They are also often harder to install. A proper location on the roof must be selected that can support the weight of the unit. Then a platform must be built and a drain pipe for the unit must be run along the roof to avoid problems with mold and corrosion. A crane must be used to lift the unit onto the roof while a team guides it into place and hooks it up.
Air conditioning and refrigeration are provided through the removal of heat. Heat can be removed through radiation, convection, or conduction. Refrigeration conduction media such as water, air, ice, and chemicals are referred to as refrigerants. A refrigerant is employed either in a heat pump system in which a compressor is used to drive thermodynamic refrigeration cycle, or in a free cooling system which uses pumps to circulate a cool refrigerant (typically water or a glycol mix).

The most recognized standards for HVAC design are based on ASHRAE data. The most general of four volumes of the ASHRAE Handbook is Fundamentals; it includes heating and cooling calculations. Each volume of the ASHRAE Handbook is updated every four years. The design professional must consult ASHRAE data for the standards of design and care as the typical building codes provide little to no information on HVAC design practices; codes such as the UMC and IMC do include much detail on installation requirements, however. Other useful reference materials include items from SMACNA, ACGIH, and technical trade journals.

We have provided Arkansas families and businesses with quality HVAC products and services for 42 years. Offering reasonable rates and personalized service, we are a dedicated team of experts equipped to handle any service requirement. Your source for modern heating, cooling, and ventilation equipment and servicing, Wilson's Heating & Air Conditioning is the HVAC specialist in Van Buren.

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:, browse a list of pros that serve your area here:, or send your info to and a project advisor will reach out to assist you. –HASupport
The University of Virginia - 2005 / The Wharton School of Finance - 2016 / U.S. Naval Aviator 2005-2015. At All Systems Mechanical air conditioning and heating, we believe that the experience our clients have is every bit as important as the products they receive. Simply put, our results speak for themselves, and we'd be happy to help. If you're in the market for a new AC or furnace, make sure that you get a fair price! Try our online calculator; click the tab on the top of this page for more information.

The performance of vapor compression refrigeration cycles[26] is limited by thermodynamics. These air conditioning and heat pump devices move heat rather than convert it from one form to another, so thermal efficiencies do not appropriately describe the performance of these devices. The Coefficient-of-Performance (COP) measures performance, but this dimensionless measure has not been adopted. Instead, the Energy Efficiency Ratio (EER) has traditionally been used to characterize the performance of many HVAC systems. EER is the Energy Efficiency Ratio based on a 35 °C (95 °F) outdoor temperature. To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER, the Seasonal Energy Efficiency Ratio (SEER), or in Europe the ESEER, is used. SEER ratings are based on seasonal temperature averages instead of a constant 35 °C (95 °F) outdoor temperature. The current industry minimum SEER rating is 14 SEER.[27][dead link]
Reinstall the access panel and disconnect block. Turn on the circuit breaker and furnace switch. Then set the thermostat to a lower temperature and wait for the AC to start (see “Be Patient at Startup,” below). The compressor should run and the condenser fan should spin. If the compressor starts but the fan doesn't, the fan motor is most likely shot. Shut off the power and remove the screws around the condenser cover. Lift the cover and remove the fan blade and motor (Photo 7). Reinstall the blade and secure the cover. Then repower the unit and see if the fan starts. If it doesn't, you've given it your best shot—it's time to call a pro.
Many homes have a forced-air HVAC system. Both the heating and the central air conditioning units share a ductwork system where they either push in or pull out warm or cooled air. There are also heating and cooling systems that don’t require ductwork — such as ductless mini-splits — but work on the same principles of heat exchange. The national average to hire an HVAC specialist is $2,920-$3,670, with costs varying depending on the work you need done and the equipment you are installing.
So, the total price to a contractor for this project is $7,195.77 (Carrier is expensive), which we’ll use to calculate a fair HVAC installation cost. As I said, we typically use 40% in the industry to cover our own personal profit, as well as our insurance and other expenses. Let’s take a look at page three of a Final Report from our own online HVAC calculator, the HVAC Design & Consultation Program.
In modern buildings, the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally estimate the capacity and type of system needed and then design the system, selecting the appropriate refrigerant and various components needed. For larger buildings, building service designers, mechanical engineers, or building services engineers analyze, design, and specify the HVAC systems. Specialty mechanical contractors then fabricate and commission the systems. Building permits and code-compliance inspections of the installations are normally required for all sizes of building.
An important component of natural ventilation is air change rate or air changes per hour: the hourly rate of ventilation divided by the volume of the space. For example, six air changes per hour means an amount of new air, equal to the volume of the space, is added every ten minutes. For human comfort, a minimum of four air changes per hour is typical, though warehouses might have only two. Too high of an air change rate may be uncomfortable, akin to a wind tunnel which have thousands of changes per hour. The highest air change rates are for crowded spaces, bars, night clubs, commercial kitchens at around 30 to 50 air changes per hour.[17]
Air conditioning units are prone to the pitfalls of wear and tear. You can prolong this, however, with proper maintenance procedures. Without regular maintenance even an immaculate AC installation in Fort Smith, Arkansas cannot guarantee performance. Our maintenance service is thorough, leaving no area unattended. If there’s a problem, we’ll catch it early and prevent avoidable breakdowns and costly repairs.
Deciding if central air is worth the cost depends on your needs and local housing market. If you live in a hotter climate, it can definitely be worth the price. Not only can it keep your home at a comfortable temperature, but air conditioning can even save lives during extreme heat waves. But in a milder zone without severe temperatures, window units, fans or the breeze from an open window could be adequate.
If your central air conditioner will not cool but you can hear it running, it may just need to be cleaned. Whether or not this is the cause of the problem, it’s a good early remedy to try. Plan to do this on a relatively warm day. Never use a power washer for this—it can damage the fins. The following are guidelines; always refer to your owner’s manual. Note: Always turn off the power before cleaning the unit.