geothermal questions and possible DIY

[buckeyefarmer]

wouldn't be much different than a deep water well open loop and returning down a separate well on the same aquifer

When I took my training they said don’t dump it back into aquifer.

 

[Valveman]

A lot of open loop heat pumps use an injection well or even inject back into the same well. If heating the water through the heat pump causes any minerals to precipitate out of solution, the solids can plug the injection well. Water test need to be done to make sure there are no solids in the discharge water, and if there are a filter is needed. With a shallow water table an open loop heat pump can be more efficient than a closed loop. But as the water level gets deeper the open loop system requires more energy. A lot of people use a Cycle Stop Valve on their open loop well pump. It doesn't matter how much energy a heap pump can save if it is cycling the well pump to death and causing expensive repairs too often.

 

[Popgadget]

The outgoing water from my heat pump is about 45 degrees in heat mode and 65 in AC. Neither is going to precipitate anything out of the water, or cause deposits to form in the heat exchanger. My supply and return wells are over 200 ft deep, but that is inconsequential, because the static water level is not very deep, and that is what determines the load on the pump.

 

[truckdiagnostics]

We are in the process of redoing ours which has been in for 25 years. We have two closed loops burried at 6 feet and for the most part it is sized correctly. One feeds the house the other the shop and office. The loop for the shop and office I have had the water in the spring when the frost goes deep going back into the loop below freezing. It was sized right for the shop then I added an air handler and water coil for the office. Having a good loop is a big deal. Loop used for the house never had issues.
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The unit in the house is a split system it makes domestic hot water then switches to an evaporator for forced air for heating and cooling. In 25 years it has had new compressor and evaporator. Unit in the shop is water to water I got it used out of an apartment building it is bullet proof. All i have put in is a start capacitor. It is 28 years old. IMO you don't want a split system there is a better way to do it. You want to use a water to water.
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When we sized the spit unit we sized it for potable hot water. Then on the AC size it was to large, and it does not like it when you slow the blower down. You don't get the dehumidification, rots out the evap core. don't know what the deal was with the compressor. How they solved the problem is they sell a split system where everything is variable. Well, the problem is everything is variable they are a control and repair nightmare. Don't want one.
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Here is how we are going to get there. Split unit from the house is going to the shop, that gets me AC in my older years and it will be happy running full out on ac and getting the right sized ducts is not an issue. A water coil does not care about the air flow across it. The coil from the office is going to go to the house on top of a forced air gas furnace that we will use as an air handler and back up. I will take the water to water from the shop and move it to the house. Here is the neat part we are going to add another water-to-water unit to the loop for the house.
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We are going to install a loop buffer tank. So the loop will go in and out and two water to water units. Now here is where this pays off in the summer. In theory if you have the same load for hot and cold water you don't need the loop because they are mixing in the buffer tank. Then when the water gets either too cold or hot we run the loop pumps. We then have 4 stages of heating and cooling. It is all plumbing, all the valves are out where you can get too, not in a box the size of a refrigerator.

 

[ponytug]

@truckdiagnostics I like the loop buffer tank idea! Stanford University redid their energy plant awhile back, and put in some monstrous hot and chilled water tanks.
Here is a photo before the insulation went on;

There are a couple of workers on floor (roof) in the lower right below for scale.

What You Don't Know About The Ice Plant

What You Don't Know About The Ice Plant

stanfordmag.org

All the best,

Peter

 

[truckdiagnostics]

With that said on the straight up geo. The correct sized and installed closed loop. Then two water to water reversing heat pumps. Buffer on the loop side. Use a chilled water coil for forced air AC. You will need a buffer here also. Then you can get your in floor from this tank in winter. (remember you have forced air gas, so you can stay on chilled water for those duel heat weeks)Then pipe to an indirect hot water tank for your potable. In our case the loop for the house will support 4 tons no problem. So when the 5 ton from the shop poops out if ever, it will become a 2 ton two stage. (we will have two 2 tons)Near as I can figure that ticks all the boxes. This thing is going to run for 25 years, it needs to be build so it is easy to repair. (its all piping and a lot of glycol)Chances are the guy that put it in won't be fixing it. What i have just described is simple and workable, with the correct shut offs and what not it should be essay to repair. The unit inside a box the size of a frig just is not.
I'll post in the next couple days what we are up too.

