According to a report on research funded by Energy Star‚ more than 50 percent of all heat pumps have significant problems with low airflow, leaky ducts, and incorrect refrigerant charge. You can improve the performance of your system by increasing airflow, sealing ducts, or adjusting the refrigerant charge.

Room heat pumps and packaged heat pumps are charged with refrigerant at the factory. They are seldom incorrectly charged. Split-system heat pumps, on the other hand, are charged in the field, which can sometimes result in either too much or too little refrigerant.

Split-system heat pumps that have the correct refrigerant charge and airflow usually perform very close to manufacturer's listed SEER and HSPF. Too much or too little refrigerant, however, reduces heat-pump performance and efficiency.

For satisfactory performance and efficiency, a split-system heat pump should be within a few ounces of the correct charge, specified by the manufacturer. When the charge is correct, specific refrigerant temperatures and pressures listed by the manufacturer will match temperatures and pressures measured by your service technician.

Verify these measurements with the technician. If the manufacturer's temperatures and pressure's don't match the measured ones, refrigerant should be added or withdrawn, according to standards specified by the EPA.

Refrigeration systems should be leak-checked at installation and during each service call. Manufacturer's say that a technician must measure airflow prior to checking refrigerant charge because the refrigerant measurements aren't accurate unless airflow is correct.