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Old 09-23-2011, 04:04 PM   #1
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Loop sanity check.


I'm planning a geothermal install and wanted to run my loop design past you guys to make sure it makes sense. The heat load part seems to make sense given the heat load of the house, but I'm not too sure of my flow and circuit part. I lost the original software that I did calculations with 5 years ago.

Now, I'm planning to have 2 350' holes (1400 feet of pipe total) using 1.25"
Pipe. I plan on running the loops in parallel. With two units (2 and 3 ton) receiving a split portion of the water at all times, it seems I'll get about 12-14 gpm thru the units with 1 26-99 pump, and 18 gpm with two 26-99 pumps. Does this make sense? I'm not sure I'm putting the right numbers into the software/spread sheets as I've never used these before. It looks like my Reynolds numbers are good, with 4 gpm in a 1.25 pipe being good.



To complicate the matter, I may want to add a 3rd unit to make domestic hot water. Then I could add in some radiant floor work in the colder areas of the house, and even a hot tub heating circuit via a heat exchanger
But how do I set this up? Use a separate pump for each heat pump?
Also, the sizing software I'm using doesn't seem to take this into account.
Ideas?

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Old 09-24-2011, 08:17 AM   #2
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Loop sanity check.


Sounds like you'll be short on loop and well depth for 5 tons.

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Old 09-27-2011, 04:07 PM   #3
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Loop sanity check.


We've get saturated sand at 15' with bands of clay separating sand, so loop conductivity should be awesome. But, I may do 2 400' holes.
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Old 09-27-2011, 08:14 PM   #4
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Loop sanity check.


Im not a pump expert, but are you going to have enough pump to push that water back up a 400 foot well, several times?
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Old 09-27-2011, 10:18 PM   #5
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Loop sanity check.


Quote:
Originally Posted by Master of Cold View Post
Im not a pump expert, but are you going to have enough pump to push that water back up a 400 foot well, several times?
On a closed loop system, height/depth has no bearing on pump size. Only the piping friction loss does. Because a pound of water weighs as much coming up the pipe as it does going down the pipe.
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Old 09-28-2011, 10:47 AM   #6
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Loop sanity check.


I'm using climatemaster's spreadsheet to calculate the flow. The issue I'm most concerned with is how to hookup the loops. Running the wells in series seems to cause to much head (pipe friction) I would need to run more pumps (in series) to overcome the pressure drop. This is less efficient. Running the loops in parallel makes more sense. But how do I run the pumps? I could have a pump for each unit, or common pumps that produce flow to all units all the time, or common pumps and insert automatic valves to isolate non running units.
If I am running just the 2 ton unit, the flow is suppose to be around 6gpm. At that flow the flow thru each well is 3 gpm, which may cause non turbulent flow with some antifreeze concentrations.
You need turbulent flow so the fluid mixes in the pipe. Otherwise heat transfer is inefficient. This is what the reynolds number shows, how turbid or laminar the flow is.

As far as I can tell, my loop design will work well, except with propylene glycol antifreeze and one small unit running. I'm paranoid about using methanol given the neighborhood is all well water.

My question now is how to plumb the heat pumps? Should each unit have it's own pump with a check valve? The pumps would be in parallel then. Or multiple pumps in series?

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