Ground source cooling
Thursday, January 29th, 2009I have a large shop I spend most of my time in, 40 x 60 x 16, heated with a Taylor water heater with radiant heat in the bathroom, office/machine room and selected places in the concrete floor out in the shop.
I recently acquired a new 15 ton heating/cooling unit – it’s the building air handler end of a chiller system. It has two coils, one copper one for heating and another aluminum one for cooling.
What I would like to do is use ground water, drill a deep well, high water table where I stay, to get down to 55-58 degree water and use a coil made from pex or some other inexpensive piping to build a close loop system to cool my shop. I need to know how big the coil needs to be and made out of what?
I’m in eastern NC and it has high humidity. When the temp gets over 80 and sometimes up to 100 degrees here it’s hot inside. I have Foil/Foam/Foil insulation on all the walls and roof, it never gets hotter inside than what the temp is outside, unlike the horse barn across the driveway.
I was thinking of using the first well to do most of the cooling and then have a second well, pump heated water from the first into the second to keep cool water going into the first cooling well, this would have the ground as the heat sink.
How do you calculate for the size and type of piping needed to get the cooling I need? I’m hoping this would be cheaper than just installing a conventional A/C system.
Hello, whoever you are since you did not sign your email:
I know it is tempting to do what you are planning because you have this air handling unit that includes coils that can be used to do this, but this air handling unit is the lowest cost part of the system. For any geo-thermal heat pump or ground-coupled system, the highest cost is drilling the wells and installing the loops. As you already mentioned, your big concern is dehumidification which requires cooler water than just straight cooling as you must lower the air temperature below the dew point to do remove any moisture with the coils.
Each area of the country has different types of soil conditions and different water table depths, so this is why there is not a simple magic number of wells per BTU, but here are a few suggestions. Normally, you need 400 cfm of air flow per ton of cooling. I would expect you will need 2 or 3 wells for your size shop.
Hope this helps,
Jeff Yago
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