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  1. #1
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    Feb 2007
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    Geothermal vs. air-cooled in South Florida

    Hey everyone. I'm looking to get some opinions on replacing my 16 year old 3-1/2 ton Florida Heat Pump geothermal unit in order to take advantage of the 30% tax incentive expiring at the end of the year. We don't have very cold winters down here, so heating is of no real concern --- but cooling is of course. My system is open-loop using a well with a 3/4 hp Flotec centrifugal pump. My concern is that with a measured well water temperature of 83 degrees and current consumption of 5.3 amps for the pump, does geothermal really make much sense over an air-cooled unit in terms of energy usage for cooling? I feel that my electric bill is rather high for my 2000 square foot home (about $250.00/month this time of year), considering we keep the thermostat at 79-80 during the day (I work from home and cannot run it any higher and remain comfortable) and 85 at night (using a mini-split to cool the bedroom to about 74 degrees for sleeping). My current geothermal unit has been trouble-free for the past 7 years that we have owned the house, with water flow rate, head pressure, suction pressure and evaporator temperature drop all within specs. I'm thinking I should be able to do a lot better than the 22.1 amps total current consumption that I am seeing on this 3-1/2 ton geothermal system (5.3 amps for the pump, 14.5 amps for the compressor and 2.3 amps for the blower). Any opinions? Thanks in advance ...

  2. #2
    Join Date
    Aug 2016
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    83? is that entering temp? that's pretty high, but still better than 100F air. Are you pulling off a well or a pond? are you discharging through an open pipe, return well or sprinkler? If you're sucking out of a well and returning back into the same well BIG mistake. And kinda the same for a pond if your supply and return are to close will raise the temp of your water and destroy your efficiency. your pump 5.3 amps I'm assuming 220V that is 1 1/2hp amperage you should be just below 3.75 amps for 3/4hp and depending on the water table you could be able to drop to a 1/2hp all you need is 10gpm. 16yrs old you prob need to clean the coil. Cut the water lines at the unit and temp plumb a small pump and bucket and circulate miratic acid through it for a couple hrs. next using a throttle cock or ball valve on the discharge side of your pump throttle the water back to 10gpm believe it or not throttling back pressure on a pump will make the amps go down (you would think it would go up). When was the last time you cleaned the Evap coil? clean that to while you're at. Once everything is clean and water supply is right check your charge it may need a boost

  3. #3
    Join Date
    Feb 2007
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    Thread Starter
    Quote Originally Posted by aquadave View Post
    83? is that entering temp? that's pretty high, but still better than 100F air. Are you pulling off a well or a pond? are you discharging through an open pipe, return well or sprinkler? If you're sucking out of a well and returning back into the same well BIG mistake. And kinda the same for a pond if your supply and return are to close will raise the temp of your water and destroy your efficiency. your pump 5.3 amps I'm assuming 220V that is 1 1/2hp amperage you should be just below 3.75 amps for 3/4hp and depending on the water table you could be able to drop to a 1/2hp all you need is 10gpm. 16yrs old you prob need to clean the coil. Cut the water lines at the unit and temp plumb a small pump and bucket and circulate miratic acid through it for a couple hrs. next using a throttle cock or ball valve on the discharge side of your pump throttle the water back to 10gpm believe it or not throttling back pressure on a pump will make the amps go down (you would think it would go up). When was the last time you cleaned the Evap coil? clean that to while you're at. Once everything is clean and water supply is right check your charge it may need a boost
    Thanks for the reply aquadave! I'm on a well and yes, that's the entering water temperature. I rechecked it with my fluke multimeter with a temperature probe this time and it is actually 81.3F (a little better). The water must return to a well, as it does not go through the sprinkler system or an open pipe. The unit is in the garage with both the 3/4 HP pump for the A/C and a 1-1/2 HP pump for the sprinkler system (pulling from the same well) outside the opposite wall (A/C water pipes and condensate drain go under the garage floor). For a sanity check, I checked the water temperature at the sprinkler pump with the A/C not running and I get the exact same temperature reading, so I'm pretty confident that the water is not being returned to the same well. The system was in the house when we bought it in 2009, so I don't know the history of the installation. I did clean the heat exchanger in the way you described last year (using RydLyme) and it made no difference in flow rate, head pressure, current consumption, etc. Needless to say, I was disappointed! I had cleaned the evaporator coil the previous year, but it wasn't really that bad and made no difference in the temperature drop across the coil at the time. But I'm still wondering about that pump! I did a quick check on the sprinkler pump and it's pulling 7.6 amps, so if all things were equal, you would be right on the money with 3.75 amps for a 3/4 HP pump, which is half the size of that pump. Of course flow rates have an impact on current consumption just as you say and we're talking about 2 totally different systems here. I'd love to replace that old flotec pump anyway. I'm getting quotes now on a new system now, but is there a particular brand of pump you feel is better than the rest? Any info is much appreciated! Thanks ...

