geothermal ground loop systems

[toplessHO]

My system has always been open loop well water discharge into sprinkler system
thoughts of closed loop slinky system comes to mind.
Looking for input. I have heavy equipment so not an issue digging.

 

[4 FN 27]

I have Wells on the house system and a loop field on the shop. Both perform well. Never had an issue in the subzero MN winters.

 

[Firebrick43]

Thats a Classic 4 FN 27 and so true!

 

[Firebrick43]

My system has always been open loop well water discharge into sprinkler system
thoughts of closed loop slinky system comes to mind.
Looking for input. I have heavy equipment so not an issue digging.

Just out of curiosity, is the current open loop system having issues?

 

[toplessHO]

yes it is having issues.
When I built the system almost 40 yrs ago I designed it for 12-15 GPM per sprinkler loop
which is what the AC unit requires.
I put in a 5 zone cycling valve with 5 zones of sprinklers flow matched to the above figure.
The sprinkler zone flow has become harder to keep constant.
The well water has lots of iron so it has stopped up a few sprinklers.
Once they get low flow the issue snowballs.Then the issues with the cycling valve.
occasionally hanging up and flowing out of all the zones at once.
The system worked fine in open loop for many years but now requires more upkeep.
Theres no need for a 1 HP deep well pump running the entire time the AC is running.
This same well/pump system supplies all domestic water.
As electricity rates have doubled for us in the last few years Im already behind the curve.
So its convert to closed loop and add some solar to power the AC.

 

[pcmeiners]

how much land do you have ?

 

[gregs]

yes it is having issues.
When I built the system almost 40 yrs ago I designed it for 12-15 GPM per sprinkler loop
which is what the AC unit requires.
I put in a 5 zone cycling valve with 5 zones of sprinklers flow matched to the above figure.
The sprinkler zone flow has become harder to keep constant.
The well water has lots of iron so it has stopped up a few sprinklers.
Once they get low flow the issue snowballs.Then the issues with the cycling valve.
occasionally hanging up and flowing out of all the zones at once.
The system worked fine in open loop for many years but now requires more upkeep.
Theres no need for a 1 HP deep well pump running the entire time the AC is running.
This same well/pump system supplies all domestic water.
As electricity rates have doubled for us in the last few years Im already behind the curve.
So its convert to closed loop and add some solar to power the AC.

Similar set-up at my house. I luckily have a good amount of land including a wooded area. I have always just let it run in the woods. The previous owner had sprinklers on a hose and moved it around the yard. Unfortunately due to the hard water it stained the brick walls, so I replumbed it to just empty in the woods. I have a butterfly valve at the unit that I used to adjust flow. Also have a set of Pete's plugs on the in/out and sorta dialed it in years ago.

 

[toplessHO]

Well the other side to look at is that potable water is a resource that we need to respect
and conserve.
I have no idea what a Pete's plug is.

 

[gregs]

Well the other side to look at is that potable water is a resource that we need to respect
and conserve.
I have no idea what a Pete's plug is.

No real difference between spraying it on your lawn vs letting it run into the woods. Probably more evaporation using it thru sprinklers. We are on sandy based soil and I am reasonable sure its making it back into the aquifer without a problem. Not to mention it sorta supports some of the wildlife.

A Pete's plug is a fitting that has a rubber seal and cap that allows you to put the probe of a thermometer into the water stream. That allows you to adjust the out going water flow by knowing the exit temperature. The inlet temperature also has one, but the stable 72 degrees is almost set in stone. Thats why I used a butterfly valve on the output so that I could throttle it and get the most efficient use of my water supply both for power conservation as well as water conservation.

 

[Jackfre]

The purpose of going with the closed loop is to protect the equipment. Open loop, as you have found, is great when everything is new, but the precipitant degrades the components. Yes, convert to a closed loop but you have to try to flush and clean the equipment in the closed loop. An alternative that I used on water source back in the 70’s when I was doing these was to use a swimming pool as the heat sink. A solar system was used to heat the pool. We were in the Napa Valley so some heat load. In FL, you are looking at cooling only and the pool ends up being for heat rejection. On one system we knew it was going to be marginal and with the high cooling demand ended up adding a small cooling tower to deal wit hthe heat rejection. I strongly suggest adding the solar to handle your electrical loads. I did it on the last house which we sold in April and I ran the place with zero PG&E bill, and that is a real number here. I bought direct and installed the system myself and did it for about half of what the pro comapanies wanted.

