Horizontal Loop Field - Advice Requested - Southeastern MA

based on his first post, he is installing the field way before he even has a house design let alone a fixed location on the property or constructed basement wall to bring the lines into so I think he is going to have to bring these loops into some sort of outside header box for future connection to a header system that goes into the house. maybe you could speak to the complexities regarding this and what that means for purging (at some point way in the future)

 

I've got PE-4710, DR-13.5. DR-13.5 has the same pressure rating as the older standard pipe (160 PSI) but it's thinner-walled, so it has less flow resistance and better heat transfer. It could be more susceptible to damage from kinking or rocks during loop installation though.

I was also going to suggest running the loops into the house and having individual shutoffs, but as @gsmith22 pointed out, that could be an issue if the location of the house is not determined yet.

 

I'll clarify the situation a bit in case it is helpful in determining the best course of action...

While the house design isn't finalized yet, the location of the house is pretty much set, other than some possible minor changes based on the final shape of the house. Does it make sense to try to leave enough length on the ends of each of the 3/4" loops to be able to run them all into the basement once the house is being built? Obviously I would need to protect the pipe from being run over, as well as possibly UV exposure if it's going to sit outside for months?

Here's a sketch (below) of the lot. The colored stuff is my sketch, ignore most of the black and white stuff in the background, I am sketching on top of someone else's old plan. You can see the 140x100 orange rectangle I drew in the backyard for the loop field, and how that can be tweaked to some degree as necessary. I drew two possible potable water well locations, I prefer the one that's closer to the loop field, and AFAIK the loop field can be within the 100' well radius, unlike the septic system, but I'm not 100% sure about that. If it is an issue, I'll just move the well to the West closer to the original proposed location. The existing cleared area is shown very lightly in the background in a faded green, and the proposed tree clearing is the normal green. This can also change/expand to some extent as necessary.

An extra 100' on each end of each loop looks to be just about enough to get me into the basement, depending on the path they take toward the house and where they enter. I assume these are usually bunched together in one trench to the house, so the extra length doesn't really count much as far as additional effective loop length? What do you guys suggest I do based on seeing this sketch and knowing the situation?

 

Is there any difference in piping to purchase if going with slinky vs. regular? In other words, are slinkys sold in a manner that they are bundled to make assembling the slinky easier, or does it come the same way no matter what, and it's up to you to just make slinkies out of the regular coils of pipe?

I reached out to one of our (excavation company) normal pipe suppliers to get some pricing on pipe. They gave me a price of $0.27/lf plus tax plus freight for 3/4" SDR11 from Centennial Plastics in Nebraska, which stocks roll lengths up to 1000':
"CenFuse HDPE 4710 (NSF 14)
Fusible, NSF 14 certified Iron Pipe Size polyethylene pipe. Perfect for geothermal, golf irrigation, mining and industrial, oil and gas, and stock water applications requiring controlled outside diameter pipe. CenFuse carries a 50-year warranty."

I shared Oil Creek and Charter with them as potential suppliers to get pricing from, since Pennsylvania is a heck of a lot closer to me than Nebraska. Thanks gsmith22 for those two suggestions.

 

Unless you plan to DIY, this is probably a good point to identify a local installer who is willing to work with you, and work with them on the configuration.

 

Some lower-priority questions as I'm thinking ahead...

