Geo-Thermal heat-pump?

[Wacky]

Any pros or cons?? My completely electric house has a outside heat-pump that is on its last legs. I was thinking of getting a Geo-Thermal heat pump/ furnace for my mid-entry home. Not sure of the costs of installation and general lifespan of the coils, or unit for that matter. Also not sure if it is as cost effective as it sounds. Any info will be helpful.

 

[Redneck in training]

I am assuming you have forced air unit. The advantage of the geothermal is that the efficiency is about the same regardless of the ambient temperature.
The longer the freezing season the better geo looks relative to an air unit. The ground loop is the additional cost the rest is about the same as air/air unit I suppose. Many utilities have rebate program for geo units that pays several hundred/ton and cheaper rate in the heating season. The life span of the geo heat pump is, according to manufacturer, about 20 to 25 years.

 

[Kays Supply]

My son sold them for a while. He had to quit because they couldn't find a driller that would backup his warranty on leaks in the Geo piping. If / when there was a leak in the underground piping the installer would say if my son's company would find the leak he would fix it for free. The wells were hundreds of feet deep. Do your homework on the piping installer as well as the HVAC installer. I just learned from another Geo installer that there is a break even point late in the heat and in the air seasons where the ground has given up it's heat and cool and the Geo unit doesn't get anymore from the ground. It is a great system just not perfect.

 

[boatyard]

Do your homework. They work best in a super insulated home. A friend has one installed at his house and he likes the idea, the reality is that his electric bill has been running about $300 per month during the heating season. If he runs the air conditioner, it cost almost as much. The upfront cost is very high. If you are on well water and the fluids in the unit leak you can have problems.
They are a great idea, but not the magic bullet that some would like you to believe.
Good luck. Let us know what you find out

 

[Tig]

I had one for 18 years and will reinstall it in my new home this fall. We drew water from a deep well and returned it to a shallow well. Very efficient and inexpensive way to heat and cool a house.

 

[Tig]

Air to air is good in fall, spring and moderate climate. But around here in the dead of winter there isn't much heat in the air to "pump". Ground temps are the same all year round.

 

[buckeyefarmer]

Check some of the geothermal threads in the past.

Some general comments regarding geothermal. Water Source heat pumps (geothermal) are much more efficient than air to air heat pumps. They are however costly to install. Most installers take responsibility for the entire install, including the loops. Most geothermal pipe is guaranteed for 40-50yrs. Some of the better known geothermal brands are Waterfurnace Envision and Climatemaster, but there are other good units. Geothermal deliver COP (coefficient of performance) of up to 5, meaning for each KW of electric used to run the system, it delivers 4 KW more of heating. This stays pretty constant, because of the constant temperature it uses for heat transfer. An air to air unit might have a COP of 5 on a cool day, but it drops significantly as the temperature drops, to the point it can't perform for heating, and has to use electric strip heat. An electic heat strip is 1 COP, 1KW of electric gives 1 KW of heat. For cooling, air to air uses SEER rating and geothermal uses EER rating, both which is btuh of cooling / watts used to produce. They are calculated differently, SEER is calculated using an average temperature, and the unit partly loaded, whereas EER is calculated at a steady state. EER of air to air is .875 x SEER. High end geothermal units are up to 30 EER while high end air to air are 15 SEER, which equate to around 13 EER. Again, much more efficient to cool based on a constant earth temperature than the hot air temperature. A good geothermal unit will be at least twice as efficient the best air to air units.
BTW, A ton is 12000 btu/h, which is derived from the amount of cooling achieved by melting 2000 pounds of ice.

 

[Raspy]

In-slab radiant heating is probably the best way to deliver geothermal heat to a house because it operates at the lowest temp and therefore the highest COP. I recently helped with one that had the tubing laid in a big pit about ten feet or so deep and maybe 50 ft X 50 ft square. I think there was 1600 linear feet of 1" poly tubing put in the ground. They get all their radiant and most of their hot water with it. They are all electric and I believe their electric bill is about $250 - $300. month, in the winter, for all heat, lights and hot water. They also have a small DWW solar system. The house is about 4,000 Sq. ft. and is at 4,900 feet elevation in Nevada.

