GeoThermal HVAC

11 years ago

We are getting quotes on a geothermal AC system. Are we over-reacting to our power bills?

The house is about 80 years old, with NO insulation in the crawlspace or walls. Attic had rock wool insulation, and we have started DIY adding R-19 fiberglass batts. This summer we had 1 1/2 inches of foam added in the attic -- this made a big difference in comfort but not in the bills.

We have 3 Mitsubishi Mr. Slims MXZ units (mini splits with 3 indoor air handlers each) and a 3 ton Mitsubishi for heating and cooling (these are heat pumps). We have 2 ventless gas inserts for aux heat (18k and 24k BTU).

The MXZ units are getting some age and we are having problems -- they were never installed properly and are about 8 years old. 6 of the units basically don't function. So -- I have 3 indoor units working out of 9 and the central 3 ton air handler... We made thru the summer, but won't put up with another summer.

We have also lost 3 trees in the last 5 years -- bills went up $100/month with cooling when we lost the 1st two.

July electric was $736 -- 6792 kWH (212/day)

Aug was $691 -- 6386 kWH (213/day)

Sep was $416 -- 4539 kWH (142/day)

Oct was $284 -- 2925 kWH (101/day)

Nov was $252 -- 2766 kWH (81/day)

my questions (pls help!) --

How much of the bill is from cooling (heating) -- and how much can I drop it?

How much better geothermal than heat pump?

We want to drill now for future plans - we plan to be here for 20+ years. We think we can re-arrange the MXZ heat pumps and get by upstairs if the downstairs has central Heat/AC. As this is a older home, it doesn't have any ductwork/etc.

We are getting quotes on 11 tons of vertically drilled wells -- with 5-6 tons to be used now on the bottom floor and the 5-6 other tons for the upstairs to be added at a later date when side of the building is open for a possible addition in 8-10 years time.

1st quote was for 1/2/3 speed GT (3 compressor in one box) with DSH for $45600.

2nd quote will be for two-stage 5 or 6 ton (not sure yet) unit with DSH -- don't have it yet.

Are we looking at the right things? We need A/C this summer!

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Comments (12)

fsq4cw
11 years ago
There is no way of analyzing your energy consumption with the information provided.

Regarding geothermal, you could consider and compare the installation of a totally hydronic system as well as a forced air system.

If you now have cast iron radiators these can be kept and used with a geothermal liquid-to-water system and adding supplemental hydronic fan coil units that would provide addition Btus in heating mode to compensate for the reduced water temperature of geothermal and to provide hydronic cooling in the summer time when air-conditioning is required. This system would be very efficient and provide approximately 1kW of heat delivered into your home for approximately 3-cents per kW, based on the figures you provided.

One heat pump could do the job; each supplemental fan coil unit could be a separate zone.
Installing a hydronic distribution system would involve drilling about 2-inch holes through walls and floors instead of installing a whole new duct system.

This method would also preserve the heritage value of your home if you presently have cast iron radiators.

