HART 1441 (Residential): Module 2 - Unit 36 Refrigeration Applied to Air Conditioning

What are the 4 main components used in both refrigeration and comfort cooling?

1. the evaporator 2. the compressor 3. the condenser 4. the metering device

What type of expansion device is used on almost all ductless split systems?

Electronic expansion valves (EEVs) are used on almost all ductless split systems.

What is dry bulb?

It is ambient temperature or room temp.

What is the A coil used for?

The A coil is used for upflow, downflow, and horizontal flow applications.

What is a package unit?

A refrigerating system where all major components are located in one cabinet.

What is a split-system refrigeration unit?

A refrigeration or air-conditioning system that has the condensing unit remote from the indoor (evaporator) coil and uses interconnecting refrigerant lines known in the field as the line set.

What is Air-Conditioning classified as in terms of refrigeration?

Air-conditioning is classified as high-temperature refrigeration.

What are the fins on an evaporator used for?

Aluminum fins attached to the coil of either type give more surface area for better heat exchange.

How often should condenser coils be cleaned?

Condenser coils should be cleaned every 3-5 years.

According to the DOE, how much airflow can be lost due to air leaks?

Conventional split systems with ductwork have the potential, according to the DOE, to lose as much as 30% of their airflow due to air leaks; not so with ductless split systems.

What is an evaporative cooler?

Devices that provide this type of cooling use fiber mounted in a frame with water slowly running down the fiber. Fresh air is drawn in and through the water-soaked fiber and cooled by evaporation to a point close to the wet-bulb temperature of the air.

What is a general rule regarding solar load in the northern hemisphere?

During the summer the top of the house is heated. During the winter the front of the house is heated.

What is another term for evaporative coolers?

Evaporative cooler are also commonly referred to as swamp coolers.

What are the three common configurations for Evaporative coolers?

Evaporative coolers come in three common configurations: the drip-type swamp cooler, the spray or slinger-type swamp cooler, and the rotary-type swamp cooler.

True or False: Hermetic compressors have only recently been designed to be cooled by suction-gas.

False. Hermetic compressors have always been suction-gas-cooled.

True or False: Evaporative coolers use 80% outdoor air and 20% indoor air.

False: Evaporative cooling units use 100% outdoor air.

When are Ground level package units used?

Ground level package units are used when the roof cannot support the weight of the unit or when servicing the unit becomes a problem.

How does heat leak into a structure?

Heat leaks into a structure by conduction, infiltration, and radiation (the sun's rays or solar load)

What is a disadvantage of a side discharge condenser?

However, any noise generated inside the cabinet is discharged into the leaving airstream and may be clearly heard in a neighbor's yard.

If a duct is running through a hot attic what must happen?

If the duct is run through a hot attic, the duct must be insulated.

What are the airflow measurements you may see in coastal areas and desert areas?

In humid coastal areas, airflow may be 350 cfm/ton, and 450 cfm/ton may be used in desert areas.

In the northern hemisphere where is the greatest solar load on a structure?

In the northern hemisphere, the summer solar load on a structure is greater on the east and west sides of the structure.

What are some advantages and disadvantages or top discharge condensing units?

In this type of unit, the hot air and noise are discharged from the top of the unit into the air. This is advantageous as far as air and noise are concerned, but because the fan and motor are on top, rain, snow, and leaves can fall directly into the unit.

What is a power ventilator?

It is a thermostatically controlled fan that cycles on when the attic temperature reaches a predetermined temperature, typically 85°F.

What is another name for a package unit?

It is also called self-contained equipment.

What temperature does R-22 boil at atmospheric pressure?

Liquid R-22 boils at -41°F at atmospheric pressure

What is the limit to how hot the discharge line should get?

Most manufacturers agree that the discharge line leaving the compressor should not exceed 225°F.

What is a multi-position package unit?

Multi-position package units have the ability to be used for either rooftop application or ground level application, and can save storage space for a wholesaler or contractor.

What are the three styles of package units?

Package units come in three styles: ground level, rooftop, and multi-position.

What are the 3 main heating options for a package unit?

Package units have three main heating options: natural gas heating, electric heating, and heat pump

Where and when were ductless spit systems first produced?

Production of ductless split systems began in Japan in the early 1970s.

What are the 2 refrigerant blend replacements for R-22 in residential and commercial air conditioning applications?

