THE REFRIGERATION CYCLE

Based on the principle that heat flows naturally from warmer areas to cooler areas, the refrigeration cycle consists of seven stages:

1. Compression of hot gas
2. Cooling
3. Condensing
4. Subcooling
5. Expansion
6. Evaporation
7. Super heating

A basic vapor compression refrigeration system consists of four primary components: a metering device (e.g., a capillary tube, fixed orifice/piston, or a thermostatic expansion valve), evaporator, compressor, and condenser.

The refrigeration system. In a typical refrigeration system, the compressor sends hot gas to the condenser. Then the condensed liquid passes through an expansion valve into the evaporator where it evaporates and collects heat from the area to be cooled. The gaseous refrigerant then enters the compressor where the compression process raises the pressure and temperature. From the compressor, the refrigerant is routed back to the condenser and the cycle repeats.

EPA Further Tightens the R-22 Spigot

Below is very important information from article in The AHR News.

It appears as if the spigot of new R-22 available to HVACR contractors has been tightened even more in 2013. Users of the world’s most popular HCFC could expect close to 30 percent less of new R-22 this year than last, according to some reports. That’s because the U.S. Environmental Protection Agency (EPA) sent, in early January, “No Action Assurance” letters to the producers and importers of R-22 and R-142b refrigerants, setting 2013 production and consumption allocations for manufacturers.
The total allowances for virgin R-22 for 2013 are 39 million pounds. That compares with 55 million pounds of new product in 2012 and 100 million pounds in 2011. And, by comparison, in 1999, the base year for all current measurements of supplies, refrigerant manufacturers were bringing more than 300 million pounds of virgin R-22 to the market.

“The latest ‘No Action Assurance’ letters extend and modify similar letters issued last year and allow companies to continue to produce and import R-22 and R-142b in the coming year,” said Charlie McCrudden, vice president for government relations, Air Conditioning Contractors of America (ACCA).

In effect, No Action Assurance letters from the EPA tell producers that they will not face fines and penalties if they keep production of new HCFCs at or below certain levels.

“The letters are necessary because the EPA has not finalized a long-pending rule that would grant the authority to produce HCFCs, known as the 2012-2014 Allocation Adjustment Rule,” said McCrudden.

McCrudden did say there could be an uptick in that 39 million target. “The EPA has yet to complete its proposed 2012-2104 Allocation Adjustment Rule. When it does, there will likely be at least 6.5 million pounds added to the 2013 allocation, which would make the total year-to-year reduction closer to 15 percent. This will be part of an adjustment required to recoup allocation losses by two HCFC producers who had completed a legal trade of allocations that EPA had failed to recognize in a previous allocation rule.”

According to McCrudden, a final ruling may not come until April.

Wake Up Call?
Whatever the final number, it will be well below the numbers established in 2012, and that is leading refrigerant suppliers to advise contractors and their customers to potentially look beyond R-22.

Gordon McKinney, vice president and COO, ICOR International, called the EPA No Action Assurance “a light switch” moment.

“Many realized at that very moment that R-22 would no longer be the most practical option for maintaining the enormous amount of R-22 systems in operation today,” he said. “Within hours of the news, the market reacted with substantial price increases.

“The consensus is that 2013 will be the first year that we will not have enough R-22 to satisfy the industry’s service requirements. This notion is quickly sinking in with distributors and their refrigerant customers.”

At the same time, National Refrigerants’ Maureen Beatty believes R-22 supplies, in some cases, may be adequate for the time being.

“While every wholesaler will not have R-22 to sell, and some who have it will not have as much as they had previously, it is our intent to continue to supply our customers with all of their R-22 needs as they continue to service existing equipment while properly planning for an orderly transition to non-ODS [ozone depleting substance] refrigerants.”

Other refrigerant manufacturers have issued similar statements to their customers.

REVERSING VALVE

Our weather has really been unstable. One day we need the heat and the next day we need the air conditioning. So this blog on the reversing valve will help you understand how your heat pump switches from heat to cooling.

Reversing valve is a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a residence or facility to be heated and cooled by a single piece of equipment, by the same means, and with the same hardware
Operation
The reversing valve has two states, relaxed and energized. The energized state is typically achieved by applying 24 volts of alternating current, which is commonly used in HVAC . The heat pump can be designed by the manufacturer to produce cooling or heating with the reversing valve in the relaxed state. When the reversing valve is energized, it will produce the opposite conditioning. In other words, a reversing valve installed in such a way as to produce cooling when relaxed will produce heating when energized. Likewise, a reversing valve installed to produce heating when relaxed will produce cooling when energized
Control
Depending on the construction and use of the heat pump, the reversing valve may be driven by the heat pump through the use of a control board, or it may be driven directly by a thermostat (typically from the "O" terminal)

TECHNOLOGY TAKEOVER: Thermostats & Controls

Trane’s ComfortLink™ II Control is a programmable control granting remote access from any Internet-enabled computer, smartphone, or tablet. The control provides live weather, temperature management, and more on a 7-inch, color touch-screen display. ComfortLink II provides room-to-room control and monitors indoor and outdoor temperatures, allowing users to adjust system settings for the highest efficiency. The system also informs owners when it is time for a filter change and when routine maintenance needs to be performed. The unit is fully upgradable with future Trane offerings. When not in use, the ComfortLink II can display a single photo or an entire slideshow of images. The unit also offers customizable home screens and a variety of optional bezels to match a home’s style.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).For more information about Indoor Air Quality and other HVAC topics,click here to visit our website.