SR
paul_joh
Original Author
11 years ago
We had radiators. We had them removed about 7 years ago. I didn't realize that they could be used to cool the house as well as heat it!
Our main concern is cooling. There are people in the area with geothermal experience and of-course heat pump experience, but almost no one know anything about radiators. There was only one person in town that even knew how the radiators worked when we removed them....
We have pretty much made our minds up to install a central system -- I just need some reassurance that geothermal is the way to go with this size system and this age house.
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We have a geothermal heating and cooling system and it was installed last year. I live in Maryland and the price of a typical system is around $24,000. Fortunately we took advantage of the 30% federal geothermal tax credit and that reduced the effective price by $7,200 to $16,800. Then we got a Maryland geothermal heat pump grant for $2,000 and a $2,500 property tax credit from Anne Arundel County which brought the price down to $12,300. We're saving about 40% on our utility bills now which makes the upfront price worth it. In terms of planting around your loop field, from what we've read, don't plant trees like poplars, willows, silver maples or elms around the piping as these types of trees have deep root systems that can wrap around pipes. Luckily the geothermal piping isn't prone to cracking and has a 55 year plus lifespan. We used Earth River Geothermal to install our system and we're glad to have made the switch sooner than later. Check out this link for relevant information. Geothermal Heating and Cooling Here is a link that might be useful: Geothermal Heat Pumps
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Here you go: After all rebates (there were several) & tax credit, my geothermal system ended up costing about $13,500. It looks like I'm going to be saving about 6000 kWh per year. When using an air source heat pump, I averaged about 27.5k kWh per year, and using the geothermal heat pump I'm averaging about 21.5k. Keep in mind that I don't even have a complete year of geothermal data, but I'm basing my estimates on what I have. Based on the numbers above and an electric rate of $0.11 per kWh, I'm saving $660/yr compared to my previous system. The ROI on that is about 20.5 years. So, if you have a working system and you're considering switching over to geo, based on my #s I'd strongly recommend against it as a 20+ year ROI is horrible. The reason I went with geo was that my old system died and needed replacement. I received several estimates for an air source heat pump, and they were around $9000. For me, it was a choice between a geo system for $13500, and an air source for $9000. I can't do much of an estimate comparing these two since I have no idea what sort of performance I'd be getting with a new air source heat pump. A huge plus for the geo system for me was that my geo system came with a 10 year parts and labor warranty. No one came even close for the air source heat pumps. Its also really neat that I don't have a loud evaporator in my back yard, but the value of that is very subjective.
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For me, I like this forum because it's real, customers have questions and guys that have some knowledge take time to answer questions. Every other forum is either too strict of what can be asked or it is too much diy. This forum most people have questions about their A/C installation quotes, What to look and shop for, which for them this forum can help or help confuse the consumer even more. Sorry I mean for christ sake All we want is a round about general price. Why does it have to be so secrete?? ahh Not here on this forum and that's why I'm here. Real people with real questions that no where else you get an answer for. I for one do not know it all, I learn every day here. Actually I like to win the lotto and forget what I know about this stuff! LOL I started in the field back in 88 changing filters, Then went to college got a degree in Business Management, HVAC and Construction Building. 1996 I became a HVAC Florida Registered Contractor Late in 2000 I moved from Fort Walton to Jacksonville as my biz partner continued to run the A/C business there. I thought I was a hot shot contractor but I found I didn't know squat! In 2000 I was hired by a hospital to be the supervisor and run the Energy Management zoning computer system over 200 systems with god knows how many zones I also programed the Electrical monitoring Computer system, and Security System. At the hospital, I took care of all the Controls from Pneumatic to DDC. Everything you could think of was at the hospital. Deep cascade Freezers to regular A/C's, chillers, boilers, everything. My office was actually the old morgue. Didn't see any ghosts either! I guess I needed to be a plumber! go figure :( I was only going to spend 2 years at the hospital but end up spending almost 7 years learning. Back in 2005 I upgraded my license to be Florida State Certified and then In 2006 I removed myself from my original contracting business (left it to my biz partner in Fort Walton) and opened up another A/C business in Jacksonville with another guy. 2007 I left the hospital to go back full time into the contracting business. Right now, Like you 'Energy Rater 1' I'm becoming certified in home energy rating. I've pass all the RESNET Testing but I have to take my Class 1 lab test later this month to become Class 1 certified. but to be honest I have no interest in rating. I only want my duct systems to be top notch. My strength for this forum, is zoning and heat pumps, I worked a lot in gas but little in 95% efficient furnaces. No need in the area I live in. Ground Geo Thermal I'm a newbie, Water Source I worked and installed many as a tech back in the early 90's. To this day I'm a Fighting General, I got some knowledge but I am also in the attic like today modifying duct in a 120F to 130F attic heat. I've read a lot of books, manuals, and whatnot, gone to all of tech training but books and that sort of stuff is boring. I like to be the Chuck Yeager and fly the machine until it breaks. My interest now is solar stuff, I have no clue on Photovoltaics but it is interesting. What is real interesting is VY Canis Majoris. I mean when we can fit a million earths into the size of our Sun then take a Billion of our Suns and fit it into VY CM. That is just huge!! but that's for a different forum. :) Here is a link that might be useful: My Business
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fsq4cw
11 years ago
Where do you live? How big is your home? What sources of energy are available to you; at what rates? Has a Manual J heat gain/loss calculation been done? Has a Manual D calculation been done to design a forced air duct system?

