Thanks to the help from my installer and many of you on this site, I finally pulled the trigger on a 2-ton vertical loop system. Below are the details:
TTV026Climate Master Tranquility 30 geothermal heat pump with integrated air handler.(EER19.9to28.00,COP4.00 to 4.6) 3 stage heat, 2 stage cool with 5kW auxiliary heater and de-superheater. 260' vertical loop
The system installed fairly well and has performed well for cooling and the limited heating so far this year (installed at end of July).

At this point, I am now getting ready to replace a 40gal 15 year old electric water heater. I've heard on this board, the de-super heater on a 2-ton unit might not be very helpful for assisting in water heating needs. Can anyone comment on this? I'm on the fence between going with an 80 gal (Family of 4) heat pump water heater vs an 80 gal Marathon electric water heater. I understand it might be worth while to hook up a buffer tank from the de-superheater - should this be an 80 Gal? Can I even get enough utility out of the de-superheater on a 2-ton unit? Is it overkill to go with a de-superheater/heat pump water heater combo? The price difference is the price of installation (I would install regular unit myself - pro has to do it for $750 rebate in MA on HPWH) after rebates assuming I don't need to add a buffer tank. My current unit is at the end of it's life so I'm not sure it would be a good idea to use it as a buffer tank....

If your family showers rather than taking tub-baths you'll do just fine with a 50 gallon heat pump water heater and a drainwater heat recovery heat exchanger rated better than 50% in the standard NRCAN testing.  Currently the only DWHR vendor on the MA approved plumbing fixtures list is Renewabilty ( PowerPipe series) others would require a variance.  You can open an account with EFI with a credit card over the phone to get the wholesale price on them (which is better than the direct-from manufacturer retail price, or the orange box store retail price.) 

From a showering point of view, a 4" x 48" or 3" x 60"  (or bigger) PowerPipe effectively doubles the apparent capacity of the tank, but does nothing for tub-fills. (The drain and the water have to run simultaneously to get the benefit.  The heat exchanger needs to feed both the hot & cold sides of the shower.) If 2 or more people insist on always taking tubbies, bump it up in size, since the recovery is slow.  The DWHR unit needs to be mounted vertically to work, since it relies on surface tension of the drain water to get it to spread out over a maximal area for efficient heat exchange.







On bigger heat pump water heaters, the 66 gallon Airgenerate AirTap ATI-66 tops the list- with all- stainless design you should be able to get at least 25 years out of it.  For the really big  'uns the Stiebel Eltron Accellera 300 has more than enough capacity, but not the stainless construction- it won't last nearly as long.

For the lower cost 50 gallon units the GE GeoSpring does pretty well, (after some early-years nightmares) now that production has been set up in the US (Kentucky, IIRC) rather than offshore sources, with harder-to-monitor & fix quality control issues.  The ATI-50 would likely last 2x as long, but it's about 2x the price too.

The complexity & cost of buffering the desuperheater on a 2-ton has pretty limited value compared to drainwater heat recovery and heat pump water heaters. If history is any guide you would probably get better payback out of putting the money into rooftop PV than further investment on desuperheater & buffer tanks on your system.

Ok, that is what I was thinking.... I've read the 80 gal HPWH do better since they can generally recover in heat pump mode for most applications. Any thoughts on the AO smith model? Also, just simply calling EFI and I can setup an account?

Aside from my main sewer stack, all of my drain pipes are copper, but I don't really have a 6' section for which to replace the cast iron stack with the power-pipe (I'm in a ranch). I could always install the power-pipe, then feed a waster pipe out of it into my drain stack but the installation won't be that straight forward.

Since your heat pump has already a DSH installed, the extra effort/cost of piping in a buffer tank is minimal.
We use the bradford white electric tanks, since they have a 2" foam insulation and are reasonable priced, and simply don'y connect the heat elements. Use a 40 or 50 gallon tank max for a 2 ton heatump. Yes, the DSH output is limited at 2 tons, but I assume it will run a lot in MA, so you will make the water with the efficiency of the heatpump.

