What is HVAC? HVAC is the abbreviation for heating, ventilation, and air conditioning systems that provide indoor climate control for residential and commercial structures. An HVAC system can be quite complex. When HVAC repair or HVAC installation is necessary, the services of a reliable HVAC contractor are required.
The HVAC industry is a huge global enterprise that provides countless career opportunities. Everything from installation, operation and maintenance, to design and construction, to manufacturing and sales, to research and education. Annual sales are in the 100s of billions in the U.S. alone. There are numerous professional, technical, and trade organizations supporting the industry; such as ASHRAE, SMACNA, ACCA, and AMCA, to name only a few.
An HVAC system is one part of the entire group of mechanical systems for a structure, which also include electrical, plumbing, and refrigeration systems. HVAC systems and individual appliances come in many types and applications.
Which HVAC System is Right for You?
HVAC systems are classified as either central or local. A central air conditioning heating system provides necessary heating, cooling and ventilation from a central place within the structure; such as a furnace or boiler room. Heated water, steam, or air is circulated through piping or ductwork throughout the structure to achieve the necessary heating or cooling required. Central systems may be radiant heat, or forced air heat.
A radiant heating system operates by transferring heat from heated water or steam that is circulated through a system of radiators or heat exchangers. Radiators transfer the heat to the area or room in which they are located; by convection, not â€œradiation.â€ Note: convection is the internal movement of currents within fluids; in this case hot fluids or steam. Radiation is heat emitted from the surface of a hot object.
A forced air central heating system works by heating an exchanger, (usually within the furnace) either by hot water, gas, electricity, or oil. Air is forced to pass over or through the exchanger, which in turn heats the air. The hot air is then circulated through sheet metal ducts which flow into each room or area of the structure through register vents.
Central air conditioning employs a compressor and condenser unit that uses a liquid or gas coolant. The coolant is circulated through pipe and cools the exchanger; air is forced over or through the exchanger, cooling the air. The cool air is circulated through the same ductwork used to provide heat, cooling the structure. This unit is placed outside the structure in proximity to the furnace or boiler room, and exchanges considerable heat to the outside air.
Local HVAC systems may include wood or pellet stoves, space heaters, and window air conditioners. These devices provide heating or cooling to the immediate area or room; they do not circulate throughout an entire structure.
Electric baseboard heat may be included with local systems, if the unit is installed into a single area or room, and uses an individual thermostat control.
Ventilation is Part of the System
Ventilation is the aspect of an HVAC system that exhausts the inside air of a structure to the outside, replacing it with fresh outside air. This helps to remove moisture, bacteria, smoke, and odors that become airborne, contaminating the inside air.
HVAC systems also filter incoming air to prevent any outside contaminants from coming indoors. Building code requirements set specified air exchange flow rates for different areas of the structure, such as bathrooms, bedrooms, etc.
Local ventilation devices include window air conditioners which have an outside air exchanger, and exhaust fans in kitchen or bathroom areas operating with an individual switch. Technically, windows which open to allow outside ventilation also qualify.
A Word About Efficiency
Energy efficiency is another important aspect of HVAC system selection. By law, the HVAC industry must provide efficiency ratings for every system or device, based on the annual cost of operating that system or appliance. When choosing a new system or device, it is wise to pay special attention to these ratings.
While water heat may be more efficient for larger buildings, central forced air systems that provide both heating and cooling functions to a structure may be the best choice.
In areas where it is available, geothermal heating is the most efficient method. Geothermally heated water is utilized in a water HVAC system that transfers the heat throughout the structure.
In a central heating system, a zoned heating scheme utilizing multiple thermostats can maximize efficiency by lowering temperatures in different areas at times when they are not occupied. Programmable digital thermostats can perform this task with ease.
HVAC Is Part of the Design
An HVAC system is an important part of every new construction project. Sometimes, when undertaking an old home renovation project, it just makes good sense to include a new HVAC system into the home renovation idea. This is especially true if the home is being gutted for extensive renovations.
In residential applications, it may be adequate to use the services of a single HVAC contractor. In large buildings such as schools, office buildings, or high rise structures, usually HVAC specifications are given to mechanical, architectural, or building services design engineers. These professionals design and specify the necessary HVAC system, then commission a special trade contractor to build, install, and service it.
Selecting the Right HVAC Contractor
Whether for a small residential application or large building, a heating and air conditioning contractor may perform all aspects of installation themselves. Or, they may sub-contract to a duct work sheet metal contractor for the ventilation ducting. Sometimes a residential general contractor has the required expertise to install and service an HVAC system, or will sub-contract the work to a special trade contractor.
Whether installing a new HVAC system, or seeking the services of an HVAC technician to troubleshoot and repair an existing system, there may be additional factors to consider.
When locating and selecting a reliable HVAC contractor, use these helpful guidelines in the screening process:
- Gather names of possible candidates from several different resources. Word-of-mouth references from friends or relatives, local yellow page advertisement, and online contractor listing/referral web sites on the Internet are all good sources.
- Compile a list of candidates that are highly recommended; either by people you know that have experience with the contractor, or contractors that receive a good recommendation from the source you locate them from.
- Once you have a list of candidates, you may want to initiate phone contact and ask questions. Ask for references from past customers, what insurance coverage they carry, and licensing and certifications that they currently hold. Some HVAC contractors have certification or qualifications that are specific to only one or several name brand manufacturers, or only one type of HVAC system. You will want a contractor certified with the name brand and type of system you are planning. Check with local building authorities to see if there are any complaints or violations on any of the candidates.
- Thoroughly screen references; ask if the work was done properly, and promptly. Would they use the same contractor in the future?
- Not all HVAC contractors do the sheet metal duct work required for a central forced air system. Find out if they will be doing the duct work themselves, or sub-contracting it out. If sub-contracting, you may want references, insurance, and licensing verification for the sub-contractor, or a warranty from the main contractor.
- Narrow your list to 3 or 4 candidates. You may want to arrange a face-to-face meeting to see whether or not you feel comfortable with them.
- Provide each candidate with exact copies of detailed information and requirements for your HVAC project. This will insure an accurate quote from each. Ask to see physical copies of insurance, licensing, or any other certifications. Ask if they will be working on other projects simultaneously with your own, and what the timeline for completion will be.
- Once you have made your selection, draw up a contract that contains detailed information about the project; detailed system specifications, materials list, pricing, payment schedules or arrangements, and timelines for the work and completion. If your project involves work with other contractors, you will want to coordinate between them so they are not in each other's way as work progresses.
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