Geothermal Retrofit
Filed under ask a geothermal expert
Geothermal Retrofit Feasibility
Q: Is it feasible to do a geothermal retrofit?
A: Sometimes it is…sometimes not.
If you’re gutting the house, a geo retrofit is as simple as a new installation. If you’re not, read on…
The primary goal is to reduce the load. This means upgrading windows and insulation first. These costs will translate into a significantly smaller geo system which will then pay for them and save more energy than geo alone. An unimproved house with a geo system will cause the geo system to be overloaded. Remember, the primary goal is to reduce the load.
The subject should then be broken down into 2 parts.
1) Do you have forced air heating with ductwork?
2) Do you have hot water heating with baseboards, radiators or radiant floors? This is called hydronic heating.
If you have forced air heating and it currently uses electricity or gas or oil, then generally the ductwork is too small and needs to be upgraded. The reason being is that the “dead dinosaur” burning furnace would deliver heat at 140 deg F and the new heat pump system would deliver only 100 deg F. (all approx values) This requires bigger ductwork to deliver the same amount of total heat. Simple, right?
An exception might be a really old house that had a big heating system designed for single pane glass and no insulation. If the glass and insulation were upgraded then the originally large ductwork would now be adequately sized. However this house would likely have been renovated at some point and the heating system could be inadequate or dysfunctional. If the basement is unfinished then ductwork upgrades are simpler than if the basement is fully finished, blocking access to the ductwork.
If you are replacing a tired air-source heat pump then the ductwork will likely be adequate.
If you have hydronic heating and it currently uses baseboard radiators that have copper tubes and aluminum fins (they’re not radiators at all, they’re convectors) then you’re out of luck unless you replace them and probably the distribution piping too.
If you have baseboard radiators that have cast-iron fins (rare) you may be in luck except you’d probably have to add more of them to make up for the previously mentioned lower output temperatures. If you have cast iron radiators (really old school) they may work but you may need to add more of them. They’ll need to be flushed and maybe some piping upgraded too.
If you have radiant floors, they are the easiest to convert, except some older floors (and still today) were/are badly designed and installed. They required high operating temps and were not that comfortable to begin with. If the radiant floors have enough tubing and loops installed the conversion should be relatively simple.
The 2 best parts of hydronic heating conversions is that you can rip out the mixing valve that used to mix down the high “dead dinosaur” burning boiler temps to what the radiant floor requires. You can also rip out the evil chimney and the CO detector. This was so inefficient due to the high temp standby losses in the mechanical room. Geo systems operate at low temps and have little or no standby losses.
The other best thing with hydronic heating conversions is that you can install outdoor reset control. http://www.tekmarcontrols.com/literature/acrobat/p022.pdf This is a further energy saving control that has been around for more than 40 years but only works on hydronic heating. At exchangenergy we install it on every hydronic system we design.
Summing up, geo retrofits can be feasible and even have a shorter payback than a new installation if you are replacing oil or propane as the fuel source. If your home meets the above criteria then a site visit is the next step.
You have a lot of great information here! I work for a geothermal heating and air conditioning company in Florida and we are seeing business soar right now. Geothermal technology is really catching on, especially with the tax credits available. Have you guys seen the same thing? Great blog! Henry
Geothermal energy seems to be a good choice for many applications. Compared to some other forms of alternative energy, geothermal energy appears to be more cost efficient for smaller applications.
We had a 6-ton GeoComfort geothermal open-loop heat pump system installed beginning last November and have had nothing but problems. First it wouldn’t heat, then it blew a capacitor and quit completely for 10 days in January. It could not heat the house past 66-68 degrees. We finally fired the installer, Massmann Geothermal and Mechanical, had it rewired and thought it was working. Our utility bills were still higher than the traditional natural gas boiler costs which will never allow us to pay for the system with reduced bills as advertised. Then summer arrived and now it won’t cool. The compressor is blown. We have spent $16,000 and are sitting in our home with fans. Anyone else having problems with their geothermal units?
Hi Kim, let’s see if we can solve your problem right here and now!
A 6-ton unit will require a minimum of 2.2 x 6 gpm = 13.2, let’s call it 15 gpm just to be safe.
That means your well and your pump MUST pump 15 gpm to the heat pump whenever it is running, no exceptions.
So, does your well and pump produce this much water on a continual basis?
We recommend your well should make 25 gpm to be safe in the long term (pumping 15 gpm to the heat pump).
This is probably the problem. There must be some means to measure or prove that you are getting the 15 gpm, not someone just telling you that.
The $16,000 sounds suspicious. We couldn’t give you a 6-ton geo system for $16,000 even if we had illegal immigrants working for us.
We install flow-meters on all our open systems so that our clients can see for themselves what the flow rate is.
We generally dislike open systems because of water quality issues.
Did you get your water quality tested? If so, please send us a copy of the test results. Some water can cause heat exchanger scaling sooner than you’d think.
Let us know your gpm and water quality and we’ll be almost there.
Question: Can you use an old 100 foot well for the geo thermal well. The well already exist in the house. It was dug 150 years ago and is lined with stone. Radiators have been removes and duct work was installed for A/C and heat.
