To Geothermal or Not, Is One Reader’s Question

Comments

1. 1

   Green Talk says

   January 16, 2008 at 10:29 am

   Readers, I received this email from Gary of Virstar Corporation. However, he did not have the benefit of reading what I wrote. He only knew my questions. Readers, before I print his comments, I just wanted to give a plug to Gary. If anyone is thinking of an installing a geothermal system in New Hampshire/Massachusetts area or needs for their system to be designed, call Gary. He is very knowledgeable and has decades of experience. See my Friends’ section that gives you a little blurb about his company.

   Gary writes:

   “We recently (Summer ’07) had a Client ask us if we could replace his existing oil-fired boiler with a Geo system if we used the existing hot water baseboard as the heat distribution source. He was not interested in Air Conditioning for the immediate future, so the heating aspect was his only concern.

   My first response to him was “No” since hot water baseboard is designed to heat with convection which requires water temperatures of 150°F to 180°F to work (according to the baseboard manufacturers and all of the “conventional wisdom experts”). Most Geo heat pump manufacturers will not support a water-source heat pump system that uses conventional baseboard and, in some cases, will void the warranty if this condition is ignored.

   Water-to-Water heat pumps typically generate hot water in the 110°F to 120°F (max) range. These temperatures work well with radiant floor systems and I suggested to this Client that we could replace his existing baseboard (copper tube with aluminum fins) with radiant floor tubing stapled up to the underside of his floors from below. This proved to be impractical since we would have to tear down the plaster ceiling in order to install the tubing for most areas of the home, and the alternative of installing the radiant in the grooved panels on top of the existing floors meant that we would destroy his very nice hardwood floors.

   This Client happened to be an extremely smart professor of engineering and we got into a lengthy discussion about heat transfer, thermodynamics, and radiant energy, and decided that we would both do some research into the subject. With help from experts such as the Radiant Panel Association ( http://www.radiantpanelassocia.....?pageid=97 ), we found two interesting solutions. The first, Speedheat4 by SpiroTherm ( http://www.spirotherm.com/docs.....eat-4A.pdf) was designed as a direct replacement for conventional baseboard and was designed to operate at much lower temperatures (120°F) and MUCH more efficiently. The second, Myson Low Surface Temperature (LST) Radiant Panels ( http://www.mysoninc.com/store......atid=19787 ) are designed to provide comfortable (and safe) heat at low temperatures (down to 109°F).

   I personally liked the Speedheat4 solution, whereas the Client liked the European look of the Myson Radiators (Myson calls them radiators, but they are actually radiant panels). In addition, the Client did some very complex engineering on the radiant heat transfer possibilities of his existing conventional baseboard and concluded that they should be able to deliver approximately 50% of their normal (with 160°F water) heating capacity if heated with water that was only 110°F. This meant that we could use the existing baseboard if we supplemented them with either additional baseboard with a Speedheat4 core or added sufficient radiant panels in key locations in his home to make up the additional heat needed.

   The Client agreed to be a “Guinea Pig”, Hydron Module reviewed our calculations and agreed to support the system, and we installed the Hydron Module Water-to-Water heat pump (vertical ground loop Geo design) and added several Myson radiant panels. As it turns out, the system works just fine, his home is nice and toasty, and he saved a ton of money by not having to replace the existing baseboard and associated piping.

   Please note that this type of system, as with any radiant heating system, has a high degree of “latency” or delay from the time that the thermostat calls for heat and the radiant system is able to satisfy that demand for heat. This is because the lower temperatures deliver fewer BTUs per minute than a conventional high temperature system. What this means to the average homeowner is that if the temperature drops severely in a short period of time, and the home is not well insulated, the home could go several degrees below the desired room temperature (i.e.- down to 67°F or lower with a thermostat set @ 70°F) before it starts to warm back up again.

   To compensate for this, a well designed radiant system should have a thermostat with an Outdoor Temperature Sensor. This sensor “anticipates” the need for heat (i.e.- change in weather/temp, time of day/Sun going down, etc.) and begins running warm (90°F) water through the radiant heat system piping before the room temperature starts to drop. Then, when the thermostat actually calls for heat, the radiant system warms to max temp (110-120°F) and is able to satisfy the need for heat in the room in minutes. The result is a VERY comfortable home that is very efficient. (It costs less money to heat a space gradually with low temp water than to bring water to scalding temps (160-180°F) and heat the space in a hurry, even though the total BTUs delivered to the space are the same.)

   With this Client, his old oil boiler was failing and had to be removed. (It actually quit working before we were able to do the installation, so he went a few weeks in November’07 with no heat except for electric space heaters.) For people that have oil or gas boilers in serviceable condition, they may want to keep the old boiler in place as a backup source of heat, but it is not necessary if their Geo system is well engineered and uses high quality equipment.