  4. #4
    Join Date
    Jul 2012
    Location
    SouthCal
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    here in socal we have only air condensers for residential. can somebody explain what is the benefit of geothermal if instead the condenser fan motor you have to use the water pump. does it have same 36000btus compressor and 1200cfm blower? regular air condenser is 14seer and i guess it equals to 3-3.5 cop. what are the numbers for geothermal?

  5. #5
    Join Date
    Apr 2019
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    How deep is your well?

  6. #6
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    Feb 2007
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    Thread Starter
    I'm really not sure, as the well was here when we bought the house. Wells down here are not very deep as a rule (20-25 ft from what I understand). I did end up replacing the A/C back in 2016. The 4 ton, 2-stage Geocool unit that I had installed has been good. I still have not changed the Flotec pump and still suspect that a new pump might be more efficient (as well as quieter). I would definitely be interested in hearing others' experiences with above ground pumps for geothermal.

  7. #7
    Join Date
    Apr 2019
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    Probably your incoming well is too shadow, aquifer in in south Florida should be around 75F .

    Do you know anybody in your area that have a well ~ 100' or deeper? ask for a sample and measure the temperature


    Do you know the model of your unit? probably you're pumping too mush water into your system. You need to measure the T in and Out and follow the manufacture specs.

  8. #8
    Join Date
    Feb 2007
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    Thanks oallsrv. Actually, I do have a friend about a mile away that has a well with water that does not stain the house and driveway like ours does. I don't know how deep that well is either though. Most of the wells in our area have a rust staining problem and some people have installed tanks that feed a rust aid solution into the inlet side of their sprinkler pumps. People say it works only so-so and is expensive. I've thought about putting in a new well (because of the rust problem) and I checked into it some years ago. I believe the guy said he goes down about 50 feet.

    I don't think that I am pumping too much water because there is a gate valve on the outlet side of the pump and as I close it (even slightly), the current consumption of the unit goes up. Conversely, I did an experiment where I fed water from the sprinkler pump along with the water from the flotec pump to the A/C and the current consumption on the compressor went down --- but only slightly (0.2 amp difference on stage 1 and 0.3 amp difference on stage 2). I do have a flow meter that I used on the old unit but I haven't tried it on this one. I know the heat exchanger in this system is less restrictive than the old one because the pump is noisier than before. As I close the valve on the discharge side increasing the backpressure, the "wooshing" sound gets quieter.

    The model # on the Geocool is GCHP01048V-RF-A-HR-TS.

  9. #9
    Join Date
    Apr 2019
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    SF stain should be tannin, tanning is vegetation decay, if you go deeper the water should be free of tannin, coolest, but hardest.

    Is your system have a valve to control the flow ? If not try to find which flow is the one that you need in your system

    FYI closing the valve is not going to reduce the current from the pump, should even go a little highest because of the pressure . To reduce the total power consumption from the pump you need to either change the pump, or get a pressure tank to turn on-off the pump automatically.

  10. #10
    Join Date
    Feb 2007
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    Thread Starter
    Right. I was measuring the current to the compressor as opposed to the pump. The more water, the less the compressor draws ...

  11. #11
    Join Date
    Sep 2002
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    To me; geothermal investment made great sense when standard AC units were 8-9-10 SEER. Because geo was so much higher - approaching 20 SEER.

    But now that air cooled systems have such high SEER ratings I think it's much harder to economically justify geothermal. Especially with an all-new installation. But even on an existing-system replacement, when the added complexity, pumping costs, and so forth are factored in - I think it's hard to make the life-cycle-cost numbers work.

