Optimizing Heat Pump Performance
Proper Maintenance Critical for Maintaining Heat Pump Efficiency
Like most HVAC equipment, air-source heat pumps can provide a comfortable indoor environment, as well as save energy, if they are installed and maintained properly. The last point is key, notes the U.S. Department of Energy (DOE), as the difference between the energy consumption of a well-maintained heat pump and a severely neglected one ranges 10-25 percent.
Regular maintenance is even more crucial for newer heat pumps, whose efficiency decreases greatly if not properly maintained, said Rob McClintock, president, McClintock Heating, Cooling & Electrical Inc., Matthews, N.C. McClintock, who also operates as a Trane comfort specialist, said, “The system must be properly calibrated, lubricated, and tuned, otherwise it won’t last nearly as long or could even fail prematurely. We recommend homeowners service their heat pumps at least once a year, though twice a year is ideal to ensure the systems are properly cleaned and tuned prior to the changing seasons.”
To ensure his customers’ heat pumps are operating at peak performance, McClintock follows the Air Conditioning Contractors of America’s (ACCA) protocol, which includes cleaning the indoor and outdoor coils, clearing the drains, and checking refrigerant charges. “Perhaps most important, however, is inspecting the ductwork. Sometimes ducts go unchecked for extended periods of time, which can greatly decrease efficiency as the result of leaks and clogs.”
Rob Lambert, product manager, Carrier, agrees that checking ductwork is important. “Sealing air leaks and insulating ductwork make an HVAC system run more efficiently. In addition, it is important to clean the coils and check for proper airflow and refrigerant charge. Also, it’s important to inspect the wiring regularly for deterioration and to make sure all fittings are tightly secured.”
Due to the fact that heat pumps perform double duty and work harder than an air conditioner, Nordyne recommends seasonal service twice a year, before cooling season and before heating season. “We recommend multipoint inspections of both the indoor and outdoor components of a split system, but below are the most important things to check on a heat pump,” said Doug Priestley, supervisor of technical service and training, Nordyne:
• Check refrigerant charge levels before each season. Having an accurate charge in the system will allow the system to run at the designed performance.
• Measure airflow performance. If the airflow is incorrect, the condensing unit can shut down on one of the system safeties. The system will not deliver the proper air throughout the duct system, thus leaving hot and cold areas in the home.
• Check and verify the operation of the defrost mode via the test pins. This allows the technician to check the accuracy of sensors used during the defrost mode, and also allows for checking the function of the reversing valve.
• Check the air filter of the system. This can prevent system shut downs on safeties.
To this list, Dennis Wood, manager of technical services, Lennox Industries, would add checking the indoor and outdoor units’ voltage and amperage, as well as the controls and safety devices (contactor, time-delay, defrost, pressure switches), and inspecting/repairing insulation on refrigerant lines. “Check and clean (if necessary) filters, coils, drain pan, drain lines, and the blower wheel. Also check the condition of belt and bearings (if applicable), static pressure of system, airflow, temperature drop across the coil in cooling, and temperature rise across the coil in heating. If the air handler has supplemental electric heat, ensure electrical connections are tight and have proper polarity, check amperage of heat strips, check operation of controls and safety devices (sequencers, relays, limits), ensure electric heat is energized during defrost, and check condition of heat elements.”
Depending on where the heat pump is located, twice-a-year maintenance may be essential for optimum performance, said Andrew Karl, split systems product manager, Goodman Mfg. Co. LP. “If the unit is subjected to high cooling hours or high heating hours, then a homeowner might want to schedule at least two preseason checkups, one before each season. A preseason checkup is always less expensive than the replacement of a major component or the entire heat pump system due to a failure that might have been avoided.”
Cleaning the condenser coil and evaporator coil are simple, yet effective maintenance operations that can improve the efficiency and operation of a heat pump, said Karl, but treating the heat pump system holistically is always a better option. “By this I mean checking the ductwork, refrigerant lines, thermostat, and other similar items. Leaky ductwork can lead to a loss of energy efficiency and shorten the life of a heat pump, and if the thermostat isn’t operating properly, the load hours on the heat pump might be unnecessarily extended. The level of performance and operational improvements possible with this type of maintenance is directly connected to the load hours that the equipment must deliver on an annual basis.”
Besides routine maintenance, contractors can take additional steps to optimize their customers’ heat pump performance. Priestley recommends offering a setback digital thermostat with outdoor-thermostat capabilities. “This type of controller adds another layer of function to the heat pump system and better manages backup heat function. Of course, the ultimate upgrade to a heat pump is a gas furnace, creating a dual-fuel system. Homeowners can set the most cost-effective set point for gas or electric heat and really maximize their energy savings.”
One important item often overlooked, but key to maximizing efficiency, is to match the indoor coil to the outdoor unit,” said Lambert. “Make sure any installation uses an Air-Conditioning, Heating & Refrigeration Institute (AHRI)-listed combination, so homeowners know they are starting off with an efficient system. A mismatched system can cause inefficiencies in performance. Also make sure that technicians adhere to manufacturer-recommended installation methods; no one knows the product like the company that built it.”
Wood noted that it is also important to make sure heating and cooling systems are sized properly to handle a structure’s heat gain and loss. In addition, the air distribution system (supply and return) must be designed and sized properly for effective and proper operation. “Sealing the duct system can minimize air loss, and increasing the R value of the duct insulation may improve system efficiency, performance, and comfort. Zoning systems, when used with a variable-speed indoor blower, will help provide additional comfort and efficiency by providing conditioned air only to desired areas.”
Karl advises against adding any chemical enhancements to the refrigerant in the unit, as this could easily void the manufacturer’s warranty. “Basically, the heat pump unit was engineered and designed to operate at a designated efficiency level. Maintenance programs should support the operational function of the unit and not alter its basic construction. Following the manufacturer’s guidelines for the installation of a heat pump should afford the best opportunity to keeping the unit operating as efficiently as possible.”
Controller Promises Savings
Contractors looking for ways to optimize their customers’ heat pumps may want to take a look at the QwikSEER+WattSaver®, which was recently introduced by Mainstream Engineering (www.qwik.com). The company developed this energy-saving device through the DOE’s Small Business Innovation Research (SBIR) program, which offers grants to help foster technological innovations.
The QwikSEER+WattSaver, which is designed to increase energy efficiency and decrease humidity, can be used with any heat pump or air conditioning system with a permanent split capacitor (PSC) motor. As David M. Parise, director of sales and marketing, explains, standard heat pump and air conditioning systems are typically installed with the blower fan set to run at a single speed, even though the motor is capable of running at multiple speeds.
“The QwikSEER+WattSaver control board monitors evaporator coil temperature and humidity levels and automatically selects the optimal fan speed based on real-time environmental conditions. In essence, it utilizes the latent capability of the multispeed PSC motor and allows it to function similar to that of a variable-speed motor,” said Parise. “Tests have shown that it can provide EER improvements of 7-13 percent, along with improved humidity removal.”
The plug-and-play design of QwikSEER+WattSaver is fully compatible with any existing system that uses a multispeed PSC blower motor, regardless of its age, said Parise. “It is also affordable for homeowners who can expect a typical installed cost of $325 - $360.”
Publication date: 5/27/2013