   One final point. I recently developed and have begun installing a simple solution that couples with a Geo radiant system to provide A/C at very low costs and can also provide supplemental heating. It is a very small Fan/Coil unit (essentially a small 12″x12″ automobile radiator with a fan behind it) that is piped the same way as the radiant floor heating and radiant panels would be. This allows the addition of forced hot air heating and forced air cooling to the same system without complex and expensive ductwork installation. Since the unit is so small (12″x12″x 12″ Long), it can be added to existing homes in many locations (i.e.- top of closets, etc.) with minimal remodeling cost.”

   Reply
2. 2

   Green Talk says

   January 16, 2008 at 10:38 am

   Gary-how do you feel about the geothermal payback in the situation you mentioned above since it seems so similar to Ronald’s situation?

   Also, I am a little confused about your air conditioning retrofit. Is there a vent that the cool air comes out? How does it attach to the radiant flooring?

   What are your thoughts on radiant cooling without the fan. Too much risk for condensation?

   What size room could this 12 by 12 coil unit provide air conditioning for?

   Gary, thank you for your great comment.

   Reply
3. 3

   Gary L. Maedl says

   January 16, 2008 at 3:18 pm

   Anna- The payback period should be in the range of 4 to 7 years, pretty much the same for a Geo system that is also doing A/C, since the cost for the Geo system would be lower without the fan-coils for the A/C.

   In addition, in the Northeast, the majority of home owners spend a much higher amount of money per year on heating than they do on cooling. Primarily, this is due to the fact that while cooling, they are only paying for the energy to reduce the temp in their home by 15°F (from 90°F outside to 75°F inside), whereas in the winter they are paying to increase the temp in their home by 45°F (from 25°F outside to 70°F inside) and by 70°F when it drops to Zero outside. Raising the temp in your home requires BTUs, and BTUs are what you pay for when you buy energy. So, since the Geo system will substantially reduce the heating bill (the main cost of energy) and Ronald was not paying for A/C anyway, the payback period is not substantially affected.

   As for our VIRSTAR Mini Fan Coils, they still require a duct to blow the air into the room and a return air duct to pull the air from the room, but the supply air ducting is very short- only a few feet long at most, and the return air ducting typically uses wall cavities. So the installation is easy and inexpensive. The 12×12 unit puts out about 13,400 BTU/Hr which is sufficient for heating or cooling about 500 sq.ft. in a well insulated house.

   Our Mini Fan Coil, in heating mode, would feed from the same hot water supply system that the radiant floor uses. In cooling mode, the Geo system switches from heating its storage tank water from 110°F to cooling the water to 42°F and the radiant floor loops (or panel radiators) are shut off. The Mini Fan Coils use this cold water to deliver A/C. Radiant floors and panel radiators cannot be used for A/C since there would be a HUGE amount of condensation that would puddle on the floor. The Mini Fan Coil has a condensation collection pan built into the box that permits the condensation to be drained away safely.

   Reply
4. 4

   Green Talk says

   January 16, 2008 at 4:06 pm

   Gary,

   Based on the northeast, if you were comparing right now a home heated with gas versus a home heated with geothermal, what kind of percentage of savings do you think they would see. I was told that I would only see about 20-30 percent in heating costs, but 50-70 percent for air conditioning. I was also told that the huge savings was in the air conditioning as I noted above. It is funny. Sometimes I even see on the internet that people should expect to see savings up to 70 percent all year round. This can be a little misleading because different climates. What seems to be the rule of thumb for heating and air conditioning?

   Is this mini fan coil only to be used with geothermal or can you use it with a conventional system? If so, this would be great for people who live in older homes which do not have air conditioning. Are these Mini coils being sold to other HVAC or geothermal companies or are they strickly installed by your company? Is there a link that you can add in your response so people can see it? Anna

   Reply
5. 5

   Gary Maedl says

   January 16, 2008 at 6:12 pm

   Anna,

   One point that I’d like to make is that we can design a Geo system for literally anywhere in the world, but if they want us to physically go to their site, we tend to stick to projects in the Northeast (all of New England, NY, NJ, PA, etc.). We also have a network of Hydron Module affiliates in almost every US State and much of Canada who can provide expert on-site installations from our designs.

   As for cost savings, there are a lot of variables that affect the system performance. The simple way to understand your savings is as follows:

   1. It takes $1.17 worth of electricity (@ $0.186/KwH including demand charges) for a high-quality water-to-water or water-to-air heat pump to generate 138,000 BTUs of heating using a Geo ground source of 55°F (typical well water temp in Northeast), and at roughly 95% efficiency, the heat pump will deliver 131,100 BTUs of that energy into your home in the form of heat.

