Avoiding Geothermal Problems in Freezing Temperatures

Geothermal doesn’t work in the bitter cold!  False.

It is now January in Minnesota, where we get excited when there is not a minus sign in front of the temperature.  Jackson Motzko, lead design engineer at NexGen Energy, is enjoying the comfort of his nice, warm home that runs purely on his five ton geothermal system and no fossil fuel or electric backup.  Motzko now has been running his system for six Minnesota winters and has faced temperatures as low as -30 F with zero problems.  He encounters people all too often that have not shared his experience or have been misinformed about geothermal systems.  He has offered up some advice for people that  might be facing challenges with their existing geothermal system or help educate those that might be considering a new install.

Storing Heat in the Soil

Ground-source geothermal systems work a little differently than systems that exchange heat with the air.  When discussing the principles of geothermal with Motzko, he looks at the ground as a place to store the summer heat.   “I think the key to getting all the benefits of geothermal is understanding how it works differently than other heating and cooling sources.  The first thing is understanding where the heat comes from.  The heat is stored in the ground during the summer.  So it’s key to be using your cooling cycle all summer long.”

During the summer, the heat pump is running in reverse.  It extracts the heat from the home and pumps it into the ground.  This heats the soil and cools the fluid at the same time.  The cooled fluid is used to cool the air in the home and the cycle is repeated.  The soil is also naturally heated by the sun as well, which makes it a great heat source during the cold months.

Rapid Indoor Temperature Changes

Motzko has also heard of many people complaining about frozen loops and points out another crucial difference with a geothermal heating system.

“The heat must be transferred through the soil.  This means there is not an unlimited supply of heat like a typical fuel system.  The supply available to you is the only what the loop can pull out of the ground and what the ground can pass to the loop.  Ground loops, over the course of a season, will pull heat from several feet away through the ground.  This heat transfer is most efficient if it happens slowly and steadily.  For this reason, it is important to keep the heat load on the system as even as possible.  One common mistake is changing the set temperature in the house using a programmable thermostat.  If too much heat is taken too fast from the soil the ground around the loop can freeze, which limits its ability to transfer heat to the loop.  Frozen ground in your loop field can leave you stuck with a big problem.”

If you want to reduce your usage on a traditional fossil fuel source, the only thing you can do it use it less.  There are plenty of fancy thermostats on the market to help turn off your system when you are not home.  They do this by lowering the set point inside the home, which lowers the duty cycle of the system.  The down side is that when you return and the set point jumps up, the system must catch up by working extra hard until it reaches the warmer set point.  Treating a geothermal system the same way can cause a very uneven demand on your loops and rapidly cool them to the point of freezing.  Maintaining a flattened temperature profile allows the system cycle on and off appropriately.
Confidence in Your System
You should have total confidence that your geothermal system will provide the heat you need throughout the winter.  We would love to hear about your experiences, good or bad, so please leave a comment or join the discussion on Facebook!

A Note to Those Suffering from Freezing Issues

If your system was improperly designed, don’t worry!  NexGen Energy loops  can be installed cleanly  near your existing manifold.  These loops can add the extra capacity you need, or replace the loss of a loop in frozen ground.  Please contact us if you are experiencing these types of problems!

 


 

Jackson Motzko can be reached directly at Jackson.Motzko@nexgenenergy.net

3 thoughts on “Avoiding Geothermal Problems in Freezing Temperatures”

  1. Found your blog post as we are currently frozen out of our geo unit in OH (we keep at a constant 68 all winter). Seems to be an issue when the outdoor temps get below 20F. Been running solely in Aux heat which is not keeping up with our house size – so staying around 62-64F. We trusted our installer on a replacement system (we bought the house with an old system ) but have come to find out just this week that our loop field may not be adequate and he’s quoting us ridiculous amounts to add add’l loop. Any advice? Thanks in advance.

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