Geothermal heat pump info
January 5, 2008
Found this site from a poster at Green Building Talk. I’m beginning to understand some of the geothermal options. For some reason I thought you could only use geothermal to run through radiant heat flooring but you can actually use it just like a regular air-to-air heat pump…so it’s basically just sourcing the energy from a different place but using ductwork inside your house that blows air around, just like a gas furnace would (and seems gas could be the backup source). This makes a lot more sense to me. Hmmm.
January 14, 2008 at 1:52 pm
An Air to Air geothermal system is no where near as efficient as Water to Air system. An Air to Air heat pump sucks the heat out of the air and uses it to heat you home (Even air that is freezing has some heat in it). Just like the a water based geothermal system, the air (or water) coming out of the system is colder than what goes in because it’s drawing some of the heat out of what goes it. The problem with an Air to Air heat pump is as the air gets colder the system has to work harder to get the same amount of heat out. When the temperature drops to around 20 degree F, the system can no longer extract enough heat out to heat your home and has to use an alternative backup heating (either electric or gas) to heat.
Water to Air geothermal system is far more efficient, because the ground water is always the same temp, around 50 degrees F, so if you wanted to heat your house to 70, and its 60 degrees out, the air to air system would be more effacement until the temp drops below 50 degrees.
Also an Air to Air system life span is around 10 to 15 years, compared to a water based geothermal system which is 25 to 30 years, and longer if you have the closed loop system. The underground coils for a closed loop system last around 50 years.
January 14, 2008 at 2:02 pm
Ok, hmmm, I guess I was thinking it would be water to air…the “energy” would come from a closed-loop system and somehow that is converted into being blown through your house? I’ve got so much to learn.
See, my original understanding was that you could only do the closed-loop system…and that it would go through radiant floor tubes in your house and circulate back out. So, it was one giant closed loop, in my mind…I never realized it could be used to heat the air and then go through duct-work in your house.
Hmmm…where’s my disconnect coming from? Any good sites? Right now I’m imagining a closed-loop system that comes in, heats the air somehow, and then gets blown around. Am I completely off? Is that a water-to-air system?
Thanks!
January 16, 2008 at 10:12 am
You can do a closed loop system, it uses something other than water, Im thinking feron. The pipe is buried under ground in your yard, the feron is pumped thru the pipe and into the Geothermal system. It uses a compressor somehow to extract heat from the feron and uses that heat, to heat the house. The Feron exiting the Geothermal system is colder, the colder feron gets pumped thru the pipe where the ground heats the feron back up to the temp it was before, it reenters the Geothermal system and the process repeats.
The ground temp is something like 50 degrees, so if you were using radiant floor tubes, that water would be 50 degrees, that be a cold floor. Now just like heating air, the geothermal system can heat water, but usually this is used to heat water for the hot water heater. This is an additional feature you can get with your geothermal system, its just an extra attachment / feature to your standard unit. Also Im not sure if the hot water is heated enough to to go directly your shower, or if it’s more like the water is preheated by the geothermal unit and hot water entering the hot water heater has to be heated a little more to give you hot enough water to shower with. This would be the water you would use for a radiant system, but I would imagine the system required would have to be bigger to handle radiant heat, but I just don’t know.
In the summer the system would works just the opposite, you would extract the cold from the feron to cool your house, the feron would enter the ground loop warmer than it came in at and the group would cool it back down. There is no external noisy compressor outside your house when you have a geothermal system. (Water to air)
There is a noisy compressor outside for a Air to Air heat pump, it runs in both winter and summer because this is where it’s pulling air in to heat or cool you house.
An open loop system used ground water instead of feron, it drawn the water up from a well or other source like a lake and extracts heat from the water, the water can either be return into the group via another well, or discharged into the ground. Mine dumps onto the ground into the woods behind my house, but in the summer its can feed a number of ponds with running water while the system is on before it goes into the ground.
January 16, 2008 at 10:40 am
So, inside the house, what does your system look like? Is it air through ducts, radiant heat, or what? Do you find it cools well in summer? We live in a hot area so that’s a big concern for us. Interesting you have an open-loop…I would love to live in the woods again, grew up in them and spent much time playing in the forest. Thanks for your help!
January 18, 2008 at 1:11 pm
The system looks like a big box in my basement, just like what my natural gas unit looked like in my old house, just bigger. Of course my last house was only 825 sq ft and this house is over 3,500 sq ft, so I would expect the box to be bigger. I don’t have the exact deminsions on hand, but I would say its 5 feet high, 4 feet long and 2 1/2 feet wide. The one side has the blower motor and the other side the compressor. Plastic/PVC piping connect the water to and from the system, the internal pipes in the unit are copper. A Vent exits from the side of the unit and venting is run in the basement to direct the heat into the 1st foot above it.
There are 2 extra pipes coming out of the bottom to heat hot water, but its not connected. I’m a little afraid to mess with it, I need the system to last long enough to save up the $ to replace it (it’s 17 years old).I got a replacement estimate of 8k, I seen one on a website for about $3,500, but that just for the unit, not installation costs. I’m not yet confident enough yet to tackle replacing it myself.
I just brought the house in November, so I have yet to see how it works in the summer. Ideally I want to learn enough about the system to repair/replace the unit myself, but at 450 pounds, I may need just a little help with it. Unfortunely houses don’t come with detailed instructions or a tech support 1-800 line I can call, I’m still learning about how the heat works, the pump, the sprinkler system, the alarm system, but I learn a little more each week about them.
January 18, 2008 at 1:33 pm
Thanks, Tech, that’s very helpful. I’m interested to see how it functions in the summer. I’ve heard they’re excellent. Was the geothermal a selling-point for you, or did it just happen to come with the house you were living in?