circulator selection

10 ' on center should work

 

I will work the numbers after the holidays!

I can probably fit more footage in.

Thanks!

 

Slinkies are easy to make when their pitch is 50% of their diameter. You can even go 8 ft OC. 3 ft diameter 650' slinky with an 18" pitch is about 80-85 ft long. Or you can do a 4 ft slinky, with 24" pitch, to make the trench shorter, about 65 ft. Many ways to skin a cat.

 

(Edit: these calculations are later proven wrong. Sorry for the confusion.)

Thanks Doc that helped me!

So here is what is hopefully my final design.
2 3ton w2w units, Manifold in the basement, valves on the loops.
In the corner of my lot I have a area 57' x 80' (could go more then 90' but want to try and keep it 80' if possible)

So 8 loops at 800' long (650' in the slinky area)(150' "header") 1" pipe
5' slinky 30" pitch 50-55' long per 650' 7 feet deep or more
10' on center (5' undisturbed ground between) (maybe a little more in 2 spots to avoid a tree and kids swing set)

2.25 gpm per loop minimum (both units running)
10.15 ft head in the loops
10 ft in the coaxial exchangers
5 ft misc (manifold ect...)

25-26 ft head total
one 26-99 on each gshp would more then cover what is needed.
(I wanted to run 3/4" pipe but the head was to high for these pumps in parallel)


1.125 gpm per loop minimum (one unit/pump running)
5.55 ft head in the loops
10 ft in the coaxial exchanger
5 ft misc

19.55-21 ft head total
one 26-99 on each gshp would more then cover what is needed.
Check valve in each pump (if possible or separate check valves)

This design should fit nicely in the yard, it should be well over what is needed for feet of pipe in the ground.
In the header trench I think it would be wise to keep the "out" pipes on one side and the "in" pipes on the other side.

 

Run 3/4" pump, your reynolds number is getting a bit too small for my taste with 1" pipe. Run the pipe which sees the combined flow inside in 1.5" or larger. I'd go 2". That way you make up for the PD in the loop field with 3/4" pipe.
Pitch is too large to get to 50-55'. I'd suggest an 18" for a 3 ft wide slinky. That should make 75-80' loops at 650' pipes.

 

This doesn't fit into the yard.

So 5' slinky at 30" pitch would yield how many feet of trench?

I did half the width for the pitch as you suggested. I opted for wider to make the trench shorter to accommodate the yard space.

I don't know what Renolds numbers are. are you saying it doesn't have enough
turbulence?

 

Andy:

I trust your math and Goggle'd your yard. I can build stair cases but always have to go look up how to do it. I have photos of gigs we have used if you would like to see them.

OSB comes 4' X 8'. The issue becomes until tied together the pipe wants to stay in the size it was rolled until forced otherwise. Once you back fill it is stuck where you put it.

 

Re did the math. that would make a 79' trench not 55' (5' x 30" pitch x 650')

Note to self always double check your math. haha

so the only way to make it shorter is to make the pitch smaller.

 

Ok Doc this has me confused, Maybe I'm not doing the math correctly.
Any time i figure a slinky with 50% of the diameter no matter the diameter I am getting about 8.28' per foot of trench.
How did you get the 4' slinky x 24" pitch x 650' pipe = 65' trench?

 

Check out this: http://www.climatemaster.com/geothermal-dealer/geothermal-sales-tools/pressure-drop-calculator/
.

 

Awesome! Thank you!

 

circumference of a circle= 2 x Pi x R = 3.14 x 3ft= 9.42 per slinky circle
4 ft circle 12.56 ft plus 2ft to advance the slinky by 24" pitch. Roughly 14.5 ft for every 2 ft of trench. 38 circles = 558 ft, then run 76 ft back. Then you usually need 20 ft for the tailings to connect to the header. So it is about 75ft, not 65ft, I usually run 600' slinkies, yours are 650'

So if you have 57' x 80' run it 8 x 4ft slinkies, 0.75" pipe with 3 ft of undisturbed ground between them. You have your loop field.

 

Thanks Doc!

Looks like I need more yard or less loop or less pitch.
Back to the drawing board.

 

didn't you say you have 57' by 80', so this should fit.

 

It fits. But results in less then 8' on center.
Even with 3' x 18" the result is less then 8' on center.

 

That is OK. Still enough to support 6 tons. You loose about 5% performance, but thanks to the amount of pipe in the ground you are fine to stay about 30F in the loop.

 

I ordered the pipe.

 

I've been playing with this tonight. Why dose the percentage of Glycol effect the Reynolds number so much?

Is it due to the poor flow characteristics at low temperatures?

 

Viscosity and specific heat.

 

Still has a low Reynolds Number with 24% Glycol