Echangeenergy, Thanks for the response. We have a variable speed well pump which pumps up to 18gpm. The variable speed pump was installed 3 days after we turned the geothermal unit on for the first time because the original pump burned out. A restrictor was installed to limit flow to 12 gallons per minute. We were told too great of a flow was an issue by a second geothermal company we hired to complete the installation after we fired the inital company. The unit completely quit running in June of 2009 after having a capacitor replaced in January and the compressor quit in June. Since that time the unit has continued to both cool and heat our home but the costs are higher than traditional heating and cooling that was in the home for 3 years prior to the retrofit. You mentioned you could not install a 6-ton unit for $16,000. At the time I wrote the comment we had spent $16,000. The original bid was $18,000 for the installation. We have now spent in excess of $20,000 and are still completely unsatisfied with the results. We even have a back-up natural gas boiler and had nothing but trouble heating our home last winter. The water quality has been checked and is high iron but otherwise very good. We have now also installed a filter on the well that is checked and cleaned every 6 months. We know the technology should work and save us money. Our original installer and the second installer were unable to get the system working and saving money. If you have any other suggestions, we would be glad to consider them.
Hi Kim,
Have you had a proper draw down test on your well? On design day, the geo system is running almost around the clock, so if your well can’t maintain proper flow in these conditions, you’ve got a problem. We like to see the draw down test show double the capacity you’d need to ensure the system doesn’t run into problems down the road. So for your system, we’d be looking for 26 – 30 gpm from your well in testing.
Proper flow: as mentioned, you need 13.2 gpm MINIMUM! We recommend setting the pump 10% over this to allow for degradation in flow over time. 12gpm is too low.
A flow meter on your well would answer a lot of questions.
The flow or lack of flow might be explaining some of the inefficiency which just provides us with more information showing the installer did not know what he was doing. Our well is 175 feet deep. Would your recommendation be to spend more money to put in a different pump to increase flow? The geo has heated and cooled our home for 15 months now but is NOT saving us a dime. Do you think increased flow would save us money or keep the unit working or both? This morning we awoke to no hot water but the geo is heating the house. We now think it is the desuperheater that has stopped working. It is just one thing after another with the geothermal. Will the expenses and the worry ever stop?
Hi Linda,
Your situation is interesting! Using existing wells is a great opportunity, but we haven’t done this type of well before.
As in any ground heat exchanger design, a number of factors must be considered, including the climate in your area, geology of the surrounding earth, diameter of the well, the size of your home, the efficiency of your home, the configuration of the heat exchange piping, the type of back fill used around the piping, I could probably come up with a few more if I tried!
If you’ve moved forward in your project, let us know how it went! Sorry it took so long to get back to you but we’ve been very busy and blogging is pretty new to us… If you email back we’ll take much better care of your questions!
Hi Kim,
Flow is the most common problem in systems, and it has to be right on both the source and load sides of the system. So your well is one consideration, your air flow in the house is the other.
Hoping your new pump has more capacity. It shouldn’t need changing, but the 12gpm restrictor you mentioned should be upsized to 14 gpm.
A static test on your sheet metal can determine your cfm. For 6 tons you’ll want from 2100 to 2400 cfm.
Reading back through your posts…high iron can clog piping and heat exchangers. If your system is fouled it could be the cause of your problems. Water quality is a key consideration when determining the viability of an open loop system.
My windows are 20 year old Marivn windows. Just he sashes were replaced but there r no drafts. I have a 12 year old Weil Mclain boiler and baseboard heating and central air.
Can you use the c/a ducting for geothermal. Can I use my boiler to supplement the geothermal system?
This is unfortunately not uncommon. Fact is Geo systems work only when properly designed and properly installed. The industry is an unregulated industry and we’ve done our part and continue to do our part in acting as “whistle blowers” to warn and educate consumers. Key issues to address:
1) Was your installer CGC Certified? If so please report your experience to the CGC- http://www.geo-exchange.ca/en/
2) Did you select an installer who supplied at least three references and who demonstrated a solid track record?
3) Did the cost of installing a system surprise you and result in your selecting the low bid? The low bid is always a recipe for disaster.
4) It sounds like your particular system is not properly sized or its flow rates are not on spec. This could cause compressor failure. Can you let us know what your heating load is and what size your system is? (You should have received a commissioning booklet detailing your heat loss calculations, your design specs and your troubleshooting tips)
5) Last but not least, has your installer been accountable and offered a warranty on their work and or to offer you after sales care on warranties for your equipment? You mentioned your equipment is “the best”…but I’m sure you recognize that a great piece of equipment is only as good as its installer.
We can only imagine how disappointed you are in your system. You’ve tried to do the right thing and in the end its cost you money and its cost our environment to boot. Do contact the CGC to see what your options are. It sounds like a mess but I’m hoping that at the very least your case helps the move towards true regulation of the industry.
Sincerely
the exchangenergy team
Hi there! Yes. It is possible to use hydronic radiators with a geo system. Unfortunately you are out of our service area and we don’t know of anyone on that side that we could recommend to do such an installation. It is strange that all of your quotes insist on forced air. The best we can do is suggest that you contact the CGC to find a contractor who really knows their stuff.
Good luck!
CGC