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GeoThermal Heat Pumps
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Author:  denni50 [ Sun Jul 23, 2006 12:01 pm ]
Post subject:  GeoThermal Heat Pumps

anyone here know anything about GHP's.

I think I'm going to have to replace my old heat pump in the fall
and am seriously considering going eco-friendly and getting a
GHP...my current unit is a Goodman Packaged Unit(everything is outside)
and I would want to stay with a similiar system.

been doing some research and getting one of these installed could cost
anywhere between 6k-11k vs 4k for a regular air unit.

Author:  Wayne Stollings [ Sun Jul 23, 2006 2:02 pm ]
Post subject: 

The last house we had in which we replaced the heat pump was about 20 years ago. At that time the systems required a lot of water and the local installers only knew to incorporate them into a large pond system.

Some of the systems I have seen referenced use a huge loop system to transfer the heat form the ground to the heat pump. The circulation pump adds to the cost of the system and the costs of operation, however the constant temperature of the ground means the system can run efficiently year round if the coils are below the frost line. When the resistance heating strips are used, usually when the temperature drops below the effective transfer point or a significant change in temperature from the set point is experienced, the energy costs are significantly higher. Thus, the more efficiently the system operates the lower the associated costs. The cost of electricity is not static so any calculations based on the current cost should be on the low side concerning the pay back.

From my experience with only replacing a unit with a higher seer heat pump, the improved efficiency really has a significant impact on energy costs and will quickly pay for the difference in initial cost.

Author:  denni50 [ Sun Jul 23, 2006 5:01 pm ]
Post subject: 

thanks for the feedback...I had just replaced the coils in the heat strips
this year..some opossum had gotten inside the unit and broke some
of the coils causing the emergency heat not to kick in...when the
HVAC guy opened up the unit all we saw was a big mat of fur and long
tail.

the problem I'm having right now is the heat strips have started working
on their own independent of the thermostat setting so I had to turn
them off via the circuit breaker....there was smoke and burnt smell
coming into the house through the vents.

The a/c works fine but come fall/winter I'll need to look into why the
heat strips are running when they shouldn't be or look into a new unit
since this one is approx 12ys. old.

Author:  Wayne Stollings [ Sun Jul 23, 2006 10:01 pm ]
Post subject: 

Depending on the aquifer level the well system would be the more expensive of the two "closed" systems, IMO. There might also be restrictions for returning water to the well given the chance (however slight) that the water could be contaminated in the process. The well we had put in on the property in VA was a shade over $5K for the well and pump, which would probably be more expensive than the coil system given the cost of trenching compared to digging a well.

Author:  Wayne Stollings [ Mon Jul 24, 2006 8:22 am ]
Post subject: 

XXMag wrote:
I'm not an expert, but don't you need a lot more linear feet of trench than you need of well? To demonstrate, if you lay on 40 degree earth then 40 degree water which one make you colder first?

Sure, trenching is cheap, but from my understanding it take oodles of it...


In your example the variable of contact is included, as water would contact nearly all of your body and the ground less than half. If you were covered in 40 degree dirt to the same level I suspect you would see very little difference in the time it took to make you uncomfortably cold.

Water does transfer heat well, but there is usually only 20-30 feet of water in a well leaving the rest of the depth for air contact which is an even worse method of heat transfer than either of the other two. Thus, you have an average heat transfer with which to compare to the more constant transfer of heat by contact with soil alone. Even if it required more footage, the cost of trenching to below the frost-line is less than the cost of a well. Given the area in which Denni lives does not have a very deep frost line and an estimated well depth, which I assumed a similar aquifer level from that in a similar area, the trenching would be a cheaper and more reliable estimate. The wells may have to go much deeper to find sufficient water and new wells being dug will affect the water level in an existing well, as would any use of explosives in larger scale construction.

With that said, the farther north you travel the possibility of the well being a better choice rises so any such decision would have to be based on the very specific location options.

Author:  denni50 [ Mon Jul 24, 2006 8:22 am ]
Post subject: 

thanks everyone....I have an older home and it uses well water for
outside use...the pump is located in a small enclosure attached to the
house...my best bet is to contact a local HVAC company and get
someone to come out and survey the property and explain what
would need to be done and $$$$$$$$....I know the break-even point
in savings would be realized in a couple years but I also think it would
give the house more value if I decided to sell before the break-even point.

http://www.geothermal-heat-pump-resource.org/

was thinking of the loop-transfer system but would that require water or
just earth?

Author:  Wayne Stollings [ Mon Jul 24, 2006 8:36 am ]
Post subject: 

denni50 wrote:
thanks everyone....I have an older home and it uses well water for
outside use...the pump is located in a small enclosure attached to the
house...my best bet is to contact a local HVAC company and get
someone to come out and survey the property and explain what
would need to be done and $$$$$$$$....I know the break-even point
in savings would be realized in a couple years but I also think it would
give the house more value if I decided to sell before the break-even point.

http://www.geothermal-heat-pump-resource.org/

was thinking of the loop-transfer system but would that require water or
just earth?


The loop transfer system they show could use either since it is a closed system. The water version they mention just lays the coils underwater, so you only need earth either vertically, horizontally, or covered in water. You could put them down your well but it would impact both systems if you had to pull the pump from the well or replace the foot valve. That would be providing there was sufficient room in which to place the lines in your existing well. The use of the existing well would make the cost much less but you would probably loose that source of outside water. It may be something to consider unless that is a more important aspect for you than the cost of the complete new system. The installer should be able to give you better advice based on the specifics of your well, its diameter, depth, depth of water, etc.

I expect he will push for a new installation in order to be able to guarantee the operation. I agree with your thoughts on increasing the resale value, just as does the addition of better insulation and more efficient windows and doors.

Author:  Wayne Stollings [ Mon Jul 24, 2006 8:43 am ]
Post subject: 

XXMag wrote:
Every project is different. You know more about denni's locale than I do. I don't have much first-hand experience with them, most of my knowledge of them is academic.

Long story short though, no matter how you set it up geothermal beats the pants off of a traditional heat pump in terms of efficiency.


True, and even the level of knowledge and experience of the installers will have an impact on what options may be available. The installers I spoke with so many years ago had no real experience in the field and were not comfortable with my closed loop system idea because they had only seen water based systems and the calculations were different for the requirements of each type.

I would also suggest that if it is affordable and there is any indication that you might want to expand the house that you size the unit up to accommodate that increase. Thus, you have a system working well within its capabilities and you do not have to add a smaller system or replace the existing one to add a room or other temperature controlled area to the system.

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