I am planning to change the heating and cooling systems for my house to geothermal with a ground loop. Here are the details:

House is in the Washington D.C. area. 

House has 3,700 square feet plus full basement.

Current equipment is 12 years old and my electric bills are quite high -- we pay 14 cents per KWH here.

First floor and basement are currently heated by a 105,000 natural gas furnace with a 4 ton blower and cooled by a 3.5 ton carrier air conditioner.

Second floor is heated and cooled by a 3 ton split heat pump (R-22).


So far I have received two proposals:

Proposal (1). 
For second floor -- Install one 3 ton Climatemaster Tranquility 27 geothermal split heat pump unit (TTS038) and
one Carrier infinity variable speed air handling unit with 15 KW electric heat kit 

For first floor and basement install one 3 ton Climatemaster Tranquility 27 geothermal split heat pump unit (TTS038) and install one Carrier performance series cased evaporator coil unit on existing gas furnace.

drill 2 (two) 325 foot deep veritcal wells with 1" to 1 1/4" geothermal well piping.

Proposal (2)
For second floor -- Install one 3 ton Climatemaster Tranquility 27 geothermal split heat pump unit (TTS038) and
one Bryant Puron Variable speed air handler unit FV4BNF005.

For first floor -- Install one Climate Master Tranquility 27 dual-speed geothermal compressor and variable speed air handler package unit TTV049 (4 ton) with 10KW auxiliary heater.

Ground loop to be provided by drilling company with separate contract. The contractor's projections assume 640 feet of boring for the 4 ton and 480 feet of boring for the 3 ton.  

--Both proposals offer the desuperheater for hot water as an option.


I have a lot of questions about these proposals but will start by just mentioning a few of the major ones.

(1) When the contractors came to my house, they both contractors told me I would need about 150 to 200 foot of ground loop per ton. They both told me that three 375 foot deep wells would probably be about right. But contractor 1's actual proposal includes only 2 x 325 foot wells. Is that enough?

(2) Contractor 2 says the Climate Master 4 ton package unit is better than a Climate Master 3 ton split unit plus existing gas furnace for the first floor and basement, especially since the gas furnace does not have a variable blower. Any comments on this.

It is difficult to compare the prices of the two proposals because one includes the wells and the other doesn't. Proposal (2) assumes a budget of $21,000 for the earth loop. Including that figure, proposal (2) would be about $9,500 more than proposal (1).

(3) A friend of mine had 5 x 200 foot geothermal wells drilled and piped for $9,000 in southern Maryland last year. Does it make sense that 3 x 375 wells in the Washington D.C. area would cost $21,000? Should I get my own separate bids for the earth loops?

Thanks for any suggestions or comments you can give me.

5, 200' wells for $9,000 doesn't make sensed that's little more than horizontal excavation and pipe cost.
I like package units better than splits personally. Assembly in a clean enviroment is generally superior to field assembly.
I don't know why there is disagreement on size. You need a third contractor to break the tie.
Get contractor #2 to provide loops in his bid if he wants the job. A guy that won't employ subcontractors for you has less liability if something goes wrong and will likely be less help in fixing it.
Verticals in our area are about 150'/ton.
Good luck,
Joe

If by southern maryland you mean the eastern shore, than that pricing is the going rate for the drilling here. Option one appears to be building you the dreaded short loop. The rule of thumb is 200' per ton of loop. So for seven tons of load you are looking at 1,400 feet of drilling that equals 2,800 feet of pipe in the ground.
Contact some loop field designers in your area and also some drillers who specialise in geothermall to get the real information for your area.
Depending on where in the metro area you are you may be looking at air rotary drilling that is significantly more expensive. Drop me a line for a referal if needed.

I've got probably a dumb question......but what if the contractor says ya need two wells dug to 350 ea.....and ya hit water at 150ft........what happens then??

Thanks for the replies. I spoke with contractor #1 today, and I think he meant to say 3 x 375 foot wells. On the size of the units, he says he included a 3 ton geothermal heat pump because he is rounding down from the 3.5 ton AC unit I have. He says a 4 ton might cool the house too quickly and wouldn't run long enough to dehumidify.

How important is it to have a variable blower with a two-stage geothermal heat pump? The alternative is to keep the gas furnace and use it with a split system. The gas furnace has a standard furnace blower with three speeds which I am told would not work as well as the variable speed blower in the package unit. How much would I lose in efficiency without the variable blower?

I like the suggestion to ask contractor #2 for a bid including the well drilling and will also try to get another contractor to bid on the job.

What is air rotary drilling and why does it cost a lot more? I think I was told that in my area the bedrock is fairly close to the surface.

Thanks again for your comments.

Water pirate will have to answer most of the drill questions, but I will mention that the proposals have both of the bidders between my 150 and his 200'/ton rules of thumb so you can likely be comfortable with that. Depth is a regional thing, we're not as rocky and I will yield to the local driller's opinions.
A different blog site has a homeowner with problems that contracted the driller seperately and there is some confusion as to who is responsible for the system's maladies. So I would insist that one guy be responsible for everything.
Regarding variable speed fans, they will save you a few dollars in electricity, but they are very expensive when they break, so I don't find the ROI compelling. In comfort however and even temperatures you can't beat 'em.
Most package heat pumps (TTV038 for instance) already have them. Why are we looking at split units?! They are not assembled in a clean enviroment and the warranties are often shorter.
Get a third opinion, insist that one guy be responsible for everything and check references.
J

If it is known that the bedrock is close to surface in your area, air rotary is going to be neccassary. Air rotary utelises a much larger piece of equipment, and the time increases dramaticaly on the time it takes to do a bore using a down hole hammer. Maybe 2 300' bores in a day using air, as opposed to mud rotary 9-11 300' bores per day.
hope this helps.
My favorite well driller in the area that does geothermal is winslow well and pump, hollywood MD

The presance of water in a closed loop geothermal bore would only increase the conductivity of the loop.  The bore still continues on to the engineered depth.

Thanks WP! I was wondering what would happen if they hit water.

Is that 3 wells total for both units, or 3 wells per each unit?   Sounds low in the first case, but it all depends on the calculations and soil and rock types encountered.