though the system, however, it is designed so well that no liquid is left to dump into the compressor, because liquid will not compress and it would break the valves inside the compressor. You see, now, that the pieces all have to fit together just like the manufacturer planned it.
Too much refrigerant or too little would prevent that “just right combination” from happening. Thus, the refrigerant “charge” must be right, the parts must be working and they must be kept clean to do the job.
To check the refrigerant action and level of charge, you will need a set of refrigeration gauges and manifold. If you do not have a set (Know more about them), there are still many things you can check and do to discover if your unit is working well.
A good thermometer, though, will be essential. You will use it all over the system. You must have one that can be taped to the copper tubing without breaking.
The first thing to use it for is checking the temperature of the air going into the indoor blower. Then check the air just inside the nearest supply air opening. The air coming out of the supply duct will be approximately 20°F. below the temperature of the returning air to the equipment.
If your cooling coil or filter or blower wheel are downright dirty, then the difference in temperature will probably be higher. This means you may have substantial generation of cooling, but not enough air to get it from the cooling coil into the rooms. You may also be close to having icing on the cooling coil (evaporator) and your electric bill will be higher.
Check these conditions to make sure they are clean. Read the section on filters if you have not done so, for this will be the cause of this dirty condition. If these things are dirty, they will have to be cleaned before you can do very many other things for the diagnosis of problems.
If the evaporator coils are dirty, don’t just brush them off and think you’ve gotten them clean. It’s the stuff trapped inside the fins within the layers that will be a problem. You will have to have a service technician remove the coils, clean them, and reinstall them for you. This may cost as much as $350.00 to $800.00, it will have to be done, but it will be worth it to you in the long run. After the cleaning, use the best filter you can acquire for future operation.
If you checked the temperature of the air into and out of the indoor unit and the differential is low, say 12°F versus the optimal 20, then you may have a cooling generation problem. The first thing to check now is the cleanliness of the outside unit coils.
Follow the precautions and turn off the power (the 230 VAC supply) to the outside unit. Check operation to make sure the power is truly off.
You won’t be able, most likely, to tell if the coils of the condenser are dirty just by looking. You will have to use the garden hose and spray into the fins of the coil and watch the other side to see what comes out. You may indeed see a bunch of stuff you didn’t expect to see. If there is the slightest amount of clogging of the coil, then continue to give it a very appreciated bath.
You may have strong water pressure, and you will have to avoid hitting the fins at an angle to prevent them from being damaged by the water. Spray vigorously, though, and give it a thorough cleaning. Don’t just stand back and sprinkle it a bit and think it is clean—it won’t be. Look over into the unit and watch the mud come out. Make sure the leaves inside the condenser haven’t accumulated to the point of restricting the flow through the coils, too.
Let it drip dry for a half hour or so and then you can turn it back on to check the temperatures again. Let it run for at least 10 minutes or more before you check these temperatures. If you get a lot of matter out of the coils, it will do wonders for the operation of the system. Recheck things now.
Please read this another article: Importance of Duct Cleaning
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