   2. One gallon of home heating oil at current costs of $3.29/Gal. will also generate 138,000 BTUs, but the average oil heating unit is only 85% efficient at best, so it will only deliver 117,300 BTUs of that energy into your home in the form of heat.

   3. Based upon this simple difference in efficiency of converting energy to heat (called AFUE for oil/gas systems and COP for heat pumps), the water-source heat pump is 10% more efficient to start with.

   4. Comparing the costs per BTU for the two types of heating ($3.29 for 138,000 BTUs with oil vs. $1.17 for 138,000 BTUs with electricity/Geo), the Geo system is 2.81 times or 281% more efficient than heating with oil at today’s energy prices. If oil prices drop, this savings will reduce accordingly. If oil prices continue to rise, this savings will increase.

   5. Use your own local prices for electricity and oil to compute what your savings with a Geo system would be.

   You are correct in the fact that Geo systems are slightly more efficient in cooling mode than in heating mode, but this difference is nominal. It comes from the fact that the temperature differential (∆T) for heating (70°F ∆T @ Zero outside) is much greater than for cooling (15°F ∆T @ 90°F outside), so the unit has to work a lot harder and longer to keep your house at 70°F for heating vs. 75°F for cooling.

   Our Mini Fan Coils can be used with any hydronic (water based) system, but a specifically designed for Geo since they can operate with low temp water (110°F) for heating. For cooling, they use 42°F water, the same as a conventional system would use. Currently, these Mini Fan Coils are sold only to VIRSTAR Clients, but that may change in the future.

   Reply
6. 6

   Houston Realtor says

   January 17, 2008 at 12:18 pm

   There was a great article about Shell’s activity in the geothermal sector in fortune about two months ago. I’d highly recommend the article for an overview of the sector and what some of the majors are doing.

   Reply
7. 7

   Green Talk says

   January 17, 2008 at 3:36 pm

   Houston Realtor, can you give us the link to that article? Anna

   Reply
8. 8

   Green Talk says

   January 21, 2008 at 3:25 pm

   Gary, can you give us a savings example of a geo system in your area. I looked at that formula and my head hurt. Also what is your feeling about dumping your heat from your geo in the summer into your hot water tank. Can this be done if you do not have a geo setup for your hot water?

   What is the payback for your hot water to be generated by geothermal?

   After I read your comment, it is amazing to me how much misinformation there is about geothermal. Everything I told you was what a few geothermal installers told me. I am glad you are setting the record straight (at least for me!)

   Readers, if you tried to open some of the links in Gary’s comments. I just updated them per Gary’s instructions. Anna

   Reply
9. 9

   Gary L. Maedl says

   January 22, 2008 at 5:36 pm

   Anna,

   For a large database of information, I would suggest that readers contact PSNH ( http://www.psnh.com/Energy/Hom....._Homes.asp ) for results on Geo homes in their Energy Star program. From my point of view, they have the most progressive energy program of all the electric utilities in the Northeast and have documented statistics for a large number of homes in their program.

   As for my Clients, we tell them to expect at least a 40% savings over any type of fossil fuel system, regardless of how new and efficient the system claims to be. In actual use, we know that they will realize a savings that is greater than 40%, but how much depends upon a lot of variables.

   But I will share this example which I found to be quite interesting. I have a Client for which we installed a Geo system (water-to-air heat pump with standing column well ground source) about 1 year ago, replacing an existing oil-fired FHA unit.

   This Client wanted to know exactly what it was saving him to have the Geo system, so he installed an EM-2500 Meter Reader ( http://www.energymonitor.com/ ) directly on his heat pump.

   Note that this is the only unit of its kind that I am aware of that can be used to measure the electricity usage of an appliance that does not have a plug, and is reasonably priced.

   He was sensitive to cost issues since he did not have PSNH as a utility, had no special Geo programs available to him to reduce his electric costs, and his rate was $0.215/KwH, high compared to rates in most areas.

   Last December we had a cold snap for almost a week. He called me and said that he thought that his Geo system might not be performing at optimum efficiency since it consumed $7.00 of electricity per day (24 hours) during the cold snap (around 5°F). For his 2,100 sq.ft. home, he thought that this seemed high.