The old radiators would have been used for heating only. Chilled water would not have been circulated to the old rads in A/C mode, as condensation would form due to sweating. However, you still have a choice as to the type of distribution method, forced air or hydronic.

Force air means installing a duct system as you have been planning, perhaps zoned. Hydronic means installing fan coil units that would be fed by insulated small diameter pipes. That would likely be a far less invasive renovation. The installers may limit you in your area; generally geothermal contractors prefer forced air. Find a geothermal contractor that has experience installing in-floor radiant heating. This would be a better choice. The best choice would be a large HVAC company that has expertise installing all manor of heating systems including geothermal hybrid systems that could be a combination of different technologies and sources of energy.

Keep in mind that forced air will require at least 2 or more heat pumps. Liquid to water, hydronic distribution can be done with just 1heat pump. This may also mean a less complicated connection to the ground loop system.

As an example of a hydronic fan coil unit see link at bottom of post. These units can heat with water temperature as low as 100ÃÂF - perfect for geothermal! They can also be ordered with hand held remote controls making each unit a separate zone by simply controlling the temperature and fan speed wirelessly.

The whole site:

http://www.multiaqua.com/

The clients that have converted from oil hot water to geothermal hydronic heating and air-conditioning, including the incorporation of their old radiators, are quite satisfied with the performance. Just find the right designers and installers in your area.

SR

Here is a link that might be useful: Multiaqua - Think Water!
paul_joh
Original Author
11 years ago
We are in Mississippi. The house is about 1800-2000 sq feet upstairs and 1800-2000 downstairs. We can purchase power @ 8.8 cents per kWH in the winter and about 10.8 cents in the summer. (Based on a bill, not the published rates -- which dont include fees, etc.) At least one person is doing the Man J calculation for the quote that I dont have yet. I believe that the other quote was seat of the pants.
The main focus of my question came because I have seen people saying geothermal is perfect for older homes because of the efficiency -- and I have seen people say to stay away until the house if TIGHT -- like new construction

We have zoned induivadue systems now that we have trouble getting service on. (Mr. Slim) Any thing that is out of the ordinary is right out! I think that you have a great background and if we were up north, we would like a lot of your ideas, but MS is a cooling dominated climate. We even have to run the AC 1-2 days in December and January!!
We are very against anything that is not at least somewhat similar to what everybody down here can work on.
My main focus was a concern about geothermal with an older home without good insulation. I have seen some people comment that geothermal is great for poorly sealed houseing (vs gas or heat pump) and I have seen people say that you HAVE to seal 1st!

Which is correct?

I understand that you have to seal -- but we need to make a decision soon and go forward. I am scared to think what it would cost to seal better than what we have done so far....
ionized_gw
11 years ago
The reason that you see it both ways WRT sealing before or after is that it makes no sense either way. Any kind of conditioning will less costly with a well-sealed structure. It does not matter it it is air- vs. ground-source heat pumps, or gas vs. propane heat.

The problem I see with you switching from the mini-splits is that with a leaky envelope and the addition of pressure differentials that come with ducted systems, you will be blowing out your conditioned air and sucking in outside air all over the place.

