I have been thinking about replacing my older air source heat pumps with ground source units.
Even with the current Federal Tax credit the ground source investment would be quite a bit
higher than a high efficiency air source installation.  Despite the attraction of being "green"
my realtor as well as my investment adviser both think the additional cost will not show up
as an increased home value.  Still I am determined to follow this route and wish to make as
few mistakes as possible.  I solicit from this forum any details that I should include in this
endeavor.

I will post specifics of my home, existing systems, local kwh rates, energy audits, et. al.  as
requested by any member.  At this point I would only be guessing at what info is important
to any given responder.

I am located in Florida, Tampa area, zip 34683, about 1 mile from the Gulf of Mexico.
The last 2 weeks have demonstrated that heating can't be ignored even in Florida,
but the main power use is cooling.  Just the basics: 3000 sq ft, 1 story home, 18K gal
pool, existing 3 ton and 2 ton air source heat pumps, both more than 25 years old.
I am a retired computer science engineer with a minor in industrial engineering.  Yes,
I've had thermodynamics courses, so I have some basis to understanding how these systems
work and responses from members, but I wouldn't quote any formulas without a reference book. 

The major problem in this area is the lack of contractors with certification and experience
in design, installation and maintenance of a GSHP system.   In the past 6 months I have
done a lot of reading and have had 2 estimates for ASHP replacement and 2 estimates
for GSHP installation.  I am fairly comfortable with one of the GSHP contractors and have
visited 3 of his installations.  

I have some specific questions about the proposed installation but would like to hear first:

What specific features should I be looking for?
What detailed questions should I be asking before, during and after installation?
What helps keep the cost of implementation down while improving system quality?
What tasks are reasonable for the homeowner to do to hold down costs?
How can I optimize my investment?
How applicable to my installation are forum messages for northern climate installations?

I appreciate any and all comments or references to existing forum topics.

Thanks,
Jim

> Despite the attraction of being "green" my Realtor as well as my investment adviser both think the additional cost will not show up as an increased home value.

I would have to agree, granite counter tops, large master bathrooms and scenic views from the windows sell houses, not when type of heating system you have.  95% of buyers couldn't care less how the house is heated or cooled, aside from if the house has central air.  Despite all the federal incentives to get more geothermal systems installed, 90% of people (and buyers) haven't a clue what geothermal heating is. I think when you go to sell your house, 9 out of 10 buyers eyes well glaze over when you tell them the HVAC system is geothermal, very few will know what your talking about and fewer will be willing to pay a premium for your house.   

I know I didn't have a clue what geo was before I purchased a house with one, I only knew that it was an efficient form of heating and cooling. I didn't know what it was, how it worked and how efficient it really is.

I have some specific questions about the proposed installation but would like to hear first:

> What specific features should I be looking for?
Efficiency of the system, standard system 300%, top of the line 500%.
 
> What detailed questions should I be asking before, during and after installation?
Experience of the installer, how many systems they did, long long they have been in business, what brand of equipment they use, warranties, etc. There is a lot of new people in the field now that the federal and state governments are offering favorable incentives, not all of them know what they are doing.  

> What helps keep the cost of implementation down while improving system quality?
Getting a Heat/Loss calculation, this ensures you get the correct size system for your house, not too small not too big.

> What tasks are reasonable for the homeowner to do to hold down costs?
Insulate, Insulate, Insulate, the more you can reduce your heat loss and smaller (and less expensive) the system has to be. 

How can I optimize my investment?
Educate yourself, the more you know the better off you'll be when shopping for a system and contractor.


How applicable to my installation are forum messages for northern climate installations?
Heating is where geothermal really shines, but that doesn't mean that cooling dominated climates can't save as well. The payback period may be a little longer though.

Do you know what type soil you have and how it varies by depth (a local well drilling contractor can probably tell you)
How shady is your lawn?
How big is your lot?
Do existing units keep the house cool?

