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updating our system?
Last Post 17 Mar 2009 02:34 PM by Brock. 12 Replies. |
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Brock
Advanced Member
Posts:599
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| 12 Mar 2009 10:01 AM |
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I am again thinking what we are going to do with our cooling situation this summer. Right now this is the way it is setup.
There are really three problems. First the heat pump is controlled by the pool calling for heat. So the only way I get cooling in the house if by heating the pool. So controlling the house temperature is basically manual. Secondly, along those same lines, I can “mix” or open the field and furnace coil to reduce house cooling in the spring and fall or close the field off in summer, but again it is still controlled by the pool calling for heat. And lastly and probably the biggest problem is needing more cooling that the pool needs heating. I didn’t think it would be as much of an issue as it was last summer. I would guess we needed twice the cooling as the pool needed heating. My solution last summer was heating an outside 1000 gallon pool and let that radiate the extra heat, which worked but again not convenient in any way.
In winter I am circulating pool water through radiant heating to supplement the natural gas furnace. Typically I can keep the house warm enough this way to about 10-15F outside temps, below that and the furnace starts to cycle.
So here is my solution to our dilemma, I am not sure if this is a good idea, crazy or just plain bad. I am also not sure how the controls will work since there will basically be “if x than y” heating cooling calls happening.
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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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geo fan
Basic Member
Posts:408
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| 12 Mar 2009 03:57 PM |
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I like it . |
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zircote
New Member
Posts:41
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| 13 Mar 2009 05:32 PM |
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Brock
For cooling the house now you are using the field water into a coil in the air handler?
House demand for cooling, the new scheme you would like to use the GSHP to produce chilled water into the coil on the air handler?
House demand for cooling and pool demand for heating the new scheme the air handler is using field water?
House demand for heating and pool demand for heating the new scheme hot water supplied to both pool and air handler?
Did I get that right? |
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Brock
Advanced Member
Posts:599
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| 15 Mar 2009 08:32 PM |
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For cooling the house now you are using the field water into a coil in the air handler.
Yes during the day when we are on peak ($.22 / kwh) I do circulate the field water through the furnace coil. This works well in the spring when the field is still cold, but as summer wears on the field warms up. Last summer we were in the upper 50's than the low 60’s through July and August, but we still got a tiny bit of daytime cooling.
House demand for cooling, the new scheme you would like to use the GSHP to produce chilled water into the coil on the air handler?
Exactly, this would likely warm the field up so I couldn't do any on peak or day cooling using the field, but running out of any cooling because the pool is up to temperature, seems worse to me.
House demand for cooling and pool demand for heating the new scheme the air handler is using field water?
Yes, in the evening when we switch to off peak rates ($.07/kwh), I close the field line, then the pool starts calling for heat and all of the cooling side of the heat pump is dumped in to the air handler coil. That is really a win / win since we need to cool the house and heat the pool. This works well from mid May-June and Sept-Oct. The problem is in late July and August I need more cooling than the pool needs heating. It is a manual valve switch when we hit the off peak times right now. It’s not a huge deal if I missed this switch because about half the cooling goes to the coil and half to the field, then the next day we would just get that cooling back out of the coil. The down side of that is much less dehumidification since the coil would be running about 50F vs. 40F without the field in parallel.
House demand for heating and pool demand for heating the new scheme hot water supplied to both pool and air handler?
Yes again, right now I can't get any air handler heating via the geo thermal; this would add that option. The catch is I could likely cool the ground more than I am now since I could get more heat out of the system this way. I do circulate pool water though the in floor radiant, which in essence does this. This also give us the ability to pull heat during the high electricity cost times from the pool and heat the pool back up with cheap electricity, basically using the pool as a 16,000 gallon heat storage tank. |
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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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zircote
New Member
Posts:41
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| 16 Mar 2009 01:01 PM |
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Brock,
The next question would be what you would like the sequence of operation for each season would be.
