Ohio The start of my Geo journey… appreciate any input!

All, I found this site about a month ago while researching interest in my first geothermal system. I am a mechanical engineer by education and have had interest in all things thermal/mechanical and have weighed options in passive solar, wood heat, etc. I love to work on things and have done all home improvements myself and build cars in my spare time so understanding and doing this myself are just as important on the journey as any financial savings I will get. With that said I realize any knowledge I have here pales compared to what you have so I was hoping to tap into the tremendous real world expertise I see on this forum. I learned from you that a Manual J calculation is the first step so the numbers below come from that calculation... I have details if you need them. Cincinnati appears to be heating season dominant with about double the BTU load in winter as that in summer so I will stay focused on the heating load requirements.

About the project. - Home is located in Cincinnati, Ohio and was built in 1978 and is 1800 sq.ft. It currently has propane central ducted heat with heat pump AC and I have a very high tech wood burning furnace I built last year that I use one or two times a week (ignoring since my use is inconsistent). My calculations show a 24K BTU heating requirement on the base house. I am beginning the permit process for a 2400 sq.ft. extension so I want to size for the addition as I go. The extension will be built to much better standards with Intus triple pane windows with heavy southern exposure, SIP walls and ceiling, etc. so it has only 13k BTU requirement netting 37K total BTU load.

Based on this it looks like I am on the line as far as unit sizing. While a 3 ton would work I am leaning towards a 4 ton to ensure sufficient capacity unless you all convince me otherwise? The cost difference is only about $800 in the entire equation and I do not want to have to run an electric heat strip later. With a 2 stage or variable system I assume I will still be able to control humidity with the AC running on low and not lose much from a slightly large system?

While I love the Water Furnace 7 heat pump it looks like I will have difficulty getting one as a retail individual so I am probably leaning towards a Climatemaster Tranquility 30 digital (I hear the Trilogy 40s still have bugs that I don't want to troubleshoot). I have also read that the Trane TVGX is similar to the WF 7 so I may see if I can get my hands on one if it would be better than the Climatemaster. It seems like the built in variable pump in the Climatemaster would be beneficial but not as readily available from a spare parts stand point... what are your experiences with these variable pumps? I plan to do a horizontal ground loop as I have plenty of space and an excavator to dig with. The soil is heavy clay and I planned to do slinky loops to reduce my digging distance.

At this point the "Kits" from people like Ingrams look nice however I would be happy to pay more for better quality pex/hardware if the expertise from you all says it is worth it for reliability or performance. I would also like to spend some time thinking through the installation options to ensure maximum efficiency. With my limited current knowledge I am thinking 4 - 800' slinkies if 4 tons.... or perhaps 8 - 400' ers to reduce pumping loss? I do plan to use a Desuper heater with a pre-tank to the GE Geo system I have now… that is easy enough to figure out and I saved my old water heater for this purpose.

Thanks again for helping me start this journey!
Tyler

 

What you plan sounds like you are on the right path.
Big fan of 7 series , but I admit I am a bit bias since we are a Waterfurnace dealer. Yes, Trane is actually made by Waterfurnace and are identical "clones". So is "Geostar" which might allow you to by them through a distributor. Yes, heard of a lot of Climatemaster trouble with their variable speed, but that is from hearsay. I'd go 4 tons for sure, your addition heatloss sounds super low. The southern exposure does not help you much during winter nights. Plus keep in mind that manual J is the 98% percentile of the average, not the peak. You likely need 5 tons if you don't want the aux heat to come on. Think about zoning since you have 2 different thermal behaviors with the 2 different buildings. Make sure you get the pressure drop down to where a single pump flow center with a variable speed pump will do the job. Crucial for the 7 series or its clones. With 4 ton 7 series we use 6x600' slinkies at 8' depth, with 400' your reynolds number might be too low to have enough turbulent flow. How long is your loop away from the house.
The pex lines are not great, but you can rent a heat gun, or hire someone who could fuse the pipes outside, that would be better. I would always go with HDPE, but I understand the limitations for DIYer. Try to go with Methanol for better heat transfer and flow characteristics as an antifreeze.
Let us know if we can help with advise, design, calcs etc....

 

PEX is infrequently used for loop piping. HDPE pipe is the industry standard. Note also that PEX is sized differently than HDPE and 3/4" PEX has a smaller inside diameter than 3/4" HDPE. PEX is Copper Tube Size (CTS) pipe with standardized OD. HDPE is Iron Pipe Size (IPS) with standardized ID. 3/4" PEX has a nominal OD of 3/4" while 3/4" HDPE has a nominal ID of 3/4". 1" PEX is roughly the same ID (0.875") as 3/4" HDPE (0.860" ID for standard SDR11 geothermal pipe).