You have 600 SF/ton - that is probably reasonable for a +25 year old house (many contractors use 500 SF/ton here in FL but studies show using 700 SF/ton will be closer to the manual J calculations or to actual load requirements)

Regarding "green" and  house price.  I think your realtor is wrong.  You flip out some really low energy usage bills and that will increase the value of the house.  It is not going to make them choose your house over another but it should increase the value of your home.  Plus, GSPH are generally very reliable.

I can't speak for that market but it's getting better here as far as Geo is concerned. If the agent is aware of the benefits, it's a bonus that can make or break a sale. Not just the money saved but the fact that there is no howling, ugly condenser sitting by the patio. The first geo system I saw was in Miami Beach, in 1968 and it was installed just because it could be hidden and not detract from the landscaping and outside experience. It was an open loop, pumping brackish water and returning it to bay. Lots of maintenance but it worked well. The house belonged to Agnelli, the owner of Fiat and he had a mistress living there, just in case.

Guess that qualifies as Emergency Heat?


> What specific features should I be looking for?
Also consider a desuperheater (hot water assist).


> What helps keep the cost of implementation down while improving system quality?
Get lots of quotes, even from installers that install equipment from the same manufacturer.  Prices vary, sometimes SIGNIFICANTLY.
Also, check references, qualifications, training from the manufacturer, and check for complaints.
Ask everyone quoting to do a load calculation to check for consistency and errors.  Mistakes can be made.
Ask everyone quoting the same questions.  You'll be surprised how much you can learn in general, and learn about the installers degree of knowledge as well.

> How applicable to my installation are forum messages for northern climate installations?
I continue to learn, just by reading.  Every installation is different.  When you become familiar with your installation, you will be able to better pick out what applies to your system and what doesn't.  You can try looking back at threads from 7 months ago to read more cooling related Q&A.

Ask the installers about one common loop for both units.  This may save some money and may provide some benefits as well.  We have 1 closed horizontal loop that is used for our 3 & 2 ton units.

Unfortunately it is halfway through a cumbersome thread, but shoppers check list answers many of your questions regarding what to ask:
1) Contractors years in business, years in geo and references
2) Manual J load*, summer and winter design temps
3) Size proposed (in tons)/percent of load covered/balance point
4) Is ductwork adequate to support system
5) Warranties
6) Refrigerant
7) Proposed loop system (horiz, vert, multipipe,etc.)
8) 1 or 2 stage
9) Price, rebates and tax credits
10) Brand, Type (water source or DX)

You are correct that payback is a bit more lengthy in cooling dominated climates and I would leave it to your perspective installers to convince you that it is worthwhile.

The green question is subjective and a tad political in my mind, but I would argue that a high efficiency ASHP that cools and heats the place for a little more KWs; is almost as green.

Let us know what you decide.
Joe

Thanks TechGrommit

> What specific features should I be looking for?
Efficiency of the system, standard system 300%, top of the line 500%.
 
Do you mean a COP of 3.0 to 5.0?  What I have had trouble with in comparing
ASHP to GSHP is ASHP ratings in SEER versus GSHP rating in EER.   If SEER is
a "seasonal average" and the season is based on a point in Maryland, I have no
clue what to expect in energy consumption for my season in west central Florida.
EER seems more precise, but then one can not expect the entering water temperature
to stay constant in a closed loop system over my season. 

I have spent a few hours reading threads from this forum (since I posted my topic)
and found positive and negative opinions on using GSHP in Florida

One of the two estimates I got was for an open loop system, but being a native Floridian
I know how much calcium build up can occur from using drinkable water pumped from
the aquifer.  I really don't want that maintenance liability though I know an open loop
system offers more consistent entering water temperatures (at least here when you
are pumping from the aquifer).

The other contractor proposed 1 closed loop for both units using vertical bores.  He also
provided an energy savings calculation.  The problem was he calculated I would save
more than I currently use for heating and cooling.  