 

[jlv03]

Just spitballing here - could you put in a tank or water storage of some sort to dump the outlet water into right away? And then put in a separate pump to irrigate as needed or when the tank was full?

At 12-15GPM, a 2000 gallon tank would buy you two hours of runtime without any sprinklers running.

 

[gregs]

The purpose of going with the closed loop is to protect the equipment. Open loop, as you have found, is great when everything is new, but the precipitant degrades the components. Yes, convert to a closed loop but you have to try to flush and clean the equipment in the closed loop. An alternative that I used on water source back in the 70’s when I was doing these was to use a swimming pool as the heat sink. A solar system was used to heat the pool. We were in the Napa Valley so some heat load. In FL, you are looking at cooling only and the pool ends up being for heat rejection. On one system we knew it was going to be marginal and with the high cooling demand ended up adding a small cooling tower to deal wit hthe heat rejection. I strongly suggest adding the solar to handle your electrical loads. I did it on the last house which we sold in April and I ran the place with zero PG&E bill, and that is a real number here. I bought direct and installed the system myself and did it for about half of what the pro comapanies wanted.

I looked at using my pool as the water source. With the current configuration of piping it was going to take a lot of work to separate it out of the house plumbing. Then there was the potential issue with pool chemicals affecting the equipment, so I looked into a heat exchanger to keep everything separated. After thinking about all that and the fact that my pool is in the 90's right now in the middle of summer, I saw no gain to be had from all the work.

I also looked into buying or building a small cooling tower and came to the same conclusion for the amount of work and expense. Not to mention the wife didnt like the idea of something like that in the yard.

I havent had any issues with the open loop system all these years. Its hard to beat using 72 degree water to heat and cool with. My system also employs a large whole house canister style filter in the water system.

 

[gregs]

Just spitballing here - could you put in a tank or water storage of some sort to dump the outlet water into right away? And then put in a separate pump to irrigate as needed or when the tank was full?

At 12-15GPM, a 2000 gallon tank would buy you two hours of runtime without any sprinklers running.

I had a friend whose parents house also had a water source heat pump. They basically did the same thing by building a small pond in the front to discharge the water to, and then had the irrigation pump draw from there.

 

[American Locomotive]

No real difference between spraying it on your lawn vs letting it run into the woods. Probably more evaporation using it thru sprinklers. We are on sandy based soil and I am reasonable sure its making it back into the aquifer without a problem. Not to mention it sorta supports some of the wildlife.

That entirely depends on how deep your source well is. If it's a shallow well, 30 feet form the surface, probably. If it's a well 100-400 feet deep, there are probably several different separately constrained aquifers between the surface and where that well is drawing from.

But I am generally in the camp of "open loop dumping of ground water onto the surface" is probably wasteful, and a closed loop system is better and more sustainable environmentally.

 

[gsmith22]

I don't have access to an aquifer that could sustain an open loop system so mine had to be a closed loop (I have 3-400ft vertical wells through rock feeding two water to air heat pumps for heating and cooling). While I get that an open loop has more moderate water temps relative to the ups and downs of closed loop temps, closed loop has 0 of the issues assoicated with pumping ground water, likely some combo of potable, sprinkler, and geo water well use, and what to do with the geo water after the heat exchange. There is no maintenace - what is in the loop stays there forever (barring some type of leak). I've often felt that people get persuaded into an open loop because of the lesser cost (think carrot dangling) when in reality closed loop would have been a far wiser choice (but more expensive) since essentially all maintenance is eliminated. My heat pumps have been running for 5 years and the only thing ever done is to change air filters on the air handlers. there is literally nothing to do with a closed loop system. I would do whatever I could to make the system closed loop.

 

[toplessHO]

Just spitballing here - could you put in a tank or water storage of some sort to dump the outlet water into right away? And then put in a separate pump to irrigate as needed or when the tank was full?