    That being said: I have a brand new 4 ton Bosch best-of-everything two-stage unit sitting here that I will sell you for cheap.

    Where are you in Florida anyway?

    PHM
    ---------



    Quote Originally Posted by geos56us View Post
    Hey everyone. I'm looking to get some opinions on replacing my 16 year old 3-1/2 ton Florida Heat Pump geothermal unit in order to take advantage of the 30% tax incentive expiring at the end of the year. We don't have very cold winters down here, so heating is of no real concern --- but cooling is of course. My system is open-loop using a well with a 3/4 hp Flotec centrifugal pump. My concern is that with a measured well water temperature of 83 degrees and current consumption of 5.3 amps for the pump, does geothermal really make much sense over an air-cooled unit in terms of energy usage for cooling? I feel that my electric bill is rather high for my 2000 square foot home (about $250.00/month this time of year), considering we keep the thermostat at 79-80 during the day (I work from home and cannot run it any higher and remain comfortable) and 85 at night (using a mini-split to cool the bedroom to about 74 degrees for sleeping). My current geothermal unit has been trouble-free for the past 7 years that we have owned the house, with water flow rate, head pressure, suction pressure and evaporator temperature drop all within specs. I'm thinking I should be able to do a lot better than the 22.1 amps total current consumption that I am seeing on this 3-1/2 ton geothermal system (5.3 amps for the pump, 14.5 amps for the compressor and 2.3 amps for the blower). Any opinions? Thanks in advance ...
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  12. #12
    Join Date
    Feb 2007
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    7
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    Thread Starter
    Quote Originally Posted by Poodle Head Mikey View Post
    To me; geothermal investment made great sense when standard AC units were 8-9-10 SEER. Because geo was so much higher - approaching 20 SEER.

    But now that air cooled systems have such high SEER ratings I think it's much harder to economically justify geothermal. Especially with an all-new installation. But even on an existing-system replacement, when the added complexity, pumping costs, and so forth are factored in - I think it's hard to make the life-cycle-cost numbers work.

    That being said: I have a brand new 4 ton Bosch best-of-everything two-stage unit sitting here that I will sell you for cheap.

    Where are you in Florida anyway?

    PHM
    ---------
    Hey there Mikey. Thanks for the offer. I am in the Fort Lauderdale area, but I ended up replacing the unit back in 2016 with a Geocool 4 ton, 2-stage model. It's been running fine. I still have that old water pump and I think I could do better than the 5.3 amps that it draws. By the way, I agree with you. Many air cooled systems are so efficient these days. I would have simply replaced it with one of those, but I didn't have a good space for the condenser unit and would require additional electrical work, etc. For a top of the line super-efficient air cooled unit, the estimate was over double what I ended up paying for the water cooled unit, including installation. This was because I got the 30% tax credit (2016 was the last year) and there was no special installation work that needed to be done, since I used the old pump (this was basically plug-n-play with a little rework of the supply and return air connections). I'm toying with the idea of using a variable speed pool pump because our water table is so high here. When I had a pool when I lived in Miami I had a connection from the well to the pool pump and I never had any pumping issues when I wanted to add water to the pool, completely fill it, etc. A future project! :-)

  13. #13
    Join Date
    Sep 2002
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    How would the numbers have looked without the 30% credit ?

    PHM
    --------



    Quote Originally Posted by geos56us View Post
    Hey there Mikey. Thanks for the offer. I am in the Fort Lauderdale area, but I ended up replacing the unit back in 2016 with a Geocool 4 ton, 2-stage model. It's been running fine. I still have that old water pump and I think I could do better than the 5.3 amps that it draws. By the way, I agree with you. Many air cooled systems are so efficient these days. I would have simply replaced it with one of those, but I didn't have a good space for the condenser unit and would require additional electrical work, etc. For a top of the line super-efficient air cooled unit, the estimate was over double what I ended up paying for the water cooled unit, including installation. This was because I got the 30% tax credit (2016 was the last year) and there was no special installation work that needed to be done, since I used the old pump (this was basically plug-n-play with a little rework of the supply and return air connections). I'm toying with the idea of using a variable speed pool pump because our water table is so high here. When I had a pool when I lived in Miami I had a connection from the well to the pool pump and I never had any pumping issues when I wanted to add water to the pool, completely fill it, etc. A future project! :-)
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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