Heating, Air Conditioning, and Refrigeration Mechanics and Installers
Heating, air conditioning, and refrigeration mechanics and installers—often referred to as HVACR technicians—work on heating, ventilation, cooling, and refrigeration systems that control the air quality in many types of buildings.
Heating, air conditioning, and refrigeration mechanics and installers typically do the following:
- Travel to worksites
- Follow blueprints or other design specifications to install or repair HVACR systems
- Connect systems to fuel and water supply lines, air ducts, and other components
- Install electrical wiring and controls and test for proper operation
- Inspect and maintain customers’ HVACR systems
- Test individual components to determine necessary repairs
- Repair or replace worn or defective parts
Heating and air conditioning systems control the temperature, humidity, and overall air quality in homes, businesses, and other buildings. By providing a climate controlled environment, refrigeration systems make it possible to store and transport food, medicine, and other perishable items.
Although trained to do all three, HVACR technicians sometimes work strictly with heating, air conditioning, or refrigeration systems. They also may specialize in certain types of HVACR equipment, such as water-based heating systems, solar panels, or commercial refrigeration.
Depending on the task, HVACR technicians use many different tools. For example, they often use screwdrivers, wrenches, pipe cutters and other basic handtools when installing systems. To test or install complex system components, technicians may use more sophisticated tools, such as carbon monoxide testers, voltmeters, combustion analyzers, and acetylene torches.
When working on air conditioning and refrigeration systems, technicians must follow government regulations regarding the conservation, recovery, and recycling of refrigerants. This often entails proper handling and disposal of fluids.
Some HVACR technicians sell service contracts to their clients, providing regular maintenance of heating and cooling systems.
Other craft workers sometimes help install or repair cooling and heating systems. For example, on a large air conditioning installation job, especially one in which workers are covered by union contracts, ductwork might be done by sheet metal workers and duct installers, or electrical work by electricians. In addition, home appliance repairers usually service window air conditioners and household refrigerators. For more information on these occupations, see the profiles on sheet metal workers, electricians, or home appliance repairers.
Power Plant Operators, Distributors, and Dispatchers
Power plant operators, dispatchers, and distributors control the systems that generate and distribute electric power.
Power plant operators, distributors, and dispatchers typically do the following:
- Control power-generating equipment, such as boilers, turbines, generators, and reactors
- Read charts, meters, and gauges to monitor voltage and electricity flows
- Check equipment and indicators to detect evidence of operating problems
- Adjust controls to regulate the flow of power
- Start or stop generators, turbines, and other equipment as necessary
Electricity is one of our nation’s most vital resources. Power plant operators, distributors, and dispatchers control power plants and the flow of electricity from plants to substations, which distribute electricity to businesses, homes, and factories. Electricity is generated from many sources, including coal, gas, nuclear energy, hydroelectric energy (from water sources), and wind and solar power.
The following are types of power plant operators, distributors, and dispatchers:
Nuclear power reactor operators control nuclear reactors. They adjust control rods, which affect how much electricity a reactor generates. They monitor reactors, turbines, generators, and cooling systems, adjusting controls as necessary. Operators also start and stop equipment and record the data. They may need to respond to abnormalities, determine the cause, and take corrective action.
Power distributors and dispatchers, also known as systems operators, control the flow of electricity as it travels from generating stations to substations and users over a network of transmission and distribution lines. They prepare and issue switching orders to route electrical currents around areas that need maintenance or repair. Distributors and dispatchers also monitor and operate current converters, voltage transformers, and circuit breakers. They must detect and respond to emergencies, such as transformer or transmission line failures.
Power plant operators control, operate, and maintain machinery to generate electric power. They use control boards to distribute power among generators and regulate the output from several generators. They regulate the flow of power between generating stations and substations, and they monitor instruments to maintain voltage and electricity flows from the plant.
Roofers repair and install the roofs of buildings using a variety of materials, including shingles, asphalt, and metal.
Roofers typically do the following:
- Inspect problem roofs to determine the best way to repair them
- Measure roof to calculate the quantities of materials needed
- Replace damaged or rotting joists or plywood
- Install vapor barriers or layers of insulation
- Install shingles, asphalt, metal, or other materials to make the roof watertight
- Align roofing materials with edges of the roof
- Cut roofing materials to fit angles formed by walls, vents, or intersecting roof surfaces
- Cover exposed nail or screw heads with roofing cement or caulk to prevent leakage
Properly installed roofs keep water from leaking into buildings and damaging the interior, equipment, or furnishings.
There are two basic types of roofs, low-slope and steep-slope:
- Low-slope: About two-thirds of all roofs are low-slope. Most commercial, industrial, and apartment buildings have low-slope roofs. Low-slope roofs rise 4 inches or less per horizontal foot and are installed in layers.
For low-slope roofs, roofers typically use several layers of roofing materials or felt membranes stuck together with hot bitumen (a tar-like substance). They glaze the top layer to make a smooth surface or embed gravel in the hot bitumen to make a rough surface.
An increasing number of low-slope roofs are covered with a single-ply membrane of waterproof rubber or thermoplastic compounds.
- Steep-slope: Most of the remaining roofs are steep-slope. Most single-family houses have steep-slope roofs. Steep-slope roofs rise more than 4 inches per horizontal foot.
For steep-slope roofs, roofers typically use asphalt shingles, which often cost less than other coverings. On steep-slope roofs, some roofers also install tile, solar shingles, fiberglass shingles, metal shingles, or shakes (rough wooden shingles).
To apply shingles, roofers first lay, cut, and tack 3-foot strips of roofing over the entire roof. Then, starting from the bottom edge, they nail overlapping rows of shingles to the roof.
A small but increasing number of buildings now have “green” roofs that incorporate landscape roofing systems. A landscape roofing system typically begins with a single or multiple waterproof layers. After that layer is proven to be leak free, roofers put a root barrier over it, and, finally, layers of soil, in which vegetation is planted. Roofers must ensure that the roof is watertight and can endure the weight and water needs of the plants.