You can buy HDPE socket fusion heating irons and other required tools on ebay. When you are done with the project, you can then sell them back on ebay and get most of your money back. Socket fusion fittings are also available on ebay or online goethermal suppliers. Buy some extra fittings, download the manufacturers installation manual, watch some youtube videos on socket fusion, and practice making connections.

If you can run your loop pipes back to the house and make the header connections in the house or basement or in a vault box just outside the house, they would be easily accessible for repair/replacement in the future.

 

Dito Arkie here. Many reasons to stay away from pex in the ground. You can bring each circuit inside, and build your header there, which I would do as a DIY. If you happen to have a leak on one of your fusions, it is easier to fix. Would you loop field be right outside your house?

 

Great info so far really appreciate it. The addition is low energy usage for sure... spending extra money to build it to almost passive house standards...I live out in the woods so we loose power for a few days at a time occasionally. Trying to keep the BTU loss low enough that I can heat with the wood burning insert with 1 load of wood a day when needed. Putting plenty of thermal mass in to reduce the temperature swings as well.

I will definitely do HDPE instead of PEX... until today I did not know the difference so I clearly have more research to do. I have plenty of outside space so would probably run each loop right off the back wall of the basement... that means I could bring each connection in doors so if I screwed one up it would be super easy to fix. Looks like I would want 3' wide by 8' deep trenches for each slinky loop... do you dig as deep for straight runs? I assumed slinkys were less digging but wanted to be sure as I know digging to 8' adds a lot of time. Happy to spend the time if beneficial for sure.

The fusion tool looks cheap enough that is no worry to buy... currently $300ish on ebay and I am happy to spend more money for quality and have never regretted buying good tools. I will dig into the methanol option a bit more... I actually always keep a drum in the house as I inject it into my supercharged cars and over the top of my diesel tow truck for power and EGT reduction. I assume the mix % is low enough to reduce or eliminate fire risk? Methanol fires are nasty... cant see them until everything goes really wrong. I will also look up Renolds # calculations when I dig deeper into exact loops... I remember the concept but am quite rusty on the equation side of things and it appears to be a sweet spot between thermal transfer and pumping loss.

I will dig into the Trane and Geostar options... would love the full variable nature of the WF 7 if I can figure out how to buy it. In my experience machinery lasts a lot longer if it is always running and the speed is varied. I have seen many motors on heavy machinery run for decades straight with no issue... power goes off once and they never turn back on.

Have a few other more crazy optimization ideas but will share those once I get the basics ironed out.

Thanks again, I really appreciate everyone's input!

Tyler

 

Some caution - Doc gave you "a" design, not necessarily "your" design. You need to nail down a few other numbers first.

 

Yes makes total sense... I am probably trying to understand too many variables at once. I think HP selection is my next variable to complete then I can really start sizing everything else. Any other key numbers besides the Manual J you think I should be looking at for HP selection?

Thanks,
Tyler

 

My heat pump selection is a bit different from yours but you can take from it accordingly:
- dealer support (I pick up a phone and talk to "the" guy and get parts)
- good literature (good for troubleshooting)
- good product (warranty, quiet, efficient, variable speed, well made)

Lots of details inside those details, but that is the TLDR.

 

You should never have full concentration methanol "in the house". We bring it in the house already diluted by 50% (1:1).
There is one thing about manual Js, but you are dealing with an 1978 built portion where it is very difficult to get good handle on how the performance actually is. 24,000 BTU/h, at what design temp. How is the insulation in the wall performing? And the air infiltration?
What I am saying is that we sometimes follow the illusion of precision. And then everything is different in the real world. You usually have the choice between 3, 4 or 5 ton with a WF made 7 series clone. You could make a good argument for each one of them.....especially for a 4200 sqf house with mixed insulation.
With variable speed the disadvantages of undersizing are the same as with 1 or 2 stage equipment, but the disadvantages of oversizing are minimal, and so are the incremental costs. So you can run all kinds of precise calculation, many input factors will be based upon a guess (is that insulation in the kids bedroom being 38 years old performing at an R-10 or R-20.....) and then you pick a 4 or a 5 ton depending which gives you the most comfort for your mind and the fact that you do not want to dip into supplement electric strip heat.
The difference between 5ft and 8 ft in the middle of the winter is 3.5 F without extracting heat. Depending what your load turns out to be (you will only find out after your first winter of operation ) 6ft depth might work equally well for you. In theory the variable speed units require a bit more loop, in reality given the same load and the same loop, a 7 series might dip 0.5 - 1F lower in the peak cold than a dual stage, really nothing to sweat about.
So as a DIY, with all the unknown variables, make sure you have a generous amount of loop, low pressure drop in the loop, and pop a 4 or 5 ton variable speed system in. You might come to the conclusion that everything else does not matter so much.