These systems work well, but are expensive to install and complicated if you get a leak.

 

[Redneck in training]

WE have two propane fireplaces as a backup heat otherwise our house is 100% electric heated/cooled by geothermal system with floor heating and forced air cooling. We heat about 3800 sqft including 1800 sqft garage that is somewhat drafty. Our unit also heats domestic hot water. Our total electric bill is in average $210/month. Heating in Jan and Feb was about $90 bringing total elctric bill to $210. July and August are about the same in energy cost. Spring and fall are below 200/month.

 

[maybar]

Any pros or cons?? My completely electric house has a outside heat-pump that is on its last legs. I was thinking of getting a Geo-Thermal heat pump/ furnace for my mid-entry home. Not sure of the costs of installation and general lifespan of the coils, or unit for that matter. Also not sure if it is as cost effective as it sounds. Any info will be helpful.

---------------------------------------------------------------------

Due to the wide variation of electric rates, for someone to tell you how much it cost to run their system is of little value to you.

A better measure would be KW used and even then their needs, climate, structure size, type of structure, windows, insulation etc.etc. would need to be similar to yours to get a comparison of any merit.

Now, if those that had a record of KW used with an original heating/cooling system over a period of a few years and compare that to their Geo system of approximately the same time that would be of some value to someone contemplating a Geo system.

And while on the subject I have a question.

With a Geo system, what do we do in the Spring and Fall transition periods when heat is desirable one day but cooling may be needed the next day? In some zones this can easily be as long as a month or more twice a year.

 

[eepete]

maybar, the answer to your question probably lies in the thermostat. I have geothermal heat pumps. The thermostats can be set to a mode where they call for heat if it's too cold, and cool if it's too hot. So you can specify a range of temperature.

One think I like about the geothermal is no outside unit to make noise. All the comments thus far are good. I'm working on getting KW hour data on energy use. If anyone use the "REScheck" software program thats on line at the U.S. DOE site, that number might be a good way to compare insulation quality of a house. Our number was 900 if I remember correctly. To get an energy star rating, I think that number has to be below 1200. Score is like golf, low is good.

We have horizontal ground loop (black PE pipes buried 4-6 feet deep). Our trenches came out about 5 percent short due to bouncing measuring wheel, so if you go this route add 5 percent to what you measure out. This error left us with some 3/4 pipe coiled up in the manifold pit (see picture).

We have a 3 ton two speed compressor unit with 2000 feet of pipe, and a 5 ton and 3 ton that share another ground loop with 4800 feet of pipe. It's been a hot summer, and the water temperature coming out of the ground is about 76 degrees. Last winter, which was a bit colder than normal for here in North Carolina, the loop got down to 50 degrees. If I were installing again, I might increase the loop lengths by 25 percent more even if it did involve yet another "discussion" with a tradesman.

We tried a pond loop, and I would not advise it. The pond water got down to a bit below 40 degrees, and that directly impacted how long it took to heat things up in the winter. All other conditions equal heating up a room from 68 degrees with the pond we had 78 degree air, with the ground loops we had 90 degree air. Big difference in how long the unit ran (and hence the cost).

From these ground temps, you can see why a well insulated house is important. You don't want to run out of ground heat or sink capacity. You can also see where the efficiency is (from a hand waving view). When we are cooling, it's like running an air conditioner when it's 76 degrees out. When we are heating, it's like running a heat pump when it's 50 degrees out.

Dual speed compressor are a must. The only time our units kick into the full power/speed mode is when we change the set temperature by more than a degree or so. For humidity control when cooling, the low speed compressor is what makes it all work.

Anyway, all good comments thus far. Like many things house related, where you are makes a big difference due to climate and (for geothermal) soil conditions.

