Thinking about buying a new Central Air Conditioning System? Here are some tips
Posted on September 15, 2015
Most standard brands available today are Rheem, Trane, American Standard, Carrier, Bryant, Lennox, York, Amana and Goodman. Other Brands such as Maytag, Frigidaire and Tappan which are manufactured by Nordyne. Non standard brands such as Florida Heat Pump (FHP), First Company and Mitsubishi.
It is very important that you purchase the correct size system for your home regardless of the size you currently have. What I mean by that is, don’t just replace with the same thing you have now. It could be mis-sized and causing you problems that you are not aware of such as short cycling (causing humidity problems) or over working (shortening its life spa.
Today’s systems are different in design then your older system. In order to achieve the higher efficiencies, they have installed a TXV valve which regulates the flow of the refrigerant. These keep the units from working inefficiently but do not allow for deficiencies in sizing.
The best way to properly size your new system is to have your contractor do a Heat Load Calculation also known as a Manual J. If not, as a general rule of thumb, 500 sq. ft. per ton of a/c living space for a single family home (example 2000 sq. ft. of a/c living space is a safe bet at 4 tons) . Factors may vary depending on exposure of home, how many windows and type, attached or free standing home, single story or 2, inadequate insulation in attic and leaking ductwork.
Your contractor should also check your ductwork in the attic to make sure it’s sized properly for the new system. Don’t assume or let him tell you it’s fine if he hasn’t looked (red flag).
Acronym for Seasonal Energy Efficiency Rating. The higher the SEER rating the lower your electric bill. Some utility companies offer rebates based on the SEER rating. 13 SEER is the minimum rating allowed by law and can go up to 21 SEER or higher depending on the brand. Keep in mind that the higher the SEER the more costly the equipment. For a single stage unit (I will explain about this later on) 16 seer is about the highest and probably the most popular now because of price.<
Types of Central a/c systems:
Split systems, package units and water source heat pumps (less common and usually in high rise condos). A split system has 2 units, a condenser outside and an air handler inside. A package unit has both in 1 on the outside. A water cooled unit has both inside and is connected to a water source.
Single Stage vs. 2 Stage:
Single stage system is the least expensive and the more common system. It uses one compressor in the outside unit (condenser). A 2 stage system has either 1 compressor that changes speeds or 2 compressors that change back and forth according to demand. A 2 stage unit also has a variable speed air handler. The benefit to the 2 stage system is better humidity control, better air circulation and quieter operation.This system will keep your home feeling more comfortable over the course of a day because it adjusts to the changing environment of your home. Factors such as outside temperature, direction of the sun as it relates to your home and humidity will be compensated by this system.Also check your old thermostat.You might have to replace it and get a new one preferably programmable type that support your system.
Types of Heating:
Heat strip, heat pump, gas furnace. A heat strip is a coil in the air handler that heats up like a toaster. The air blows over it as it goes through the air handler. A heat pump uses a reverse cycle on the compressor to produce heat and can be supplemented with a heat strip for additional heating (used in cooler climates). A gas furnace gets its heat from natural gas and is used in colder climates.
Refrigerant Line Sizing:
These are the the copper pipes that carry the refrigerant (or freon) back and forth from the condenser to the air handler. There are 2 lines. A liquid line and a suction line. They must be the correct size according to the manufacturers specifications. Make sure that your contractor checks them to see if you have the right size for the new unit. Don’t assume they are correct even if you are replacing with the same size a/c. They may never have been correct. Under sized lines cause premature failure of the equipment due to low lubrication of the compressor and will lower the SEER rating that you are paying for. If a contractor does not check these (red flag).
Rule of thumb.
1.5 to 2.5 tons minimum size is 5/8 and 1/4 up to a 50′ run.\
3 to 3.5 tons minimum size is 3/4 and 3/8
4 to 5 tons minimum size 7/8 and 3/8
Electrical wiring also needs to be sized properly. Don’t assume because you lived in your home for 20 years and your a/c has worked fine and you’ve never had a fire that it’s ok. Breakers also need to be sized properly. Again, don’t assume that what you have is right or safe. Make sure your contractor checks this without you asking. if not (red flag).
Rule of thumb for air handlers<
up to 30 amp breaker #10 wire and you can use a 5 kw heater
up to 45 amp breaker #8 wire and you can use a 8 kw heater
up to 60 amp breaker #6 wire and you can use a 10 kw heater
Rule of thumb for condensers
Varies by size and brand but wire sizes and breakers listed above are the same.
Manufacturers, Utilities and Government Rebates:
Manufacturers have rebates usually in the spring and the fall. The higher the price of the equipment, the higher the rebates (typically up to $1200). Keep in mind that the dealer absorbs half the cost of the rebate, so it gets built into the price to the consumer. Here is a link for state, local and/or utility incentives in your area http://www.dsireusa.org/. Power utilities may also have rebates for repairing ductwork and replacing insulation in the attic. Federal Energy tax credits ended on December 31, 2011 but legislation is in congress for new tax credits.
Hiring a Contractor:
Your local power utility company may have a list of participating contractors for any utility rebates. Better Business Bureau is good if you take the time and check how many complaints a particular contractor has (too many and red flag). Angie’s list is also good. The best way to find a contractor is by word of mouth. Ask your neighbors, friends and co-workers. If they’ve had a good experience, they will surely let you know, if not then you know which contractors to stay away from. Get 3 estimates. If you do your research and call reputable contractors, then 3 should be enough. Too many will definitely get you confused. Make sure that they leave you a written estimate with all work to be done as well as model numbers and prices. If all these things are not on the proposal or if they tell you that they don’t pull permits for the job then beware. Most cities require permits even if your replacing with the same thing. This is to make sure that your contractor did all the work according to code and that your home is safe.