GSHP ?

Steve Ebels_3

I don't normally do much with heat pump service but a friend of mine asked if I'd take a look at his. So I did :( and here's the deal. I think the reversing valve is not functioning based on the following observations.

Thermostat is set to cooling and is wired correctly. The incoming water is warmer than the discharge water. Compressor is running and pulls nominal amperage. The unit is blowing hot air into the house. The coil on the reversing valve is powered and magnetized.

So, is there a possibility that the coil is bad or is he reversing valve stuck and how would I tell?

Eugene Silberstein 3

Try This...

If the heat pump system is pumping hot air into the house and the water entering the heat exchanger is warmer than the water leaving the heat exchanger, it definitely seems that the system is operating in the heating mode. Since most heat pump systems are designed to fail in the heating mode, I will assume that such is the case with this one. (Unless you know for sure that the system fails in the cooling mode)

Here are a couple of things to check:

With the system operating, remove the coil from the reversing valve. You should hear a whhhiiiisshhhhhhhhh of refrigerant in the system. This is the sound of the system switching over from heating to cooling or vice versa. If there is no whishing sound, the reversing valve may very well be stuck. If such is the case the valve must be replaced. Of course, the refrigerant must be properly recovered before the repair is made.

Take temperature readings about 3 inches from each port on the reversing valve. Use a high quality thermocouple thermometer to do this. Be careful, as the compressor discharge line can be very hot. The compressor discharge port (the port that is by itself on the valve) and the line leading to the condenser coil (outdoor coil in cooling, indoor coil in heating) should both be hot and at the same temperature, give or take 2 or so degrees.

The other two lines, the suction line to the compressor and the line from the evaporator coil, (outdoor coil in the heating mode, indoor coil in the cooling mode) should both be cool and should be just about the same temperature.

If the suction port to the compressor is much higher than the line coming from the evaporator coil, it is very likely that the reversing valve has an internal leak. One way to confirm this is to take system pressure readings. The suction pressure will be higher than normal and the discharge pressure will be lower than normal.

If push comes to shove and the reversing valve needs to be replaced, here are a few tips:

Inspect the new valve for dents, scratches and other imperfections. The internal slide may not operate properly if the body of the valve is damaged.

Make certain the new valve is configured and piped in correctly. The line that is by itself is connected to the compressor discharge, the center port on the valve is connected to the compressor suction, and the other two ports are connected to the indoor and outdoor coils. Check the piping diagram of the new valve and compare it to the actual piping of the system and make certain that the refrigerant will flow to the desired coil in the desired mode of operation.

Obtain a specialty torch tip made specifically for reversing valves. One such tip is the "tuning fork" by Uniweld. It allows you to heat all three ports at the same time, making valve removal a snap.

Use an oxy-acetylene rig to remove and install the new valve. Oxy-acetylene torches heat quicker and reduce the possibility of damaging the valve.

KEEP THE VALVE COOL WHILE BRAZING! Use a heat trap paste to keep the valve as cool as possible during the brazing process. Overheating the valve can damage the internal slide mechanism. BE VERY CAREFUL!

If no heat sink paste is available, use damp rags but be sure to prevent water from entering the piping circuit. Water in the system = ACID production.

By the way, there is a really cool book on heat pumps in the "Shop for Books and More" section of this site (if I do say so myself).