orlie
New Member
Posts:6
 |
| 22 Nov 2009 07:48 AM |
|
Hi,
I am in the process of having a geothermal lake loop installed in the Hudson Valley, NY. The lake is 38 acres and 260 feet from the house. The pipe will be 2 separate sets of lines buried in a 4 ft trench and extend into the lake about another 150 feet. At that distance we can have a depth of anywhere from 8 feet to the bottom up to 12-13 feet to the bottom. The coils will be sitting up at least 2 feet high once they are settled on the bottom so if we leave the coils in 8 feet of water, part of the coils will only be at 6 ft.
My question is whether I should push the contractor to achieve the 12 foot depth for all coils or is the 8 ft depth equally efficient?
We are in the process now, so I am hoping for quick responses as we will likely have to deal with this tomorrow
Thanks
|
|
|
|
|
|
|
engineer
Veteran Member
Posts:2749
|
| 22 Nov 2009 07:59 AM |
|
Paging Mark Custis... |
|
Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
|
|
|
orlie
New Member
Posts:6
|
| 22 Nov 2009 09:13 AM |
|
Sorry, I don't understand the comment? "paging Mark Custis..." |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 09:23 AM |
|
Generally, the deeper the better. 6' is marginal. Why will the coils be up 2' off of the bottom? |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
orlie
New Member
Posts:6
|
| 22 Nov 2009 09:41 AM |
|
Each run of piping goes into a line of 3 consecutive sets of coiled piping laying on the bottom. They put spacers within the coils to separate the pipe to some degree, but the coil remains about 2 feet thick, so the top side of the coil is about 2 feet off of the bottom.
As it is now sitting in the water, one run of coils is only in 8 feet of water and the other is in 10 feet; but without going a greater distance out into the lake and by displacing the coils sideways about 20 yards, we could achieve 13 feet of depth. This seems very desirable to me, but I wanted a professionals opinion as well.
Thanks again! |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 10:08 AM |
|
The loop you describe works well for cooling dominated climates, not as well for heating dominated. For heating dominated a slinky coil is recommended for lake coils.
see attachment
|
 Attachment: pondloops2.pdf
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
orlie
New Member
Posts:6
|
| 22 Nov 2009 12:56 PM |
|
How great is the difference with efficiency between the 2 types and why is there a preference from North and South? In either case aren't we looking for the same amount of heat transfer?
Thanks for all the help...
|
|
|
|
|
Down2Earth Geothermal
New Member
Posts:59
|
| 22 Nov 2009 01:02 PM |
|
For heating, the depth won't be as important since water is most dense at 39 degF. Warmer and cooler than 39 it is lighter so in the winter when the lake is iced over (as it will be in NY) the water near the bottom will be 39 degrees. http://www.dnr.state.wi.us/lakes/publications/under/mixing.htm
If you have a large cooling load, deeper is better as shown in the summertime temperature gradients at the above link.
-Adam |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 01:08 PM |
|
In cooling mode, you are heating the pond. Warm water rises to the top of the pond. You don't need to to worry about over heating the pond.
In heating mode you are cooling the pond. Cool water stays at the bottom of the pond mostly. You can freeze the water around the tight coils. This is the reason for spreading them out in Northern areas.
As Adam noted water is the most dense at 39°. The problem with the tight coils is the pipe is exposed to less volume of water. By spreading the coils out, you increase the volume of water to exchange heat with.
I have no idea how much efficiency difference there is. I haven't done any of the tight coils and only a few of the slinky type. |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
orlie
New Member
Posts:6
|
| 22 Nov 2009 01:10 PM |
|
So are you saying that whether the coils are at 6 feet or at 12 feet, it would all be 39 degrees anyway, or would there still be a transition of temperature along the bottom and it would be more reliably 39 degrees at 12 feet. Also, any further comment on the design using the coils of pipe instead of slinkys. Our primary use will be for heating and I do not expect to use the system for cooling at all... Bottom line of the questions I am posing is whether we should go to slinky design and whether we sholuld displace what is there to the deeper locations?