R-410A and R-407C are the two refrigerant blend replacements for R-22 in residential and commercial air-conditioning applications. R-410A is designed for new applications and R-407C can be used in new and retrofit applications.

What temperature does R-410A boil at atmospheric pressure?

R-410A boils at -60°F at atmospheric pressure.

How are reciprocating compressors usually cooled?

Reciprocating compressors used in air-conditioning are mainly cooled by suction gas and air passing over the shell of the compressor.

What is the most common style of package unit?

Rooftop package units are the most common in the field.

How are rotary compressors cooled?

Rotary compressors are cooled with the discharge gas leaving the compressor.

What is the difference between a power ventilator and a solar-powered ventilator?

Solar-powered attic fans operate in the same manner as traditional electric-powered attic fans except solar-powered attic fans receive their power from photo-voltaic cells (solar panels) located on the roof.

What is the H coil used for?

The H coil is normally used in horizontal applications where space is limited, such as crawl space, attics, basements, and above drop ceilings.

What are the two basic types of equipment for air-conditioning purposes?

The Two basic types of equipment for air-conditioning purposes: package equipment and split-system equipment.

What is an advantage of a side discharge condenser?

The advantage of this equipment is that the fan and motor are located under the top panel

What is the supply temperature that should be expected in the average system?

The air leaving the air handler could be expected to be about 55°F in the average system.

What does the air-side of an AC system consist of?

The air side of an air-conditioning system consists of the indoor blower as well as the supply air and the return air ducts.

How is coil temperature controlled?

The coil temperature is controlled with the airflow across the evaporator coil. More airflow will cause higher coil temperatures, and less airflow will cause lower coil temperatures.

What are the coils and fins made out of in the condenser?

The coils are copper or aluminum and have aluminum fins to add to the heat exchange surface area

What are the 3 different designs for the evaporator?

The different designs are known as the A coil, the slant coil, and the H coil.

How does the drip-type evaporative cooler work?

The drip-type evaporative cooler uses a pump to lift a column of water to the top of the evaporative pad, where the water drips down and wets the surface of the pad. As the hot, dry outside air passes through the wet pad, heat causes some of the moisture from the pad to evaporate. The evaporating moisture absorbs heat from the air stream passing through the pad, and the air stream is cooled.

What is the evaporator?

The evaporator is the component that absorbs heat into the refrigeration system.

What is the most popular configuration for condensing units?

The most popular configuration for condensing units in residential equipment is the top-discharge design

What should the return temperature be in the average system?

The return air will normally be about 75°F.

What are two types of natural ventilators?

The ridge vent is cut along the top of the entire roof ridge. Another vent, called a soffit vent, typically runs along the bottom of the roof overhang.

How does the rotary-type evaporative cooler work?

The rotary-type evaporative cooler uses a motor to rotate the evaporative pad in the water sump. As the pad rotates, it becomes wet and functions in a manner similar to the other two types just discussed.

What is a slant coil?

The slant coil is a one-piece coil mounted in the duct on an angle (usually 60° ), or slant, to give the coil more surface area. The coil can be used for upflow, downflow, or horizontal flow when designed for these applications

How does the spray or slinger-type evaporative cooler work?

The spray or slinger-type evaporative cooler uses a pump to spray water onto the evaporative pad. Just as with the drip-type swamp cooler, the moisture from the pad evaporates, cooling the airstream.

What is Wet Bulb temperature?

The temperature caused by the cooling effect of the humidity in an area

What is Dry Bulb temperature?

The temperature your thermostat is measuring

What are the three kinds of attic ventilation?

There are three kinds of attic ventilation, power, natural, and solar powered.

What must a power ventilator have and why?

This fan must have a high-limit control to shut the fan off in case of an attic fire. The power ventilator would just feed air to a fire.

True or False: The shorter the line set the more efficiently the system will operate.

True. The shorter the line set, the more efficient the system will operate.

What is the typical dry bulb and wet bulb of room air?

Typically, room air may be 75°F dry-bulb and have a humidity of 50%, which is 62.5°F wet-bulb

Why is it advisable to have more than one coil in parallel?

When a coil becomes too long and excessive pressure drop occurs, it is advisable to have more than one coil in parallel.

When must a distributor be used?

When there is more than one circuit, a distributor must be used to distribute the correct amount of refrigerant to the individual circuits