Brock
Advanced Member
Posts:599
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| 23 Apr 2008 01:28 PM |
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Ok, I am new to geothermal and this forum (great by the way).
We are about to move in to our new home and it has a 4 ton field with a geocomfort GWSR048 unit. We have an indoor pool, 16,000 gallons and primarily that is why we went with geothermal. The rest of the home is 2200 sq ft with the nothing but the pool and mechanical and a bathroom in the walkout basement, we are crazy water people. So they started the system up last week and I am beginning to understand what this all is and does and how it works but have a couple of questions. We are running Time of Use so we only run the geothermal unit off peak when electricity is $.0566/kw.
When we first started it all up about a week ago mid 30’s at night and mid 50’s during the day mostly. We are in Green Bay, WI.
field out 35F
return 40F
geo out 100F
geo return 90F
pool in 55
pool out 57 (at 25 gpm)
So seat of the pants BTU's looks to be about 30,000
Now a week later
field out 30F (or below, pipes covered in ice)
field return 36F
geo out 110F
geo return 102F
pool in 76
pool out 78F
The heat gain has slowed to about 1 degree every 6 hours and the rest of the house is heated to 60F right now (still under construction), so we are warming up the whole basement floor along with the pool shell. The pool is covered to avoid that heat loss. Again seat of the pants puts this at 22,500 BTU. Does this seem normal?
My two concerns are the heat exchanger between the geo unit and the pool seems small and the delta T seems high. My second concerns is the size of the field big enough for this load? |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Apr 2008 07:32 PM |
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Brock,
I am not sure how you composed your post, but it unreadable for the most part. Can you repost and make it readable? |
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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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Brock
Advanced Member
Posts:599
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| 23 Apr 2008 07:45 PM |
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Woops, Did that fix it? |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Apr 2008 07:54 PM |
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Seat of the pants here, but I don't think that a 4 ton unit is big enough to heat your house and pool.
How hot are you trying to make the pool?
You have extracted a lot of heat from your ground loop. You have about reached the end. What degree of freeze protection do you have in the ground loop? |
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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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Brock
Advanced Member
Posts:599
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| 23 Apr 2008 08:28 PM |
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Oh, sorry the geo unit is only to heat the pool (de-super-heater for a pre hot water tank), not the house heat. The odd thing we did was connect a parallel line from the geo field to a coil in the furnace, so in summer we can heat the pool and cool the house. This is how it all started, in our last home I use a water to air heat exchanger (a marine A/C unit) to heat the pool and cool the house and it was only 1 ton which kept the pool up to temp but wouldn’t increase the temp, just maintained it.
I figured the field is cooling down because we are trying to heat up so much water and the surrounding ground and basement. The pool shell is lined with 2 inch of high density foam and the foundation also has 2 inches of foam as well. I am hoping once the pool is up to temp and just trying to maintain the temperature it would be fine. I have no idea if 36 is really cold or if I should not worry about it since it is just the initial heating.
My biggest reason for asking is because they are going to do the final grading and if we are going to expand the field we have to do it soon. Our HVAC guys says we are in range but I ahve no idea if that is right or not for our climate. |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Apr 2008 08:53 PM |
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OK that makes more sense.
How hot are you trying to heat the pool?
What degree of freeze protection do you have in the ground loop?
If the pool is almost up to temp and you are freeze protected to 20°F then you might be OK |
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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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Brock
Advanced Member
Posts:599
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| 23 Apr 2008 09:09 PM |
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The 16,000 gallon pool will be kept at 90F and the 1000 gallon hot tub will be kept at 100F. The switching is all set on the pool side and works fine. The heat pump can bring the hot tub up to temp pretty quickly.
I was told we had freeze protection to 8F. At what point am I running comparable to a resistance heater? Is it based on the field return temp or ? My HVAC guy said we were still saving energy to 20F, so am I to assume that’s when the COP hits 1?
Thanks, I am learning a lot! |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Apr 2008 11:57 PM |
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At 20° incoming from the loop your COP should still be about 2. Most heat pumps shut down at that point.
I don't think you have resistance heat on your heat pump. Usually only forced air units have resistance heat. Unless you have an electric water heater some place in your system.