TECHNICAL TERMS (continued)

HVACR
Heating, ventilating, air conditioning, and refrigeration.

REFRIGERANT
A fluid that absorbs heat at low temperatures and rejects heat at higher temperatures.

REFRIGERANT CHARGE (or, “charging the refrigerant”)
The procedure an HVACR technician performs to ensure that the system has enough of the right kind refrigerant for peak operating performance.

R-22
A refrigerant containing chlorine used in air conditioning systems. The EPA has mandated that R-22 cannot be manufactured after 2010 because it has been linked to the depletion of the ozone layer and global warming. Most commonly referred to by its trademarked name, Freon.

R-410A
The refrigerant that replaces R-22. It does not contain chlorine and is not hazardous to the environment

UNDERSTANDING HEAT PUMP SEQUENCE OF OPERATION

Cooling Cycle
Mechanical: Heat pump cooling operation is similar to the operation of a standard cooling system.
1. The compressor pumps out high-pressure, superheated refrigerant vapor.
2. The vapor leaves the compressor and passes through the reversing valve.
3. It flows through the outdoor vapor line to the finned outdoor coil. Air from the outdoor fan removes heat from the refrigerant vapor. When enough heat is removed, the vapor condenses into a high-pressure liquid. The liquid temperature is slightly warmer than ambient air temperature.
4. This warm, high-pressure liquid leaves the outdoor coil, and flows through the copper refrigerant liquid line.
5. At the end of the liquid line, the refrigerant passes through a metering device, reducing its pressure and temperature.
6. As the liquid, under reduced pressure, enters the indoor coil surface, it expands and absorbs heat from the indoor air passing over the finned surface. Heat, from the indoor air, causes the low-pressure liquid to evaporate and cools the indoor air. The refrigerant is now a cool vapor.
7. The refrigerant vapor travels through the insulated vapor line to the reversing valve. The reversing valve directs the refrigerant into the accumulator.
8. The accumulator controls liquid refrigerant and refrigerant oil flow back to the compressor.
9. Refrigerant vapor flows through the suction line to the compressor. The cycle then repeats.
Electrical: The electrical cycle is also similar to a standard cooling system.
1. The thermostat calls for cooling.
2. This sends a 24-volt signal through the "Y" terminal to the compressor contactor in the outdoor unit. The compressor and outdoor fan start.
3. At the same time a 24-volt signal flows through the "G" terminal to the indoor blower relay. The indoor blower starts.
4. The cooling system is now in operation.
5. The thermostat satisfies and ends the call for cooling.
6. This ends the 24-volt signal to the compressor contactor and the outdoor unit stops.
7. This ends the 24-volt signal to the indoor blower relay and the indoor blower stops.

Heating Cycle
Mechanical: System operation is basically the same as during the cooling cycle. The difference is the position of the reversing valve that reverses refrigerant flow.
1. Setting the thermostat to the heat mode automatically powers the solenoid valve in the reversing valve.
2. The compressor pumps out high-pressure, superheated refrigerant vapor.
3. The vapor leaves the compressor and passes through the reversing valve.
4. Refrigerant flows through the insulated, indoor vapor line to the finned indoor coil. Air from the indoor blower removes heat from the refrigerant vapor warming the indoor air and heating the house. When enough heat is removed, the vapor condenses into a high-pressure liquid. The liquid temperature is slightly warmer than indoor air temperature.
5. This warm, high-pressure liquid leaves the indoor coil, flows through the small copper refrigerant liquid line, and exits the building.
6. At the end of the liquid line, the refrigerant passes through a metering device in the outdoor coil, reducing its pressure and temperature.
7. As the cool liquid, under reduced pressure, enters the outdoor coil surface, it expands and absorbs heat from the outdoor air passing over the finned surface. Heat, from the outdoor air, causes the low-pressure liquid to evaporate. The refrigerant is now a cold vapor.
8. The cold refrigerant vapor travels through the larger, outdoor vapor line to the reversing valve. The reversing valve directs the refrigerant into the accumulator (if the system has an accumulator, otherwise the compressor acts as the accumultor).
9. The accumulator holds liquid refrigerant and refrigerant oil and controls their flow back to the compressor. They flow out through a small port inside the accumulator bottom.
10. Refrigerant vapor flows through the suction line to the intake of the compressor. The cycle then repeats.
Electrical: The heating electrical cycle is similar to the cooling cycle.
1. Setting the thermostat to the heat mode automatically powers the reversing valve solenoid.
2. The thermostat calls for first stage heat.
3. This sends a 24-volt signal through the "Y" terminal to the compressor contactor in the outdoor unit. The compressor and outdoor fan start.
4. At the same time a 24-volt signal flows through the "G" terminal to the indoor blower relay. The indoor blower starts.
5. The heating system is now in operation.
6. If first stage heating is not enough to heat the building, the second stage thermostat bulb makes a call for more heat.
7. A 24-volt signal flows through the "W2" terminal to the heating relay in the indoor air handler.
8. This sequencing relay cycles on electric elements to add more heat to the indoor air stream.
9. As the building warms, the second stage call for heat ends.
10. This breaks the 24-volt signal to the "W2" terminal and de-energizes the heating relay.
11. The electric heat element(s) cycle off.
12. The first stage thermostat call satisfies and ends the call for heat.
13. This ends the 24-volt signal to the compressor contactor and the outdoor unit stops.
14. This ends the 24-volt signal to the indoor blower relay and it stops.
15. The system is now off. The reversing valve pilot solenoid stays energized as long as the thermostat is set for heating.

