Winnipesaukee Forum - View Single Post

jeffk · 02-12-2013, 08:55 AM

I did a little poking around and came across a company in Minnesota that does geothermal and they explain cold weather issues on their web site.

First, in cold temps the system runs for a long time and the ground around the system loop cools faster than the ambient 50 - 55 degrees can restore. So the loop water DOES get cooler and the heat pumping process becomes less efficient.

There are a couple ways to deal with this. First, simply make the loop longer to provide a larger heat reservoir. Of course this costs more. Maybe it's cheaper to simply throw a backup heat source into the design to handle the colder temps. You trade lower initial cost for higher operating cost. The key of course is hitting the right balance point. You don't want to be using the backup frequently and losing the cost efficiencies of the geothermal. In some installations it might not be possible to have a larger loop and the installer just puts in a backup system to deal with colder temps. Not a problem if he is honest and up front about it.

The second way to deal with it is more interesting. Heat pumps started in the south, primarily as cooling units that could also heat. They were designed with cooling in mind. However, come up north and that gets flipped around. Here, heating is primary with a bit of cooling tossed in. When you design for heating you can get far better heat extraction. Some companies (GeoSystems is the one the Minnesota company uses) realized this and redesigned part of their line for cold weather use and are able to get far better heat extraction in cold weather. The Minnesota company claims they can provide 100% of heating using geothermal although they still recommend a backup heat source anyway. So, not all heat pumps are created equal. Even a good company may not make heat pumps that work best in cold climates.

I now understand some of the issues and possible solutions.

Here is the link to the company web site.

02-12-2013, 08:55 AM	#56
jeffk Senior Member Join Date: Feb 2004 Location: Center Harbor Posts: 1,247 Thanks: 216 Thanked 484 Times in 278 Posts	Some answers I did a little poking around and came across a company in Minnesota that does geothermal and they explain cold weather issues on their web site. First, in cold temps the system runs for a long time and the ground around the system loop cools faster than the ambient 50 - 55 degrees can restore. So the loop water DOES get cooler and the heat pumping process becomes less efficient. There are a couple ways to deal with this. First, simply make the loop longer to provide a larger heat reservoir. Of course this costs more. Maybe it's cheaper to simply throw a backup heat source into the design to handle the colder temps. You trade lower initial cost for higher operating cost. The key of course is hitting the right balance point. You don't want to be using the backup frequently and losing the cost efficiencies of the geothermal. In some installations it might not be possible to have a larger loop and the installer just puts in a backup system to deal with colder temps. Not a problem if he is honest and up front about it. The second way to deal with it is more interesting. Heat pumps started in the south, primarily as cooling units that could also heat. They were designed with cooling in mind. However, come up north and that gets flipped around. Here, heating is primary with a bit of cooling tossed in. When you design for heating you can get far better heat extraction. Some companies (GeoSystems is the one the Minnesota company uses) realized this and redesigned part of their line for cold weather use and are able to get far better heat extraction in cold weather. The Minnesota company claims they can provide 100% of heating using geothermal although they still recommend a backup heat source anyway. So, not all heat pumps are created equal. Even a good company may not make heat pumps that work best in cold climates. I now understand some of the issues and possible solutions. Here is the link to the company web site.