Installation will determine how equipment will operate do you have a out door stat for the heat pump? The most important thing, when buying furnaces and air conditioners is proper sizing and installation of equipment. The proper sizing and installation of a furnace or air conditioner will determine three things, comfort, efficiency, and longevity.
Sizing and Installation
Your new heating and cooling system should be a custom fit for your home. Sizing and a handful of other installation practices can dramatically affect how well your new equipment will deliver comfort and savings. Expect to pay a little more for a good contractor who follows these practices.
Calculate the size of equipment
For starters your new furnace, boiler, heat pump or air conditioner should be sized to fit your home. You can request a copy of the design load calculation used to determine the right size of equipment for your home. A good contractor will not size your equipment solely on the square footage of your house or assume that your existing equipment was sized properly in the first place. Proper equipment sizing is based your home's heat loss during cold weather and heat gains during warm weather. For more information about sizing use the new Central Air Conditioner Sizing Tutorial.
To complete the design load calculation the contractor will need to take measurements during the initial visit to your home and ask you some questions. The calculation is usually done using software, and should be based on professional guidelines such as Manual J from the Air Conditioning Contractors of America (ACCA) or similar method. Oversized equipment can cause reduced comfort and excessive "air" noise. Oversizing will shorten the life of the equipment by causing it to cycle on and off more frequently than a properly-sized unit. Undersized equipment, with airflow that is too low, can reduce the efficiency of the air distribution and accelerate wear on system components, leading to earlier failure.
After the design load calculation is completed, ducts, supply registers, and return grilles can be sized and selected using professional guidelines in ACCA's Manual D or similar method.
Proper refrigerant charging
If your are installing a new central air conditioner or heat pump you should know that recent field studies suggest that approximately 75% of installed cooling equipment may have incorrect amount of refrigerant. Incorrect refrigerant level can lower efficiency by 5 to 20% and can ultimately cause premature component failure, resulting in costly repairs that could have been prevented. A good contractor will use one of three methods, recommended by equipment manufacturers, to verify the correct refrigerant level. These methods include super-heat, sub-cooling, or weigh. Ask your contractor how they verify the refrigerant level is correct.
In addition, you should know that since 1992, in order to protect the earth's atmosphere (ozone layer), all technicians must be certified to handle refrigerant. Ask them to show you proof of refrigerant handling certification.