My own "guestimate" showed a better return for GSHP, but only when I assumed the
GSHP systems lifetime was double that of an ASHP system (my current ASHP has
operated for  over 25 years with few repairs).

So if I want to decide between ASHP and GSHP based on total costs (initial investment,
maintenance and operating costs) I am at a loss in how to do this precisely for my
location and my climate.

Yes, You are correct, when I say 300 to 500%, I'm really talking about 3.0 to 5.0 COP. Techinally COP is the proper expression.  Unfortanely there no way to convert SEER or EER to COP, no clean way anyway, it's possible to get rough approximation numbers, but they don't convert cleanly.   

Dispite what other people say, I still say Granite countertops sell houses, not how sexy or efficient the HVAC system is.

Operating cost calculation software is very accurate these days.
When I said leave it to the installer to convince you I would presume cost projections to be part of the presentation.
If there is a terrific disparity in expectation- " The problem was he calculated I would save
more than I currently use for heating and cooling." Find out why. Things such as different set points can impact the numbers. My software defaults to Tulsa OK as the weather average, so if I don't select Lansing MI, my heating bill projections are rather optimistic....lol
As far as COPs since that is heating it is less important to you, but most average COP's are low to mid 3's. Peak efficiencies listing by any manufacturer are not reality based numbers.

I think that savings is going to be among the least influincing factor in your decision. I also think that anyone selling any product would be foolish to promise you 25 years out of your next appliance. Part of the longevity of your old equipment is attributable to what I call the '72 Impala factor.....nice no frills 350ci engine that never breaks, course it might guzzle a little extra gas.....therein lies the trade off, no?
Joe

Thanks Alex.

The original house built in 1980 was 2,000 sq ft with the single 3 ton Weathertron HP.
Around 1987 we added 1,000 sq ft and the 2 ton Trane HP, redoing some ducts so
that the house was zoned to master BR, kitchen, dining, living and family room on
the 3 ton unit putting 3 BRs and 2 baths on the 2 TON unit.  Both units have needed
few repairs and have been able to keep the house comfortable though we do have
some warmer spots at various times of the day due to solar gain.  The Manual J
calculation shows we need about 4 1/2 tons.

Soil type:  Based on what I have dug, down to about feet, I see only sugar sand.
I have a 4 inched cased well for irrigation.  The driller said they hit rock at about
50', then the aquifer at 85'.   Water level comes up to about 11' below the surface
and my submersible pump is 35' down.   This is consistent with what I have heard
from a homeowner north of Tampa (Land O Lakes area) who had vertical bores
for a geo system in new construction.

Shade:  There are numerous mature trees on my lot.  In addition my lot slopes up
from the west to the east so we get early morning shade from neighboring lots
as well.  Some part of the area where a loop would be placed does get full sunf
for a good portion of the day.

Lot size:  I have just over a 1/2 acre lot, somewhat pie shaped so there are more
sq ft behind the house than in front.  The back lot line is 160'.  However between
trees, pool and utilities the contractor proposing a closed loop system thinks
vertical bores is the only way he can build a good loop.

To date I have only found 2 contractors (with decent experience) that do geo
systems in the immediate area (Pinellas, Pasco, west Hillsbourogh) county.
HVAC contractors well know in the area when asked about geo say
"Our only experience is in replacing geothermal systems with air source systems."
Of the two, one pushed open loop, the other has done all types including
closed loop in water, horizontal closed loop, and vertical closed loop.

FYI:  The closed loop system proposed would be a single loop serving
3 ton and 2 ton Waterfurnace Envison equipment with desuperheaters.
All others quote a 4 ton + 2 ton units (their thought process is that 2 speed
equipment that is slightly oversized will be able to use stage 1 longer
and have the capacity for hotter than average times, while a 3 ton might
go to stage 2 more often.