At 12-15GPM, a 2000 gallon tank would buy you two hours of runtime without any sprinklers running.

still gotta pay for that tank to be filled
closed loop pumps are much smaller than deep well pumps

 

[gsmith22]

still gotta pay for that tank to be filled
closed loop pumps are much smaller than deep well pumps

yes this! carrot dangling and all that. I haven't studied the issue in depth but my guess is the long term costs (maintenace and electric) for open loop dwarf the short term costs of installing closed loop. my closed loop pumps draw like 100W operating at full speed - they are variable speed so mostly operate at like 20 to 40W.

 

[toplessHO]

Ive been doing geothermal for 45 yrs.
We tried the pool at one customers.
It got too hot so the engineer came up with a statue of a naked kid(think like Greek statue)
that was peeing and the water was cooled by ambient air before it went back in the pool.
Quite the conversation piece too.

Look up TempMaster and Maurice Sheer. Hes the one that opened my eyes to geothermal.

 

[toplessHO]

down here we never needed closed loop
plenty of water that was 72*.
But times have changed.
Ive gone thru 2 Geo units
Fla Heat Pump and now Bard
Before that I installed TempMasters

 

[toplessHO]

Ive been doing a lot of research about the ground loops.
I have 2 ideas on how to build my loops.
My house is about 15 ft higher than my pond.
Thinking about head loss and circulating pump being able to do this
good thing is in a closed loop the push makes up for the pull.
Gsmith what are your circ pumps?

 

[gsmith22]

down here we never needed closed loop
plenty of water that was 72*.
But times have changed.
Ive gone thru 2 Geo units
Fla Heat Pump and now Bard
Before that I installed TempMasters

this is precisely my point. you get lulled into thinking I have lots of water available at 72 deg so it makes lots of sense for me to try and use it via open loop. and then you spend years fighting all the negatives that the 72 deg water-o-plenty made you ignore

 

[toplessHO]

how much land do you have ?

plenty for a closed loop system

 

[gregs]

I must say its about the same amount of time at my house. The original owner had it built geothermal in the 80's and the Franklin(I believe) held up fine. After I bought the house I had a friend with a connection at Trane and he got me a new WSHP in the same configuration. Thats when I replumbed everything and dialed it in. Part of it was to make sure the well system worked correctly and didnt short cycle. My well does not run the entire time the a/c is on. The well runs about 2 minutes and then is off for about 8-10 minutes. I kept the original WSHP and my brother is currently using it in his shop. He made it portable on wheels and runs a garden hose to it. Its temporary until he finishes a typical HVAC system.

With the efficiency improvements over the years I would contemplate replacing it with a standard air source heat pump. The only problem is the amount of work to run electrical and lines outside. Sometimes you dont fix whats not broke.

 

[toplessHO]

this is precisely my point. you get lulled into thinking I have lots of water available at 72 deg so it makes lots of sense for me to try and use it via open loop. and then you spend years fighting all the negatives that the 72 deg water-o-plenty made you ignore

actually it comes down to my newest well thats about 5 yrs old.
Old well had great water,I even pulled the condenser loop out of my old Fla Heat Pump when I replaced it,
and cut it in half to see if there was any scale build up. All it had was a brown tarnish on the copper.
New well not as good,lots of iron oxides Wells are about 50 ft apart and close to same depth so luck of the draw.
I used the solution that changes color when the condenser is clean.... It never did the color change so I quit doing the reverse flush/cleaning.

 

[gsmith22]

Ive been doing a lot of research about the ground loops.
I have 2 ideas on how to build my loops.
My house is about 15 ft higher than my pond.
Thinking about head loss and circulating pump being able to do this
good thing is in a closed loop the push makes up for the pull.
Gsmith what are your circ pumps?

i have two waterfurnace heat pumps that were paired with individual pressurized flow centers. both flow centers are connected to a common ground loop. Each flow center has a variable speed pump. you don't necesserily need the variable speed ability of the heat pumps or flow center pumps but it makes the system amazingly efficeint and year round comfort is chef's kiss. Waterfurnace uses Geo-flo flow centers - mine are the Flo-link style. each flow center has a grundfos magna geo 132-40 pump.

