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Maintaining A Heat Pump

Most heat pump manufacturers delight in telling you that a heat pump is not a household appliance, implying strongly that you ought to keep your hands off. They’re probably right, but then a heating system that cost you several thousand dollars probably shouldn’t break down at the first frost. Where’s the middle ground? There’s no question that routine maintenance is up to you. At the very least it’s your job to change or clean the filters once a month. In winter shovel snow or ice away from the outdoor unit. In summer wash it down with soap and water. Beyond that, talk with your repair person. Find out what a maintenance package costs and check your warranty to see whether you can do the sorts of things described in this part without voiding the warranty. You’ll be surprised at what you can do and how much you can save.

MATERIALS: Household oil, germicidal cleaner for coils, bleach, disposable air filter (if applicable), necessary replacement parts

TOOLS: Screwdriver, wrenches, or both; shop vacuum with brush attachment; 20,000-ohm, 5-watt resistor; two wire leads with alligator clips at each end; multimeter

Outdoor maintenance

1 BEFORE YOU CAN DO ANY MAINTENANCE, YOU’LL NEED TO TURN OFF THE POWER at the circuit breaker or fuse panel and at the cutoff switch outside the home.

2 TAKE OUT THE SCREWS OR BOLTS THAT HOLD THE FAN COVER IN PLACE. Remove the screws or bolts holding the casing around the unit and take off the casing. OIL THE FAN MOTOR. Look for oil ports on the fan motor. If they exist, squeeze in a couple drops of household oil.

3 DIRT IN THE COILS CAN LOWER A HEAT PUMP’S EFFICIENCY BY AS MUCH AS ONE-THIRD. Most manufacturers recommend flushing out the dirt with a garden hose, spraying as best you can from the inside toward the outside. While you're cleaning, scrub the fan, taking care not to bend the blades. Check to see if any of the fins are bent. If so, straighten them with a fin comb.

Indoor maintenance

The indoor end of the heat pump looks much like any forced-air furnace but with no flame. Instead of fire, the furnace has a series of coils that look similar to those on the outside. The purpose of the coils is different: The outdoor coils are either absorbing or giving off heat, depending on whether the pump is heating or cooling; the indoor coils are bringing the air blown across them to the desired temperature. The coils and the filters that clean the air that goes across them need regular maintenance.

Maintenance is largely a matter of keeping things clean. Like the air filters on any other forced-air furnace, those on a heat pump must be cleaned regularly. Dirty filters drastically reduce the efficiency of a furnace. Having spent the money for an efficient furnace, it would be a shame to send all that heat up the stack. Despite the filters, dust and dirt are likely to build up on the inside coils. This will be less than what you find in the outside coils, so don’t even think of hosing it down. Do the job with a vacuum cleaner. The best time is at the beginning and end of the heating season. During cooling season, dust may stick to condensation on the coils.

Heat pumps can develop that classic smell you get when you first turn on the air-conditioner in a motel room. A germicidal cleaner for coils, applied according to manufacturer’s recommendations, will help to clear the air. Underneath the coils you’ll find a drain pan that collects water that drips from the air-conditioner coils. A clogged drain hole spells trouble, so as long as the unit is open, take a look and clean it out as necessary. Once you’re done with the furnace, walk around the house to make sure the vents are open and aren’t blocked by rugs or furniture. Blocked vents mean that the compressor has to run longer to bring a room to the desired temperature. Excessive use costs money and shortens the life of the compressor and valves.

1 DOUBLE-CHECK THAT THE POWER IS STILL OFF, remove the access panel, and look for the filter or filters. You’ll find them near the coil. Pull out the spring-like retaining arm and remove the filter. Vacuum and wash reusable filters with the hose; replace disposable filters.

2 DIRT ON THE COILS NOT ONLY REDUCES EFFICIENCY, it can also be the source of dirt, spores, and odors that get blown through the house. Turn off the power, put a soft brush on a shop vacuum, and thoroughly vacuum and brush the coils. Wash the coils with a germicidal cleaner designed for indoor coils. Vacuum the blower wheel on the fan.

3 STANDING WATER IN THE DRAIN PAN IS A SIGN THAT THE DRAIN HOLE IS PLUGGED. Mop up the water and unplug the drain hole. Rinse with a mixture of 1 part household bleach to U parts water. Put the filters back in and put the access panel in place. CLEAN THE BASE PAN AT THE BOTTOM OF THE UNIT, and make sure none of the drain holes are plugged. Replace the cover.