Sounds like this was taken directly from the "bad sales lines" book and is intended to instill fear.  I'd asking them for a list of references of people where they removed geothermal systems and installed a conventional system.  I'd be surprised if they come up with a list of more than zero references, but you never know until you ask.  You will learn something about the contractor whether they come up with these references or not.

On the equipment we have, 1st stage runs at 2/3 of unit capacity.  If the equipment you are looking at is similar, a 3 ton unit would run at 2 tons in 1st stage, and a 4 ton unit would run at  2.67 tons in 1st stage.  The installer should be able to run figures for both systems and tell you how long each system would run in each stage based on historical temperatures for your area.  He should also be able to provide you with operating costs as well.  Running at 2 tons would make for longer run times and better dehumidification compared to running at 2.67 tons.

Key to make this work near Tampa would be a loop design that keeps EWT at or below 90 nearly always and with reasonable pump power or else air source will win the day.

Hey Engineer,

What's your opinion on pump and dump with high calcium water?

My own (Envision 038) is open loop with moderately hard water, but I don't have water test numbers. I assume scaling will eventually affect the unit, and I expect I'll notice it in the form of increased compressor amps during cooling season. I don't particularly fear that, figuring I'll run icemaker cleaner through the heat exchanger to dissolve the scale.

Meanwhile I do interesting things with the discharge water, such as keep a kiddie pool warm in summer and run it through a snowgun in winter

My first thoughts were the temperatures at depth will always be 72.  But a little consideration and one realizes that for a closed loop exchange all the heat wont
be transferred, and the soil around the loop pipes will rise in temperature as well.  Every loop exchange will have its own unique pattern and capacity of heat
exchange, so what should be done to assure an EWT during the cooling season.   Since our heating season is so short here the loop "condition" isn't likely to
be helped much that way.  I also have a standalone pool heat pump to extend the swimming season (we were in the pool on Christmas Day), but had not
considered adding that heating load to the proposed geothermal installation.  One, we don't need to heat the pool during the cooling season - so we wouldn't
make use of the hottest exchange temperatures, two, the pool heat pump is fairly new, three, the geothermal hp for the pool was quoted as an extra $6000.
We had planned to add to the exchange loop a heat exchanger to provide some capacity to the pool.  Now thinking about conditioning the exchange loop,
maybe adding the geo pool hp to the installation would remove enough heat from the exchange loop during the winter months to really help the cooling
season.  Does anyone in Florida have any numbers for their closed loop and the effect on it of adding a geo pool hp?  I will ask the contractor I've been talking
to if he has instrumented EWT on any of the installations in this area.

I haven't' measured the water temperature from my well, but I will soon.  Generally people think of the aquifer water being at a constant 72.  So pump and dump
would satisfy the above of an EWT below 90 therefore tipping the decision to GSHP.   For my installation I would need a second well (around $5000) for the source
while the existing well would be used for the dump, leaving my submersible pump and continue using it for irrigation alone (and topping off the pool).
My fear with this option is the cost of maintenance.  Most of our drinking water supplied by the county is pumped from the aquifer.  If your home does not have
a water softener, you find calcium deposits quickly start clogging the aerators on all your faucets while also plugging up shower heads, not to mention
water marks on sinks, faucets, shower walls, etc.   I've never seen an ad here for a service to descale heat exchangers.  I would need to determine the frequency
and cost of that service and add the cost to the comparison of GSHP to ASHP alternatives.  Does anyone in Florida have these numbers?

Posted By 1FloridaNative on 01/17/2010 11:43 AM
"Are the numbers often published in specs as "partial" by manufacturers essentially the stage 1 values? eg,  Envision model 038, ECM blower, Closed Loop, Cooling Brine Full Load 77°F Part Load 68°F, FULL 40,200 Btuh, PART 30,100 Btuh so in this example stage 1 is 75% but the point being I can get the values and compare for what each contractor proposes."