 

[IXLR8]

I want to redo the heating/cooling system in my house. Researched geothermal, closed loop is not used around here due to all the trees. Open loop is what all the installers are familiar with. I was told they drill one well/ton of cooling, for me that would be 4 wells. Total system cost, just over $40K. Top of the line variable speed air to air system with propane backup was going to run $14K. As much as I like the idea of a geothermal system, I'm not sure I would ever make up that $26K difference.

 

[ponytug]

I want to redo the heating/cooling system in my house. Researched geothermal, closed loop is not used around here due to all the trees. Open loop is what all the installers are familiar with. I was told they drill one well/ton of cooling, for me that would be 4 wells. Total system cost, just over $40K. Top of the line variable speed air to air system with propane backup was going to run $14K. As much as I like the idea of a geothermal system, I'm not sure I would ever make up that $26K difference.

This is exactly the issue with geothermal.

Geothermal has some theoretical efficiency advantages, but isn't very much compared to modern air source heat pumps. On a ROI basis, the added cost of a geothermal installation can't come close to making up the lower upfront costs and generally high efficiency of air sourced heat pumps.

Locally, the ROI on geothermal is never.

All the best,

Peter

 

[Popgadget]

As a long time geothermal user and advocate, I agree with your assessment. The air to air units have gotten exponentially better over the decades. It is 19 degrees as I type this, and the air to air in my shop is doing fine, has not needed the propane furnace at all.
Of course the open loop geo in the house is also doing well and has no backup heat source, as it is never needed. But it would be hard to justify today.

 

[Grumpycat]

This is exactly the issue with geothermal.

Geothermal has some theoretical efficiency advantages, but isn't very much compared to modern air source heat pumps. On a ROI basis, the added cost of a geothermal installation can't come close to making up the lower upfront costs and generally high efficiency of air sourced heat pumps.

Locally, the ROI on geothermal is never.

But often it does. It can not when it costs $200/hr to dig a ditch.

 

[LD1]

I want to redo the heating/cooling system in my house. Researched geothermal, closed loop is not used around here due to all the trees. Open loop is what all the installers are familiar with. I was told they drill one well/ton of cooling, for me that would be 4 wells. Total system cost, just over $40K. Top of the line variable speed air to air system with propane backup was going to run $14K. As much as I like the idea of a geothermal system, I'm not sure I would ever make up that $26K difference.

That's not open loop. Open loop would only require 1 or 2 wells....depending on where you choose to discharge.

4 vertical wells is still closed loop. They just put the loop vertically in the wells instead of trenched horizontally in the ground.

And $10k per well seems a little steep IMO.

Maybe 10k for one water well I can understand. Because alot of cost to mobilize and ser equipment up. But 4 wells in one location for $40k just don't seem right. But I'm not a water well guy.

For 4-ton worth of horizontal loops, you only need an area to excavate that's about 80' x 120'. So unless you are in a complete dense forest, or on a small city lot.....I'd still look at horizontal loops

 

[Shblack]

Soil conditions are important! We tried the trench / slinky approach, I was going to dig the trench. Soil is gravel (former creek bed) with a water table that can get within 2’ of the surface when wet. It was wet when I dug the trench, water was 2’ down, contractor specified a 5’ deep trench. Sidewalks kept collapsing, trench full of water, ended up being 8’ wide in places. Couldn’t use the trench, unsafe to enter, pipe would have floated during install. Filled it in, went with 2 -300’ wells.

Friend was installing a system at the same time, planned on vertical wells. Site had a thick overburden of broken rock, well driller couldn’t set the casing with the equipment he had, every time he would pull the drill to set the casing the rock would shift and interfere with setting the casing. Ended using a horizontal loop in a trench.

Water furnace series 7, works well even when it got down to -3F in Tennessee this Christmas.

 

[IXLR8]

That's not open loop. Open loop would only require 1 or 2 wells....depending on where you choose to discharge.

