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Originally Posted by redmondtech

I have been installing and servicing geothermal now for about three years. the company i work for is the biggest geothermal installers in central PA
A few questions i must ask:

Why are you going open loop?
What we have found is that the open loop system needs to have more flow then closed loop system due to the loop water and not being able to take advantage of an antifreeze. which brings up another problem what happens when temp. gets below freezing? even though the loop will be below the frost line (and since you are going with wells it is a better advantage) But pulling up ground water will bring in sediment which is going to plug your coaxle coil quicker then a closed loop would. and another problem with open loops or pump and dump is what happens when north carolina has a drought which occurs often in the southern climates. (i have a sister that lives in creedmore NC which is close tothe durham area.

Another good note to think about is each ton should have around 200 ft per ton or for every 1200 btu

First, if you are going open loop then you don't have to really worry about loop size. You simply need to insure that the inflow and return wells are as far a part as possible (at least 50 feet). If you can have them at different depths that helps also. Do make sure to go deep enough to avoid drought issues.

Redmontech: Your post confuses me on several fronts. You state open loops need more flow because they can not take advantage of antifreeze. Everything I ever see is that the antifreeze has less heat transfer than water and requires more pump power too. This should mean that an open source unti would require slightly less flow - not more. Can you explain your logic or why your company is seeing the reverse of what engineering predicts and most other companies have found? Thanks.

the wife will never ride this one, she likes the Ultra Classic

Right on it sounds like a sweet bike. I told my wife I need to get a another bike. It's been awhile since I've had one. She said ok as long as it has a side car for our daughter and she rides on back. She almost killed me when I expressed, That would defeat the whole pupose of getting a bike and the one I get won't have a passenger seat.

GSX1300BK it's 181.5 hp @ the crank or 163-165 hp @ the rear tire

ROFL 2nu2no. I was lokking at your avitar and at 1rst thought it was black trash bags at 2nd look. I thought No, it looks more like black fish. Then I realized it was the mid section of a motor cycle. Time for an eye test I guess.

Phosphates in a Geo are you kidding

Even the Bismarck sank! , Redundancy, beak it up 1st floor an independent zone, then 2nd & 3rd a zoned second system.

Original post was in March. The system is probly in already with the schedule he gave. I also wondered about the multi stories and single system not zoned. What really caught my attention was the difference in load cals from NC to ORE. His calcs were so close to even "lol" ours here are like 107k loss to 88K gain and we're way dry, no latent. Always learning on here.

Originally Posted by mikeweber3

Jab,

I question the wisdom of using one system on a 3 story house. Are you putting in a zoning system?

Mike

I agree, you need two system in order to have a comfortable temperature range in side your home. If you go with the two systems approach you will elimate furture headaches. Duct zoning system will work, but are complicated and you will need to have a good service company to handle your service. I never found a good zoning system or at least every time I did the company would go out of business and parts became scarce.
I'd talk to your contractor about putting in a condenser in the loop to allow the A/C unit to run on a closed loop system and the well water to run through the remote condenser on an open loop.
I had a Florida Heap Pump system in my home in Charleston SC and the condenser on the first floor would only last for 4 years before fouling up. I used the Copper Nickle condenser system but the problem was the fouling by the sediment in the well water. I was going to install a plate heat exchanger in the condenser loop, but sold the house instead.

Originally Posted by mikeweber3

Jab,

I question the wisdom of using one system on a 3 story house. Are you putting in a zoning system?

Mike

I agree, you need two system in order to have a comfortable temperature range in side your home. If you go with the two systems approach you will elimate future headaches. Duct zoning system will work, but are complicated and you will need to have a good service company to handle your service. I never found a good zoning system or at least every time I did the company would go out of business and parts became scarce.
I'd talk to your contractor about putting in a condenser in the loop to allow the A/C unit to run on a closed loop system and the well water to run through the remote condenser on an open loop.
I had a Florida Heap Pump system in my home in Charleston SC and the condenser on the first floor would only last for 4 years before fouling up. I used the Copper Nickle condenser system but the problem was the fouling by the sediment in the well water. I was going to install a plate heat exchanger in the condenser loop, but sold the house instead. Good luck on the house

Originally Posted by jab490

So the final decision was to go with foam in the roof and 3rd floor but batt insulation everywhere else. This was to eliminate the need for mechanical ventilation. Hopefully this compromise will find the sweet spot between being tight enough to hold the comfort of the house but not so tight that we need a dehumidifier or mechanical air exchange. Also, with the mechanical air exchange, the cost of foam was getting prohibitive.

As for the water, it gets pumped back into the well and is used like any other well water (eg., bathing, drinking, washing). The water isn't contaminated by the HVAC system. Still, the state performs a yearly test of the well to confirm that the water is safe.

Does all of this sound reasonable? Thanks for your input.

You're pumping back into the same well?!?!?!

How many systems?

Jab,

I question the wisdom of using one system on a 3 story house. Are you putting in a zoning system?

