Would a geothermal system with 16 85-ft wells work as wells as one with 6 200-ft wells?

Can a geothermal system work just as well with multiple shallow wells vs fewer, deeper wells?

We moved out of the greater Washington DC area last year looking forward to a quiet retirement in the northwestern area of Virginia. We had an unpleasant surprise with almost $4300 in propane cost more than $1340 in electrical for our 3,080 square foot, two-story home. We needed to make some changes.

The long and short of it is, we have gotten bids from four geothermal installers. In reviewing the bids, most were drilling six to eight 200+ feet deep vertical wells. However, one installer proposed a geothermal system with sixteen 85-feet deep wells for a Climatemaster Digital series split 2 stage heat pumps models TES049 and Climatemaster Digital series split 2 stage heat pumps models TES049. He has said by not having to using the costly well drilling rigs and instead using a different type drill, he was able to lower the cost of his bid. At $38,000, his bid was about $5,000 cheaper than other companies for similar installations.

He had good references and has installed geothermal systems for more than eight years. He is not accredited by IGSHPA but has passed a certification program from Waterfurnace on service and installation of geothermal systems, Climatemaster for their digital geothermal systems, ground loop design and installation, geothermal pipe fusion. He has a master HVAC license in VA as well as WV and hold a Class A Contractors License in the State of VA and a WV Contractors License, both of which are unlimited licenses. In VA that is the highest contractor’s license level.

Again, can a geothermal system work just as well with multiple shallow wells vs fewer deeper wells?

 

Yes.

The loop portion of your system is all about feet of pipe in the ground to perform the exchange. If you have the room to drill 16 85' bores you may have enough room to do a horizontal system which may be even cheaper depending on excavation costs in your area.
Eric

 

Has a heating and cooling load calculation been performed to confirm required capacity / tonnage?

8 tons seems like an awful lot of capacity for a 3kSF home in a relatively mild climate.

If load is truly that high, seek low hanging fruit on the load side (air sealing, insulation) to bring it down.

Sizing for cooling load and making up a small to moderate amount of additional heating load with backup heat is often the best strategy.

Ensure ducts can deliver required airflow; often higher for heating via geo compared to propane.

 

I copied and pasted from the wrong cell of the speadsheet I was using to compare bids. The correct model for the split unit to service the attic is a 2 ton system, Climatemaster Digital series split 2 stage heat pumps models TES026, Does that make more sense now?

 

There is a lot of exposed rock that argues against doing a horizontal system

 

I will say no. The top ~20' of the soil horizon is not the same. So a 200' borehole is better than 4 * 50' boreholes as you have only 20' in this profile vs. 80'.

 

Even six tons sounds heavy.

Chris makes a good point about upper ground profile; OTOH horizontal loops systems whose entire length is less than 8' below ground level can be made to work very efficiently in many locales.

 

I grow so tired of the " Which is better question". The heat exchanger design is all about feet of pipe in the ground. We all know the amount of pipe goes up and down for any given load based on the design that is chosen. The real design choice is : cost to install vs. longevity, there is a different answer to that question for every project.
Eric

 

Eric and Curt are both spot on

 

The comparison is between
16 loops at 185' = 1360'
and 6 loops at 200' = 1200.

I agree with all that has been said

 

As a homeowner, my advice would be to make sure those "good references" are for geothermal systems that are installed using shallow wells such as you are describing. References for other types of installations are not guaranteed to be relevant, IMO.