Wisconsin new geo system sizing plan and help

so just got a new house very near perficat for me and been looking into geo systems for sum time. so this what i know. house 1300 sqft rounded up a tad. by my math should need 300 ft per ton and a 4 ton heat pump. i live in wi. the soil is loamy silt 49-1/2 in deep the bed rock slops from 10ft at rear of property to 15 by the house. it is poorly drained soil. and since a steamfitter by trade the piping the ezy part. i think 1 1/4 hdpe should be right. it alows for corect flow rate while not having a screaming velocity. the ditch plan i got is make a single trench lest 3 ft wide. so can run the supply and return apart but next to eachother. this where im not fully sure tho. should i run them 2 ft apart or use the slinky design witch ive been told is not a good idea. im all ears for help and advice. i think need 1200ft of hdpe pipe.

 

oh and house newly insulated also.

 

Hello and welcome Alex!
4 ton for 1300 sq ft sounds awfully oversized. A proper load calculation is really the best way to size the equipment.
Good luck with your install - keep us posted.

Just a homeowner here...

 

I agree with Stickman, the most efficient system is the right sized system. You mention newly insulated( hopefully air sealed as well) So the heating/cooling loads should be much lower then 4 tons.

Also just a homeowner....

 

New built house? Or new bought house? 1200 sqf house with newer insulation should not take more than 3 tons, unless you plan to leave the windows open.

Now, there goes more into loop design than ton/sqf.

You need more than just pipe diameter and trench lengths. And do not listen to anybody who tells you that slinkies are bad. A well designed slinky works well in just about any environment. We use them in 80% of our cases in Buffalo NY climate, with excellent results.

You need a certain velocity to support some minimum amount of turbulent flow, so your water mixes nicely within the pipe. You also need to minimize your pumping power, and you need to keep your length in mind to reduce the flow resistance.

In my book, a 3 ton system is well supported by 5 slinkies circuits in parallel, 600 ft of pipe each, in (5) 65ft trenches, 3/4" pipe in the trenches, 6-8' deep.

You could use (2) 1.25" circuits, 2ft apart, 900 ft each, in (2) 450ft trenches instead. Bring the 2 circuits separately in the house, so you can turn them off individually during purging (as a DIY), and make sure you get a none pressurized flow center, so you don't need a purge cart.

Keep asking questions....and keep reading here.

 

never thaught turbulence in a pipe was good... usally eats away at the pipe just behind the weld area. hpde is very resistant stuff so gess wouldn't be much a problem. when did my first post i re ran the numbers and learned more how a geo system works. 3 or 3.5 geocool should be good fit still over sized on cooling side but heating the main concern. that said 1 in could be used. to hi a velocity little heat will be exchanged. to little tho? i just know that heat pump 3 ton needs least 9 gpm. im really liking this form guys bring up things hadent thought of. or had no idea about. as far as installing a slinky vs cercets is one better than the other? got 1.32 acre to work with and drilling is out of the question. tear-en up the yard not a problem tho. 6 to 8 seams shallow to me. ten the min id wana do down. it maybe fine 6-8ft way. but frost in the area has been known to go deep deep.better safe than sorry. the way i see it either make a hole 100ft long by 20 wideish or make ten ft wide hole by 50ft? with slinkys? my plan was to run it in one continues run and just 2 holes in basement small holes at that. am i off in my thinken? is 1200ft of pipe to little? id rather have to much pipe in ground than not enuff but a 10 percent over what i need what im shooten for.

 

house built in 1945 newly percused. my mistake sorry.

 

a 1000 ft per ton seams very very hi. most ive seen is 600 ft per ton. a 65ft hole to fit than much not to bad. just seams like alot to me.

 

You need a bit more pipe in the hole if you go with slinkies....You don't have your loads down, so if you are guessing, what you do, you have to make sure your cover yourself for the worst case scenario.
Most importantly, you need to listen here seriously, you are all over the place.
For a 3 ton system you can use 1 pipe, 1800 ft if it is straight pipe. But it has to be 1.5" pipe....not sure if it is worth it for you.

 

gess best to just find a licenenced installer in the area and have them do all the work. thaught i had a clue on this clearly not even close.

