Air conditioner size is measured in “tons.” However, the tonnage of an HVAC unit is not actually based on its weight. A “ton” is simply a measure of an air conditioner’s ability to cool your home. One ton is the ability of your air conditioning system to cool 12,000 BTUs (BTU stands for British Thermal Unit) in an hour. Likewise, a “2-ton” central air conditioner is able to cool 24,000 BTUs per hour.
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.
The three major functions of heating, ventilation, and air conditioning are interrelated, especially with the need to provide thermal comfort and acceptable indoor air quality within reasonable installation, operation, and maintenance costs. HVAC systems can be used in both domestic and commercial environments. HVAC systems can provide ventilation, and maintain pressure relationships between spaces. The means of air delivery and removal from spaces is known as room air distribution.
Multiple inventions within this time frame preceded the beginnings of first comfort air conditioning system, which was designed in 1902 by Alfred Wolff (Cooper, 2003) for the New York Stock Exchange, while Willis Carrier equipped the Sacketts-Wilhems Printing Company with the process AC unit the same year. Coyne College was the first school to offer HVAC training in 1899.
Natural ventilation is the ventilation of a building with outside air without using fans or other mechanical systems. It can be via operable windows, louvers, or trickle vents when spaces are small and the architecture permits. In more complex schemes, warm air is allowed to rise and flow out high building openings to the outside (stack effect), causing cool outside air to be drawn into low building openings. Natural ventilation schemes can use very little energy, but care must be taken to ensure comfort. In warm or humid climates, maintaining thermal comfort solely via natural ventilation might not be possible. Air conditioning systems are used, either as backups or supplements. Air-side economizers also use outside air to condition spaces, but do so using fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate.
Whether or not central air adds value to your home depends on your location. You probably won't recoup the entire cost for the installation, as it is an expensive project that isn't as flashy as something like a new deck. But this invisible upgrade can help you sell your home if you live in a hot climate. And many buyers are willing to pay a bit more for a working AC.
Many disconnect blocks contain two cartridge fuses. Check them before you proceed with repairs (Photo 3). A blown fuse is a sign of a failing part inside the condensing unit. So don't just replace it and think you've solved the problem. Instead, replace the parts we show here. Then install new fuses and fire up the unit. If it blows again, call a pro—you've got more serious issues.
These are the prices for a proper installation from a professional – as a word to the wise, HVAC systems require fine tuning and the custom fabrication of parts during installation to work properly, otherwise they will likely fail prematurely. But there are plenty of people who will do it for cheaper than this, using substandard, used, or stolen equipment (stolen from construction sites and new housing developments). Or, they are using unskilled laborers with no experience, etc. But HVAC is not a “we’ll figure it out trade;” there is a right way and a wrong way to do things. There are just too many predatory companies out there, so be careful. I’d highly recommend not skimping on your HVAC contractor. If you go cheap, you will typically pay more in the long run...and in California, that will be a lot!
An AC contactor is a $25 mechanical relay that uses low-voltage power from the thermostat to switch 220-volt high-amperage current to the compressor and condenser fan. AC contactors can wear out and are at the top of the list of common air conditioning service failures. Even if your AC contactor is working, it pays to replace it every five years or so. Unscrew the old AC contactor before removing the wires. Then move the wires to the new unit (Photo 6).
Installation: The old furnace is disconnected from the ductwork plenum, exhaust flue, gas and electrical hookups. In most cases, a new plenum must be made onsite or ordered from a local sheet metal fabricator. A new vent might be required too. The furnace is set and reconnected. Adjustments to the blower fan speed and burner are made to optimize furnace performance for your home and climate.
Before opening the electrical cover on the A/C unit, be sure to shut off all power to the compressor unit and the indoor furnace or air handler, and verify that it is off. Note that this may mean shutting off a circuit breaker that serves the furnace and air handler, and then, near the compressor, pulling out the disconnect block (or shutting off the 220-volt power) to the outdoor compressor.