GEOTHERMAL FURNACE

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Has anyone ever done one of these? What kind of circuits are there? How many? What amperage? I guess they dig some sort of hole or trench that gets heat from the earth or something. What kind of equipment am I looking at hooking up here?
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
From an electrical contracting standpoint, it's no different hooking up a Heat Pump. The only difference is that instead of a refrigerant and an air-to-air heat exchanger, it's a liquid heat exchanger using the gound as the heat sink and water as the medium. Biut electrically, I don't think there is any difference.
 

jumper

Senior Member
From an electrical contracting standpoint, it's no different hooking up a Heat Pump. The only difference is that instead of a refrigerant and an air-to-air heat exchanger, it's a liquid heat exchanger using the gound as the heat sink and water as the medium. Biut electrically, I don't think there is any difference.

So, there is no cooling tower in this type of system?
 
I am pretty sure there is a 60 amp and a 30 amp double pole for 2 pieces of equipment. There is something with a standby water heater as well. I am going to meet with the guys tomorrow that will be doing it
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Does anyone here know how these units compare to Fossil fuel or electric heaters. Meaning cost operate , BTU heat per KW of electricity. I hear so much about efficiency over fossil fuel or Electric being leaps and bound better but if you are only heating and no cooling I don't see the advantage.

Thanks
 

realolman

Senior Member
I have one... It is fabulous.

I don't know how it would be if you had to pay to install it yourself because I think it is pretty expensive... but we got it in the house we bought, and I feel as if we got it for nothing.

And nothing is about what it costs to operate.

We pay less for electricity than we did at our last oil, hot water house, and the heat is included in the electric bill.

.... you can't beat it with a stick

And one other thing I discovered ... get yourself all new appliances.
 

stickboy1375

Senior Member
Location
Litchfield, CT
I have one... It is fabulous.

I don't know how it would be if you had to pay to install it yourself because I think it is pretty expensive... but we got it in the house we bought, and I feel as if we got it for nothing.

And nothing is about what it costs to operate.

We pay less for electricity than we did at our last oil, hot water house, and the heat is included in the electric bill.

.... you can't beat it with a stick

And one other thing I discovered ... get yourself all new appliances.


You're kidding yourself if you think you're magically getting heat for free.
 

kwired

Electron manager
Location
NE Nebraska
You're kidding yourself if you think you're magically getting heat for free.

I have one also and love it. No you are not getting heat for free. Your electric usage is for pumping refrigerant and pumping water, both of which cost less to do than creating the heat you do gain - which is extracted from the water you are pumping. You are not creating heat you are moving it.

Difference between a ground source heat pump and an air to air heat pump is with the air to air the efficiency declines as outside air temperature decreases, and eventually you need a back up heat system to take over. With ground source the source remains at a fairly constant temperature year round so efficiency stays about same no matter how cold it is outside. I never even turn on breakers for my electric back up heat unless the heat pump has a problem.

The cost of my geothermal unit was about the same as cost of air to air unit. What is expensive is installing a ground loops. Where I am at water availability is not an issue so I did not have to spend money on a ground loop, we pump water from our domestic water well through the system and discharge it back on the ground. I have very sandy soil so it soaks back into the ground fairly quickly. In the summer we use discharge water for watering the lawn.
 

realolman

Senior Member
You're kidding yourself if you think you're magically getting heat for free.

what I meant was the house we bought was one of the lower priced ones we looked at, and was a much nicer house in a better location than the more expensive ones... AND it had geothermal heat.

I did not have to pay to install geothermal heat. I feel like I got it for free.

It was advertised as having a "heat pump" ... I went to look at it fully expecting to have to install a heating system. In my neck of the woods an air to air heat pump ain't gonna cut it. The geothermal works great. You actually ARE getting heat from the ground for free, all you have to do is extract it. Bout like putting water in your refrigerator, and then getting the heat out the back of your refrigerator... refrigerators don't cost much to operate and the water comes from the ground, and returns to the ground to be warmed again by the sun.

My electric bill is less than it was at my other place and the heat is included.... seems pretty magical to me... but at my age, I'm pretty cynical ... I don't kid myself about anything. :)
 
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Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
My electric bill is the same year round within a few dollars. 2000 sq ft on the top of a hill, where wind speed is measured in chain links. No kids at home, just 2, uh, not quite of retirement age. We have what is called a Pump & Dump. Pump the water from the ground, extract or add heat to it then dump it out into the pasture. The domestic hot water is warmed prior to entering the water heater in the process but I have not studied it for just how much that helps. Zoned with most of the bells and whistles. Not cheap. We lucked and got the tax credit and a rebate from POCO. The back up strips do not come on even in the coldest weather, unless you bump the stat up several degrees.

and yes we have done several. My unit is fed with a 2 pole 30, a 2 pole 40 and a 2 pole 50. Typically one or two 260s and a 230
 
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kwired

Electron manager
Location
NE Nebraska
My electric bill is the same year round within a few dollars. 2000 sq ft on the top of a hill, where wind speed is measured in chain links. No kids at home, just 2, uh, not quite of retirement age. We have what is called a Pump & Dump. Pump the water from the ground, extract or add heat to it then dump it out into the pasture. The domestic hot water is warmed prior to entering the water heater in the process but I have not studied it for just how much that helps. Zoned with most of the bells and whistles. Not cheap. We lucked and got the tax credit and a rebate from POCO. The back up strips do not come on even in the coldest weather, unless you bump the stat up several degrees.

and yes we have done several. My unit is fed with a 2 pole 30, a 2 pole 40 and a 2 pole 50. Typically one or two 260s and a 230

As far as heating domestic hot water goes - when you are using your heat pump for cooling you essentially are getting free hot water unless your using hot water faster than the heat pump is heating it, then your regular hot water system will have to back it up. The domestic hot water generation portion of the heat pump simply is a separate heat exchanger that passes the hot refrigerant (containing heat that was extracted from the air in your house) and exchanging it with water pumped from your hot water system. This is heat that cost you nothing when cooling your home, if you don't put into your hot water system you just pump it outside your home and get rid of it.
 

kwired

Electron manager
Location
NE Nebraska
Has anyone ever done one of these? What kind of circuits are there? How many? What amperage? I guess they dig some sort of hole or trench that gets heat from the earth or something. What kind of equipment am I looking at hooking up here?