GET PROFESSIONAL HELP - Heat pumps are extremely sophisticated furnaces. Simple maintenance is a matter of having the time. But the best way to guarantee the system won't crash when you need it most is to check and maintain the refrigerant system. This requires a pro. A pro will check everything, one of the most important being the refrigerant level. The technician will visually check for leaks, monitor temperature in different parts of the system, and perhaps take a couple of readings with a gauge. If the test shows that the coolant level is low, recharging the system is in order, a task that only a licensed technician can do. Have a local HVAC company make a yearly inspection for refrigerant and other problems. You'll save yourself a cold and sleepless night.

Diagnosing a pump that won't start

Not all heat pump repairs are the do-it-yourself type. Any problem with the compressor, for example, requires a technician licensed to work with refrigerants. About all you can do on your own is wreck the pump and ruin earth’s ozone layer. The homeowner with a basic knowledge of electricity can fix motor problems, but before you do anything or call anyone, check the obvious. Is the power on, both at the circuit breaker and at the external cutoff? Are the thermostat wires all connected and is the thermostat set to the right temperature? If the compressor is warm it may be temporarily overloaded. Let it cool and try again. If none of the suggestions above and none of those below solve the problem, call a technician. It may be the compressor, or it could be any one of several circuits that need a professional’s expertise. Discharging capacitors can be dangerous.

1 IF YOU’VE RULED OUT THE OBVIOUS, THE PROBLEM MAY BE IN THE MOTOR CIRCUIT. Remove the covers to the outdoor unit and test the capacitor, which stores energy to help the motor start. Make a capacitor discharger from two leads and a 20,000-ohm, 5-watt resistor. Put a lead on each of the capacitor terminals and leave them there for about 10 seconds. This releases the stored energy and the circuit is safe to work on.

2 TO TEST THE CAPACITOR, set the ohmmeter on your multimeter to RX1. Put a meter lead on each side of the discharged capacitor. A digital meter will show resistance rise and then fall. On analog meters the needle should move across the scale and then back. If it doesn't, replace the capacitor.

3 BEFORE YOU REPUCE THE CAPACITOR, DISCONNECT THE WIRES, labeling them and marking the corresponding terminals too. Unscrew the screws holding the bracket in place and take out the capacitor. Replace it with an identical model.

4 IF THE CAPACITOR CHECKS OUT, TEST THE MOTOR WINDINGS. Set the ohmmeter to RX100. Put one of the probes on the compressor discharge piping. Put the other on the R (run) terminal, then on the S (start) terminal, and finally on the C (common) terminal. If the meter moves when the probes are at any of these points, the motor windings have short-circuited and you’ll need to replace the motor.

Diagnosing ice buildup on outside coils

Some ice buildup on the outside coils is normal—so normal that the system actually has a defrost cycle. The problem usually occurs when the outdoor temperature drops below the boiling point of the coolant—around 15°F (-9.4°C).The temperature drop causes the coolant to liquefy and act as a refrigerant on the outdoor coils. To prevent this, a defrost cycle kicks in at about 28°F (-2°C). The heat pump temporarily runs backward, melting the ice. The auxiliary heat source in the house kicks on, and both you and the outdoor coils are warm. Sometimes, however, things go wrong. This may be something like a faulty valve, which requires a trained technician who can work with refrigerants. But just as often, it’s a problem you can solve yourself. Simple maintenance chores on a regular schedule will save you money and keep you warm.

1 IF ICING OCCURS, FIRST CHECK THE THERMOSTAT. Make sure it's set to heating, not cooling, and that the room temperature is above 55°F (13°C). If not, reset the controls as needed and the problem will likely go away. Then go outside and make sure the outdoor coil isn't blocked by snow or leaves.

2 CLEAN THE AIR FILTER. A dirty or clogged filter will keep the fan from blowing enough air over the indoor coils to warm them adequately. When the refrigerant makes the trip back outside, it can't give off enough heat to defrost the coils. No matter how clean you think the filter is, take it out, and vacuum and wash it (or replace a disposable filter). Put parts back in place, and if nothing else, you’ve eliminated the filter as a problem.

3 THE REVERSING VALVE, FOUND IN THE OUTSIDE UNIT, is responsible for running the system in defrost mode and must be replaced professionally. You can, however, diagnose and fix the solenoid and the needle valve that controls it. To check the solenoid, turn off the power, remove the cover, and look for a valve that has six tubes going into it. The solenoid coil is attached. Remove the wires going into it and put the ohmmeter leads where the wires were. If the reading isn't between zero and infinity, you'll need to replace the coil.

4 TO REPLACE THE COIL, REMOVE THE NUT HOLDING IT IN PLACE and slide it off its stem. Slide an identical replacement coil over the stem and tighten the nut over it. Reattach the wires.

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