Your contractor will do a load calculation to determine the proper central air conditioning unit for your home. This calculation accounts for the climate, size, shape and orientation of your home, as well as its square footage. A professional will also look at the insulation, windows, walls, floors and other materials that compose your home. He/she will then examine any leaks, seals and existing ducts or vents.

The HVAC industry is a worldwide enterprise, with roles including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry was historically regulated by the manufacturers of HVAC equipment, but regulating and standards organizations such as HARDI, ASHRAE, SMACNA, ACCA, Uniform Mechanical Code, International Mechanical Code, and AMCA have been established to support the industry and encourage high standards and achievement.
Important Tip: Don’t just pay attention to the high-end of the price range! – which is what I know you are all looking at, but also look at the low range. If a contractor is cheaper than this, ask “why?” Usually it is because they don’t have liability insurance, workman’s compensation insurance, are unlicensed, all of the above, or worst yet, they don’t use HVAC technicians. You are spending a lot of money.  Make sure that they are licensed (In California, check here at CSLB License Checker) and insured.
Our unit is 16 years old and we've had it checked out recently since it seems to be running excessively. Over all the tech says it is putting out well; it's the correct size, we have no shade and we've been having extreme heat with high humidity. The info you provided is very helpful and will help us make an informed decision when the time comes. Thank you so much.

HVAC System Quality Installation Contractor Checklist -- This checklist identifies all of the steps the contractor has taken for the Energy Star Certification and identifies what work the contractor has done. If the system is later modified, this checklist can help identify what was done to proper Energy Star specifications and what was added later that may not meet the requirements.

My point is that the brand of equipment you choose is going to affect your HVAC installation cost greatly. People often call us for an air conditioning installation job and say, “I would like to install Carrier equipment.” Now, if you are a future client of ours, I’ll have to warn you – I can be a bit of a smart-ass. Why can’t work be fun? Besides…I was in the Navy for 11 years, what do you expect. 
The use of furnaces, space heaters, and boilers as a method of indoor heating could result in incomplete combustion and the emission of carbon monoxide, nitrogen oxides, formaldehyde, volatile organic compounds, and other combustion byproducts. Incomplete combustion occurs when there is insufficient oxygen; the inputs are fuels containing various contaminants and the outputs are harmful byproducts, most dangerously carbon monoxide, which is a tasteless and odorless gas with serious adverse health effects.[14]

They work less jobs, thus increasing profits – think about it…if they got only half of the jobs, then they only pay half of the money required to pay employees, expenses, etc., but still have the same amount of net profit. In fact, if you do the math, they actually make more profit that their competitors do…twice as much, once you factor in their savings form only doing half of the jobs at the same amount of profit (Total Revenue – (half the normal expenses) = twice the profit). In other words, they save money by doing half of the jobs as others, for the same profit, thus increasing their overall profits.
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.
I'm very glad that I found another guy to come replace the circuit board and put it away from the water, fix the water leak, and also find and fix another impending failure.  All of that was for much less than HVAC Service wanted to charge for repair or replacement. The other guy did a great repair, so I'm confident it will not break down again, but if it does, I will not call HVAC Service. Don't get suckered by their Yelp Deal.
A dehumidifier is an air-conditioner-like device that controls the humidity of a room or building. It is often employed in basements which have a higher relative humidity because of their lower temperature (and propensity for damp floors and walls). In food retailing establishments, large open chiller cabinets are highly effective at dehumidifying the internal air. Conversely, a humidifier increases the humidity of a building.
After one company just took a cursory glance at our A/C and found nothing wrong, I called HVAC. I called them mostly based on Michael W's post on 8/10/14 where he told us the owner, Alberto, took his feedback and took it SERIOUSLY. That speaks VOLUMES to anyone who has been around long enough to know the characteristics of the serious players are and those who are the wannabes.
7 To test it, turn the thermostat to OFF, reset the power at the disconnect next to the compressor and the main panel. Set the thermostat to a temperature below the room temperature, and then switch it ON. To avoid straining an air conditioner’s compressor, wait at least five minutes between turning it off at the thermostat and turning it back on. You should hear the outdoor compressor run and see the fan turning inside the top. If the fan isn’t turning, look for an overload button or switch to reset (not all types have this).