A few other details would be handy:
1. Currently what is your total heating system for the house and the load
2. Currently what is the total cooling system for the house and the load
3. Is the pool indoors or out, how tightly does the temp need to be controlled
4. Does the pool require the whole 4 tons of the Geo system
5. What time of day do your rates for electric change?
John
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Brock
Advanced Member
Posts:599
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| 16 Mar 2009 09:05 PM |
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Currently what is your total heating system for the house and the load
Mostly we use in floor radiant from the pool, with the natural gas furnace (90,000 BTU) as a "back up". I don't know what the load calcs were, I saw them, but at the time they didn't mean anything to me at the time. We can keep the house at 73F when it's 15F outside using about 8 hours of runtime on the 4 ton geothermal unit or about 30 tons a day. The pool uses about 7 hours of runtime to maintain its temp or about 25 tons a day. The problem is I am assuming this at 4 tons, but I know with an EWT of 34 the rating is reduced, but not sure by how much.
Currently what is the total cooling system for the house and the load
The only cooling we have is from the geothermal system when we heat the pool. Again, 8 hours a day in the hottest part of summer isn't enough. If I can dump heat to our garage floor via radiant or an outside pool in the hottest part of summer running the full 14 hours off peak is enough cooling for the house.
Is the pool indoors or out, how tightly does the temp need to be controlled
The pool is in the basement, indoors. The pool room is negative pressure from the house via an HRV. Basically the HRV pulls from the pool room dumps outside, and then the HRV dumps the fresh air back in the house. There are 2 vents between the house and pool room to allow the air to leak back in to the pool room. The ceiling of the pool room has 16 inchs of blown in (not sure what) and the walls are 6 inches of batt.
The pool can vary about two degrees total and this system also heat the hot tub. The pool is 16,000 gallons in size with a 750 gallon hot tub. Both the pool and hot tub have 2 inch pink foam outside their shells from the underside.
Does the pool require the whole 4 tons of the Geo system
Nope, 8 hours to heat the hot tub up to 100F once a day and keep the pool at 90F. If I don't heat up the hot tub, I can get that down to 6.5 hours of heating needed. In summer we regularly heated up the hot tub two or three times a day to get more house cooling.
What time of day do your rates for electric change?
In winter we have cheap rates from noon to 4 pm and then again from 9 pm to 8 am. In summer we have cheap rates from 7 pm to 9 am. |
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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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engineer
Veteran Member
Posts:2749
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| 16 Mar 2009 10:23 PM |
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Could you run some of the pool water through an outdoor fountain / pond to dissipate heat both sensibly and via evaporation?
Stated another way, add a wet cooling tower that comes on only when cooling load is high and pool becomes too warm.
This might drive up pool chemical consumption.
Another option might be a dry cooler operated at night (this is essentially similar to an automotive radiator with pool water in it and cool night air blown across its fins)
In other words, continue using pool as heat sink but find a way to dissipate extra heat from it during summer peak cooling. |
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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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Brock
Advanced Member
Posts:599
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| 17 Mar 2009 12:58 AM |
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:) That is exactly what we did last summer. We ran two 1.5 inch lines out to a 500 gallon kids pool and heated it up. In the hottest part of the summer I left the pool open all night with a small fountain running in it. This did / does work, but not automated in any way. I had to run the lines out an open window and manually switch a bunch of valves over. Don't get me wrong it was great to sit in the pool at night at look up at the stars, but just not convenient.
I did think about the idea of dumping the heat from the pool through an old car radiator at night as well. Also last summer I did have two of the four 250 foot radiant lines to the garage floor connected up and dumped heat in to that, now I have all four connected and a better pump situation and I could likely dump more heat that way as well.
Overall efficiency wise wouldn't I be better off cooling the house with 60F or 70F ground water than trying using the 90F pool water and dumping that excess heat somewhere else?
And control wise, I could just set my thermostat and forget it, not looking ahead to see it was going to be sunny and warm so I better run a night or two with heat dumping to the kiddie pool. Not to say I don't want the other options or ideas, I do. |
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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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zircote
New Member
Posts:41
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| 17 Mar 2009 09:21 AM |
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Brock,
Sorry for all of the questions, but a couple more I hope you will indulge me with.
Is the pool water isolated from the Heat Pump by a heat exchanger?
Is the house radiant isolated from the pool water?
How many loops in the field? How is your loop field connected to the heat pump? Are the loops connected to a header and flow center?
As for the efficiency of cooling the pool water with some external method, to later turn around and demand the Heat Pump to reheat the pool in order to cool down the field to cool the house is counter productive.
It may work more efficiently in the summer to demand the same amount of heat from a smaller source. Your LT will go down and provide the cooling you need.
