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Geothermal Heat Pumps

Posted: Wed Jan 20, 2016 7:33 pm
by 4nursebee
Does anyone have one or know about them?

I've heard they cool well in the summer and do a nice job removing humidity/moisture, is this true?

I've heard they heat very well without using back up heat strips, is this true?

If you are willing to share project costs or suggestions, please do.

Thank you.

Re: Geothermal Heat Pumps

Posted: Wed Jan 20, 2016 7:45 pm
by David Jay
Geothermal has a high initial costs but low operating cost. So you spend money to save money.

You have to run the numbers. If you live in a Northern state and have natural gas, it takes a long time to pay back. This especially true with the lower NG prices of recent years.

If you are both heating and cooling with electricity, the payback is better.

Last time I asked about the cost to convert a home (that has existing ducted central heat/air), I was told $7,000. But that was more than 5 years ago.

Re: Geothermal Heat Pumps

Posted: Wed Jan 20, 2016 8:20 pm
by Drewman
We moved into a home built in 2005 that was a geothermal retrofit after high propane bills. They spent close to $20,000 with the trenching, 5 ton waterfurnace 5 series and a couple other addons like thermostat and reusable filters and duct work corrections. The home is 3200ftsq with additional 1200 of basement that is empty but still temp controlled. Our bills have gotten up to $298 in winter keeping the house at 68 (ohio). Summer they have gotten down to $100. This includes our well pump for water as well. We have been pretty pleased but glad we didn't get the install cost - granted some may argue it was included in our purchase price but I think we still got a deal. I plan on spending an additional $10K for a high efficiency wood burning fireplace eventually so it's not perfect.

Check out the geoexchange forum. There is a heat pump testimonial section. You can also view several live feeds!

Re: Geothermal Heat Pumps

Posted: Wed Jan 20, 2016 8:23 pm
by Toons
A couple of general remarks.
No personal experience here,but my brother who lives in Virginia invested in a geothermal unit.
The initial outlay was rather expensive but the operational costs ,as have been mentioned, have been low.
He is very pleased with the results.

Re: Geothermal Heat Pumps

Posted: Wed Jan 20, 2016 8:26 pm
by dougger5
4nursebee wrote:Does anyone have one or know about them?
We've had 2 over the last 10 years. Same house - had it installed as part of construction of the house, so I can't give you before/after utility costs. The first one was plagued with mechanical issues, so much so that though they didn't give us a new one for free, it came at a deep discount.

I feel good about the 2nd one, a few years on. Much better compressor. Brand is Waterfurnace.
4nursebee wrote:I've heard they cool well in the summer and do a nice job removing humidity/moisture, is this true?
BTU's is BTU's, so any unit, geothermal or air source, can be sized so as to perform well for temperature/humidity control in the warm months.
4nursebee wrote:I've heard they heat very well without using back up heat strips, is this true?
I'd say the compressor is used more effectively/efficiently at low outdoor temperatures, and the aux heat (electric coils) will be used less, but probably not never if it gets into the low-teens/single digits. We're in SE PA, and the electric bill is skewed higher in the cold months.

If it helps, we're 2500 sq ft, two stories, and the highest winter monthly bill last year was $292, highest summer bill was $175. We're all electric...so maybe that higher winter bill is due to using the oven more often, rather than the grill :wink:

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 7:08 am
by Valuethinker
4nursebee wrote:Does anyone have one or know about them?

I've heard they cool well in the summer and do a nice job removing humidity/moisture, is this true?

I've heard they heat very well without using back up heat strips, is this true?

If you are willing to share project costs or suggestions, please do.

Thank you.
If you have gas heat and live in Continental USA I generally would not bother. Natural gas is cheap enough in the USA to offset the advantages. Even in New England I suspect (gas is expensive, but so is electricity).

If you are "Green" then given the emissions intensity of much of the US electricity network (you can be using "clean" kwhr but that means someone else may be using the dirty ones) even a high efficiency HP is not necessarily that green compared to a HE natural gas furnace.

