Heating, ventilation, and air conditioning (HVAC[1]) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation, as HVAC&R or HVACR or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers).
At the state level the rebates are still substantial. For example, switching to a zoned system can get you a $100 rebate from various A/C companies, and state rebates are also included. In Pennsylvania a high-efficiency air conditioner alone can get you up to $300, and a high-efficiency complete HVAC system can see up to $1000. Maryland's incentives get up to $1,250, with a $100 rebate on a tune up of an existing system.
An alternative to packaged systems is the use of separate indoor and outdoor coils in split systems. Split systems are preferred and widely used worldwide except in North America. In North America, split systems are most often seen in residential applications, but they are gaining popularity in small commercial buildings. The split systems are a great choice for small buildings where ductwork is not feasible or where the space conditioning efficiency is of prime concern [20]. The benefits of ductless air conditioning systems include easy installation, no ductwork, greater zonal control, flexibility of control and quiet operation [21]. In space conditioning, the duct losses can account for 30% of energy consumption [22]. The use of minisplit can result in energy savings in space conditioning as there are no losses associated with ducting.
From Day 1, Alberto walked us through the process, and present us with a variety of options based our budget for the project. His customer service is the best as he did not oversell any services and did not nudge us towards buying a unit that would stretch our budget. On installation day, HVAC Services sent out a crew of 6-7 guys, all of whom were very polite and kept their work areas clean, and installed the whole system the same day.

Unfortunately, manufacturers and contractors don’t publish this information…it’s a secret. Why? Who knows…but we have access to a full contractor pricing database of 1,000’s of different units in our online HVAC installation cost calculator, so let’s choose one for our example calculation. We’ll go with Carrier equipment, since our readers always bother us about them (despite us telling them that they are overpriced):
Don Vandervort has developed his expertise for more than 30 years, as Building Editor for Sunset Books, Senior Editor at Home Magazine, author of more than 30 home improvement books, and writer of countless magazine articles. He appeared for 3 seasons on HGTV’s “The Fix,” and served as MSN’s home expert for several years. Don founded HomeTips in 1996.
Monday the following week, no phone calls, or follow up.  I call to get an update and am told that they cannot install my system because they don't have time.  I ask what does that mean, one year? One week? Until the end of summer they say.  What does that mean I ask?  They say at the end of September.  I say thank you for wasting 1 month of my time.
My mom just received service from this company. She paid $609 to have her frion replaced. After two uses the AC stops working. A young rep comes out to the house again and notifies her that her entire AC unit and furnace need to be replace for just shy of ten grand, though when her frion was refilled she was told that her system should last another five years. When they came back to tell her how her entire system needed to be replaced, they were generous enough to offer her a $300 credit on the nearly $10,000 estimate of replacing the entire system that was working fine until they touched it. My best assumption would be that there is a mishap with the system is due to their negligence. Id suggest using another company other than these scam artists.
Outdoor Fan Motor -- The outdoor fan, also called the condenser fan, is exposed to external conditions. As such it is most prone to dust and debris and the extreme weather. In desert climates, the outdoor fan motor is subject to heat not only from normal operation but from the outside temperature as well. As it starts to fail, the fan may work fine in the cooler morning hours but stop by afternoon. This can shut down the entire system for hours. When they stop running completely, your air conditioner will no longer work. Running a faulty fan will lead to compressor failure, which is a very costly repair.
Wiring up the thermostat is usually pretty straightforward if an old one is being replaced. If a thermostat is being put in where one had never been before, that could involve running new wiring. The placement of the thermostat is also important so that its sensors can get an accurate reading of the temperature. A thermostat that is blocked by a bookcase or other large furniture will not get a good reading and will not perform efficiently.