Your set up is very interesting with all of the different demands on the system.
Complete automation could be done but it may be beyond your Pain($$$) thresh hold. But a good deal of it could be done with out to much trouble. |
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Brock
Advanced Member
Posts:599
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| 17 Mar 2009 11:20 AM |
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John the questions are great, it forces me to step back and re-examine the system as a whole.
Is the pool water isolated from the Heat Pump by a heat exchanger?
Yes, it actually has two 150,000 BTU exchangers in series between the heat pump and pool water.
Is the house radiant isolated from the pool water?
Nope, I have two 2 inch lines running from the pool in two locations in to the utility room. Then from one line I pull the water and through a pump, which is then split to the two major zones. Each major zone dumps back in the second pool line. The pool is kept at about 90F
How many loops in the field? How is your loop field connected to the heat pump? Are the loops connected to a header and flow center?
I don't know, I only know it is a 4 ton field. There are just two 1.5 or 2 inch lines running down under the house and I believe they going to a point about 15 feet from the basement and then split up. Unfortunately they ran that all in one day and of course we were out of the state when it happened.
As for the efficiency of cooling the pool water with some external method, to later turn around and demand the Heat Pump to reheat the pool in order to cool down the field to cool the house is counterproductive.
My thoughts exactly.
It may work more efficiently in the summer to demand the same amount of heat from a smaller source. Your LT will go down and provide the cooling you need.
What would the smaller source be? Do you mean using the ground as the heat dump?
Your set up is very interesting with all of the different demands on the system. Complete automation could be done but it may be beyond your Pain($$$) thresh hold. But a good deal of it could be done with out too much trouble.
My biggest hurdle is getting around the control side and the fact a cooling call from the T-Stat becomes a heating call if the pool is calling for heat, which also reverses some valve calls.
I think the simplest thing would be to just add another heat pump (maybe 1.5 ton) that only gets its call from the t-stat and keep the two systems separate (sharing the field), but that would be a minimum of $8k. If I can figure out the control side it should just be the cost of the valves. |
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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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zircote
New Member
Posts:41
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| 17 Mar 2009 12:05 PM |
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Brock,
My first thought for spring, summer and fall house cooling,ie; squeeze the same amount of pool heat from a smaller source, would be to modulate the entering water supply to the heat pump.
The field, from your posts, seem to be able to easily support the heat demand of the pool. By reducing the flow or using less of the field at any one time to generate the heat will lower the leaving water temp which is being used to cool the house. The entering water temp could control the volume of flow or section of the field being used to maintain a fixed LWT.
I will get back to you on the other, gotta go.
John |
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zircote
New Member
Posts:41
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| 17 Mar 2009 02:19 PM |
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Brock,
Forgot to ask what temp water is the heat pump producing?
I missed a key point that you made earlier on the valve set up currently.
I may be confused but presently for cooling you disconnect the field all together?
To start with a simple reconnection of the air handler,
Using the field connections to the heat pump in and out and the field in and out,
Field out to the heat pump in, heat pump out to the air handler in,
air handler out to the field out.
This should lower the returning water temp. Most of the heat extraction is coming across the air handler coil and the field would lower the temp a few more degrees.
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Brock
Advanced Member
Posts:599
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| 17 Mar 2009 02:34 PM |
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Ok, I think I get what you’re saying about the flow rate or using only “part” of the field, but in the end 4 tons of cooling is 4 tons of cooling, right?
I do see this with the coil right now. When cooling the house and heating the pool if I have the fan set to speed two I see coil temps of 35F in and low 40's out (EWT to geo). If I run the fan in speed three I see 40F entering the coil and upper 50's out. I run up to speed four I see about 50 entering the coil and mid 60's out. I think that is the point I get the most cooling for the house and heating for the pool as well, but I don't get the dehumidification, speed two does that the best, speed three seems to be a good compromise.
The output of the geo unit is typically 10-12F above whatever the water temp is. So heating the pool at 90F I am running about 101F, but heating the hot tub up to 102F I see about 115F or so. Initially we had a single heat exchanger and while heating the hot tub we were approaching 130F. Flow on the pool side of the heat exchanger is about 30 gpm, so that wasn't the problem; I think it was just surface area, adding a second heat exchanger helped out 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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