What You Should Know About Air Conditioners Before You Buy.
Important information to learn before buying an Air Conditioning system.
The proper size for equipment is really a matter of definition. Equipment that is "too big" will keep people comfortable when there is a large cooling demand, but it will hurt performance and be a burden the rest of the time. Often times, equipment that is "too small" will not satisfy the cooling needs.
According to American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) recommendations, a system should be designed so that it runs full time for 2.5% of the summer season. Builders and contractors often oversize because they think it will reduce service calls. Field studies show that central air conditioners are, on average, being oversized from 24% to over 100%. Oversizing has a bad effect on energy use, comfort, equipment life, and system costs.
Getting the right refrigerant charge is another critical field adjustment factor that is often overlooked. The effect of improper charge depends on the type of refrigerant flow control device being used in the system. A system using fixed orifice flow control is more seriously affected by improper charge than a system using a thermal expansion valve (TXV). How common are improperly charged systems? The North Carolina Alternative Energy Corp examined air conditioning manufacturers' efficiencies versus the actual efficiencies that resulted after installation.
- 90% of the units tested exhibited some sort of energy wasting problem.
- 50% had an improper refrigerant charge
- 40% failed to meet minimum air flow criterion. 20% were barely inside the range specified by manufacturers.
- A deficiency of only 20% indoor air flow reduces the SEER rating by 17%.
- A 15% return air leak from a 120 degree attic can reduce a 12 SEER to a 6 SEER!