Ask Angie: Heat and drought can challenge geothermal units

Dear Angie: I have a ground-source geothermal heating and cooling system. This summer, we've endured a significant drought and heat wave in our area, and I've noticed that our geothermal system has not been cooling our home as effectively it normally does. I know the unit relies on steady ground temperatures to dissipate heat. Could the dry ground and extreme temperatures be affecting the performance of the system? —Cathy H., Carmel, Ind.

Answer: Unfortunately, some homeowners with geothermal systems are experiencing problems with the units not sufficiently cooling their homes. The dry ground and high temperatures definitely are affecting how well some units perform.

Ground-source geothermal units use an underground loop system to bring heat from the earth into the home during the winter and pull heat from the home back into the earth during summer. Loops can be buried vertically or horizontally, depending on the type of soil, the size of the yard and other factors. Systems with horizontal loops seem to be affected more by the dry conditions because they're not buried as deep as vertical systems. The ground needs to be moist and cool for the system to operate as it should.

Obviously, that's been a major problem in parts of the United States this summer with the lack of rain and the unusually high temperatures at night, when the ground is normally able to cool off.

The extreme weather could be why your system isn't performing up to its normal standards, but it could be related to how the system was installed and the number of loops put in during installation. Systems that aren't sufficiently sized to handle extreme weather won't operate as efficiently. That's why it's important for homeowners adding new systems to hire qualified companies whose workers are trained and experienced to work with that specific system and who properly calculate the heating and cooling load needed for your home.

Unfortunately, there aren't many solutions for homeowners with geothermal systems struggling to meet the cooling demand. If you don't have watering restrictions, then soaking the ground over the loops could help solve your problem. If you are under water restrictions, you could explain your problem to your water company and ask for an exemption. You could look into having a geothermal company add more loops deeper in the ground, but that would be a major investment for an occasional problem.

A simpler solution could be to install a backup cooling source, such as a window air-conditioning unit. I recommend that you talk with a reputable geothermal specialist who is trained and qualified to work on your specific equipment to see what your options are.

Fortunately, the extreme weather shouldn't cause permanent damage to the unit. The systems are designed with safety mechanisms in place that automatically shut down the unit when it senses that conditions are too extreme. If your system shuts down, you can have your installer check the water and air flow and refrigerant levels. If those check out, the installer probably will recommend that you reset the unit to operate at higher temperatures.

This is a problem this year for some owners of geothermal units, but you shouldn't experience problems with heating during the winter even if temperatures get very cold outside. Geothermal systems come with a backup source to provide heat if the geothermal unit can't provide enough heat.

This story was originally published August 10, 2012 at 12:05 PM with the headline "Ask Angie: Heat and drought can challenge geothermal units."