I think you are correct on the terminology (either Partial Load or Part Load).  Using your example, I assume the calculation is 40,200 x 2/3 (or about 0.67) = 26,800  (not quite 30,100).  Guess there are a lot of variables depending on conditions and the 2/3 capacity that I have seen quoted for WF equipment is an approximate figure.  Using the detailed tables should be more accurate.  The installer should be able to make quick work of these calculations for you.

I am just not convinced that I would oversize my unit and then count on the low speed being the solution. A properly sized unit is already oversized most of the time. The reason is that a properly sized unit should handle all but the one or two absolute hottest days of the year. And these days are only super hot for a couple of hours a day thus your thermal mass will carry you through in almost every case (not 100% but most cases). I would go with a properly sized unit and toss a wee bit of extra insulation in the attic or maybe add reflective barriers over the hot rooms - this should definitely let you get a properly sized unit instead of oversizing.

I asked about trees and soil type to see if it made sense to use a horizonal loop. The shade is definitely beneficial. Of course a vertical loop will be more efficient. If you add a venturi port infront of your unit you can clean the calcium from the unit yourself with an extremely dilute HCl or even a vinegar solution. Of course products made specifically for cleaning the units are better (yes, I am a chemist and a chemical engineer so I would feel comfortable doing this but you may not).

I do not accept the belief that a properly sized unit will provide any noticable improvement in humidy control than a unit one size too large. Studies by the FL Solar Institute support this belief. That said I like my two speed ASHP because the air is moving more so I don't need to run ceiling fans as much.

One thing to keep in mind is that while we don't use a lot of heat here in FL, it does still get cold. I have not seen my power bill for this last cold spell but I expect it to be a doozy. Keep in mind that efficiency seems to drop faster for heating than cooling (in ASHP that I have looked at).
'
The installer is dead wrong about the "conditioning." You state that you hit groundwater at about 10 feet. Groundwater is rarely stagnantf. This means the heat generated during the summer is carried away (same for the "cold" generated in the winter). A residential field is just too small to meaningfully condition a loop. Okay, for the purist, yes, it might be possible to condition it for a day or two but generally we don't have 30 degree weather followed the next day by 90 degree weather. Thus the conditioning would be irrelevant. If the groundwater flow is significant then you benefit as this improves the heat transfer.

Alex,

Thanks for your comments.  Certainly there is an air temperature below which it is not worthwhile to use an ASHP to heat your home.  Yes, I have
auxillary heat strips in both my current ASHP air handlers and they did cut in as we saw temperatures in the mid to high 20's even near the coast.
I just received the highest electric bill I have ever gotten (heating or cooling).  Progress Energy tiers their rate, so after the first 1,000 KWH you
pay an extra 2 cents per KWH.

Interesting view of conditioning.  Just to be accurate in my deep well (and in previous shallow wells) the water level rises to about 10 ft of the surface
in the well pipe (casing), but that isn't the level of the water table.  I have dug to 10 ft and still have a dry hole.  The shallow wells were jetted and
hit the water table within 20 ft, but I have no precise measurement.  The deep well was drilled, but the well driller only told me that the rock layer was at
50 ft (hence 50 ft of casing) and they drilled to about 85 ft to get a good supply of water.  He did not mention conditions encountered getting to the
rock layer.  I have not had this water tested for minerals, bacteria or pH.

The proposed installer (I have not yet signed a contract) told me that when he drills vertical bores he stops at the rock layer.  So I am assuming each
vertical bore would be 50 ft down, with maybe the lower 30 ft being in saturated soil (based on my old shallow well installations).  If an exchange field
at my location would have most heat carried away (or carried in during heating), then is there any advantage of installing a closed loop exchange field
over using pump and dump at my location?  Alex, do you have experience in removing scale from a unit using an open loop?

As to sizing I would agree that "right sizing" is what should be used.  Extra insulation is something I would certainly consider.  Soon I have to decide to
go forward rather than continuing to analyze, just wish there were more local contractors with substantial geo experience.