Pete

 

[roamerr]

Pete makes a good point on noise. My Parents (live in Southern VA)Waterfurnace Geo system makes no noise inside the house. They have a 10 x 10 room off the garage that houses the system since they have no uunit outside. They also have a 600 ft ground loop buried 6 ft deep.

The quietness has a value that is not in a calculation.

 

[maybar]

maybar, the answer to your question probably lies in the thermostat. I have geothermal heat pumps. The thermostats can be set to a mode where they call for heat if it's too cold, and cool if it's too hot. So you can specify a range of temperature.
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Thanks for the clarification. I think I was having a mental lapse and getting in-slab radiant and Geothermal cross bred.

 

[jimgerken]

Wacky: How old are you? I ask because my brilliant wife came up with a revelation as we researched the geo systems. There is a payback period for the extra expense of a air-source heat pump combination with gas unit, and another bigger jump in payback period when you go with geo thermal. Geo almost doubles the price of the system. So, let's say you are going to live in the house 25 years. In that time the system probably pays itself off, but also needs repair or replacement. Now suppose you might leave the house in fifteen years. No payback possible.

Its not a perfect answer, but factor in your age and the payback period. Myself, I am 50 this year. If I build in the next couple years I will certainly use an air-source heatpump combined with LP furnace. This gives me my air conditioning, and saves me 600 gallons of LP per year (estimate), for an extra $1800 over a simple LP high efficiency furnace and standard central air conditioner. 600 gallons at $1.50 per gallon makes the air source heatpump a two year payback. Unless I am missing something, this combo cannot be beat for payback period, and the two systems (LP furnace and air-source heatpump) back each other up somewhat. If you have natural gas available, you will have to do your own math.
Air source heatpumps have benefitted greatly in the last few years from compressor technology improvements. Check them out. Your dealer will give you the facts, but try to steer you to geo as the profits for them are much higher.
With air source heatpump and gas furnace combo, nothing is buried and inaccessible, so service is much easier.
Many people (including me) have had air source heatpumps in the past and have had poor performance from them. But the compressor improvements have improved their performance greatly. And combining them with a gas fired system allows them to work when air temps allow good efficiency and shut them down / switch to gas when they are not economical.

 

[Redneck in training]

---------------------------------------------------------------------

Due to the wide variation of electric rates, for someone to tell you how much it cost to run their system is of little value to you.

A better measure would be KW used and even then their needs, climate, structure size, type of structure, windows, insulation etc.etc. would need to be similar to yours to get a comparison of any merit.

Now, if those that had a record of KW used with an original heating/cooling system over a period of a few years and compare that to their Geo system of approximately the same time that would be of some value to someone contemplating a Geo system.

And while on the subject I have a question.

With a Geo system, what do we do in the Spring and Fall transition periods when heat is desirable one day but cooling may be needed the next day? In some zones this can easily be as long as a month or more twice a year.

Here are my electric stats year to date. The lower chart is heating the upper is the rest of the house. To get total add each month together. Our standard rate is $0.11/kWh while heating rate is $0.041 but only in heating season. The house is about 3800sgft of heated space. 2400 sqft of AC space.
To answer your question about Heat/Ac switching. If you have forced air geothermal there is very little difference between air to air and geo. If you have floor heating embeded in concrete and well insulated house the floor has enough thermal mass that it takes several days before you percieve discomfort. My system automatically switches between heating cooling only if the heating or cooling demand lasts at least 6 hours. Since the thermostat pulses and the pulses are summed to reach 6 hours it takes about a day to switch.

 

[Redneck in training]

Pete makes a good point on noise. My Parents (live in Southern VA)Waterfurnace Geo system makes no noise inside the house. They have a 10 x 10 room off the garage that houses the system since they have no uunit outside. They also have a 600 ft ground loop buried 6 ft deep.

The quietness has a value that is not in a calculation.

I second that. The quiet operation was very important to me.