Mike

So the final decision was to go with foam in the roof and 3rd floor but batt insulation everywhere else. This was to eliminate the need for mechanical ventilation. Hopefully this compromise will find the sweet spot between being tight enough to hold the comfort of the house but not so tight that we need a dehumidifier or mechanical air exchange. Also, with the mechanical air exchange, the cost of foam was getting prohibitive.

As for the water, it gets pumped back into the well and is used like any other well water (eg., bathing, drinking, washing). The water isn't contaminated by the HVAC system. Still, the state performs a yearly test of the well to confirm that the water is safe.

Does all of this sound reasonable? Thanks for your input.

I have been using an open loop geo in Texas for about 15 years and have put in several closed loop and lake loop systems. My groundwater temp is 59F. Rule of thumb is 3 gpm of condenser water per ton. i use my waste water for irrigation on my farm. What are you doing with waste water?

From an energy standpoint, reducing the load and size AC you need is the best approach, but with foam insulation and an oversized unit you will have comfort problems due to lack of dehumidification. The unit won't run long enough to remove the latent heat. You may need to piggyback a dehumidifier on the AC system

Thanks for that interesting information. As it turns out, we have a surprising 20 gpm flow rate from the well and about 50' of extra well depth. So although the ground water level can certainly drop during a drought, our contractor suggested that if we just cut down on water usage for an hour or so, our well should replenish quickly because of this high flow rate. Hope that's true. My wife and I aren't big risk takers, but we do like the "green" aspects of this. If all works out reasonably, we'll be glad we made the choice. The fact that so many folks who work in this industry day in and day out are willing to help on websites like this only adds to my confidence.

Thanks again to all.

good discussion

jab490

If your loop is undersized of course your system is going to run un-efficiently. poor water flow in the summer months running a/c will over heat the compressor heating the windings in the motor and giving you less compressor life. you would be constantly failing either thermal cut out or high pressure depending on the safty device.
poor water flow in the winter would freeze your water coil and starving the compressor of refrigerant either way is no good. but you have been doing your research and getting good information from everyone good luck ad your doing it right.

Also about the different entering water temp. for different regions in the united states is an answer that i dont have but that is a great suggestion for the loop footage. i will find out and post back
Good Luck,
Brian

Originally Posted by jab490

Thank you for looking at the information and providing feedback. I greatly appreciate the second opinion, and it is reassuring to know things don't look dramatically out of line. Our contractor has since provided me with the entire manual J calculation (about 10 pages, more or less). Is there one particular thing I should look for in those calculations? At this point I need to decide if using foam throughout the house - rather than just in the finished 3rd floor attic - is worth the additional $5000 cost for the insulation and air exchange system. If the HVAC is boarderline, I'd spend the money on the foam. If we are well within specs, I would save the money.

Thanks again for your time and knowledge.

Did he do the manual J assuming the foam insulation or batts?

I'd say a 5 ton looks right, but be careful about open loop. I ran open loop for awhile, and I clogged my water lines with rust build-up. Also, redmondtech said open loop requires more flow. That's wrong. I believe it's just the opposite. With open loop you can run less flow because you are getting "new" water all the time. In a closed loop you need more flow because you're essentially recycling the water. Without knowing more about your lot it's hard to argue one way or the other (open vs closed). Obviously your contractor was good enough to do a manual J and select the right size unit so he/she seems respectable, but remember that it's pretty important to get your loop right. Geothermal only turns out to be wonderful when your loop is right.

Thank you for looking at the information and providing feedback. I greatly appreciate the second opinion, and it is reassuring to know things don't look dramatically out of line. Our contractor has since provided me with the entire manual J calculation (about 10 pages, more or less). Is there one particular thing I should look for in those calculations? At this point I need to decide if using foam throughout the house - rather than just in the finished 3rd floor attic - is worth the additional $5000 cost for the insulation and air exchange system. If the HVAC is boarderline, I'd spend the money on the foam. If we are well within specs, I would save the money.

Thanks again for your time and knowledge.

It looks like you are OK.

Call me if you have any questions.

My phone number can be found on my website posted at the bottom of this message.

Geodean suggested I ask for the BTU/hour load. I requested this information from our contractor who responded:

heat loss: 60269 BTU's
heat gain: 55716 BTU's

He did not provide a per hour figure. These numbers do not mean anything to me. Can anyone explain?

I am trying to arrange a meeting with our contractor ASAP so he can explain the assumptions that went in to his calculation and, hopefully, he can show me how he calculated that the system he plans to install can handle the load. But I'm not sure I can pull it off before the system is installed due to my own out of town work schedule. So any information anyone can suggest from these numbers and the information in the first post would be most appreciated. Our contractor seems very reasonable, and I have no reason to suspect he isn't well-qualified. Based on other threads on this website, I'm just concerned he is using all best-case scenario assumptions.

Also, if it looks like we are undersized and it's too late to change (contract signed, system ordered, partially installed?), would foam insulation (open cell, 2x4 walls + 8" attic) rather than batt (R-13 walls, R-30 attic) make much of a difference in the ability of the HVAC system to handle the load? It means adding a $2500 ERV air exchange system plus the added cost of foam.

Thanks again.