Thanks again |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 01:13 PM |
|
Your best option will be to go slinkies in the deepest part of the lake. You have to balance that with logistics and cost. |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 01:28 PM |
|
Great link Adam |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
orlie
New Member
Posts:6
|
| 22 Nov 2009 01:39 PM |
|
OK, the reality of the situation is that the workers put the coils in the lake on Friday when I wasn't here and one set of coils is in 10 feet and the other is only in 8 feet. The lines to the coils have not been weighted down yet because they didn't have enough blocks. I don't know how difficult it would be to displace the coils, but without adding more pipe they could also have reached 12 foot depth simply by going sideways about 40 feet.
I did not know they were going to use the coil system instead of slinkys nor did I know slinkys would be superior.
So I am trying to find out what I should do next and how much efficiency I could be losing in the years to come---thus determining my action plan for tomorrow.
I have been told by the contractor to only expect a 4 or 5 degree temperature difference between the out and return lines of pipe, so if that is true, and if the bottom is 39 degrees, I would think that icing should be unlikely? Does that make sense, or would you also question the 4-5 degree differential?
Thanks for the continued help. |
|
|
|
|
fsq4cw
New Member
Posts:64
|
| 22 Nov 2009 05:33 PM |
|
Just my 2¢. I would not recommend doing a lake loop in a pond of that depth. Nowhere near deep enough for my liking.
SR
|
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 05:42 PM |
|
Posted By fsq4cw on 11/22/2009 5:33 PM
Just my 2¢. I would not recommend doing a lake loop in a pond of that depth. Nowhere near deep enough for my liking.
SR
How exactly is this going to help the person with the problem?
|
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 22 Nov 2009 05:49 PM |
|
Posted By orlie on 11/22/2009 1:39 PM
OK, the reality of the situation is that the workers put the coils in the lake on Friday when I wasn't here and one set of coils is in 10 feet and the other is only in 8 feet. The lines to the coils have not been weighted down yet because they didn't have enough blocks. I don't know how difficult it would be to displace the coils, but without adding more pipe they could also have reached 12 foot depth simply by going sideways about 40 feet.
I did not know they were going to use the coil system instead of slinkys nor did I know slinkys would be superior.
So I am trying to find out what I should do next and how much efficiency I could be losing in the years to come---thus determining my action plan for tomorrow.
I have been told by the contractor to only expect a 4 or 5 degree temperature difference between the out and return lines of pipe, so if that is true, and if the bottom is 39 degrees, I would think that icing should be unlikely? Does that make sense, or would you also question the 4-5 degree differential?
Thanks for the continued help. the 4-5 ° differential depends entirely on the gpm flow through the unit. I have seen 10- 12° on some units. Your options are kind of limited now. I would try and get the loops into the deepest part of the lake. Show the print out to your contractor. Ask him why he is doing coils in the North. Ask him for other jobs that he has designed the same as yours. You might be OK depending on the load of your house and the size of your loop. Your contractor needs to prove to you that what he has done will work. Ask him for the calculations to support his design.
|
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
joe.ami
Veteran Member
Posts:4377
|
| 22 Nov 2009 08:44 PM |
|
At the end of the day the contractor is on the hook if the system doesn't work. Manufacturers I've worked with ask for 8' deep average and it sounds like you are there. Minimum does not equal bad. If there is enough footprint (length of pipe) it will be fine. Other mitigating factors (i.e. spring fed) may shrink depth and foot print requirements.
Do not worry about spilled milk. Let's talk if it doesn't work.
Joe |
|
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
|
|
fsq4cw
New Member
Posts:64
|
| 23 Nov 2009 09:00 AM |
|
Posted By geodean on 11/22/2009 5:42 PM Posted By fsq4cw on 11/22/2009 5:33 PM
Just my 2¢. I would not recommend doing a lake loop in a pond of that depth. Nowhere near deep enough for my liking.
SR
[/quote]
How exactly is this going to help the person with the problem?
Perhaps it may not help the original poster but hopefully it may sway others contemplating a similar heat exchanger. As An accredited geothermal installer and designer on both sides of the 49th parallel I would advise against a pond loop in this situation… but that’s just me.
SR
|
|
|
|
|