Defrost Cycle
Mechanical: In heating mode, the outdoor coil is the evaporator. Moisture from the outdoor air condenses on the cooler coil and normally runs off. During the colder part of the heating season, this moisture freezes and blocks air movement through the coil. The frost is removed in the defrost cycle.
1. The heat pump operates in the heating mode.
2. The defrost control detects the buildup of ice on the outdoor coil.
3. The reversing valve solenoid de-energizes, directing hot gas from the compressor to the outdoor coil to defrost.
4. The outdoor fan stops. If it didn't, cold air from the fan prevents the melting effect of the hot refrigerant.
5. As the temperature of the indoor air drops, controls energize the electric heat elements to warm the indoor air.
6. When the defrost control detects the ice has melted, it terminates the defrost mode.
7. The reversing valve shifts to the heating position and directs hot refrigerant gas to the indoor coil.
8. The outdoor fan operates.
9. The electric elements cycle off.
10. The unit is now in the normal heating mode.
Electrical: A defrost control must recognize when there is a layer of ice on the outdoor coil and when that ice must be removed. There are several different types of defrost controls. While they vary in the methods used to recognize when defrost is necessary, they all take the same action. These controls also must determine when the ice is gone and terminate defrost.
Electrical: Setting the thermostat for the emergency heat mode de-energizes the compressor contactor in the outdoor unit and the indoor blower relay. A call for heat energizes the heating relay in the indoor air handler. This brings on the electric heating elements.
In some cases, selecting emergency heat also powers an emergency heat relay. This relay's contacts electrically bypass any outdoor thermostats used to stage the electric heat elements. This provides the thermostat with full heat from the indoor electric elements.
1. Moving the thermostat selector to the emergency heat position breaks the electrical circuit to the compressor contactor and the indoor blower relay.
2. This action powers the red emergency heat warning light.
3. A thermostat heat call energizes the electric heat relay.
4. The electric heat relay contacts close powering the heat elements and the indoor blower.
5. The heat call ends and the thermostat de-energizes the electric heat relay.
6. The electric heat relay contacts open de-energizing the electric elements and indoor blower.
7. Moving the thermostat selector to the heat position completes the circuit to the compressor contactor and indoor blower relay.
8. The red emergency heat light goes out.

TECHNICAL TERMS (continued)

13 SEER (we discussed SEER in our previous post, so we all know what that is)
This is the new minimum efficiency standard (effective January 2006) for an air conditioner or heat pump. All new units must now meet this standard. Previously manufactured equipment may be used, sold, and installed.

COP
Coefficient of performance, an efficiency ratio that compares the amount of heat delivered to the amount of energy used. As with MPG on a car, the higher the score the more energy efficient the equipment is

HSPF
Heating Seasonal Performance Factor, an equipment efficiency rating. As with MPG on a car, the higher the rating the more fuel efficient the equipment is.

TECHNICAL TERMS (continued)

EER (Energy Efficiency Ratio)

A ratio to determine the energy efficiency of an air conditioner. The higher the EER rating, the more efficient the unit. EER ratings are generally lower than SEER ratings because SEER ratings are seasonally adjusted while EER ratings are calculated against a fixed ambient temperature.

Efficiency

A measure of how much energy is used to accomplish a cycle, measured by Seasonal Energy Efficiency Ratio (SEER) or Energy Efficiency Ratio (EER). The higher the rating, the more efficient a system is and the lower your energy consumption will be.

SEER

A rating that expresses the efficiency of air conditioning equipment throughout an entire average cooling season, including both the hottest and coolest days. It stands for Seasonal Energy Efficiency Ratio. The higher the SEER rating, the more efficient the system