 

[toplessHO]

I must say its about the same amount of time at my house. The original owner had it built geothermal in the 80's and the Franklin(I believe) held up fine. After I bought the house I had a friend with a connection at Trane and he got me a new WSHP in the same configuration. Thats when I replumbed everything and dialed it in. Part of it was to make sure the well system worked correctly and didnt short cycle. My well does not run the entire time the a/c is on. The well runs about 2 minutes and then is off for about 8-10 minutes. I kept the original WSHP and my brother is currently using it in his shop. He made it portable on wheels and runs a garden hose to it. Its temporary until he finishes a typical HVAC system.

With the efficiency improvements over the years I would contemplate replacing it with a standard air source heat pump. The only problem is the amount of work to run electrical and lines outside. Sometimes you dont fix whats not broke.

talked neighbor into going geo when he built his house. Hes now on his 2nd unit. The new one has a SEER over 20.

 

[toplessHO]

i have two waterfurnace heat pumps that were paired with individual pressurized flow centers. both flow centers are connected to a common ground loop. Each flow center has a variable speed pump. you don't necesserily need the variable speed ability of the heat pumps or flow center pumps but it makes the system amazingly efficeint and year round comfort is chef's kiss. Waterfurnace uses Geo-flo flow centers - mine are the Flo-link style. each flow center has a grundfos magna geo 132-40 pump.

do you have heat recovery?

 

[gsmith22]

current weather in NJ is probably like central florida more or less most of year. both of my heat pumps and flow centers have used a combined 475kWh in July to cool a 3300sq ft house. my deep ground temp is ~55deg. loops are currently running at ~65 deg.

My deep ground temps and loop temps are probably not what you will get though. Your deep ground temp is probably your ioncoming water temp so ~70 and since you will be cooling and your loop system will be sized for cooling, you should see higher temps in the loop in summer (~90?). My system is designed for heating which is about twice the cooling load so summers are when my system takes a break because the loop is way oversized for cooling. for instance, in winter, my loop temp hovers around upper 30s to low 40s in the winter.

 

[gsmith22]

do you have heat recovery?

not sure what you mean? I have desuperheaters on each heat pump that heat domestic water for hot water

 

[toplessHO]

not sure what you mean? I have desuperheaters on each heat pump that heat domestic water for hot water

yes AKA heat recovery
50 yrs ago first house had a sardine can 2.5ton unit.I was going thru the Carrier training course and got interested in heat recovery.
Condenser fan went out and compressor blew on the sardine can.
I got the idea to make a water heater and also installed a high pressure cutout to protect the new compressor.
I built my heat exchanger by rolling out 50 ft of 3/4" copper and pulled 60 ft of 3/8" inside it. I then rolled it back up
and connected a Teel circulating pump to it.
Long story short I came home one day,other half said AC sounded funny and steam was coming out of water heater.
Wire to condensing fan broke and the heat recovery unit heated the water until steam was coming out of the pop off valve in water heater.

I had built and installed plenty of those heat recovery units.There was even a company based here called ECU that made them
I bought one and dissected it . 5 ft of tubing brazed side by side. what a heat exchanger!

 

[gsmith22]

my summertime loop water temp doesn't get warm enough to produce extra heat for the desuperheaters. I think I remember reading in the waterfurnace specs it has to get to 70 loop temp before even producing heat in the desuperheater (its 65ish now at the height of summer). But fall, winter, and spring, I bascially get free hot water. I also have a heat pump hot water heater as the primary hot water heater but it barely runs in the fall and spring, doesn't run in the winter, and is really a summer thing. I suspect you would be opposite - your loop temp will get hot in the summer and you can steal heat then probably not so much in the winter

 

[toplessHO]

my temp going in is around 75
going out around 85

I doubt I will do that good with closed loop
but wont be paying for a well pump to run.

 

[pcmeiners]

With a closed loop you would only need a small iron filter on the water input, once water is in the clsoed loop you would not need anymore filtration. With a ground closed loop you would need to go down at least 6 feet to hit soil which will remain at the years average temperature which is still around 70-81 degrees.
Surprising even in very deep well the water temperature is very high, so a closed loop down a well is not the most efficient due to temperature.