1. Say at the end of the day, my well-insulated 4000sf house is able to get away with a single 5-ton WF 7-series for heating/cooling. I am on-board with the benefits/comfort of the 7-series and would definitely consider foregoing the radiant in this sort of scenario. I understand the 7-series paired with IntelliZone2 supports 6 zones. Is it reasonable/feasible to try to heat/cool an entire 4000sf house with this single unit and 6 zones? That number of zones doesn't seem to be a problem for me, as I start listing desired zones (master suite, first floor living areas, second floor, basement, theater, plus an additional zone to maybe break up the 2nd floor bedrooms into 2 zones or something else), but I guess I am wondering if it's reasonable to hit such a wide variety of areas with a single unit?
2. On the radiant item, if I went with a 2 ton water-to-water for DHW, would it make any sense to pick a couple rooms to put radiant in, and have that unit be able to switch between radiant in those rooms and DHW? Not trying to over-complicate things, and don't have my heart set on radiant, but I'm just wondering if that's a reasonable thing to do.
3. On the dedicated theater, it is going to be totally sealed and sound-proofed (floating slab, isolated walls and ceiling), so it should be at least as quiet as a typical recording studio. Any thoughts on how to approach the HVAC in there? With it being so quiet in there, I want to do what I can to make the HVAC as quiet as possible, so while I have some things in mind such as larger than normal ducts/vents, mufflers/dead vents, I know you guys know a ton about this stuff and might have some great ideas.

 

I am starting to talk to local installers, I'm just not sure with so much unknown with the house design if I'm going to be able to finalize who I want to work with this far in advance.

I am considering DIYing the field and flow center and then bringing someone in for the rest.

 

He can leave the lines (tails) coiled up outside until he pours the basement walls. Make sure that he tapes the pipes again to ensure no insects etc get in there. You want to cut the tip off to ensure that you hear air entering the pipes. They are under negative pressure. If you don't hear anything, do not use the pipe.

 

13.5 SDR pipe is kinking a bit too easy for my taste, we tried it but went back to SDR 11.

 

The (5) ton 7 series should have no sweat to heat your house. Keep in mind that the variable speed kind of dummies down to a dual stage for each zone once you zone it. Also just because it can have 6 zones max does not mean you should over do the zoning. Lesser complexity is key.
Theater is tough. Not really, but has high internal gains, and high peak occupancy (higher internal gains), thus likely needs cooling all year around.Yes larger duct work is key, but ducts need to be balanced with the rest of the house. You might need cooling there, when the rest of the house needs heating. The 7 series is the most advanced for air unit on the planet, but it cannot do heating and cooling at the same time.
Radiant: Yes, you can have radiant for a few rooms. Did I mention to avoid complexity if possible. You now need a tank with a heat exchanger for hot water, since now you have to separate the portable water from the water in your radiant. You don't want to drink your coffee with the water running through your floor pipes. You also need a buffer tank for your radiant. Plus a 3 way motorized diverting valve, maybe 2 of them, depending which ones you choose. Now you have to control everything. And program everything.

So throw your slinkies or straight pipes in. 600 ft of slinky, 100 ft to the loop field, 100ft back, 800ft loops. 6-8ft down, 8-10ft O.C. You said you have no issue to put in 8 ,9 or 10 loops. So put in 10 loops. Since you said you want to put in the flow center yourself, now would be the time to do the pressure drop and worry about pumping solutions. Pressurized or non-pressurized? Non Pressurized!

All has time, put in your loopfield and worry about everything else later. Did I mention to keep things simple...!!!

 

Zoning dampers can quite working; I know! Less zones for simplicity. I would think with 4000' 3 zones or 2 zones should be plenty.

 

Interesting. But the only way to avoid that is to use a single zone? In any case, noted on minimizing complexity.

What are some reasonable approaches for this? Exchange air (quietly) with the adjacent room? I would imagine that with the sealed space the air would get stale anyway and so exchanging the air is necessary, even ignoring temperature? Dedicated mini-split for cooling the theater, when necessary, during the winter? Dedicated geo unit for the theater?

Got it. Radiant probably not worth the added complexity/cost, then.

I'm trying to register at Geo-Flo to use their calculators, but there is currently an issue with their registration form. It says the passwords don't match even when they most certainly do, with countless attempts using multiple passwords and in multiple browsers, and won't let me submit the form. I will contact them to try to get an account created. Edit: They are aware of the issue and are going to manually create an account for me.

