3. Intro to HVACR - Four Components of Indoor Comfort Control (Unit 2 of 2)

Fours Components of Indoor Comfort Control

Comfort control involves temperature control, humidity control, air filtering management, and air flow. In the field, you'll use these components to accomplish indoor comfort control.

Central Air Conditioning

Central Air Conditioning You can change a ducted (or forced) warm-air distribution system to a central air system with the addition of an evaporator, as shown here. See Pic Central Air System with an Evaporator and Refrigerant Lines You can use this kind of air-movement system for cooling a home. The image shows the same home hot-air furnace shown before, but with one additional component - an evaporator coil housed in the blower section of the furnace.

Humidity Control - Adding Humidity - Bypass system

Humidity control is one of the four components of the indoor comfort-control system. In cold climates, where the heating system dries the air, it's often necessary to add moisture to the airflow. Adding Humidity One popular method of adding humidity is a bypass system as shown in the image. Here, a duct(humidifier) runs between the supply and return plenums. See Pic Duct Running between a Supply and Return Plenum

Humidity Control - Adding Humidity - Motor driven water wheel

A motor-driven water wheel, shown in part B of the image, rotates in a pool of water and delivers the water to the airstream where it gets absorbed. See Pic A Motor-Driven Water Wheel A control device, known as a humidistat, will open or close a damper to this bypass system based on the humidity needs of the building. Water sprays and steam injection are another possible way to add humidity to a building.

Warm-Air Distribution Systems

A second method of heating an area uses the transfer of air. The term for this home heating system is a ducted warm-air or forced warm-air distribution system. The diagram shows the furnace used for hot-air heating. See Pic Shown are the components for a ducted warm-air or forced warm-air distribution system for a home or small business. Warm-air distribution systems typically follow these common steps, although they may have additional features.

Basics of Residential Cooling

Basics of Residential Cooling 1) Adjusting the thermostat Adjusting the thermostat to a lower temperature turns off the furnace's gas or oil burner. 2) Turn on the air-conditioning system. The AC system supplies liquid refrigerant to the evaporator coil in the blower housing. 3) The house begins to cool. Cold air exits the evaporator coil and passes to the home through the air supply plenum to cool the home. The air-conditioning system can be a dedicated cooling-only system, or it can be a heat pump. In the case of a heat pump, the furnace section that contains the oil or gas burner may or may not be eliminated from the heating/cooling system. Now you know what's involved in a complete small indoor comfort-control system. The home air becomes heated or cooled depending upon the thermostat setting and air temperature. In the supply or return duct for the rooms, a damper controls the airflow. Also, a filter, located in the furnace, filters out air impurities. By scaling up the size of these components, you can heat a factory, hospital, warehouse, gymnasium, factory, or other such area.

Filtering Systems - Electrostatic System

Electrostatic System One of the most efficient air-cleaning systems is the electrostatic air-cleaning system. Here's a typical electrostatic system. See Pic An Electrostatic System In an electrostatic system, a very high voltage passes across two sets of wire mesh screens. The first screen charges the air and the impurities in the air with a high-level positive charge. As the air passes through the negatively charged screen, the positively charged dirt particles collect on the negative mesh screen. In an actual electrostatic system, there are many mesh screens stacked together on insulators in positive-negative/positive-negative arrangements. These arrangements are called cells, and many such cells make up a complete unit known as an electrostatic precipitator. Some manufacturers produce air filters that are self-charging and use the electrostatic precipitator principle without using a power supply, which is highly efficient.

Filtering Systems - Standard pleated paper filter

Filtering Systems One of the most common methods of cleaning the air uses the standard pleated paper filter. The paper filter element has pleats to increase the surface area of the filter that becomes exposed to the airflow. The paper element filters are discarded after each use. Reusable filters made up foam or metal-mesh filters are also available. You can clean these types of filters by washing the filter element. The filtering systems also use fiberglass elements, which are disposable.

Heating Systems

In most homes, the heating system may be part of the central comfort system or installed separately along the wall. The central system will have forced air, too, and it can be electric or natural gas. The wall mounted system can be baseboards or radiators. It can use hot water (hydronic) or steam and can be heated by coal, natural gas, propane, or fuel oil. Hot water, or hydronic, systems start with a furnace or boiler. Here, a fossil fuel burns and its heat transfers to the water to make the hot water that circulates through the building provide heat to baseboard elements in each room.

Key Points Introduction to HVACR - Four Components of Indoor Comfort Control - (Unit 2 of 2)

Key Points * Home heating systems used for warming a space include baseboard, radiant heat, and air-movement systems. * Baseboard and radiant heat systems can be electric or hydronic. * Hydronic systems use a fossil fuel-based furnace or boiler to heat water that's then circulated through the baseboards. * Ducted warm-air or forced warm-air distribution systems use an oil or gas burner to generate heat. In these systems, a fan or blower moves cool air across a heat exchanger and then forces the newly warmed air through ducts to the various rooms in the house. * Ducted warm-air or forced warm-air distribution systems allow for the addition of central air-conditioning, humidity control, and air-filtering, which baseboard and radiant heat systems don't allow for. * Humidity control systems can add moisture to the air using a water wheel or remove moisture from the air using a desiccant wheel.

Process of a Warm-Air Distribution System

Process of a Warm-Air Distribution System * 1) An oil or gas burner heats an area inside the furnace, and the flue takes its exhaust gases away. * 2)The heat exchanger transfers this heat energy to the air. * 3) A fan or blower moves the air past the heat exchanger and moves the heated air throughout the home.

Humidity Control - Removing Humidity - Desiccant-covered motorized wheel

Removing Humidity In the summer, you may need to remove humidity from a building. This process often happens automatically as warm, moist air passes over a cold evaporator coil. The moisture in the airstream will condense on the evaporator and collect in a drain. Another system of removing moisture is to use a material such as a desiccant. You would normally find desiccant material in a small packet in the shipping boxes used for electronic equipment and other household goods. It's possible to use a desiccant wheel in a cooling system, as shown in the image. This desiccant wheel can be located in either the return or supply plenums, but you would normally find it in the return plenums. See Pic A desiccant-covered motorized wheel can remove excess moisture from the airstream. In the simplified diagram, the dampers are open, and air is passing over the desiccant wheel. As the air passes over the wheel, moisture is absorbed. After a timed interval, or a sensed moisture limit becomes exceeded, the dampers will change position to bypass the air around the desiccant wheel. At the same time, a heater/blower system energizes to heat and dry the desiccant-coated wheel. Once the desiccant dries, the dampers transfer back to absorb more moisture from the building's air.

Warm-Air Distribution Systems (Cont.)

The pathways for air distribution are called plenums. These are square — or rectangular — connected cross sections of metal or fiberglass board that come in various lengths. They typically run from the furnace at one end of the home to the opposite end of the home, where they're capped. These plenums run through parts of the floor joists called chases, or you'll find them hung from the floor joists. From these large supply and return-air plenums, smaller ductwork is run into each room to allow air to move into and out of each room. The diagram shows a room that has a wall register on each end wall. See Pic In a hot air heating/air-conditioning system, the air flows from a supply plenum to a return plenum. In a ducted warm-air or forced warm-air distribution system, the hot air supply plenum passes air through a smaller duct to a wall register or floor register. A damper inside the supply duct controls the amount of heated (or cooled) air that enters the room. A return register on the opposite wall allows air to move out of the room to be reheated (or re-cooled). Returning the air to the furnace greatly increases the efficiency of the system.

Practice: Heating Systems

What are the steps in the process of a warm-air distribution Systems? See Pic