   I asked him how much oil he could buy for $7.00? Answer- a little less than 2.5 gallons. I told him that with 2.5 gallons (@ 138,000 BTU/Gal at 85% AFUE), he would get only about 300,000 BTUs of heat for his home. Since his home consumed about 50,000 BTU/Hr (based on the energy calcs that we had done and a study of his oil purchases going back 4 years) when the temp outside was 5°F, I pointed out that $7.00 worth of oil would only heat his house for about 6 hours.

   He would have needed $28.00 worth of oil to heat his home for 24 hours, the same amount of time that the Geo system heated his house for only $7.00. This means, under those particular conditions and with current oil prices, his Geo system was operating 300% more efficiently than his old oil system!

   Now, PLEASE, don’t go running off and start telling everyone that you read that Geo is 300% more efficient than oil FHA. This was only a snapshot in time and he was not measuring the cost (nominal) of running the well pump that feeds water to his heat pump. If he added in the cost of operating his well pump, then this efficiency increase would actually be closer to 200%. And if oil prices dropped tomorrow to $2.00 per gallon, then the efficiency gain (@ $0.215/KwH) would drop to about 68% (including pumping costs).

   Regarding your questions about generating domestic hot water with Geo, this is a special aspect of water-source heat pumps which can get really confusing. Domestic hot water (DHW) is typically kept at around 130°F in your hot water tank. Some people like it hotter, but let’s use this number so we don’t have to worry about children scalding themselves.

   Water-source heat pumps work by “pumping” or transfering heat from one location to another by using the process of refrigeration. When they are in heat mode, they pump the heat from the earth into your home and the earth gets a little colder while your house gets a lot warmer. In A/C mode, they pump the heat from your home into the earth and the earth gets a little warmer while your house gets a lot cooler.

   There is a part of the refrigeration process that is called “Superheat”. Due to the laws of thermodynamics and heat transfer, this Superheat cannot be used in the actual heating or cooling process. It is like a byproduct and is pretty much the same whether you are using your heat pump to heat or cool.

   Many of the better water-source heat pump manufacturers offer an option that captures this Superheat for use in heating domestic hot water. Hydron Module calls this device a “DeSuperheater” and it costs around $700.

   This DeSuperheater gives you essentially free hot water, but only when the heat pump is running doing its normal job of heating or air conditioning. When it is “nice” out (spring, fall) and the heat pump is not running, the DeSuperheater is not running either. Note that it is only about 10% more efficient at producing this DHW in the summer (A/C mode) than in winter (heat mode). On average, here in the Northeast, the DeSuperheater saves about $132 per year in energy used to produce DHW, but you do get a $300 Federal Tax Credit for installing the unit. So it pays for itself quickly.

   You could use a Geo system to produce DHW all of the time, but water-source heat pumps can produce water temps up to a max of about 120°F. If you want hotter water, you need to use some other heating source to make up the difference.

   The “heated” water that is sent back to the earth when a heat pump is in A/C mode is only about 70° to 80°F, depending upon your well temp. So it is a misconception to think that it would be efficient to configure a water-source heat pump to produce all of your hot water while it was in A/C mode.

   Reply
10. 10

    Tim Tuttle says

    May 5, 2015 at 3:01 pm

    Just wanted to add some experience to those questioning geo in the north-east. We live as far north as you can go north in New York state. We have a small 1200sf single story well insulated home. July 2014 we installed a 2 ton Hydron Module water to air system with a 1200 ft horizontal ground loop at 7′ deep. There is a 5k electric coil for backup but the breaker has never been turned on. From July 30th 2014 to April 15th, 2015 the unit used 3680 kW hours of electricity. That was for cooling August through the end of Sepember and heat / hot water all winter. We set the thermostat on 72 when it was installed and havent touched it since. Performed flawlessly for both heating and cooling. Comparitively speaking, our heat bill the prior winter was $950 with a high efficiency propane furnace. We also have a 10k solar system which covered all of our electric needs including the heating and cooling. The past twelve months yielded us a power company credit of $149.82! Geo does work well in the north -east.

    Reply
    • 11

      Anna@Green Talk says

      May 5, 2015 at 9:06 pm

      Tim, did it struggle when it was really cold. Mine couldn’t reach 64 this February. My electric back-up was turned off.

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      • 12

        Tim Tuttle says

        May 6, 2015 at 8:58 am

        We never dropped a degree all winter. Our area has a typical frost depth of 4′ and this winter some others water pipes were freezing at 6.5′. Was a great test for a new system. I think the depth of the ground loop and the type of soils has alot to do with sustained cold winter as we had this year. Where we buried the loop was 7 1/2′ of pure red sand and went straight to blue clay. the ground water table was at 5′ in July. I believe the combination of the sand and constant contact with the ground water attributed to maintaining temp for a very brutal year.
        Sorry to hear you were having issues.

        Reply