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Discussion Starter #1
Mind talking about the geo job? I've been interested in geo for a while. None of your competitors can see in the bussines lounge. Well, unless they knew in advance and posted 250 times between now and award.
 

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Mind talking about the geo job? I've been interested in geo for a while. None of your competitors can see in the bussines lounge. Well, unless they knew in advance and posted 250 times between now and award.
I don't mind. I won't talk $$ till after 2:00 on the 12th:)
 

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Fine by me. What is the geo unit for? Commersial, resi? Is it multi purpose? What kind of loop are you going to use?
High School. there are 90 wells going to 71 heat pumps. Also 2 - 750,000 btu condensing boilers for those cold days. The heat pumps are all pretty small using either 3/4" or 1" lines. There are also 7 RTU's with 1.5" - 2.5" lines off the loop.

The loop is 6" HDPE fused connections. It holds a butt-load of fluid. I'm presently torn between $4000 worth of methanol and a feed tank for the system or $14,000 for propelyne glycol and a 1" RPZ hooked directly to the loop with PRV and fast fill. $10,000 isn't a terrible amount of money on this job.
 

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Discussion Starter #5
Doesn't the glycol transfer heat more effectively than methanol? Why propyl and not ethyl glycol?

When you say "the" loop, I guess that means its a common loop to all the heat pumps? How is it piped?

Are the heat pumps only providing space heating and cooling, or are you heating DHW with de-superheaters as well?

Sorry if I’m hammering you with questions but it’s not often I get to pick someone’s brain about this type of thing.

 

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Doesn't the glycol transfer heat more effectively than methanol? Why propyl and not ethyl glycol?

When you say "the" loop, I guess that means its a common loop to all the heat pumps? How is it piped?

Are the heat pumps only providing space heating and cooling, or are you heating DHW with de-superheaters as well?

Sorry if I’m hammering you with questions but it’s not often I get to pick someone’s brain about this type of thing.
Glycol jumps to 25% to have equal heat transfer properties as 15% methanol. Propelyne is a food grade product. Super safe. You can drink it. Ethylene makes you a little bit dead if ingested.

The 6" loop runs around the entire perimeter of the building. Each heat pump has 2 taps. A supply and a return. Each heat pump has it's own pump module to pull fluid out of the loop as needed. Domestic hot is still a stand alone system. 1 100 gallon 199,000 btu WH at each facility with a 500 gallon holding tank.
 

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Discussion Starter #9
Interesting. So I guess there is a main circulator pump that moves the main run of the loop?

Doesn't propylene break down after a while and then it needs to be changed? I know that is always a concern when designing an indirect solar system. Maybe it doesn't matter as much in geo do to the mild temps?
 

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Thread bump to show as new thread.
 

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Interesting. So I guess there is a main circulator pump that moves the main run of the loop?

Doesn't propylene break down after a while and then it needs to be changed? I know that is always a concern when designing an indirect solar system. Maybe it doesn't matter as much in geo do to the mild temps?
There are two 4" main circulating pumps on the loop.


I don't see propelyne glycol breaking down. It's enemies are heat and light I believe. The temp swing from season to season in the loop is not much.
 

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Why is it called geo-thermal? I envisioned tapping into steam heated by molten lava.
 

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Discussion Starter #13
That is called "high temperature geo thermal".

We are talking about low temperature geothermal. It's just a heat pump that circulates are heat transfer fluid thru pipes in the ground. They are more energy efficient because once you go 5' into the ground the temperatures don't fluctuate very much season to season. In the summer an air source heat pump is trying to dump heat into 100F air which is difficult. A water source heat pump is trying to do the same thing but the ground is 70F so it doesn't have to work that hard. The same holds true during the winter. An air source unit has to try and pull some heat out of 30F air while the geo unit is working with the warmer 70F ground. It makes a big difference in winter because a geo unit will not ever have to switch to aux heating while the coils defrost. An air source unit is basically worthless when it gets close to freezing out and that is when you need it most.
 

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Our ground temp is around 57 degrees year round.
 

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Hopefully I'll get to show you all photos of the job.
 
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