# Bring the lake to the house?

Discussion in 'Surface Water Loops' started by graydon, Sep 26, 2012.

1. ### graydonNew Member

I have read lots and lots and so far have seen noone do this. I am thinking about bringing the water from the bottom of our lake through a 2" pipe up to my house. In the house, I'll have a heat exchanger to transfer the heat from the lake water to a process fluid (antifreeze) which will then go through my Waterfurnaces. I'll use a big Grundfos pump to pump the water from the lake and through the heat exchanger. Calculations from the Grundfos spec sheet indicate I should be able to flow at least 200 gpm through this 2" pipe. I'll use a VFD to control the speed of the pump according to inlet and outlet temperatures in the heat exchanger. As the outlet gets too cold, I'll speed up the pump. The process fluid will run through a coil of copper tubing in the heat exchanger (a basic shell and tube heat exchanger) thus delivering the lake's heat to the Waterfurnace.

My question is this, if one were to run your pond loops with copper tubing with water constantly flowing past the loops (which is essentially what is happening in my heat exchanger), how many feet of copper tubing would I need per ton? What do I need to figure out in order to make this prediction?

Any ideas?
Thanks,
Graydon

2. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

Calculation

You only need to figure out how cold the outlet water can get to. That is why this doesn't work in northern climates (don't know where you are).

If you have water coming in at 36F in the middle of winter, it gets pretty difficult to pull heat out of it without freezing everything up. Of course you can just pump like hell to keep a temperature drop down to only 1C. But still...

Anyway, your best bet is to use delta t's as a flow control.

3. ### graydonNew Member

Agreed on the freezing. We're in Michigan. I expect best case the water from the lake will be about 39 deg F and at low flows, I need to pump it back to the lake before it goes below 32 degF. I can control the pump with thermocouples in the water to make sure the pump turns on when the water approaches 32 degF. Also, the water will pick up a little heat in the ground on the way back to the lake because the plumbing is all well below the frost line. So, best case, I should have a 7 deg delta T and over 200 gpm heat source. That should work out to roughly 700k BTU/H. Correct?

Thanks,
Graydon

4. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

Pumping

Yes about 700 kbtu's. But that is a lot of pumping. More like a placer mining operation

You won't pick up much ground heat at those flows. If you did, it would quickly cool the ground anyway.

You will want to be a few degrees above freezing for your shutoff.

I do know a diy who did this in my area. He proudly told me how he only has to switch to wood heat for a few months in winter Not really a system I can recommend to my clients, but you seem prepared.

5. ### Howard EkMember

Regards,
Howard J. Ek, PE

You can have it with quality; You can have it fast; You can have it cheap. Pick any one.

6. ### graydonNew Member

Howard,
Thanks, I would like to hear what you did. My email is graydon at gdsamps dot com I couldn't find the link to PM on this site.

-Graydon

7. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

The coldest point is not at the end of the discharge line but inside the heat exchanger, where you need a certain delta t differential to transfer heat!
Similar in closed loops, the loop never freezes, it is always the end (exit) of the heat exchanger!

8. ### jrhMember

How are you going to keep the fish out?

9. ### graydonNew Member

My youngest son is a great fisherman. I am going to station him by the inlet with his baddest fishing pole.

Seriously, I put well points on the ends of both pipes. I don't think I really needed it on the discharge back to the lake, but if I ever wanted to switch pipes, or use both as suction lines, I could do so.

10. ### zacmobileGuest

I shudder to think how much it would cost to move that volume of water, is there a reason why you don't want to put the heat exchanger in the lake?

11. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

Ditto

Or just go pump and dump

12. ### waterpirateWell-Known MemberIndustry ProfessionalForum Leader

I have mentioned this before about biologics. do not underestimate the ability of bilogic beings or material from fouling a well screen/point. Everything from tad polls to the green and brown algae blooms on the intake and discharge. Useing raw water here from a surface supply was tried and abandoned more than once.
Eric

13. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

I've come to understand the lake is not one we can put pond loops in.

14. ### tugguyNew Member

Joe
What is meant by the statment the lake is not one we can put pond loops in?

15. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

I visited the project. The lake was not the sole property of the original poster.

16. ### tugguyNew Member

Ahh sooo Bummer well I own mine so that hurdle is jumped now for the huge rock and dam between my basement and the pond!