 

looken at pipe flow rates 1 /1/4 will be ok. at 9.5 gpm the pressure drop is .66psi per hundy feet. house heating load is 20 btusqft.

 

What type of anti-freeze did you consider when determining that pressure drop?

 

water/alchol. keeps it from freezing and not loze efficiency like propaline glycerol does.

 

Depends on what id "OK" for you.

If you are at 20 BTUs/sqf, a 3 ton would be adequate to cover your load. To cover a 3 ton in Wisconsin, you would need about 1800 ft of pipe in the ground if you are going straight pipe. With 9 gpm and 20% methanol, you have about 38 ft/hd pressure drop through the loop. Add about 10 ft/hd of pressure drop for the heatpump itself, and you end up with 48 ft/hd. You are running a Reynolds number of 6000 in the loop, which tells you that you are squeezing too much water through too small of a pipe. What pump were you planning to use, and who do you want to pay for the pumping power?

To use 1.5" pipe gets you down to 20ft/hd, for 30ft/hd total, which with a single 26-99 grundfos will get you 8.5 gpm. To go with (2) circuits, 900 ft each, you will get down to 5.7 ft/hd, and about 16 ft/hd for the whole system.

 

hard numbers i like that. i havent given much thaught to the pump size in all honesty. i work with pumps near daily. never had to size one tho any thoughts?

 

well geo cool makes that geo pluse single and dubble pump for the larger line size it look like would meet the pumping requirements. but is there better out there for less?

 

Geo-Flow and B&D MFG also make non-pressurized flow centers with single or multiple pumps. If a single Grundfus 26-99 will work, that would be the recommended configuration for lowest initial and long term costs. I don't have any experience with either of these units; just pointing them out as other options. I was initially going to get a B&D QT flow center until I decided on a Climatemaster Tranquility 30 geothermal unit with internal variable speed loop pump.

 

Part of the problem is that good and efficient geo systems should be designed to use the least amount of power when operating. It is a wrong approach to put the pipe in the ground, and then size and find a pump which is large and powerful enough to get you your target gpm.

A good designer designs the loop field for the smallest amount of pumping power needed, and then gets the most efficient pump to pump the water through. So the pump should not designed to fit the loop field, but the loop field should be designed to fit the most efficient pump.

Which is why I said "Depends on what is "OK" for you." when you said "looken at pipe flow rates 1 /1/4 will be ok. at 9.5 gpm the pressure drop is .66psi per hundy feet."

 

fair enuff. problem is im not a geo engineer. in just a normal steamfitter trying how to heat and cool my house cheaply and safly. so to the efficiency idea. a 3 loop system with a 1.5 header supply and return 600 ft per loop straight runs 300 down 300 back 2ft centers. 1" pipe. how would that be more efficient than a 1800ft big loop? this idea baffals me. to me a big loop would need less enargy to be moved. than a smaller pipe shorter loop. in a header there is always a dead space at the end cap. fluid maintains temp but dosent move and it creates turbulence. also the small pipe being smaller has more friction on it even tho its shorter. help....

 

Pressure drop depends on flow and length.

So running 3 loops in parallel, each one only sees 3 gpm, for 9 gpm total. While pressure drop increases with flow in a square function, length only increases pressure drop in a linear function.

With your examples, pushing (20 % methanol mix) 9 gpm through a single 1.5" pipe 1800 ft long, your PD is 20.3 ft/hd. Splitting this up in 3 circuits of 1" pipe has 3 effects:
1) Having 1800' of 1" pipe would raise your PD to 107.5 ft/hd, due to the smaller pipe diameter.
2) But then splitting the flow between 3 circuits to 3 gpm/circuit reduces that PD from 107.5 ft/hd down to 15.7 ft/hd (assuming you have still 1800' of pipe per circuit).
3) But you only need 1800' total, thus you can reduce the length of each circuit to 60', which reduces the the PD down to 1/3, or 5.2 ft/hd.

So now you just reduced your pressure drop for the 9 gpm you need from 20ft/hd with 1.5" pipe to 5 ft/hd with 1" pipe.

Don't forget to add the 10ft/hd of PD for the heat exchanger inside the heat pump.

You can design your header without dead cap space at the end.

Hope this helps explaining it better.