If you’re purchasing from a big-box store, you can expect to pay approximately $120-$1,000 for a window unit. Window units are appealing for their quick setup and relatively low cost, but they can use more energy over time than central air and only cool the room in which they’re installed. The price will vary depending on the type of air conditioner you buy and its cooling capacity. Window units, which require minimal installation, are one of the most affordable options on the market. Portable air conditioners don’t have the cooling power of a window unit, but they do have the perk of being transportable from room to room. Expect to pay between $225 and $800 for a portable air conditioner, on average. The cost of an air conditioning system with coils, condenser and line (not including installation or ductwork) can range from approximately $2,000 to $4,000 or more. If you don’t have (and don’t want to put in) ducts, a ductless mini-split air conditioner is a good option, although pricey up front. Pricing can range from $650 to $4,250 per unit on average; you’ll need one unit for each room in which you want temperature control.
Compressor -- Compressors are outdoor components in your system. The compressor is the pump that circulates the refrigerants through the air-conditioner. You can hear it when it's running so you'll know if it's working just by listening. If it starts getting louder, your compressor is about to fail. If it makes no sound when it should be on, it has already failed. Compressors fail for a number of reasons. Most often they fail due to strain from another failed part such as the fan motor. Electrical storms can also damage compressors. If the sound from the compressor gets louder or if you see a decrease in performance, you should have your compressor checked. A failed compressor will not heat or cool your house.
Hi John, Thanks for reaching out, we would be happy to help you connect with a pro for your project. You can submit a request to our pros here: www.homeadvisor.com, browse a list of pros that serve your area here: http://www.homeadvisor.com/c.html, or send your info to emailus@homeadvisor.com and a project advisor will reach out to assist you. –HASupport
The HVAC installation costs below are based on residential installations only, and are priced for a single unit. Two units should be about twice the price. “Tim, shouldn’t there be a discount?” If people start giving you discounts, they are probably charging you too much to begin with.  That’s our philosophy anyway. Twice the parts and time should be twice the price from a fair contractor. The prices listed include component parts (with warranty), labor, and all materials for a complete HVAC installation.

Engineers have pointed out some areas where efficiency of the existing hardware could be improved. For example, the fan blades used to move the air are usually stamped from sheet metal, an economical method of manufacture, but as a result they are not aerodynamically efficient. A well-designed blade could reduce electrical power required to move the air by a third.[28]
Is there a such thing as a PQ-15 valve? No…but how do we know? And oh, by the way, there are only two types of line-sets: 3/4 inch, and 7/8 inch. All modern equipment runs on a 7/8 inch line-set, so the only time they’ll have to change something is if you have antiquated 3/4 inch line-set from the 60’s or 70’s. I’m digressing though…the point is that they can easily prey on uninformed consumers…like you, baby bird! Don’t worry though…you’ll be flying by the end of this article.
When central air conditioning service fails during a heat spell, you may have to wait days for an HVAC repair technician or an ac contractor to show up, and you'll probably pay at least several hundred for the repair. But if you're comfortable working around electricity and are willing to spend about $50 on parts, you can probably repair your air conditioning service yourself in about two hours and save about $225 on parts markup and labor.
Filtration systems -- A second-stage filter is sometimes inserted & used to remove particulates such as pets, smoking or cooking, as well as other odors, gases, and VOCs (volatile organic compounds). A HEPA filter is also available to remove spores, pollens, bacteria and lung-damaging particles. There are also systems that use ultraviolet (UV) light to protect against bacteria and germs.
Contact/Relay -- Relays are electronically controlled switches that activate the various components of your HVAC system. They manage everything from the power going to the motor to automatic dampers, humidifiers, etc. Most of them are controlled by the thermostat. The most common failure for a relay is being stuck in the "open" position. Separated from its assigned contact point, it fails to complete the connection and send the message to whatever it was supposed to operate. This failure usually occurs from use over time. Each time a relay connects and sends its signal, the electrical arcing from point to point eventually causes wear and tear.
Heating, ventilation, and air conditioning (HVAC[1]) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation, as HVAC&R or HVACR or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers).

Consequently, this water must exit the air handler—typically through plastic pipe or a drain tube. That drain tube goes directly outside, often terminating near the compressor, or to a floor drain or to a small electric “condensate pump” located by the air handler. Where a condensate pump is used, it connects to a 1/2-inch vinyl or rubber tube that exits outdoors or to a drain.