Posted By sbeausol on 15 Oct 2013 08:11 PM
Ok, that is what I was thinking.... I've read the 80 gal HPWH do better since they can generally recover in heat pump mode for most applications. Any thoughts on the AO smith model? Also, just simply calling EFI and I can setup an account?

Aside from my main sewer stack, all of my drain pipes are copper, but I don't really have a 6' section for which to replace the cast iron stack with the power-pipe (I'm in a ranch). I could always install the power-pipe, then feed a waster pipe out of it into my drain stack but the installation won't be that straight forward.

I set up an account with EFI over the phone 5-6 years ago- it took less than 10 minutes.  I don't buy a lot of volume from EFI, but they're a first-rate vendor (they don't mark up shipping with handling fees, the goods are usually shipped the day they receive the orders, etc.)

Slab-to-joist-edge in my basement averages about 88" and the main drain tees in at an angle, but I was able to squeeze in a 4" x 48".   Figure out how much vertical space you have to work with, and get the biggest one that fits- both length and diameter count, since the heat transfer efficiency is all about maximizing surface area. Even the  4" x 30" or 3" x 42" units deliver better than 40% return efficiency at 2.5gpm (higher for lower flows), which is enough to make a difference in apparent-capacity & efficiency.

The economics of drainwater heat recovery pencils out quite well when it reduces the size & complexity of your hot water heating.  They are dead-simple no-maintenance dumb-as-a-box-o'-rocks devices with a 40+ year anticipated lifecycle.  At current MA power rates it still works from a NPV of utility cost savings point of view for a family or four too, even at DSH or heat pump water heater efficiencies.  

The fact heat pump water heaters it reduce the latent cooling load even when there is little to no sensible load works for New England basements with no slab insulation as well. In homes that need a basement dehumidifier to keep the RH in the basement under control, heat pump water heaters reduce the duty-cycle- putting that heat-of-vaporization into the hot water tank rather than raising the temp in the basement the way standalone dehumidifiers do.

No beta to share on the AO Smith heat pump water heaters.  I've read some posters on other forums steering people away from the Rheem heat pump heaters, but have no details as to what the issues with them are.

You may want to quote it out with/without the DSH buffer, but the MA subsidy for heat pump water heaters is substantial, but in general most financial analysis on the whole package (DSH + buffer + controls)  rarely works out in this climate, even when bundled in to the subsidy for geo.  It tends to pencil out better is for larger units, in cooling dominated climates.  Whether the post-subsidy cost of the DSH buffer offers that much in price/performance is something I don't have a direct feel for (too few datapoints to work from)  but I'm a bit surprised that they would install the DSH on the original system without any storage capacity (unless there's no way to un-bundle it.)

Anyone looking to reduce water heating costs should review their shower head flow rates. If necessary, boost water pressure (to perhaps 70 psi) to allow lower flow at similar comfort.

I'm with DJ - since the geo HP already has the DSH, go ahead and plumb in a buffer tank; 50 gallons should be ideal.

Going large on the HPWH makes sense. The AO Smith 80 gallon model commands a premium but is well-regarded. The Smith models are substantially louder than the GE Geospring, but that loudness arises from a bigger compressor and much larger fan, both of which aid in recovery and performance in colder ambient conditions.

The drainwater system is probably also worthwhile; Dana explains it well. However it is only effective when large hot water draws are immediately drained, as in showering. Most other hot water draw events (baths, clothes washing, dishwashing) have a time delay between the time water is drawn and water is drained, denying the simultaneous flows required for a drainwater recovery system.

For northern applications it would be interesting to consider putting the low side (evaporator coil) of a heat pump water heater within a buffer tank that detains departing grey water long enough to have its heat extracted, but that is a conversation for another day.

Finally, I can't agree with raising domestic water pressure as Jonr suggests since it is complex and costly. Instead seek one of the many improved showerheads that deliver comfort at both reduced flows and modest pressures.