If you are "extreme Green" and you can self generate a large proportion of your electricity (wind turbine or solar or mini hydro) then it would beat gas (but you will still be importing from the grid at peak times).

However if you are on propane or electric baseboard or heating oil, then it's well worth looking into (although current low oil prices probably mean it is uneconomic, and I believe propane roughly tracks heating oil). A relative, on a ridge in central SW Ontario (so say -30 in winter with windchill, and 90+ in summer) installed GSHP over baseboard heating and payback was less than 10 years.

They also had an airtight wood stove. That's a common combination with a HP.

You should be able to get Coefficient of Performance COP of 4.0+ with a GSHP (4 kwhr of heat/ coolth for every 1 kwhr of electricity).

As long as you are above 0 degrees F you shouldn't need the strip heating (might even be lower than that).

One thing is HPs work well with things like underfloor heating, but they usually produce cooler air or hot water than a NG furnace. The smaller the gap between input temperature and output temperature, the higher the efficiency/ COP. So HPs work best with well insulated and fairly airtight homes, which can be heated up and then left. Whereas with a gas furnace the trick is to turn the heat down when you go out or go to bed, and then when you get back/ up, whack it up to full blast. That works fine in a leaky older home.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 7:35 am
by 4nursebee
I have about a 10kw solar photovaltaic system, recently doubled in size and converted over to "net metering". The first month we had 50 kw peak credit, 150 off peak credit. Then it got cold, all credit gone.

Our Goodman heat pump has generally worked well for 13 years except for 3 refrigerant recharges. The heat strips don't really come on unless we turn the heat up. The system is running pretty much all the time REALLY ticking me off using up all this power. Sure it is maybe $2.50 a day, but when the power bill comes it is gonna cause some serious rethinking...because we were expecting to only pay for water and about $50 a month for the honor of being grid tied still.

The guy that upgraded our solar ( who has a business relationship with a geothermal company) stated that his geothermal blows out really cold air and draws moisture out very well, kind of like a faucet on continuous drip, not just a drip a minute. We find that a dryer house in the summer really enhances our comfort. He also stated that his heat blows out so hot one can't stand to be too close to the heat vent, all of this without backup heat strips being on. Right now, the hot air coming out our registers is only 3 degrees warmer, hence it feels cold. MY HVAC man says this is normal, as it is cold the system has to work real hard without turning on the heat strips. But as it works real hard my power bill goes up up up.

As we approach FIRE, getting big expenses out of the way would be nice, hence the consideration of new heat pump vs geothermal. Geothermal sites suggest they use much less power compared to normal systems. If they draw moisture out well I would not need a dehumidifier running, and the chance that the air would seasonally feel hotter or cooler has great appeal.

Edit, our home is already very tight ICF, one of the tightest 5 or 10 homes my utility ever tested. We've since finished off some attic space which is not as tight.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 8:21 am
by Carl53
We bought a home with a "Cadillac" geothermal system in 1989. I loved that system. It heated the house with warmer heat than a typical air heat pump, the backup heat only came on after it had been below -10F for a day, heated all of our hot water and could heat the in ground pool. Eventually parts failed and the company was out of business. I found out that just replacing the main heat pump and getting only some of our hot water from it was going to cost 8000 in the late 90s. I was able to install gas for not much over half of that and have not been disappointed, although both the gas furnace and hot water tank have both been replaced. If gas is not available this is probably the way to go as there are often government incentives to ease the initial burden.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 9:01 am
by Valuethinker
4nursebee wrote:I have about a 10kw solar photovaltaic system, recently doubled in size and converted over to "net metering". The first month we had 50 kw peak credit, 150 off peak credit. Then it got cold, all credit gone.
Depending on where you live and how cold it has been, this is not surprising.
Our Goodman heat pump has generally worked well for 13 years except for 3 refrigerant recharges. The heat strips don't really come on unless we turn the heat up. The system is running pretty much all the time REALLY ticking me off using up all this power. Sure it is maybe $2.50 a day, but when the power bill comes it is gonna cause some serious rethinking...because we were expecting to only pay for water and about $50 a month for the honor of being grid tied still.
Heat pumps tend to run long and slow (ie relatively low temperature output) against fast and hot (gas furnace). The efficiency of a heat pump is a function of the difference between the outside temperature and the inside (a fridge in a hot kitchen has to work harder-- same principle).
The guy that upgraded our solar ( who has a business relationship with a geothermal company) stated that his geothermal blows out really cold air and draws moisture out very well, kind of like a faucet on continuous drip, not just a drip a minute. We find that a dryer house in the summer really enhances our comfort. He also stated that his heat blows out so hot one can't stand to be too close to the heat vent, all of this without backup heat strips being on. Right now, the hot air coming out our registers is only 3 degrees warmer, hence it feels cold. MY HVAC man says this is normal, as it is cold the system has to work real hard without turning on the heat strips. But as it works real hard my power bill goes up up up.
Your HVAC man is right. I don't see a GSHP (geothermal) will be that much different *except* they are more efficient (as a result of taking in their hot/cold from ground which is a fairly even temperature all year round-- usually c. 50 degrees F (10 degrees C).