Back to your question of what do you have to hook up there, it really depends on the design of the system. It has all of the basic elements of any other heat pump. A compressor, a reversing valve, and two heat exchangers - one for refrigerant evaporation, and one for refrigerant condensing. The two heat exchangers reverse duties depending on whether you are heating or cooling the building.

So at a minimum you will have a circuit for the compressor -this circuit usually also supplies a blower for the indoor air movement. They often also power water circulating pump from this circuit. The unit will be marked with minimum ampacity and maximum overcurrent protection for this circuit just like any other air conditioning unit.

If the unit has electric back up heat it will be heat strips just like any other typical air conditioning air handler with resistance heat strips. Typically you will have 10Kw max per circuit just like other heat strips.

So for a unit with up to 20 Kw backup heat you will need the heat pump circuit, and two 10 kw heat strip circuits.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
if you are only using the system for heating and have no need for cooling is this type of system worth it?
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
if you are only using the system for heating and have no need for cooling is this type of system worth it?

How long is the heating season? How many days will you be using it? Doesn't matter if it is heating or cooling, other than hot water, it is a very efficient system. Next is how long are you going to live there? How old are you? Propane is very high, is nat gas available? Have the money? You will be putting your money into a hole in the ground with geothermal, that is for sure.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
The geothermal systems are fairly efficent over the air type heat pumps, especially up north where a standard heat pump is virtually worthless. But where I get a laugh from is the self contained heat pump water heaters, since most water heaters are inside the house, it helps the air conditioner during the summer, but steals the heat from the house during the winter, so your furnace is working harder. Might be Ok in some place like Florida where theres not really a winter.
 

bpk

Senior Member
A huge factor in the efficiency is the contractor who installs it. There are different types like slinky coils buried in a trench, coils in a nearby pond, or we just did one with 16- 200 foot deep wells. You definetley want to find a contractor (or work with one) who knows there stuff.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
This is all great information. what I would like to do is try to figure out what the differences are in terms of KWH, of Geothermal heat pump v Electric resistent heat and Geothermal heat pump v Propane or Nat gas

I have seen a chart of efficiency.

Resistence electric 100 %

Gas to air heat exchange 89%

Geo heat pump 300%


what I cannot grasp is how you can get beyond a 100%. How do you get more energy out than you put in? Is there a simple way to explain this. :?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Has anyone ever done one of these? What kind of circuits are there? How many? What amperage? I guess they dig some sort of hole or trench that gets heat from the earth or something. What kind of equipment am I looking at hooking up here?

There are a few different setups. Basically they dig a well that is used for the geotherm unit/s. They run the line into the building and from there you either have to wire a single dp circuit for the unit or a dp crcuit and another circuit for the pumps. I have seen the unis either self contained or with separate pumps. The self contained units are a snap but the others are a little trickier but not bad. You may also have gas , electric or no backup heat depending on where you are from.
 

kwired

Electron manager
Location
NE Nebraska
This is all great information. what I would like to do is try to figure out what the differences are in terms of KWH, of Geothermal heat pump v Electric resistent heat and Geothermal heat pump v Propane or Nat gas

I have seen a chart of efficiency.

Resistence electric 100 %

Gas to air heat exchange 89%

Geo heat pump 300%


what I cannot grasp is how you can get beyond a 100%. How do you get more energy out than you put in? Is there a simple way to explain this. :?

With a heat pump you are not creating heat you are moving it. That is where it gets its name from - it pumps heat from one heat exchanger to the other - and can be reversed to heat or cool, You can get above 100% efficiency from an energy consumption standpoint because you gain more heat than what would be produced by the energy you used from your utility provider. So for your 300% example you will get 3 times the amount of heat than you would get from electric resistance heat out of the same KWh of electricity. Keep in mind that poor installation, dirty filters, and other things can effect this, but also effect other heating methods also.

With the 80 and 90 % on gas heating units that is the efficiency of the use of the gas, and has nothing to do with whether it cost more or less to operate than other energy sources. Many people have confusion with this also.

All that most users of the equipment are really concerned with is how much will it cost to heat or cool my space, then they get all of this other terminology they don't understand thrown at them in a way to support whatever unit the seller is pushing. The information is not false, they just tell you what they want you to hear.
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
An air-to-air heat pump has a "coefficient of performance" or COP. This number times 100% is the overall efficiency compared to heating with resistance heat. Mine has a COP close to 4 when it is 55F outside, 3 at 42F, 2.5 at 30F, and 1.8 around 0F. So its efficiency depends on the outside temperature. One other factor with air-to-air heat pumps is the outside coil gets frosted at temperatures below 40F. That allows the coil to seem like it is in a 30F or 20F ambient environment when it is really near 40F, so the efficiency drops. The heat pump will reverse for a short time periodically (runs in air conditioning mode) to warm up the outside coil and melt off the frost. This is another inefficiency (but it is still more efficient to melt the frost than to leave it all frosted).

Ground source heat pumps are like an air-to-air heat pump where the air is always around 50F. They don't freeze up (so no wasteful reversing) and have great efficiency for both heating and cooling.
 
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