Hi Guys- I’ve been reading this forum for a few months now with great interest. You clearly know a lot about this field and it has been interesting learning from you. I’m considering installing my own geothermal system at my residence. I work in the engineering side of the HVAC industry, am licensed, etc. so I’m not exactly your average DIYer. That said, I understand the potential to get into this over my head and for things to go sour during construction, which is why I wanted to seek out the opinion of the construction professionals who frequent this forum (if only as a sanity check). Thanks so much in advance for reading.

DESIGN INFO
Estimated sizing is 3-4 tons with 10 kw-20 kw supplemental electric resistance heat. I’m leaving myself a few sizing options to allow myself flexibility in picking the unit, but I’m leaning towards a 3 ton CM Tranquility Digital Unit with a 15 kw electric resistance heater.
1) Where you live: Central NY Area, HDD65: 6834 CDD50: 2500 (90.1-2007 D-1)
2) Heat loss/gain calculations for your home: I’ve run the calcs a variety of ways, loads come to 36 kbtu/h - 48 kbtu/h depending on internal loads, whether unfinished basement is considered, and winter design temp, house is 2400 sf, 25 years old, good insulation. Sizing is driven by heating load.
4) Type of loop field (open/closed/vertical/horizontal) size and design parameters: considering 4 150 ft trench slinky loops (4ft/ft), buried to 7 ft, .75” HDPE, 17% methanol, 30 EWT
8) Percent of load to be covered by geo and balance point, ~19 F per CM, 96% heating load

I’d like your feedback on a few questions:
1. My biggest concern is warranty protection. I discussed this issue with a CM engineering sales rep at a recent trade show. While he discouraged me from doing this myself, he indicated that I would be covered under the CM warranty if I purchased the unit from my local rep (instead of some online store). Do you guys have any feedback on this issue? Are you aware of any geo contractors that assist DIY installers in the CNY area? I’m willing to pay someone to validate that the install was done right and that my design is ok/submit the warranty docs to the manf.
2. Am I correct that I should be backfilling my trenches with sand to promote heat transfer around the loops prior to backfilling with the excavated soil?
3. I like the Climatemaster TE (Tranquility 30 Digital) series because it reduces the number of parts I need to install. It includes a VS internal flow center and internal diagnostics. The downside with this system from my perspective seems to be that a flush cart is required to fill the system. Do you guys have any experience with the Climatemaster TE series? Would you recommend using internal flow centers (like Climatemaster TE) or an external flow center?
4. I recently attended a GSHP design seminar that questioned the value of 2-speed compressors and VS compressors in GSHP systems due to the lack of reasonable AHRI criteria to compare these systems at part load. What is your opinion on the performance of these systems in real life? Are there actually measurable savings? (Single speed units are much cheaper).
5. I have an electric air source heat pump water heater. Will this cause any issues when connected to the HWG in a GSHP? All of the literature I can find is based on electric resistance or gas-fired DHW.

Thank you so much in advance!

Ok, lets see if I can answer a few of these.
1. Warranty - Personally, I would never send in warranty docs and validate an install for a DIY customer, why would I put my liability and name on the line for somebody else's installation and design. When you read these forums look at how many people blame the manufacture of geo equipment when it does not work and in the end it is not working from a bad install or bad loop. Somebody validates your system and it doesn't work you are going to call them and complain, I would not want that liability.
2. When you say "sand" do you mean a sandy loam or literally sand?
3. Never used climatemaster I am a WaterFurnace dealer.
4. I have seen a difference between 2 stage and variable speed vs single stage. It is also more comfortable, better for zoning and quieter using multi stage equipment even if there is minimal savings.
5. I have hooked up desuperheater to heat pump water heaters and it works just fine. All a DHW does it take incoming water and heat it so with a desuperheater you put higher incoming water into your heat pump water heater.

@SkyHeating

1. I definitely respect/appreciate what you're saying from a professional liability standpoint. Thanks for making that point. Let me ask then - what is the scope of the typical DIY assistance services provided by members of this forum?
2. To be honest, I'm not sure. Let me ask you: What is typically used for backfill of a horizontal slinky loops? My experience is mostly with vertical commercial designs.
3. OK
4. Thanks! We typically specify and install VS, modulating (digital scroll) and 2-speed compressors in nearly all applications. I don't understand how these could possibly be a bad thing in this application, but figured I would ask after hearing that statement.
5. Thanks!

we normally use native soil around slinkies if rocks are not present.

1) You need a local partner contractor. It does not have to be someone who regularly installs geo, however Climatemaster does tend to require a little bit of training to sell you product. In the absence of help from a CM dealer you can get a Comfortaire which is made by Climatemaster.
2) Why would you take the time to truck in sand? Sounds like your research included a little DX content.
3) I am a CM installer The internal flow center is a nice feature. You will not to flush any system you purchase.
4) I think I was the last guy pushing single stage equipment. There is little savings with the 2 stage equipment, but they do tend to heat and cool more evenly.
5) Heat pump water heater and DSH work fine together providing you employ a bufer tank.