Because it is more efficient you can run it hotter in winter and colder in summer (at the output end).
As we approach FIRE, getting big expenses out of the way would be nice, hence the consideration of new heat pump vs geothermal. Geothermal sites suggest they use much less power compared to normal systems. If they draw moisture out well I would not need a dehumidifier running, and the chance that the air would seasonally feel hotter or cooler has great appeal.

Edit, our home is already very tight ICF, one of the tightest 5 or 10 homes my utility ever tested. We've since finished off some attic space which is not as tight.
The tightness of your home will include all contiguous spaces ie includes the attic.

If you have good R values and an air tight home, a HP (ASHP or GSHP) should work well. The main thing is it will need to run much or most of the time, not in short bursts. It's a different way of using a heating/ cooling system.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 9:03 am
by Valuethinker
Carl53 wrote:We bought a home with a "Cadillac" geothermal system in 1989. I loved that system. It heated the house with warmer heat than a typical air heat pump, the backup heat only came on after it had been below -10F for a day, heated all of our hot water and could heat the in ground pool. Eventually parts failed and the company was out of business. I found out that just replacing the main heat pump and getting only some of our hot water from it was going to cost 8000 in the late 90s. I was able to install gas for not much over half of that and have not been disappointed, although both the gas furnace and hot water tank have both been replaced. If gas is not available this is probably the way to go as there are often government incentives to ease the initial burden.
Natural gas has just become so cheap in continental USA that GSHPs only make sense in high heat load areas (midwest & NE and maybe some mountain states) where NG is just not available.

I doubt at current oil prices (and propane which tracks oil) they make much sense against heating with *oil*. However in the long run oil prices may rise again (perhaps at least to $60/bl) and so there is that advantage.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 9:05 am
by 4nursebee
Considering my current and future solar, only electric systems are my choice.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 10:30 am
by Valuethinker
4nursebee wrote:Considering my current and future solar, only electric systems are my choice.
There are high performance ASHP (Japanese) that rival the performance of average grade GSHP. The latter has, theoretically, better performance. But not always in practice.

Have a look around at the ASHP market, see what is available.

The deal breaker is probably what your temperature extremes are. If you have a lot of winter days down at 10 F then GSHPs could well perform significantly better.

Re: Geothermal Heat Pumps

Posted: Thu Jan 21, 2016 10:31 am
by Valuethinker
4nursebee wrote:I have about a 10kw solar photovaltaic system, recently doubled in size and converted over to "net metering". The first month we had 50 kw peak credit, 150 off peak credit. Then it got cold, all credit gone.
One possibility is sunlight hours? Depending where you are in the USA, December-January can be very gray. You can get 10% of the insolation you would get on a sunny day.

Have you checked your output? As well as your consumption?

Re: Geothermal Heat Pumps

Posted: Fri Jan 22, 2016 7:59 am
by magellan
dougger5 wrote:BTU's is BTU's, so any unit, geothermal or air source, can be sized so as to perform well for temperature/humidity control in the warm months.
While I agree that a well designed ground source geothermal system can effectively control humidity, I don't agree with your BTUs is BTUs statement.

