Geothermal Heat Pump Maitenance and Troubleshooting

You've likely heard that Geothermal heat pump systems have few moving parts, and because those parts are sheltered inside a building, they are durable and therefore reliable. The underground piping often carries warranties of 25 to +50 years, and GHPs for 20 years or more.

However, even the best laid plans sometimes can go awry. A ground source heat pump system may not work as intended. What should you do if this happens?

Fortunately, troubleshooting a GHP is straightforward, as is the regular maintenance required by these systems.

Regular maintenance: the key to system longevity.

Low maintenance is one of the big benefits of ground source heat pumps. According to a 2008 study done for the Geothermal Heat Pump Consortium (GHPC), buildings with GHP systems had average total maintenance costs of about one-third that of conventional systems.

The piping is the workhorse part of the system. Because it is underground or underwater, little maintenance is required. Occasional cleaning of the heat exchanger coils and regular changing of air filters are about all that is necessary to keep the system in good running order.

In all cases, refer to the manufacturer's operating and maintenance instructions. This information should remain with the equipment owner or operator. For more detailed information, consult the manufacturer's service instructions.

Inspect the air filters at least every three months. A heat pump should never be operated without filters in place. How often they get replaced depends on the building occupancy.
Check the condensate pans for proper drainage and algae growth every three months. If algae is apparent, consult a specialist for proper chemical treatment. In most cases, an application of algaecide every three months will eliminate the problem.
Clean the water pump filter every three months.
Service the whole system at least once a year. This should include a visual inspection, refrigerant leak test, evaporator coil cleaning, and inspection of the compressor, fan, and pump motors. Record these values in a log book so a deteriorating condition can be detected before component failure. Repair any deficiencies.

The refrigerant cycle should be serviced by a competent technician, preferably one who is factory trained by the manufacturer.

Troubleshooting checklist

When there is a problem with a geothermal system, it makes sense to look at all of its parts. The refrigerant circuit should be the last part contractors look at, because it's factory assembled and sealed. Typically the refrigerant circuit is not the source of problems, so expert suggest to always look at all other avenues first before putting the gauges on the machine.

Water problems can be a source of trouble in open-loop systems that use conventional well water. Very clean, clear water is needed, and even in areas of the country with pretty decent water, mineral deposits and other biological deposits can seize up a system. If trouble is identified early, then a technician has the opportunity to clean the problem area. Most people don't take the time to open up the water side of a system.

The reason is that the geothermal system is really two different entities - there's the loop component and the heat pump component. A mechanical technician may look at the heat pump component but not bother to look at the water side of the system, which may need to be checked by a plumbing technician. That usually means any water chemistry problems go unnoticed until a serious issue develops.

Another regular culprit for improperly performing GHP systems is the ductwork. Common duct problems include:

* Uninsulated ducts in unconditioned spaces;
* Disconnected, torn, or damaged ducts;
* Blind-alley ducts;
* No return-side ductwork;
* Supply- and return-side leakage;
* Poor duct layout; and
* Unbalanced airflow.

Correcting these issues can be time consuming and/or costly, so it's best to make sure the ductwork is designed correctly to begin with.

Occasionally a GHP system has component failures, and sometimes the customer understands neither what a GHP system does nor how it should perform. "This can mean there are operator errors," says Eigenrauch. "A few problems can be caused by the building envelope, so a thorough analysis of the building's thermal qualities and air infiltration is important.

"Proper GHP system sizing is more of a science and is not a guessing game, so a 'holistic' approach needs to be taken when assessing the building."

Eigenrauch described a brand new house with a geothermal system in the Northwest. The homeowners had a problem: The geothermal system could barely maintain either the forced-air system or the in-floor system. It could not support both systems at the same time, as originally designed.

"The contractor came in and did a thorough energy audit, including a blower door test and an infrared scan. It really opened some eyes, because it wasn't the geothermal system at all. It was the structure, which was very leaky. It took a long time, but they sealed up the ductwork, as well as other envelope leaks, and now everything works fine."