Is there any upside/downside from a header/flow center/pressure drop perspective with using 12 loops vs 10 loops vs 8 loops, etc? I think I'm going to open up the entire loopfield area (or large portions at a time) and just spread out straight pipe loops within that area, so I can very easily do 8 longer loops, 10 medium loops, 12 shorter loops, whatever makes the most sense for pressure drop and the inside header/flow center. So yes, I will follow your advice, non-pressurized for sure, and how can I optimize this loop field from a pumping perspective? I know that more circuits with same total flow rate will have less pressure drop, but I'm trying to figure out at which point is the pressure drop reasonable enough to be efficient with pumping, and additional circuits is just more penetrations, header building, etc, with little benefit?

 

Pressure drop: What antifreeze are going to use. What concentration?

Zoning: I did not say no zones. If it would be my house, 4 zones would be fine. Basement, First and second floor, master bedroom. No need to go to 6.

Theater: Yes, dedicated heat pump away from the room for noise insulation is a solution. Small air coil for chilled water with an ultra quiet ECM fan. Many ways to skin the cat.Something to sleep over a few nights...

 

I was assuming Methanol (based on a previous recommendation from you) and I was guessing 15% concentration.

Here's my attempt at a pressure drop calc. 25 ft of head with 10 loops, goes down to 24 with 12 loops. How does this compare to a typical scenario?

 

Attached is your pressure drop. You can shoot for the 18-20 gpm range, that is with the 2 ton heat pump for domestic hot water. So 7 tons total.
You want to design for very low pressure drop to reduce your pumping power. I still assumed that you run each pipe out and back, and bring in each pipe individually. You can always purge your loop field yourself with your circulation pump, and you don't have to do any header worries and fusions outside. Best for DIY. Inside you can have your header, 0.75" ball valve, one for every circuit.

You can play with the numbers.

 

Thanks!

So, with the numbers you have entered as an example, 10 circuits of 600' with 120' of 2" header, it seems that the FCV1 would be appropriate? From what I've gathered from reading other threads, this is good because it is a single pump, which is preferred over dual pumps for obvious reasons.

I think I've seen in other threads where you are helping with design you try to use a single 26-99 pump, while it appears the FCV1 uses a Magna Geo 32-140? Should I attempt to design the field to a point where the FC1 is usable? Edit: Never mind, it looks like that pump is the ideal match for the 7-Series.

For example, if I remove the 120' 2" header you have in there, and instead go with 12 circuits of 700' (I realize this includes the ~200' to get to/from the house so it's really 500' of real effective loop per circuit), it looks like pressure drop is in line with the FC1 at about 17.5 gpm. Is that doable? Is it worth increasing the number of circuits and/or reducing circuit length even more to try to reduce pressure drop even further? What would you do?

 

The FCV1 now comes with a different pump, the UPMXL 25-124. The 25-124 cannot handle as much pressure drop, but it is more power efficient than the 32-140. You can refer to the attached. Design it to work with the 25-140. Less pressure drop is always good, because it saves you money. You dial-in the Min/Max pump power at setup. I have 4200' of pipe in the ground and I can get 13.5 GPM with the 25-124 set at only 85% power. The tools on Geo-Flo will tell you the projected power consumption for your pump, given the PD. Mine is projected to use only $38/yr.

 

that is interesting about the pump change. My flow centers were installed in Oct 2019 (after the announcement) and I got the 32-140s. By the time the pumps wear out, looks like I will have to get new flow centers too.

 

I had mine installed in Oct 2019 too. According to geo-flo and the assumptions made in the calculator, the 32-140 annual operating cost is a few bucks less than the 25-124 for my single 4T. Seems strange given the lower wattage figures in the announcement. You must need a high PD to see the savings.

 

yes, the 25-124 has lesser max pressure than the 32-140. It is usually 0.5 gpm less, not really relevant.\

If I were you, I would run 10 lines out there, and 10 lines back. Keep them separated in 2 different trenches, so you pick up some more heat when running them out to the loop field.

Next question: How do you make your hot water?