Dehumidifying works by passing humid air across a coil that's a much much lower temperature than the air's dew point. The greater the difference between the dew point temp and the coil temp, the more moisture gets removed. It's definitely possible for a system to remove a lot of BTUs from the air without removing any moisture.

For example, if the air temp is 85 degrees, the coil temp is 71 degrees and the dew point is 70 degrees, you could eventually cool down the air to 75 degrees by repeatedly passing it over the coil. However, in this scenario you won't remove much humidity from the air.

OTOH, if the coil temperature is 40 degrees, passing a smaller amount of air across the coil will cool the room to 75 degrees. However in this case, passing the moist air across the icy cold coil will remove much more humidity.

With these two examples, the same amount of heat (number of BTUs) is removed from the air. Yet in one case much more humidity is removed because more moisture condenses on the cold coil as the air passes over it.

Edited: Updated to reflect Epsilon Delta's point below.

Re: Geothermal Heat Pumps

Posted: Fri Jan 22, 2016 10:43 am
by Epsilon Delta
magellan wrote:
dougger5 wrote:BTU's is BTU's, so any unit, geothermal or air source, can be sized so as to perform well for temperature/humidity control in the warm months.
While I agree that a well designed ground source geothermal system can effectively control humidity, I don't agree with your BTUs is BTUs statement.

Dehumidifying works by passing humid air across a coil that's a much much lower temperature than the air's dew point. The greater the difference between the dew point temp and the coil temp, the more moisture gets removed. It's definitely possible for a system to remove a lot of BTUs from the air without removing any moisture.

For example, if the air temp is 85 degrees, the coil temp is 71 degrees and the dew point is 70 degrees, you could eventually cool down the air to 75 degrees by repeatedly passing it over the coil. However, in this scenario you won't remove much humidity from the air.

OTOH, if the coil temperature is 40 degrees, passing a smaller amount of air across the coil will cool the room to 75 degrees. However in this case, passing the moist air across the icy cold coil will remove much more humidity.

With these two examples, the same number of BTUs are removed from the air. Yet in one case much more humidity is removed because more moisture condenses on the cold coil as the air passes over it.
It's true the two situations are different, and that the temperature of the coils matters, but they definitely remove different amounts of energy from the air, unless your using a very narrow definition of "air", considering it separately from the water vapor. Condensing the water vapor to produce dryer air requires removing about 20 times as much energy as simply cooling the moist air but staying above the dew point.

Dehumidifying costs for two reasons: 1) the coils need to be colder, which lowers the efficiency of the heat pump. 2) Condensing water vapor requires removing a lot of energy.

Re: Geothermal Heat Pumps

Posted: Fri Jan 22, 2016 7:28 pm
by ace1400
I recently replaced a ground source heat pump system (GSHP) with an air source heat pump system. I would not purchase GSHP system after what I learned trying to fix our system. The box itself (from water furnace or climate master) are extremely expensive ($7-10K for just the box - I needed two) and the system design for a GSHP system is extremely critical and apparently done wrong frequently. Look at the forum (https://www.geoexchange.org/forum/forum ... oting.279/) to see how often bad design is the reasons experts cite for a system's poor performance. When the "design" is buried in your yard, you can't change it economically. Once the company that installed goes out of business (which also seems frequent), no one else will warranty anything associated with the system - there is so much they cannot see, cannot assess and have no idea how well or badly the original install was done that you are on your own. That $20K for the new units I was quoted (at 12 years old they are at end of life according to all three organizations that deal with them in my area) was for install and "we hope it works but who knows."

What to do? I went with a variable refrigerant flow air source heat pump. Much cheaper to install, and more efficient in my climate than the theoretical performance of my previous GSHP's. The Mitsubishi S-Series are fantastic and the install is idiot proof compared to the GSHP. Anyone can work on them if they do break. And the HVAC forums I haunted prior to purchase had numerous whines from HVAC installers complaining about the Mitsubishi systems - once they install one for a customer, they never get called again. The system just works.