You might try turning the system off for a few days to give the ground loop time to recover. You are pulling heat out of the loop faster than the ground right around the pipes can transfer. By giving it a rest, the temp should come back up a few degrees.
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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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Eric D
Basic Member
Posts:104
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| 24 Apr 2008 06:49 AM |
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When was the ground loop installed? The ground loop might not be up to full transfer capacity. Was the loop washed in or just trenched, placed and backfilled? Depending on installation process it might take sometime before the loop heat transfers at its best. If possible you might want to soak the earth above the loop areas to see if this helps along with Dewayne's suggestion of giving the field a rest. Keep time of how long the rest is and the loop temps after word. The numbers will be useful for keeping track of loop efficiency for comparison in the future.
Regards, |
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| Eric D<br>Southern Michigan |
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Brock
Advanced Member
Posts:599
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| 24 Apr 2008 10:27 AM |
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Unfortunately we were out of town when they buried the loop last fall. I do know it was 10 feet deep and 8 or 10 feet wide and 250 feet long. The ground above the loop is sinking, understandably. I like the idea of soaking the field. The return temp is slowly rising, on Monday morning after running 60 hours straight the return was at 36.1 and this morning it was at 38.0 so it looks like it is rebounding while only running 13 hours a day instead of 60 straight.
You’re correct, there isn't any electric resistance backup to heat the pool, I was considering adding an electric 12kw inline heater, but if the geo's COP is still around 2 even at 20F I will just let it run, much more efficient. |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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fsq4cw
New Member
Posts:64
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| 25 Apr 2008 10:18 PM |
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“I was told we had freeze protection to 8F.”
If this is so, you have too much freeze protection and too much is not better. Your solution may be too viscous and require more pumping power than otherwise necessary.
SR
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Brock
Advanced Member
Posts:599
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| 25 Apr 2008 10:27 PM |
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He did a "PT" test, I am assuming that is pressure and temperature? He said we had 10 gallons per minute on both the hot and cold side, not sure what it is suppose to be.
So are the mid 30's on the field return normal temps for upper mid west this time of year? |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 25 Apr 2008 11:26 PM |
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Normally you want 3 GPM per ton, so you should have 12 GPM.
My loop is coming in at 42°, but then I not trying to bring 16,000 gallons of water from 55° to 90°. Do you realize that 4,665,000 btus are needed to get your pool up to temp.
You might already know this, but a ground loop and a heat pump is not like a gas line and a boiler which will give you infinite heat as long as you pay the bill. The ground gives up heat rather slowly. If you exceed the rate at which heat moves through the ground, then your loop temp will drop and eventually, you will have to stop and let the loop recover.
You situation is not normal so you can't compare what your loop is doing to what other loops are doing. Once your pool is heated and all you have to do is maintain the temp, then your loop will start acting more like a normal loop.
Good luck and keep us posted. |
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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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Brock
Advanced Member
Posts:599
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| 26 Apr 2008 11:07 AM |
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Yes I realize its probably over 5 million BTU's including the hot tub and the surrounding concrete. What I didn't realize heat pumps weren't meant to be run flat out. I had assumed that if I had a 5-ton field and a 4-ton heat pump the field should be able to keep up. So what happens to people who heat in winter and in January need to run 24x7 to keep their houses warm? I understand for home heating some are designed to add electrical backup heat but do their fields freeze up running steady, do they typically drop in to the 20’s? Are fields typically sized to handle say 50% run time?
I totally agree that once the pool is up to temp I think I will see the field rebound (especially in summer), I am just trying to understand how much extra heat I could pull in winter. If I end up needing 6 hours of run time a day to maintain the pool/hot tub I had hoped I could "steel" some of that heat for in floor radiant heating so the furnace would run less. If I can't, I can't, but it would be great if I could. Since right now the unit is running any time we are off peak (cheap electricity) I had hoped I could continue to do that and steel that extra heat for what ever. So while heating up the pool is indeed unusual is this telling me I shouldn’t run 13 hours a day every day and try to take advantage of that extra heat during winter?
I guess what I really want to know is it a problem to normally have the field return running in the mid 30’s or even the mid 20’s or should I back off on my loads to keep the field in the low 40’s? Will this really hurt anything beside efficiency (still cheaper then natural gas)?