19 is a cuspy balance point if I read your design temp correctly as 1. I would shoot for the mid to low teens. Perhaps you can do that with load mitigation or perhaps it isn't really that high.
I do not understand how you are getting a 1 ton difference in your calculations. If you have lived there some time why not find out load from actual consumption.
Do you have 4 tons worth of duct?

@Geodean

Excellent, thanks. We do have rocks present here, which is why I was considering using something else for backfill.

@joe.ami
Thanks!

1. I'm working on finding that contractor now. If you guys have any suggestions (or if any of you work in the CNY area and are willing to install customer-supplied equipment), please contact me! I'd prefer to avoid dealing with sheet metal .
2. No, I'm avoiding geothermal DX. Too many potential issues and cost implications for Cu. Our soil is wet, rocky clay @ the depth I'll be excavating to. Hence, my concerns. I may just bring in topsoil from another nearby property for backfill.
3. Great thanks.
4. Thanks. So, the consensus seems to be: 2-stage and VS can't possibly be bad, especially for occupant comfort (temp swings). However, energy savings may not be large and cost increases are significant when comparing 1-speed to digital scroll, 2 stage, or VS compressors. That was the basic point of the speaker at the design seminar.
5. Thanks. FYI, HPWH is used in heat pump only mode to maximize energy savings and dehumidification. Are you recommending a two-tank installation because the HPWH is only heating with the single (bottom) section? Or is there something else here that I'm not understanding?

Agreed. Keep in mind that I'm an engineer, so these calculations are going to push on the conservative side. I'm not really crazy about the 19 F balance point, particularly in this climate zone. Here's why that's happening: TE series is only available in 3t and 4t units. 4t unit results in much lower balance point, but requires a significantly larger loop to get good COP and has a significantly higher estimated annual operating cost ($100 or so) using my 4x150 slinky loop design. 3t unit results in higher balance point, but has a smaller loop size and reduced annual operating cost due to higher COP. There is of course more utilization of electric resistance in this scenario, which shows up in the bin hours.

Internal loads are estimated based on my knowledge of the envelope, occupants, and infiltration. Estimated envelope load is approximately 46.5 kBtu in heating, minus internal gains (CM wants me to model internal gains as 6 kbtu/h which is probably reasonable during occupied periods). In terms of envelope, we regularly perform blower door testing and do "good". Most low hanging fruit (e.g. spray foam, additional batt insulation in attic space, other air sealing) has unfortunately already been addressed by me.

Yes, the ductwork should be fine for 1400-1600 CFM.

As I look at this further, and based on the answers to #4 above, I'm leaning towards dropping from the TE product line and moving towards something much simpler/cheaper, like the TS product line. TS042 ECM seems like a much better match for my space. To be honest, with the HPWH (~2.3 COP within 50-70 F space). I'm not entirely convinced that the HWG is necessary, particularly during winter months. FYI, switching to TS042 ECM without HWG drops balance point to 13 F. Balance point with HWG is 17 F.

#5 - Most installers on the forum will always recommend a two-tank installation. First tank is a un-powered buffer tank... second tank can be your choose. A two-tank operation ensures you don't accidentally dump heat from the water heater back into your ground loop.

You may want to be a bit more precise with you location.... CNY covers a wide area.

@dgbair

Thanks!

Fair enough. I'd rather not be too specific in a public forum, but I'm in the eastern suburbs of Syracuse.

I would just bring in enough sand to protect the pipe and then use the native.

Being you are in NY, I'd assume your Air Source HPWH is inside the conditioned envelope. That being said, the heat you put into it (during heating season) will come from the house, which came from the GHP which came from the ground. Your paying to move it twice. First move from ground to GHP to house at a cost of 1 BTU electricity for 4 BTU heat. To move those 4 BTU from house to water at COP of 2.3 would be 4/2.3=~ 1.75BTU. So for 1+1.75 BTU of electric, you get 4 BTU of hot water. 4/2.75= 1.45. A net COP of 1.45 for hot water in heating season. I'd think again about DSH. Just get as much hot water as you can straight from the GHP at the higher COP.

This is a completely different story if you are in Florida and have much more cooling than heating requirements. In NY where you are in a heating dominated climate, the DSH may be worth the cost. I am in Southern Maryland and have a GHP and air source HPWH. great benefits in summer for my basement and basement humidity. It does chill the basement greatly though in winter.

@geodean
That's the plan, thanks.

@mtrentw
Interestingly the conclusion of a DOE sponsored technical paper at the ASHRAE conference was that most residential HPWH in the Northeastern US were operating at ~1.5 COP (I'll have to find that paper, very very interesting)... maybe I'm not losing too much after all.