Re: Geothermal Heat Pumps

Posted: Fri Jan 22, 2016 10:30 pm
by dougger5
Epsilon Delta wrote:
magellan wrote:
dougger5 wrote:BTU's is BTU's, so any unit, geothermal or air source, can be sized so as to perform well for temperature/humidity control in the warm months.
While I agree that a well designed ground source geothermal system can effectively control humidity, I don't agree with your BTUs is BTUs statement.
Ok, I could have been more specific: Total BTU's is total BTUs. The point I was attempting to make is that one can select an air source indoor coil to have the same delta-T as that of a ground source indoor coil, given the same entering air conditions and design ambient conditions. This is in terms of performance, not necessarily efficiency.

If you select a coil to get between two points on a psych chart, it doesn't matter if it's GSHP, ASHP, chilled water, absorption process with ammonia, or whatever.

Re: Geothermal Heat Pumps

Posted: Sat Jan 23, 2016 12:51 am
by HighC
Hi All,

I have been working in the geothermal heat pump industry for about 10 years for a company as an engineer and software developer who develops tools for designing these systems.

Here is my take:

1) If a geothermal system is well-designed and properly installed, it will perform more efficiently (~35% more efficiently for cooling against a regular unitary A/C systems and ~300%-400% more efficiently against a typical gas furnace. This efficiency boost is based on fundamental physics.

2) The key to getting a good system is (just like for anything else), finding a good contractor. These are few and far between for geothermal because the market is small. Many systems are designed and installed by people with no experience or qualifications. These systems don't work right. It will be challenging for a non-industry insider to find a firm that is skilled and experienced rather than inexperienced and possibly lying through its teeth to get your business. Some of our best customers make over half of their revenue fixing poorly designed/installed systems. They call this "geo janitorial" work.

3) The majority of the people that I know who work in the industry have geo in their homes and they save significant money each year compared to conventional hvac systems. They save money because they designed then properly, financially modeled them properly and installed them properly. If I lived in a place where electricity was not 25 cents/kWh, I would have geo in my home in addition to my solar panels.

4) Just because a geothermal system is more efficient it does not mean you will save much money. With a (well designed) geothermal system replacing a conventional heating/cooling system, your total energy consumption will drop but your total kWh consumption will increase. In areas with high electricity costs, it is hard to justify these systems on the residential side of things. In California, for example, electricity is too expensive in most cases to justify geo. In some states, utilities have special low electricity rates specifically for geothermal heat pump systems. There is a lot of variety from location to location regarding support for these systems. One size does not fit all.

5) If you care about C02 emissions and climate change and see where the long term trends are slowly heading towards with grid electrification, it becomes clear that eventually our homes will be 100% electric and powered by clean electricity and heated/cooled by air-source and ground source heat pumps. Gas furnaces are an evolutionary dead end. However, it will be awhile before we get there as a society. Did you know that during World War II the US switched very quickly back to coal furnaces to save oil for war? It takes about 20 years for a society to make a big transition in heating/cooling technologies based on history.

6) The most important thing for a good geothermal design is a accurate assessment of your cooling and heating needs over an entire year. This is called a "loads analysis." Most HVAC contractors know how to do a "peak" analysis to determine how many BTUs you need on the hottest day of the year and the coldest night of the year. Few HVAC contractors know how to do an annual analysis to figure out the cumulative BTUS you need over the course of the year. You need to know the cumulative BTUs over the year to size a geothermal system properly. If you don't have that info you are guessing, which leads to system failures. If your contractor isn't providing you with this information about your building, you should find a different contractor.

7) I am happy to answer any specific questions regarding this topic if you have them.

Re: Geothermal Heat Pumps

Posted: Sun Jan 31, 2016 5:02 am
by 4nursebee
Update: Thanks everyone for the comments and ideas. Our contractor more than a week ago was waiting on our wall insulation numbers to plug into his load analysis software. We gave him the number and are still waiting on a estimate, we expect it to be a lot of money.

Since then we are learning more about ductless split HVAC systems and think we will end up with one of those. High SEER, high COF, zoned is easy, no duct losses, increased guest comfort.