Geo-Thermal heat pumps

Scotty370 · Feb 22, 2010

At the end of my Amish/Electric thread, LD1, brought this subject up. Any success stories out there? Or, wern't you talking Geo-Thermal, and I missed the boat? ~Scotty

galen1115 · Feb 23, 2010

Well yes I feel good about the decision to put one in my house. I was getting 250 dollar a month electric bills in the winter for heating a vacant vacation house, with stat set at 55 degrees. I had enough of that and took advantage of the local electric coop rebate program. 750.00 per ton back direct to me, besides the 30% direct tax credit the government gives. I installed an open loop system. Constant 56 degree water temperature year around. My stat is now set at 65 degrees and my electric bill is now 45.00 a month. I will add that the old electric furnace was 10 seer. Installed in 2002. Builders grade. I now have a Water Furnace. You can PM me if you like if you want more details. They are expensive units but if you can take advantage of some rebate program then it takes the bite out of the conversion.

irvingj · Feb 23, 2010

Scotty- do a search for heat pumps.... What's now called "geothermal" used to be called "water-source." There've been quite a few discussions on TBN about these.

I have one in my house, which was built in 1986. Still working. Mine's a closed-loop system, running right down the well hole alongside the water pump.

My system runs at about 3.25:1 (compared with electric, which is assumed to be 1:1). That is to say, for every KWH I put in, I get 3.25 KWH back out in terms of heat. Newer systems, with variable-speed scroll compressors and variable-speed fans, claim as much as 5:1 under the right conditions. "Water Furnace" as a brand seems to be well regarded.

As an HVAC co-worker used to say, "Remember- it costs less to move heat than to create it!" Right on. I've never regretted the decision to go with my Water-Source (sorry, guess I'm just old school

) heat pump.

eepete · Feb 23, 2010

I've got three Water Furnace units in a closed loop system where there are loops of pipe in the ground. Two of the three units have developed leaks in their coils, one was changed out the other is too slow of a leak to find. It's sad they can't beef that part up a bit.

I'm pleased with the systems though. All 3 units have variable speed fan and two speed compressor. The two speed compressor really pays off in the summer when they run at low speed. It takes a lot more of the humidity out. Note any multi speed compressor system does this.

Another win is an option on the units where they can heat or help heat your hot water. It's called a "desuperheater" or something silly like that. In the summer time, where we get lots of air conditioning usage here in NC, we turn off the hot water heaters. The way it works is like this:
In the summer, the freon coming out of the compressor is at about 140 degrees. This is heat you must get rid of before you reduce the pressure to make all the cold freon needed to cool the house. So the desuperheater units run this freon through a small heat exchanger, and also has a pump that circulates water from your hot water heater as long as the incoming temperature from the hot water heater is less than 130 degrees. After the freon has run through that exchanger, it goes to the main heat exchanger that uses the ground temperature to get rid of / absorb the heat.
In the winter, the same process occurs but the pump in that heat exchanger runs at a lower speed. This is because you want the hot freon to heat your house. So in the winter the system can help to maintain your hot water temperature, but not as well as in the sumer where it can do it all.
So we have two 80 gallon hot water heaters on two of the units so that all this free (well, ok, "pre-paid for") hot water can be saved.

Finally, don't use a pond as your heat exchange mechanism. We did it, and the performance was bad for heating because the pond was giving us 40 degree water, vs. the ground which gave us 50 degree water. It works, it's better than an air unit, but for the savings (which was about 30% less than an in ground) it was not worth it.

And yeah, I like it better when it was called water source and geothermal meant hot springs and steam from the earth. Another reason I don't like marketing people

Pete

irvingj · Feb 23, 2010

eepete--- the reason it's called a "desuperheater" is this: any heat (temperature rise) above that which is required to turn all liquid into gas is called "superheat." Kinda like water that's been boiled, in a closed container, so that all the liquid has turned to steam and the temp rises above 212F. If it's 225F, you have 13 degrees of superheat.

In a refrigeration system this is generally non-productive heat (though not always).

On the discharge line, right off the compressor, the gas is the hottest and is usally superheated... the addition of a small refrigerant-to-water heat exchanger there is what cools the gas down a bit and tranfers that heat into your DHW system.

