Is it worth it in central FL
Last Post 20 Feb 2009 09:19 AM by joe.ami. 44 Replies.
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bmancanflyUser is Offline
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05 Feb 2009 04:20 PM
I just bought a house in central FL.  It needs a new HVAC unit.  I will be completely renovating the house myself - as I've done with others before.  I was considering a geo unit.  But almost all the available info deals primarily with heat vs a/c.  We use both heat and air here but primarily air.  I'm a very accomplished DIYer and found this site http://geothermaldiy.com/index.html.

I feel that I can do it myself but don't know if the additional cost (probably $4-$5,000) over a conventional air to air heat pump is justified in central FL.

BTW my city tap water which enters the house from about 4-5 ft underground is consistently 70 degrees.


geo fanUser is Offline
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05 Feb 2009 04:37 PM
If you can get it done for 5k more the federal rebate ( if it passes ) will likely pay a good chunk of that difference
a desuperheater and a super eff ac will make very short work of the balance of the investment
best of luck


engineerUser is Offline
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05 Feb 2009 04:49 PM
Your deep earth temperature is probably 72-73 degrees. I'm near Jax, mine is 71.

Done right, geo can work for AC. To start, run the numbers, starting with Manual J building load. Know that air source system SEERs are rated at a benign 82 outdoor and 80 indoor temps.

This paper digs into real world performance vs SEER and HSPF ratings. Geo systems are rated using EER and COP, more straightforward ratings.

http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-413-04/

Key will be to ensure water loop temps are better than (cooler in summer, warmer in winter) air source equipment ambient temps.



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>
bmancanflyUser is Offline
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05 Feb 2009 07:56 PM
Thanks for the feedback.

The supplier recommended four 125 ft trenches, 6ft deep and 3 ft wide, containing 750 ft of 3/4" pipe (per trench) slincky style for this 1700 sq ft well insulated house. Does that sound about right for a 3 ton unit in FL. Six ft deep seems a little much for this far south.


AltonUser is Offline
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05 Feb 2009 08:33 PM
If you plan to do the HVAC work yourself, you might want to check with the local code official.  In my area, only a licensed installer can pull the permit.


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engineerUser is Offline
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05 Feb 2009 09:54 PM
Deep is good. We're not worried about frost depth in Florida but instead trying for lowest EWTs during long hot summer.

I'd want to see a Manual J whole house load before signing off on 3 tons for 1700 SF, especially if house is tight. I highly recommend 2 stage unit to combat high humidity.


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>
joe.amiUser is Offline
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06 Feb 2009 07:42 AM
Thats a lot of loop, but I don't know the area.
J


Joe Hardin
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bmancanflyUser is Offline
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06 Feb 2009 08:16 AM
Does 3 tons sound to big?

I thought the loop seemed bigger than I was expecting. But I don't want to under size it either.


joe.amiUser is Offline
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06 Feb 2009 08:25 AM
Need loss/gain numbers to comment on unit size.
J


Joe Hardin
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trigby13User is Offline
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06 Feb 2009 02:09 PM
I am a GC in California getting ready to build a home for a client in Micanopy, Florida. I am trying to find a sub contractor to talk to about a geothermal unit for this new home. Trying to learn about it as well as get a quote. Does anyone know of any good people to do this in the area? This is 15-20 miles south of Gainesville.


engineerUser is Offline
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06 Feb 2009 07:53 PM
I'm an hour from Gainesville and could definitely hook you up with a competent installer via the WaterFurnace distributor in Daytona. I'm an engineer easing into this field owing to a lack of competent contractors in the Jacksonville area. I want this to take root down here and the only way for that to happen is to design and deploy systems that provide a clear efficiency and comfort advantage over air source.

I could provide as little or as much assistance as you deem necessary - if nothing else help head off foulups. PM me or email waterleo at comcast dot net.

Joe - absent open loop, I'm learning we need a bunch of ground loop to keep EWTs reasonable all summer. I've seen 7 275' bores put 100+ degree water into a 6 ton unit - not good, to say the least.



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>
joe.amiUser is Offline
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06 Feb 2009 11:48 PM
ok curt, just off the cuff, around here verts run 1/2 the length of our slinkies, so if thats true there, his 4 times 750 for a 3 ton would be close to your 7 times 550 for a 6 ton. don't know that it's apples to apples, but it jives with the numbers here.
your thoughts?
j


Joe Hardin
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engineerUser is Offline
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07 Feb 2009 06:06 AM
That makes sense. Lots of sandy soil here and occasional droughts during summer. Dry sand conducts heat poorly. The poorly performing 7 bore system became a little better with addition of a second pump. I still harbor suspicion of poor distribution among bores but that part is buried without pics and landscaped.