New Orleans must be North of Mississippi because there are people here that work on the Mistsu mini-splits. The service manuals really look a lot simpler than the tech manual for my car. It might be really worth your while to fix the indoor units. Have you contacted Mistubishi to find trained people in your area?

http://www.mitsubishicomfort.com/

Ground-source heat pumps will be very expensive to install. There is probably a steeper learning curve for installation and repair of that than for mini splits. If I were looking for quotes for that, I would be looking at IGSHPA installers.
fsq4cw
11 years ago
Geothermal can be a good choice for any house well insulated or not. Either way you will save money on energy. Having a well insulated home will mean that you can install a smaller system saving money on installation.

Insulating and "tightening up" the envelope brings its own challenges as well. You then have to be concerned about IAQ in addition to all the costs of insulating. You would have to install an HRV or ERV, depending on the climate you live in. All this adds to the cost as well. I would not be overly concerned about insulating. Besides, with today's 2-speed compressors and variable speed blowers the system can self adjust to any improvement to the envelope you may choose to do in the future by regulating itself to operate at a lower capacity at even higher efficiencies.

Either forced air or hydronic cooling will work well. However if there were no one in your area that does hydronic, the forced air would be a better choice, as this would be the norm.

"My main focus was a concern about geothermal with an older home without good insulation. I have seen some people comment that geothermal is great for poorly sealed housing (vs. gas or heat pump) and I have seen people say that you HAVE to seal 1st!

Which is correct?"

This is what we did in our home. It is over 50-years old with no insulation in the walls and older'60's slider' windows. It leaks like a sieve but who cares; we want some fresh air. We installed geothermal and are saving about 82% compared to how we heated before.

Which is correct? You decide; there is no hard and fast right or wrong, only what is right for you and your budget.

Keep in mind though that you are looking at one very expensive system!

As a conventional alternative, I would also recommend looking into the Carrier Infinity Greenspeed heat pump system.

SR

Here is a link that might be useful: International Ground Source Heat Pump Association
ionized_gw
11 years ago
Given what fsq4cw pointed out, I have to amend what I wrote. If you are investing big bucks in a premium HVAC system it might be better to seal the place up first so you don't have to buy as much costly equipment.
aj33
11 years ago
Here is a proposal I got yesterday. I have removed all references to the company name etc. It is an estimate. House is not built yet.

People experienced in HVAC matters - please comment on proposal especially on the cost part.

Thanks.

AJ

Here is a link that might be useful: hvac proposal
fsq4cw
11 years ago
Re: aj33

I'm confused. Is this system a HDPE liquid to air system with water and antifreeze in the ground loops or is it a DX system? Their web site seems to indicate that they do DX. Seems like a rebranded Earthlinked system to me.

Their web site uses the IGSPHA logo yet I can't find them on the IGSHPA web site as an accredited geothermal installer or accredited geothermal anything! If this is the case they should not be using the logo.

Know what you're buying. Know who you're buying from. Be careful about anything sign!

SR

Here is a link that might be useful: International Ground Source Heat Pump Association
fsq4cw
11 years ago
Re: aj33

In fairness to the original poster, I would suggest that you start another thread.

SR
aj33
11 years ago
Agreed.

My intent was more to provide the original poster another data point rather than solicit comments on my quote. My apologies...

AJ
green_grandma
11 years ago
Going back to basics, the #1 best investment for any HVAC energy efficiency project is improved insulation. Personally speaking, I would invest first in 'tightening up' your house via increased ceiling and wall insulation, improved windows etc. before making any decisions regarding heat pumps. The obvious reason of course is that 'tightening up' your house may allow for a major reduction in the size ( thus cost ) of a new central heat pump.

As to the virtues of geothermal versus air source heat pumps, it boils down to two things ... the future availability of the geothermal tax credit, and the cost of drilling wells that will provide an adequate ground water supply under local conditions. You can buy a LOT of extra electricity for an air source heat pump if you can save $10,000+ by not drilling wells !

GeoThermal HVAC

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