 

I am not an expert but I can offer advice from the diy side of things.

Climatemaster Geodesigner software is a neat way to get ideas of how changes in loop design will affect performance. It's free and pretty easy to use.

http://www.climatemaster.com/geothermal-dealer/geothermal-sales-tools/geodesigner/

DIY tip for connecting HDPE pipes-
1" pex fittings will work in 3/4" sdr11. I used the 1" pinch clamps with a little strip of 30ga sheet metal as a shim.
Sounds hokey but it works great and is done easily with supplies readily available to a diy.

 

I have had no complaints on the climate master variable speed stuff, except for the cost. The best diy advice I can offer is to run your loop tails into the basement. That means no joints outside. Pressure test everything prior to backfilling. While the engineer in you is pushing for variable speed equipment, it is adding a layer of complication and trouble to the diy in you. I would select good standard equipment and install a pressure less flow center for any diy.
hope this helps.
Eric

 

From an install point of view, there is really not more complexity to bolting in a 7 series versus a single or dual stage. The factory setting on the unit allow you to just turn it on and let it run. Not sure what the complication and trouble could be.
Agree that the none pressurized flow center is a must for DIY.

 

none?

 

non-pressurized! Thank you Mark for catching a typo.

 

Hi all, time for an update after dozens of hours of further reading/ research.

I have called, e-mailed or stopped by 17 Waterfurnace, Trane and Geostar installers or distributors and it looks like these are harder to get than I imagined. While I think I could get a Geostar with a 12 hr drive I am worried at this point about even trying to get parts for these brands as a DIYer.

Based on that I think I am leaning towards a Climatemaster Tranquility 30 4 ton unit. My question at this point is if I should do the variable flow center with it or not. I know if I do that I will need to build a flush cart. That does not look very difficult and I can always find other uses for a 2hp pump. With that said if I could figure out an external non-pressurized flow center that is still variable it simplifies life greatly and would be preferred. I see they exist... Does anyone know if the Climatemaster controls will control an external variable unit?

I have been playing with 3 different loop field configurations using Climatemaster software as well that I will share once I finalize the heat pump design... It looks like I can keep the head loss rather low to minimize pumping loss while still maintaining a nice Reynolds number.

Thanks again to all for the extensive knowledge you have shared.

Tyler

 

Ok going to start digging over the weekend. Since the house only has 24k heating requirement currently I planned to start with a 400' trench, run 3 - 3/4" loops of 800' SDR... 3 out at 8' deep and 3' back at 6 feet deep... I will keep the trench 24" wide for simplicity. This is basically the exact distance to my barn so I can run bigger electric and water to the barn at the same time which has always been on my to do list. This will give me a Reynolds number of 4577 with 32.7' head pressure (11GPM).

When I build the house extension I will add a second loop of the same dimensions... taking head pressure to 9.74' and Reynolds at 2860 (15GPM).

Does anyone see any major issue with this approach? I still need to look up the variable pump specs as I think I will have higher pumping loss with the first trench until I get around to the second. I validated the Magna 25-140 the climatemaster comes with will support the flow requirements.

Thanks,
Tyler

 

Good luck.

 

To stack them up does not give you the same performance. Heat comes from below, and the 8' deep pipes will steal some heat needed from the ones above.

It is better to run them next to each other. Also, your loops will be below freezing, it is a bad idea to put a water line in the same trench.
Why don't you put in the whole loop including the one for the extension now?

 

Thanks for the valuable feedback Doc.... 6 loops in a trench was one of my concerns when I wrote this and part of the reason I ultimately planned on 6 loops of 800' for a 4 ton system. I can absolutely do all loops at once... just means I will be running equipment more next week to get to a Dec. 31st start up.

I can also go down to 4 pipe trenches and do an extra trench if you think it is that big of a deal?... cost is only my time and fuel. I used Climatemaster's geo design software and only saw a $10 difference a yr. in electric usage doing two 6 pipes vs. three 4 pipes or slinkies. I know these calculators are not always accurate and not sure if they include pumping loss so that's why I value everyone's real world input so much.

Anything else I am planning that makes you guys nervous? If anyone things I am way off I would very much welcome that input... if not I am sure I will learn a few lessons along the way... always part of the fun of the journey!

Tyler

Oh and water pipes to barn are only used in the middle of the summer.

 

All I can tell you that I have some stacked up pipes in my back yard, and they do not perform as good as they should per software. Nothing in principle wrong here, just saying that spreading things out more if you have the room is better. I would put in more circuits and make them shorter, just like 600' each, much better pressure drop, lesser pumping power.

Keep in mind that water pipes can freeze even if you don't use them....