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>
bmancanflyUser is Offline
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07 Feb 2009 07:41 AM
Interestingly, i spoke with a guy at Eaglemountain Geothermal yesterday and he seemed emphatic that the 4 x 750 slinkies would be far more than was necessary here. He said he recommended two 3 ft wide trenches 130 ft long with slinkies, probably 900 ft of 3/4" pipe in each trench.

BTW I live very close to a lake, so the soil here is very wet. Actually, if I go down 6 ft the trenches may fill with water. Unfortunately, I don't have access to the lake so I can't put the pipe in the lake.

I do have a pool. Can the pool be used to cool the water before entering the slinky in the trenches?


joe.amiUser is Offline
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07 Feb 2009 08:07 AM
Damp soil does move heat much better. So which guy you gonna believe? Maybe a third opinion to break the tie? The heat the pool cool the house concept is not new, but you will need an efficient heat exchanger, a unit with on demand hot water (not getting great reviews here), or you could use the DSH.
Re distribution, Engineer, I spoke with a guy here who has done a lot of repairs and his mantra is there is no issue with disparite sized loops (or the path of least resistance is in flux). It makes sense if you think about it, as long as no air is present, forced water will move through paralell circuits evenly regardless of length. As hot water boiler guys, we've known this for years, but put on a geo hat and we forget.
It souds like you may still be a little short looped if you get to the 100* mark again, The same guy I mentioned above has done add a loops after the fact as well as mixed horiz. and vertical in his repair work.
Joe


Joe Hardin
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engineerUser is Offline
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07 Feb 2009 01:10 PM
Pool trick could work - if we ever put in a pool I'll rig something to heat it off the geo during cooling season.I can think of 3 caveats:

1) Need a way to bypass heating the pool or it could become too hot in late summer

2) Chlorinated pool water is corrosive - many heat pump pool heaters have titanium heat exchangers

3) I'm having such a good experience with DSH - provides nearly all my domestic hot water use during summer that I'd hesitate to give it up to the pool.

I don't know enough about horizontal to be able to say whether 4 x 750 will work for 3 ton, although it matches the local distributor's rule of thumb - 1000' / ton. That the soil is wet or saturated is even better.

My earlier question was directed toward being certain that 1700 SF required 3 tons - I'd want to see the Man J to see if 2.5 might suffice. Oversizing is a definite no-no down here in the swamp.

I'm having trouble wrapping my mind around the idea that flow will equalize among loops with differing total equivalent length. My concern with the 7 bore house is that 1 or more loops might be at a flow rate low enough so as to lack turbulence. That's theory only - no idea if it is a real problem.




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>
geo fanUser is Offline
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07 Feb 2009 01:27 PM
If it is piped first supply last return ( order on the header ) flows should be equal or very close


Palace GeothermalUser is Offline
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07 Feb 2009 01:37 PM
Posted By engineer on 02/07/2009 1:10 PM

I'm having trouble wrapping my mind around the idea that flow will equalize among loops with differing total equivalent length. My concern with the 7 bore house is that 1 or more loops might be at a flow rate low enough so as to lack turbulence. That's theory only - no idea if it is a real problem.


All of the design classes I have attended stated that loops lengths can vary up to 10% without any serious impact on flow.


If dividing the flow into 7 paths drops the RE # is another issue all together.


A 7 loop system tied into a reverse return header will have equal flow through all loops.  Some will not flow more than others.


engineer,  do you have the WF Excel program that calculates PD and RE ?



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
bmancanflyUser is Offline
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07 Feb 2009 01:43 PM
First of all,  thanks so much for all the comments. I've learned a great deal from this website.

I wanted to get a general sense of what a system should look like in my situation, before getting too involved. The 1000' per ton helps. I really am not that interested in heating the pool but thought I could use the pool to dissipate some of the heat generated by the system in the cooling mode. I'm actually thinking of filling the pool in (at least partially) and using it as a koi pond. That's what got me thinking of geo in the first place. Since I already have a huge hole in my yard that needs to be filled.............

Engineer, I agree with you on the potential for a 2.5 ton unit. I've got new low E windows a very well insulated attic and the property is very shaded.  My experience here in FL is that A/C guys try to sell you an oversized unit (or they don't know how to size them properly) and you end up with a house that feels like a meat locker.  Very cold, but high humidity.

One last question. Could I dig a trench say 5-7 ft deep, lay a row of slinky, back fill say 2 ft, and lay another row on top of the first in the same trench. Thereby doubling the feet of pipe in that trench.




engineerUser is Offline
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07 Feb 2009 02:05 PM
I know that's done with straight pipe, not sure about slinkys. Too much pipe in a given trench has a diminishing return.

You nailed the humidity issue. The 026 models, approx 2.5 ton, are the smallest available with 2 stage compressors, which I highly recommend down here.


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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