 

[Dargo]

When I built my home the Geo-thermal systems were pretty new but I seriously considered one because I knew I would be living here until they plant (or roast) me and the home is reasonably large. The prices were just out of this world high and they hit rock at about 20' deep in most places. I was looking at about a 40 year pay back cycle. By then, I figured the system would be shot and I'd need to replace it anyway. The highest SEER A/C units available were about 13 and my NG furnaces are about 93%.

Now comes the staggering part. Even having gone with the most efficient equipment available at that time and insulating as much as possible, I'm seeing 4 digit utility bills each month! Yes, my home is large and we have a 1500 sq. ft. guest house that is generally occupied, but still.... It seems like there is a better way. In the winter it's a bit less because I burn quite a bit of wood in a high efficiency wood burner with a catalytic converter and all.

Anyone else seeing 4 digit utility bills? Man, talk about depressing! I do have 2 moving out next week to go to college, but that creates a whole new set of expenses.

 

[ctgoldwing]

Great thread discussion with a lot of good info. As usual, there is no one answer

Where one poster is paying just over $.04 per kw for heating, here in Connecticut I pay almost 5 X that amount

Depending on your location, the requirements for heating vs cooling may be far different.

One poster mentioned that geo heat pumps can get to 30 SEER ratings. There are air to air systems available today that can get to 23+ SEER. Its an economic decision - the additional cost of the installation vs the payback over a REASONABLE time period because of lower operating costs. I would personally nix any system that couldn't show a 7 year breakeven point.

My daughter just bought a small condo nearby. It had straight electric heating / cooling - a ducted system with coils in the air handler. Yesterday they finished installing a high efficiency air to air heat pump system. I expect her annual electric bill (before estimated at almost $4k) to drop at least $1k. With the utility rebates and federal tax credit it will end up costing her about $1500. Payback in less than 2 years btw although I could have put a 23 SEER unit in, I didn't. The payback stretches out beyond the time I think she will be living there.

I would always analyze the potential payback. You don't need Excel, a paper & pencil will do fine!

One last comment has to do with insulating. No matter how you heat or cool insulation is most often your best investment.

 

[eepete]

Now comes the staggering part. Even having gone with the most efficient equipment available at that time and insulating as much as possible, I'm seeing 4 digit utility bills each month! Yes, my home is large and we have a 1500 sq. ft. guest house that is generally occupied, but still....

Anyone else seeing 4 digit utility bills? Man, talk about depressing!

Yep, that's depressing . I have 6,000 ft conditioned space plus basement which just has one 10" source and return duct to keep it from getting stale. Most of the time, we have 1500 square feet zoned off (the upstairs) with just the dampers down to about closed.

So that leaves 4500 sq feet we keep happy. It breaks down to 2200 sq feet at 78 during the summer, and 68 during the winter. Then there's about 800 sq feet for the master suite which is 68 at night in the summer, and 62 (set point for heat) in the winter. Finally, my work are is about 1500 sq feet, it stays between 68 and 74 year round.

So I have: (wish tab characters worked...._
Area -- Summer Temp -- Winter Temp
2200 -- 78 -- 68 (62 at night)
800 -- 68 (74 during day) -- 62
1500 -- 74 -- 68 (62 at night)

Average usage per month for a year is 2900 KWH for a bill of $290 per month. Peak in summer is about 3400 KWH, low in mid seasons is about 2100 KWH. I'm working on tracking this better. Solar panels I put in should cut those amounts in half (with 12 year payback).

No kids, from what I hear that can add 50 percent to you bill, make you go gray early, and take 10 years off you life :laughing:. Of course I also here that it's a good life :thumbsup:.

The foam insulation we have cost twice what fiberglass costs, about an 8 year payback.

Pete

 

[whistlepig]

Although I'm a few years from retiring the Geothermal we have will make it much easier to live on the fixed income that comes with retirement. Payback on an investment is an important consideration. Making this investment and having paid for it while I am still working is a very important part of my retirement plan.