EDIT: Just looked up the paper from NREL/DOE. Typical COP for 50 gal HPWH in NE region is ~1.1 in unconditioned space, ~1.3 for 80 gal HPWH in unconditioned space. The huge problem I have with this study is that they assumed the use of electric resistance backup heat for times when the HP could not meet load alone. IMHO, occupants should adjust their behavior to keep in pace with the heat pump or another tank should be installed! The GE Geospring heater they used (the 50 gal unit) has controls which seem to overuse electric resistance, whereas the Bosch 80 gal unit tested uses heat pump more. I think the 1.3 is a more accurate estimate for unconditioned basement spaces./END EDIT

Assuming that the basement is conditioned, you're absolutely right about the HPWH. It makes no sense at all to steal heat from the geo system. It's probably worthwhile in that scenario (depending on ambient, of course), to turn on the electric resistance heat in the HPWH. The tricky thing here is that my basement isn't currently conditioned. The walls aren't even insulated completely down to the slab. To that end, I've always assumed that the basement would eventually start pulling some heat from the ground if the temperature got cold enough down there. Maybe my logic is flawed?

Ok, I thought about this a little more and I might be thinking about the DSH wrong. If I can use DSH @ 3-4 COP it will always beat out HPWH at 1.5-2.3 COP, regardless of placement in the building envelope. The only concern is the requirement to upsize the heating capacity of the geo system and the size of the well to provide DSH in peak heating.

Ah, first world problems...

Have you not lived in the house long enough to get load from actual usage vs "calculations"

No, unfortunately not here long enough for measured usage.

Assume 80 gallons of hot water a day. Almost 700 pounds.
Raise it from 50 to 120*. Takes 49,000 BTUH.
Spread that load over a 24 hour day it's 2,000 BTU load, or an additional 1/6 a ton.

You don't need to upsize the unit or loops, just use what you've got. Maybe there are a few days where you need a bit of aux.

Here's a re-post from some time ago that might be relavent.... We live in West Michigan, have 3 ton wshp DSH piped to std elec buffer tank and GE HPWH as our powered tank. The setup has worked fabulous so far... we are coming up on the third year since we added DSH and HPWH. ----------------------------------------------------------------- Abstract... Based on before and after tracking we are saving more than $400 per year on hot water costs due to the addition of the DSH and the GE HPWH (was elec resistance before). Payback (for unit, extended 10 year labor warranty, and piping materials) should be right around 3 years. Intro... In December of 2011, I connected/piped and enabled the desuperheater on my Climatemaster TTV038 (open loop pump and dump, source well has about 45' lift, and consumes ~800 watts at 1st stage flow where it runs a vast majority of the time). I installed a new GE Heat Pump Water Heater as my powered tank, and repurposed my existing dual element electric tank (50 gal) as the buffer tank. At about the same time I replaced my old upright frost-free freezer with a new energy star (manual defrost) freezer. There are several relevant points that took place since the desuperheater was enabled and HPWH was installed: 1. A record or near record warm summer 2012 2. A colder than average winter 2012-2013 (based on local HDD data) 3. Our family grew in size. Based on data logger information from my original standard electric tank heater (prior to the DSH/HPWH tank install) and total cold water consumption read from my water softener…. I’ve assumed the same proportion of hot to cold and estimated that my domestic HW load has gone up by 15-20% 4. Our family’s comfortable winter t-stat setpoint went from 67 to 68F 5. Added (2) small noise maker fans that run at least 10 hrs per night (sometimes they are left on during the day! :)) 6. We stopped using our outdoor clothesline to dry most of our clothes, alternate method is electric dryer (we are off the NG grid of course). After subtracting out the effect of the new freezer (based on before and after KiloWatt meter readings) AND eliminating the data from the record warm weather from 2012 (Jan, Feb, March, April)…. the combined effect of the above changes has been an overall average decrease in energy consumption of 152kWh per month or about $313 per year at current rates (actual monthly savings is greater in the summer months, but there is noticeable savings in the winter/heating months too). Factoring in the increased HW use over that period, shows that the new equipment DSH/HPWH is actually saving us an additional ~$100 per year (assuming 10.5 gal/day increase, 68 water DT, 0.89 de-rated electric efficiency including average measured stand-by losses). So for me the combined savings for the GE HPWH & DSH is more than $400 per year or about (17% of my total energy at the time when I installed the units). Total cost for me - ~ $1,200 (including 10 year labor warranty on HPWH, piping, fittings, insulation, etc.) Simple payback - ~3 years (less as we continue to use more HW, and local electric rates go up). This was a pleasant surprise being a more northerly location (West Michigan), where in general the HPWH concept isn’t as favorable. Based on COP data for the GE HPWH and knowing approximately how much HW we use, it is clear that you can’t get to the savings I’m seeing with just cheaper HW. So it would seem that a good amount of the savings I’m seeing is coming from both the longer more efficient run times in the heating mode (as the DSH and HPWH move almost the entire HW load onto the GSHP during the heating season), and the cooling side effect of the HPWH in the hot summer. My summer electric bills are only slightly higher than the shoulder months, due to the cooling benefit of the heat pump water heater.