HeatPump

Back in February 2006, the Bangor Daily News published an op-ed I wrote asking: Why doesn't every new home utilize a geothermal heat pump for heating and cooling? The op-ed described my experience with installing a heat pump at my home and my motivation for doing so. Here is that op-ed. The next section has pictures that tell the story about the installation. After 14 years of heating and cooling my home and with basically no maintenance costs, my ground source heat pump is still working well. Today there are government incentives for installing heat pumps in homes.

By David LaBrecque, Special to the BDN • February 9, 2006 8:21 am

Free heat from a geothermal heat pump warms my kitchen as I write this commentary. For every dollar of electrical energy that goes into the heat pump, I get 3.6 dollars of electrical heat. That’s 2.6 dollars of free heat. And by purchasing clean green power from hydroelectric dams and wind power, it’s possible to heat one’s home without burning oil and without generating global warming gases.

The idea of installing a geothermal heat pump began in 2004 when I read about how the polar ice caps are melting at a record pace and how atmospheric carbon dioxide was at record levels and increasing dramatically. The possibility of peak oil production occurring in this decade accompanied by increasing demand for oil in China has made oil prices skyrocket.

I watched as President Bush set up a string of permanent military bases in the oil producing regions of Iraq. I watched as our own Maine National Reserve troops were sent to oil-rich Iraq with the false goals of fighting terrorism and weapons of mass destruction. I watched as oil companies made obscene profits while people suffered. Something had to be done. The freedom we should be fighting for today is freedom from Middle East oil.

So, how does one economically heat one’s home without oil and without pollution? Natural gas is a clean-burning fuel but it still increases carbon dioxide in the atmosphere and contributes to global warming. Solar is good, but there just isn’t much sunlight available in January in Maine when we need the most heat. Geothermal heating coupled with green power produced from hydroelectric, wind and solar power met the requirements.

Green power does cost a little more than the standard offer. But even though electricity is expensive in the Bangor area, my heating costs will be less than heating from oil. Some drawbacks are the high installation cost and that geothermal heating is not well-established in Maine. To extract heat from the ground, one must bury a large amount of pipe in the ground. Still geothermal heating is a well-established technology. Ninety-five percent of new homes in Sweden have installed geothermal heating. Five hundred thousand units have been installed in Canada and the United States.

To minimize the installation cost, I decided on a smaller hybrid system that I installed myself for about $3,000. I estimated that this system could produce about 75 percent of my yearly heating needs since maximum heat loads are only required on the coldest days. My current oil furnace would provide the extra heat needed to warm the house on those days. As an added benefit the system would provide low-cost air conditioning in the summer while providing domestic hot water and heat for my swimming pool.

So, eight weekends later, twice as long as planned and with a series of intense learning situations otherwise known as correcting my own mistakes, I had a working geothermal heat pump. On Jan. 1, warm air came from the register.

Of course I am still on a learning curve but the success I’ve had with this system so far makes me wonder why most new houses aren’t built with a geothermal heat pump for heating and cooling.

David LaBrecque is a research associate in the Chemistry Department at the University of Maine.

Heat pumps for heating and cooling a home can be divided into three categories: Air to Air, Well Type and Ground Loop. Air to air is the easiest and least expensive to install. It's like an oversized air conditioner. The downside is it is not as efficient as the other two types and may not work well on the coldest days in the Winter when it is needed most. The well type is the most expensive, but it doesn't matter how cold it is outside because it is extracting heat from deep underground where the temperature is pretty constant. It also does not require much of a backyard area. The major expense comes from digging a series of wells, the number of wells needed will depend on your homes heating needs. The last type is a ground loop heat pump. Pipes for circulating an antifreeze liquid are buried as deeply underground as an excavator can dig. Excavators cost less, but ground temperature 6' to 8' below ground level varies with the seasons. Given my budget, I opted for the ground loop approach. The first step is to hire and excavator to dig the pipe trench.

Expect huge piles of dirt. My trench was about 300 feet long and ranging from 6 to 8 feet deep. This was about as deep as this excavator could dig.

The excavator operator was an older guy, close to retirement, and he gave me a good price. He warned me not to go in the trench because it could suddenly collapse on you. After he had dug the trench, it was my job to throw the 6 3/4" black plastic pipe in the trench. I wanted to space them apart with a long pole and a rake, but the task proved difficult. So I settled for just leaving the pipe where it landed in the trench.

Somehow the pipes have to come into the basement where the heat pump is installed. There are twelve holes drilled through the basement wall here. Three are on the left and are just out of sight. Leaking into the basement is a concern, so silicon sealant was used to seal these holes around the pipes. Note the drainage pipe that was cut during the excavation. Proper ground drainage should be installed to minimize basement leaks. The excavator operator advised me that the pipes should be continuous through the entire trench with no couplings. He told me he had never seen pipes leak that were continous stretches of pipe, but he has seen couplings leak.

The neighbors could hear the excavator and see large hills of dirt growing in an area close to their backyards. One neighbor thought we were building some huge building near their property. It's a good idea to let your neighbors know what you are doing and that in a day or two, the area will be back to normal and all signs of the excavation will be gone.

The pipes have to come into the basement and go into input and output headers. The headers can be made out of low-cost PVC pipe. I added extra T's and valves onto this header in case I wanted to expand the loop. For example a rooftop solar hot water collector and tank could be used if I had extracted too much heat from the ground. That is I had cooled the ground around the pipes to temperatures below freezing where the heat pump could not operate well. These T's were also used for filling the pipes. It's important to get all the air out of the pipes. Professionals bring in special pumps to do this quickly. If you have time like I did, you can keep adding the antifreeze solution to the pipes over a few weeks as needed, until all of the air, the bubbles in the high point in the clear pipe on the right are gone.

Here is the installed hot air heat pump. I paid about $1700 from a Florida company for this 20,000 BTU heat pump back in 2005. The specs on this particular model indicate it can extract heat from 30 degree F ground loop water. Note the green circulator pump that circulates ground loop antifreeze liquid through the pipes to the header. The gauges on the pipes measure the difference in pressure across the heat exchanger in the heat pump. These will indicate if the liquid is freezing. I also attached the probe from an indoor/outdoor thermometer to measure temperature of the water coming back from the ground loop. Initially I would have to turn off the heat pump when the return antifreeze water was getting too cold. I added an Omega controller (not shown) to automatically shut down the heat pump when the return water was too cold and to keep circulating the water until the ground temperature and the water had come back up to temperature. This was back in 2006 and I haven't made any significant changes since.

Geothermal pump gives free heat