Adjusting Heat Pump Refrigerant Charge
Packaged heat pumps are charged with the refrigerant at the factory under controlled conditions and rarely need adjustment. Split- system heat pumps are charged in the field where there is a greater chance of error. If the performance of a split-system heat pump closely approximates the manufacturer’s listed SEER and HSPF ratings, then the system probably has the correct charge. If the performance fails to meet the listed ratings, then there is either too much or too little refrigerant in the system.
Note
Section 608 of the Federal Clean Air Act mandates the requirements for handling HVAC refrigerants, including their reclaiming, recovering, and recycling. All HVAC technicians who handle refrigerants must be certified to do so. City, county, and state governments may also have ordinances governing the handling of refrigerants.
Measure the temperature and pressure readings on the heat pump system and compare the results with those specified by the manufacturer. If they do not match, refrigerant will have to be added or withdrawn.
Note
Refrigerant measurements will not be accurate if the airflow is incorrect.Therefore, the airflow must be measured first, checked against the heat pump manufacturer’s specifications, and corrected if necessary before the refrigerant measurements can be ade.
Troubleshooting Heat Pumps
Table 10-1 lists the most common problems associated with the operation of a heat pump. For each symptom of a problem, a possible cause and remedy are suggested.
Make certain that the thermostat is set higher than the actual room temperature and the selector switch is on heat if heat is needed, or that the thermostat is set lower than the actual room temperature and the switch is on cool if air-conditioning is desired. If the thermostat is programmable, be certain the batteries are fresh.
Test for power to the air handler by moving the fan switch from auto to on. If the blower runs, the air handler is functional. If nothing happens, check the circuit breakers on the air handler cabinet and the breakers or fuses in the main panel. If any breakers are tripped, reset them at once.
Caution
Do not reset the circuit breakers if they trip a second time. Deadly high-voltage conditions exist inside the air handler cabinet and nside the access panel of the condenser. Let a qualified service-person open them.
If the air handler runs constantly but cannot satisfy the thermostat setting, it is possible the backup heat is running but the condenser is not. Some condensers have the high-pressure cutout switch externally accessible. Look for a button sticking out of the cabinet in the vicinity of the refrigerant pipes. Press it in. If the machine starts up, the head pressure got too high, possibly from turning on and off too quickly, from too much or too little refrigerant, or from an electrical interruption. As the unit ages, the switch can weaken and pop easily. If the condition repeats itself often, have a service technician check it.
Warning
Because all the controls are internally mounted and high-voltage iring is exposed, only a qualified and experienced HVAC technician should open panels. High voltages can result in serious injury nd even death.