Page 32.....

https://pubs.usgs.gov/bul/0701/report.pdf

At your 1 hp pump draw now could be 1100-1300 watts, no idea what a well closed loop would draw,

Sounds like you need to count on enough solar power to make up for the less efficient geothermal in Florida vs up north where the ground/well temperature is much lower.

 

[toplessHO]

With a closed loop you would only need a small iron filter on the water input, once water is in the clsoed loop you would not need anymore filtration. With a ground closed loop you would need to go down at least 6 feet to hit soil which will remain at the years average temperature which is still around 70-81 degrees.
Surprising even in very deep well the water temperature is very high, so a closed loop down a well is not the most efficient due to temperature.

Page 32.....

https://pubs.usgs.gov/bul/0701/report.pdf

At your 1 hp pump draw now could be 1100-1300 watts, no idea what a well closed loop would draw,

Sounds like you need to count on enough solar power to make up for the less efficient geothermal in Florida vs up north where the ground/well temperature is much lower.

rating of the geo thermal units is still higher than an air to air in our area.
Our ground water temps are close to what you set your thermostat at for year round comfort.

 

[pcmeiners]

"rating of the geo thermal units is still higher than an air to air in our area."

Agree, but it would be nicer if your ground temp was 20 degrees cooler for the cooling efficiency.

 

[gsmith22]

"rating of the geo thermal units is still higher than an air to air in our area."

Agree, but it would be nicer if your ground temp was 20 degrees cooler for the cooling efficiency.

deep ground temps are the average air temperature of an area. The passing of time and relatively stable climates have caused that to occur over millenia. So you aren't going to find a location with dramatically different air and ground temps except at the extremes of summer or winter. So 70 isn't bad for cooling in florida because the air is so much hotter (ignoring how heat pumps can dehumidify too).

as far as air source heat pumps go, they are much less efficient at the extremes of winter/summer because of the medium of heat transfer. No one would actively choose an air source heat pump over a ground source heat pump except for the fact that it costs money to install these things and ground loops aren't cheap. Effectively, you pay upfront for the most efficient process (ground source) or you bleed money over the life of the system (air source).

 

[fitter30]

Slinky system need to do your homework for the heat transfer of your type of soil and tonage of equipment. Being on a open loop have the condensers have to be acid cleaned from all the minerals in the water? Must have a large system most open loops design is 2 gpm per ton with 60-65° water.

 

[jlv03]

If you have a pond, why not drop a plate in it and do a closed loop system that way?

 

[pcmeiners]

"So 70 isn't bad for cooling in Florida because the air is so much hotter (ignoring how heat pumps can dehumidify too)."

You should read before posting, I already stated that and posted a US geographical survey Pdf as to Florida ground temperature.

 

[Fav Onefour]

my temp going in is around 75
going out around 85

I doubt I will do that good with closed loop
but wont be paying for a well pump to run.

Ten degrees is what we aim for in our closed loop systems until they are close to threshold. With a right sized closed loop field, you should still see numbers in that range.

I'm up north and we size stuff for heating. Some area utilities wanted us to install full backup heating systems so they could "flip" the switch. We ended up with a lot of geo systems that had threshold capacities around zero F temp. They were cheaper without the capacity for the last 20-30 degree range. Temps don't hang around that point very often or long, so the idea of using alternate heat source became the norm.
Most of the heating stuff doesn't matter in this discussion. What does matter is how often we see our systems run at max capacity. Around here, almost everyone has Pete's plugs and they know their line variance. I'm heating with ground temps that start at 44F and slowly drop. I can still pull ten degree variance with the loop field cooled down to near freezing temps.

Another item to note about systems in our area. They are primarily closed loops with food glycol. Open loops were prone to freezing at the dump. The main issue I see with closed loops needing maintenance is when someone is being cheap. I've seen a few where the guy says his well water is good enough to fill the loop. A bunch of those dirty water systems are expensive and painful to run. Most of the cheapos end up doing a full system flush and clean fill after a couple rounds of acid bath on their exchangers.
Use good water and auto cycle your pumps in the off season. The loop will be close to no maintenance.