4 vertical wells is still closed loop. They just put the loop vertically in the wells instead of trenched horizontally in the ground.

Considering all the discharge was going into the creek behind my house... I would consider that open loop. They were instant that they needed to drill 1 well per ton of cooling. I told them that seemed excessive, their reply was "that is the way we do things". So.. they are not 'doing things'.

 

[Valveman]

One of the good things about open loop geo is that it can utilize an existing water well. You should not need a well for every ton, but rather 1.5 GPM for every ton. If one well can make 6 GPM it will work for a 4 ton unit. If you don't have a good place to dump, you may need to drill an injection well. But many people use what is called a standing column design, which pumps and dumps back to the same well. If you have to drill wells for an open loop geo it can get as expensive as the closed loop designs. But using a well that was already drilled for house water doesn't add any cost to an open loop geo system.

 

[dodge man]

Keep in mind the tax break on geothermal. My opinion is the biggest factor is how easily the horizontal ground loops can be installed that makes geothermal practical.

 

[Popgadget]

Considering all the discharge was going into the creek behind my house...'.

In that case, if your existing well can supply 6-8 gpm in addition to what you use now, you don’t need to drill any well, and geo makes a lot of sense.

 

[Shblack]

One of the good things about open loop geo is that it can utilize an existing water well. You should not need a well for every ton, but rather 1.5 GPM for every ton. If one well can make 6 GPM it will work for a 4 ton unit. If you don't have a good place to dump, you may need to drill an injection well. But many people use what is called a standing column design, which pumps and dumps back to the same well. If you have to drill wells for an open loop geo it can get as expensive as the closed loop designs. But using a well that was already drilled for house water doesn't add any cost to an open loop geo system.

Standing column concept sounds attractive, maybe pull from the bottom, return to the top. Don’t need a lot of flow, larger water volume and far better thermal conductivity to the earth than 1 ½” HDPE / bentonite clay. Down side is minerals / silt in the water damaging the equipment over time. Not sure I would want to share this well with domestic water, though.

 

[IXLR8]

In that case, if your existing well can supply 6-8 gpm in addition to what you use now, you don’t need to drill any well, and geo makes a lot of sense.

I actually have 2 wells on the property. One supplies the house, the other for the irrigation system. We almost never use the irrigation system, but the HVAC tech didn't want to hear about using it. If I had a clue how to install a geothermal system I might try it myself, but I don't have the knowledge or tools. Also, I am a little concerned that the well water is fairly hard and full of minerals. Within 50 miles of me I only have 3 HVAC companies, only 2 of them do Geothermal and one of them installed the HVAC mess I have now and I wouldn't use them again. My options are limited for Geothermal and I am afraid even if I got a system installed, what would it be like to get service if needed. As much as I would like to go Geothermal, I just don't think it is in my future here. My property is also heavily wooded and I don't have an 80' x 120' area clear within 600' of the house.

 

[Popgadget]

A modern open loop is a very easy install. Ductwork, which any HVAC contractor should be familiar with, electrical supply, thermostat, water in and out. The modulating valve for water out to your creek is supplied with the unit, No aux or backup heat.
If you ordered it with a hot water loop for an indirect hot water tank you will have to plumb that loop as well. The variable speed circulator can come preinstalled if ordered with the unit.

 

[LD1]

Considering all the discharge was going into the creek behind my house... I would consider that open loop. They were instant that they needed to drill 1 well per ton of cooling. I told them that seemed excessive, their reply was "that is the way we do things". So.. they are not 'doing things'.

You had a moron for a contractor...plain and simple.

The main benefit of open loop is a single well...and/or already having a well completely eliminating the need for any heavy equipment.

Someone wanting to dri one well per ton....you might as well go closed loop and never have to worry about water quality, discharge water, or runny dry. Or the high amperage a deep well pump pulls.

So your contractor was an idiot.

And if you already have an unused well, a DIY Geo is as easy as it gets. You don't need a manifold or flow center or anything. And geo's....since all the refrigerant is contained within the furnace itself, they come pre charged. Some you don't even need an HVAC license.

It's as simple as setting a furnace, tying in ductwork, supplying electric, and water supply and return.