Can you tell I am a newbie to this? |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 26 Apr 2008 10:01 PM |
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My only source of heat for my house is my heat pump. My loop temp didn't drop below 40° all winter. Even on the coldest night my heat pump never runs over 50% of the time. When properly designed and sized, everything works just fine.
Sounds like maybe you better increase you loop field while you still can.
The only downside to a cold loop is less efficiency. Remember that your heat pump will shut off when the loop temp gets down to 20 maybe 25.
How many feet of pipe do you have in your ground loop? Is it 2 pipe trench, 4 pipe, or slinky? What type of soil do you have? |
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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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Brock
Advanced Member
Posts:599
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| 26 Apr 2008 10:39 PM |
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Ok, I think I get it now. I guess I will just watch it and see what happens in the next week or so before we do the final grade. Our HVAC guys is satisfied with the field temps given we are running as much as we are. The pool should get up to temperature early this week, but after that it will only have to maintain the temperature. I guess I know if it ran this steady and it didn't drop below 36.1F (so far) I am in pretty good shape because I likely wouldn't run it this much even if I were doing extra heating with it.
I am not sure what is in the trench if it's 2 or 4 or slinky. I sort of got the impression there were 4 pipes 2 feet apart, but I am guessing. I will have to ask.
The one concern he and I share is when switched to the hot tub the output is up about 125F and returning about 118F, with the pool water entering at 100F and leaving at 102F. So we are planning on adding a second heat exchanger to get those temps lower on the geo side. He was more concerned about the unit shutting down due to high temps and I would like a bit more efficiency, well and for it not to shut down.
Thanks again, I am learning a lot! |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Brock
Advanced Member
Posts:599
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| 05 May 2008 08:55 PM |
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With a week of running with the pool & hot tub up to temp and cycling normally and we are sitting about 39.0 as a low on the field return thermostat. When it is running I typically see right about 40.0 now, once in a while as high as 41. I now understand what you mean about the ground recovering, I had thought if I cooled it down it like I did, the ground would stay cold much longer (a couple of weeks), but it has been slowly rising in just a couple of days. I was worried for nothing.
Thanks! |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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GeoTemp Services LLC
New Member
Posts:24
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| 08 May 2008 10:40 PM |
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This should be broken up with a separate geo system to accommodate pool demand alone. I would also seem to say this system is also undersized for such demand. 48,000 seems ok for house alone although i have no data on the living space. Find it hard to believe Geo Comfort would agree with this set up. Im a geo Comfort installation company and this is something the uper brass would not allow this. |
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Brock
Advanced Member
Posts:599
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| 08 May 2008 11:50 PM |
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You are correct, our system was designed to only handle the pool and hot tub. Even then I believe they oversized it. From our experience with our last indoor pool we used about 2 hours of run time on a 200,000 natural gas boiler with 75% efficiency or 300,000 BTU a day. This of course was lower then any load calculation they could come up with for pools so they went with a 4 ton unit. We have a 90,000 BTU forced air natural gas, but again I am going to try to use as much heat as I can from the geo unit without dropping the field to cold in winter, way cheaper then natural gas since we have electricity at $.05/kw off peak.
When the pool was installed I had them run to extra lines to the utility area in the basement so I could pull water out of the pool and return it to another location. So last weekend I took a small circulation pump sucked out some 90F water and ran it though one of the in floor tube and sure enough it took the cement slab from 58F to 74F over the weekend. The heat pump for the pool still ran less the 25%. It also took the entire house from 60F to 66F. Granted it was 40F at night and 60F during the day, but it actually worked. My big advantage is I can use the pool as a huge heat sink and heat it with cheap off peak electricity via the geo unit but draw heat from it anytime. If we were to loose grid power I should have heat for quite a while drawing heat from the pool and I have enough solar and battery capacity to run circulation pumps, fridge, freezer and some lights.
If I am correct and I need just 1 ton to maintain the pool and I can use 1 or 2 tons of heat to warm the floor and in turn heat the house. I will let the natural gas do the rest I will be happy and pay much less to our local utility. |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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Palace Geothermal
Veteran Member
Posts:1609
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| 09 May 2008 10:03 AM |
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Brock,
Glad you are feeling better about your system. You seemed in panic mode on your first post. It sounds like you have a great set up now. |
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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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