Replies

1. 
   mike_guertin | Nov 27, 2004 03:34am | #1

   I've installed a few on homes I've built. There are lots of pros and cons but most of them are dependent on the type of geothermal system you use and the delivery system throughout the house.

   And unlike gas or oil systems where you can get a 250000 Btu unit for just a few $ more than a 70000 unit - a 6 ton geothermal costs almost twice what a 3 ton unit costs. Since you're house is ICF you should be able to take advantage of a very small system provided the roof and windows are also well sealed and insulated as your walls are. Make sure any installer does an accurate take off - and then downsizes.

   In a nutshellL
   Pros:
   Technically a 'green' system though it uses electric.
   Usually longer lived than a gas heat system.
   both AC and heat from same unit
   Some states give you great rebates (check w/ state energy office as well as electric utility. We got 50% paid for from electric company which made one install much cheaper than conventional system.)
   No chimney necessary
   No chance of CO poisoning (except from your car/garage)
   No fire hazard from combustion chamber or gas leak

   Cons:
   Usually costs more
   All electric (in event of power failure with gas system you can use a generator to operate it - YOu'd need one hellofa generator to overcome the compressor / fan start on a geothermal)
   May cost more to operate depending on cost of electric vs gas and how tight the house is.
   Prone to installer problems - you need to get someone who really knows geogthermal to do the job.

   ground source problems:
   Avoid open well systems (AKA 'Pump and dump' or 'reinjection' systems). They rely on a separate well pump to deliver a specific volumn of water to the exchanger. Low water flow will screw up efficiency and perhaps cause lock-out. The minerals in ground water can eat up the exchanger.

   Use a closed loop 'slinky' system OR closed loop well system where separate pipes circulate a closed loop of transfer fluid through the well and geothermal pump. Doesn't use well pump but low head circulator.

   DX (direct expansion) systems are supposed to be most efficient but I have been reluctant to use them. 1:I don't like the idea of putting copper tubing directly underground around me (minerals eat it up) and the system is prone to refrigerant leakage if installer mess up (just like AC). The ground loop systems have a factory loop that is sealed and under warrantee.

   If you do choose a system I recommend paying a little more for a desuperheater to prewarm the domestic hot water. You can link an electric hot water tank or use a 'preheat' tank. Again, the installer has to know his stuff to do it right.

   There are loads of web pages both from MFG and from government and university labs that can give you additional information.

   MG

   PS Avoid electric coil backup. They often kick just to goose the system when the thermostat calls for heat. They use tons of juice and will eat up any economy you get from the geothermal. Only install one if you have it on a manual override only.

   
   

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   Edited 11/26/2004 7:38 pm ET by MIKE GUERTIN

2. 
   junkhound | Nov 27, 2004 03:34am | #2

   Edit:  Be sure to take advantage of any rebates as MIKE said.  Put a regular air-air HP in Illinois for Mom and she gets 1/3 of the cost of my install costs off her utility bills -  she likely won't pay any utility bill at all for over  a year. DW has a deathly fear of gas since a neighbors house exploded when she was a kid, Mike's other points on safety are quite appropriate if your DW is like mine. 

    

   1. "geothermal' does not exists in drilling to any economical depth in S Ohio (thanks for the location).

   2. If you mean, Ground source heat pump, (vs geothermal as in places like Klamath falls OR where there is 120 deg ground water or Rotorua NZ where there is gorund steam, etc.) then you are in a good location. 

   3. Pros are lowest energy cost, cons (unless you are consumate DIY with your own bakchoe, etc) are cost of installation vs. payback.. You need to do a cost trade spreadsheet on your estemated costs and payback vs expected energy cost, interest rates, and cost of construction. If you can't do that simple trade yourself, probably can't do the total low cost DIY route.

   That all said, best of all world is a custom DIY (get your EPA F22 licence to buy refrigernt) on the web for a simple test and $25) system with dual HP evaporators with separate TX , one for your ground source, the other for air.  That way, whichever is warmer is what heats your house.  If not DIY, expect to pay upwards of $10K for such a system, 100% DIY you could probably do it for under $2K less your own labor. Oh, you will probably need to accumulate anouter $1K of HVAC tool, let's say $6k for a decent used backhoe, and you come out $1k ahead plus now you got a backhoe, vacuum pump, gauges, etc. ..

    

   Have FUN!

   
   

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   Edited 11/26/2004 7:40 pm ET by JUNKHOUND