IdahoGEO
New Member
Posts:17
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| 14 Feb 2009 01:32 PM |
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Which one will deliver the warmest EWT in winter? Assuming ~1 acre pond with 10 tons of loop in it. Soil is damp silt & clay. I'm thinking a horizontal slinky ground loop will provide warmer EWT's during heating season?
Wouldn't it be more eff. for heating if the loops were say 3 feet below the bottom of the pond as opposed to being sunk in the pond?
Thanks... |
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engineer
Veteran Member
Posts:2749
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| 14 Feb 2009 04:15 PM |
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3' below bottom of a pond could give great results, but how do you bury pipe there? Can the pond be feasibly temporarily drained? |
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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>
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IdahoGEO
New Member
Posts:17
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| 14 Feb 2009 04:23 PM |
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Sorry, forgot to mention the pond doesn't currently exist. They're getting ready to excavate a huge hole! I've told the owner we should just "piggy back" off the pond excavation. Dig a few feet deeper and place loops under the pond. I wanted them under the pond, instead of IN the pond, because I'm thinking we'd see warmer EWT's in Winter. Is this a good assumption?
The bottom of the pond will be lined with some clay material to hold water, but I feel sure there will be a certain amount of leakage that will saturate soil around the loop. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 14 Feb 2009 07:15 PM |
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Will the pond freeze over in the winter? If so, the temp at the bottom of the pond will be 39° .
We went to trouble shoot a job yesterday with a pond loop. The pond is not big enough for the load and it appears that the pond is frozen solid. We ran the loop pumps and checked the loop temp and it was at 32° |
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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 |
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IdahoGEO
New Member
Posts:17
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| 15 Feb 2009 10:15 AM |
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Approx how big was the pond, and how much capacity was in it? In this case, the HP could still pull some heat from the ice couldn't it?
I'm sure the pond will freeze over in winter. Ponds here in Idaho have had ice on them for probably 20 - 25 days off and on this winter. I think pond loops are somewhat abstract as far as design goes? I've also heard the water at the bottom will be 39 degrees.
The pond should be about an acre of surface area, and it will be plenty deep. I'll have about 10 tons in it, so it'll probably work fine if I get enough pipe in there. However, I think my loop will be warmer in late winter if I'm in the dirt 3-4ft below the bottom of the pond. I'm assuming the silt / clay there will be warmer than 39? I'll have to install more pipe in the dirt, but that's alright. Performance is paramount with this owner.
Thanks for your input guys...
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Palace Geothermal
Veteran Member
Posts:1609
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| 15 Feb 2009 10:38 AM |
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The pond is probably 1/2 acre with 20 tons of heat pump.
It is up in the mountains and has had ice on top for 3 months now.
I think your ideas are sound. Be sure and let us know how it goes.
The heat pumps were still pulling heat from the ice, but capacity had diminished to the point that back up was needed. |
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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 |
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IdahoGEO
New Member
Posts:17
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| 15 Feb 2009 12:53 PM |
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Thanks for input. I will push to get loops buried underneath the pond, instead of in it. It'll be easy at the same time as pond excavation.
I will post results on this project. It'll require much more attention to detail than our typical RNC installations. We will condition 7,100 sqft with one 6-Ton water-2-air (6,000sqft + 1,100 basement). Water-2-water will be used on same loopfield for ~3,000 sqft detached shops / appt. Very tight home. My heat load is currently at 82K BTU/hr. We won't install ele. back-up. Owner likes to burn (two wood fireplaces).
Does that frozen pond have an airrator / fountain help it keep from freezing? May not help in that cold of climate. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 15 Feb 2009 01:08 PM |
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Fountains actually make a pond freeze faster. They are good when cooling by helping to keep the pond temps cooler. |
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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 |
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Bergy
Basic Member
Posts:277
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| 15 Feb 2009 04:55 PM |
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I would not recommend burring the loops beneath the pond. Water in contact with the entire surface area of the loops pipe makes for high rates of heat transfer. As far as the pond freezing... The surface freezing over is no problem. You need to make sure it doesn't freeze solid from top to bottom.
A single 6 ton unit for an 82,000 Btu load? Our 6 ton unit running with 30* EWT, 18 GM, 2350 CFM and 70* EAT will produce 58,000 Btu's of total Heating capacity (HC). At 40* EWT 67,000 Btu's HC will be produced. What will you do if the Heat Pumps compressor goes out in the middle of winter? Unless the fireplaces are sealed units, they will push more Btu's up the flue than into the room.
I assume that the heating loads, in Idaho, are about twice the cooling loads. I would design a system to provide 93% to 98% the the required Btu's, backed up by some electric resistance.
Bergy
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IdahoGEO
New Member
Posts:17
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| 15 Feb 2009 06:15 PM |
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Bergy, not quite sure I understand your comment about high heat transfer rates on a saturated loopfield? The soil out there is beautiful silt / clay mix. I'm thinking a lot of moisture (leakage from the pond above) would be great for us? Plz expand.
I understand your comments about the load. Seems a little crazy because of the size of the home. But, I've oversized my last two closed loop jobs. A 4,200 sqft home that I had a calc for 69,000 BTU/hr. We put a six ton system with 3 zones (homeowners really wanted three zones). The loop is running at 44 degrees right now, and the system only stays on anywhere from 12 - 15 minutes at a time (first stage). The other one was a load calc at 31,000 BTU/hr and I put a 4 ton on it because of the HC at 30 EWT. That home is 8" SIPS - guy turned his a/c on 3 times last summer.
So the owner of this job is hugely into conservation (solar & wind). Conditioned attic, 100% closed cell insulation. Wants to try and be off grid in years to come. Someone will always be at home during the day, and he loves to burn wood. What's a guy to do? I don't want to add a second system (15 more amps). |
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Palace Geothermal
Veteran Member
Posts:1609
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| 15 Feb 2009 06:21 PM |
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If your goal is to have warmer EWT's then being buried below the pond will help. If you want to save on pipe and and will accept lower EWT's then in the water is the place to be. |
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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 |
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joe.ami
Veteran Member
Posts:4377
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| 15 Feb 2009 07:32 PM |
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Deeper you go the more stable (higher winter) temps. Water will transfer (what heat there is) more quickly. Depth and surrounding conditions matter, as does foot print. All trades, if you use the same size loop deeper in the pond or under it then you will get higher winter EWTs, just as surely as deeper in ground without a pond around.
j |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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engineer
Veteran Member
Posts:2749
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| 15 Feb 2009 08:12 PM |
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Is there any danger of damage to pond loop piping if the water immediately around the piping freezes? |
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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>
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Palace Geothermal
Veteran Member
Posts:1609
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| 15 Feb 2009 08:14 PM |
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I don't think so. The pipe is flexible enough as to withstand the pressure of freezing. Even if water freezes inside of the pipe, the pipe will not be damaged. |
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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 |
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engineer
Veteran Member
Posts:2749
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| 15 Feb 2009 09:40 PM |
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I was thinking more along the lines of part of the pipe being in ice, part not, and the tendency of sheets of ice on ponds and lakes to shift, buckle and move owing to wind, temperature changes, and water level changes. |
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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>
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joe.ami
Veteran Member
Posts:4377
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| 16 Feb 2009 10:08 AM |
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It is certainly important to have a big enough deep enough pond so that removal of btu's doesn't turn the whole thing into a block of ice or even adversly impact the fish you paid for to stock the thing :)
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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