What is needed to add air conditioning to my furnace?

1. You must have a central furnace with duct work. Air conditioning can't be installed on a boiler, radiant heat systems or space heaters. We must have duct work present.

Evaporator Coil

Pictured left is an evaporator coil for an upflow furnace.

2. An evaporator coil must be added to the furnace. In the case of an upflow ( vertical ) furnace, the coil will sit on top of the furnace. Therefore there must be sufficient height in the basement, as this coil is about 2 feet high for a 10 S.E.E.R. and over 2 1/2 feet high for a 12,13 or 14 S.E.E.R. If you have a horizontal furnace as would be found in a crawl space, the coil installs at the end of the furnace and again, there must be sufficient room.

3. Once the coil is installed at the furnace you will need to run ( 2 ) copper lines from the coil to the out door air conditioning unit which is called a condenser.
Obviously, the longer these copper lines have to be, the higher the job costs. There are, however many other issues such as codes that must be taken into account that will determine where the condenser can be installed. This is one reason an on site evaluation is needed. Additionally an E.P.A. Refrigerant Certification is needed to handle Freon! You need to have a licensed HVAC Company involved in many issues, even IF you can do much of the work yourself!

4. Once the condenser is installed, an electrician needs to run main electrical power to it.
The condenser will operate using 230 volts of electricity. This means your main panel must have space available for a ( 2 ) pole breaker and also the main box you have must have the capacity needed electrically.

5. Your thermostat will need to be changed to a Heat/Cool thermostat if you have a heat only model. Also the wiring from your furnace to your thermostat needs to have at least ( 4 ) conductors to be able to utilize the new condenser. If you have only ( 2 ) conductors as is with most heat only systems, we will need to pull new wire to the furnace. If the existing thermostat wiring is stapled to the studs behind the sheet rock this may be a problem to be dealt with.

6. Your new air conditioning system will be cooling your home, but it will also be removing moisture during those hot days of summer. This moisture is drained from the newly installed evaporator coil by a P.V.C. drain line. Normally, in a basement you drain it to a floor drain if one is present. If you don't have a floor drain you will need to install a condensate pump and wire it into the existing furnace. This pump will then pump the condensate water out side to a desirable spot. This is another reason for an electrician.

7. There are general rules of thumb to size an air conditioning system but they are un reliable since a house with loose single pane windows, poor insulation, sky lights to name a few will need a much bigger unit than a new home sitting in the shade. Remember, any Heating and Air Conditioning company makes more money the bigger the size. Many times we hear clients say the " bigger the better ". (The correct way to size a heat or ac system is to do a HVAC heat loss/heat gain calculation.)
This is as far from the truth as it can be. Number one, too big a unit will cost more to install, it will not de-humidify properly and it will cost a fortune to operate! If your existing furnace doesn't have a big enough blower and accompanying duct work, there is NO point in going " bigger ". Still another reason for an on site evaluation.

8. Someone needs to discuss all the different efficiencies that are available to you. The higher the efficiency, the lower your monthly electrical bill will be, however the up front costs go up as the efficiency gets higher. Obviously, a person selling the home in ( 2 ) years will probably not get the difference in cost back as would a person staying ( 5 ) years.

These are just some of the things involved with installing air conditioning. When people call us on the phone asking for a ball park price it is very hard to do.

This is why we have made this page for our web site. We hope it helps to explain why we need to come out and look at your home. This is an expensive addition to your home and needs a lot of attention from you and us, working as a team. We however, working from the web can't see your home. You should consult a couple of HVAC Companies to go over all that is involved. We are only publishing this page to help our clients BEGIN to understand, there is a lot to discuss and understand!


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