Mine has that, and goes one step further: there's a second refigerant-to-water heat exchanger, larger, that can transfer all heat picked up by the water loop into my DHW. It can either run on its own, or, if hot water's called for during A/C, it can take the heat from the house and put it into DHW. Slick. Unfortunately, it's a one-off custom-built unit; too bad --to my knowledge, such a system isn't commercially available. I have an idea that when the current system is replaced, I'll lose that ability.

Hope this clarifies things a bit. WBB in NH

eepete · Feb 23, 2010

Wow, thanks for the explanation

I remember that from physics/chemistry and the dreaded thermal dynamics classes, it just never clicked. I hope the rest of my explanation was OK.

You one-off unit sounds neat. There's a lot of great things like that in various areas that never see commercial fruition.

Pete

Diamondpilot · Feb 23, 2010

I think the cost of install on a existing home is the issue. You can get a good 3.5 ton heat pump and hook that into a good propane furnace for a lot less money. My looking at it around here that is the way to go. People I talk to with Geo systems want to talk about how much they save but not how much it cost. From what I gather it was going to take 15 years to pay back.

Chris

galen1115 · Feb 23, 2010

Be glad to talk about the cost of a Geo system DP. At $1.76 a gallon for propane thats = 2640 a heating season for 1500 gallons. Just to heat the house not water also. Which would be minimal. There is no grantee that propane will stay at $1.76. My Geo system cost me 21K, with rebates and tax credits, my system ended up costing me 13K. Not to mention the hot water as a free by product. It was a no brainer for me. Do you think people just go out and spend 20+ grand for a heating system and not figure the payback? Your not the only person on here that files fight plans.

AHNC · Feb 24, 2010

Is this a retro-fit or new construction? My problems with gothermal are the water side, which can be very expensive the first time and maybe more expensive the 2nd and 3rd time. It happens. the other problem is the cost. A well designed and installed system can be very efficient as noted here, but still very costly. Finally, most homes duct systems were not even remotely done efficiently. The DOE says that duct losses can account for 18-42% energy loss. Rarely is a residential duct system sealed properly. Typically the older it is the worse it is.

My standard disclaimer. I am in the business (HVAC/P&H) and some of the products I represent I'll reference here. What is your current system? How old? Does it do a decent job? What is your distribution system, pipe or duct? Single or two story? etc.

What I'm doing at home is not replacing my perfectly good gas fired boiler. I am adding to it with some Fujitsu Mini-split heat pumps. There are other quality brands...all Japanese. As I have hydronic heat, this allows me to add AC very efficiently and the heat pumps are very efficient on the heat side. The Fujitsu's are inverter contolled (variable speed) 410A refrigerant. A few weeks back it was 8F outside an my 15kbtu heat pump was pumping out 104F air. Normally I wouldn't run it that low. I will run it above 15 all the time. If you check out the bin numbers (historical weather data over a 20 yr period giving the number of hrs per year that the temps are in 5f increment ranges) it tells me that in my local area, Boston, it is 15f or less 9% of the heating year hrs and in fact the vast majority of the heating load is above 30F. You can check out your local hrs at www.miniheat.com. Just put in some numbers to get to the table and check out your local hrs.

Now this works for me as my kids are long gone and my wife and I still live in a 4br colonial, for some reason. Anyway while we have 3000 sq ft we actually live in about 750. I have the boiler on deep setback and heat the family room and kitchen to a very confortable range with a Rinnai Energysaver gas fired DV wall furnace and the Fujitsu. I have radiant heat in the bathrooms and they just do their own thing I don't have any friends so I never have to worry about people coming over and having to turn up the heat. I heat my water with a Rinnai tankless and I represent them also. This ends up being a pretty efficient system. Both the Fujitsu and Rinnai tankless qualify for the tax credit as well as local rebates.

I have a friend who in summer 08 when things were going nuts energy wise, and otherwise too, who said he was going to put in a water source hp. Only $35K He ended up putting in two Fujitsu 19 seer hp's and has been thrilled with them. In the next 12-24 mos you will see air to water hp's that will equal the efficiency of the water source. What I said to my firend who put in the 18's was that the water source can be a great system, but he would have had to replace his total duct system, so 35 became somewhat higher as the ducts were all sheetrocked in.

Now that we are beginning to pay attention to energy, there are a lot of things on the horizon. Do small incremental things that are manageable cost and let's see where the next few years take us. I am very excited about the air to water units. Put your first dollars into the envelope of the house always.

One thing I am looking at for my home is canada.com. I know a fellow who works for them in CA. He says it is a pretty good deal and I have excellent solar exposure. More on that later.

Good luck!