Installing our first water-2-water system (rough-in next couple weeks).  Main house 7,100 sqft will be heated with WaterFurnace water-2-air.  Shop and 2 apartment areas will he heated with a water-2-water system.  WaterFurnace EW Series.  Both systems will run off the same ground loop.

I plan to use Titus commercial grade air handlers with a 5-row coil.  Air handlers will condition air in both heating and cooling.  Single storage tank system (manual change-over from heating to cooling).  Water-2-Water is selected because the spaces to be served are in multiple areas that we can't run air duct to.  Running load water lines underground over the detached shop, etc.  One heat pump will serve min (3) air handlers.

So my concern is in cooling mode.  I assume I can chill the tank down to 45 degrees.  Just don't know how the air handlers will perform?  I will have load calcs, but are there correction factors that I don't know about with chilled water systems?  How can I be sure I'll have the right capacity in cooling?  Dehumidification?  Heating dominant climate here, but I've just never done this system.  I'm also concerned about short cycling the heat pump.  How can I set up the system to say... kick on when the storage tank is 95 degrees, and shut off at say 110 to avoid short cycle?

Please drop me a line if you know what I should be concerned about on this design & thanks for your help.  This is a great site I just found last week.

There are no load calculation correction factors, other than piping loss/gain. For the cooling, the gain will be negligible--you are insulating all supply and return water lines, right?

As far as cooling capacity, you have to look at the tables for the air handler. They should show you gpm, cfm, water supply temp, delta T, and associated BTUh capacity.

For short cycling, you shouldn't have a problem. Water to Water, or in my case, refrigerant to water, does the best job at maintaining tank temp to what it's set to, whether heating or chilling.

Control stategy is most important. A stop and start system is not the best way. Look into Honeywell Aquastats or Johnsen controls to help set temp on your tank. 119gallon storage tank recommended. Tekmar offers great controls, look into a 260 or a 263 with indoor and outdorr sensors. Water Furnace offers specs for heating and cooling outputs for they're EW series, make sure the air handlers are set up to handle the cfm and btu required. Water Furnace now has 4 position air handlers available up to 5 tons capacity. Make sure the groundl loop is sufficient for your project. We see more problems with improper sizing than anything else. Splitting the loop can result in flow issues. Make sure your headering is correct.

Thanks for your help. I am planning on giving Titus my load, cfm, and EWT requirements, and have them help me select the air handlers. I will look into the controls you've suggested. I guess I will have to insulate load water lines since some will travel underground.

Headers for the ground loop is also a concern I have. I'll be completing the loads this weekend, and sizing the loopfield. If I scanned my ideas for header design and posted, would you guys have a look and let me know what you think?

Also, I was hoping to use a "non-pressurized" flow center from B&D this time around. Haven't done that before either.

We just had an EW installed on an elevated deck in our shop. 4500 ft. of slinkys 8 ft. down. We have a 3000 sq. ft. ICF shop with 17 ft. ceiling (heated with infloor to 45degrees) 3000 sq. ft. residence with hot/cool deck in the air handler in the residence and about 800 sq. ft of residence with radiant heating to show clients "this is what radiant is, now move over to this room this is concrete slab on grade only without radiant heat. Pick your option"

So, three high velocity grundfos pumps; two to infloor heat and one from the shop to air handler in the residence. We only have an 80 gallon storage tank, (I leave the strips off so far) and now lately a buffer tank for the DSH. I am told there is only one "stage" to this system.
The first two months electric was disappointing, (maybe our expectations were unreasonable) the water temp was set at 120, with the storage tank strips set to come on at 115 degrees for backup, I don't think they ever came on, as I've been working in the shop and watching the water temps and run cycles. And there were a few weeks the temp didn't get above 5degreesF. The installer came back last week and installed some new controls on the storage tank that would turn the geo on only when there is a call, however waterfurnace did not really advocate this. They also reset water temp to 100 though we have no idea what the ideal is. We just wanted more air circulation to keep the 2 floor consistent temps, as there are many more windows downstairs. The system hardly runs maybe a three minutes every 18 minutes, temps are between 35 daily and 10 at night in N. Wyoming. Everything is ICF and spray foam.
The installer did some head scratching before installing a three way valve to allow cooling, at the air handler, which I don't understand.

The installer told me prior to the install "no way you will ever need to dehumidify in Wyoming" and included a duct humidifier in the price of install, but due to a last minute Christmas eve purge and initial setup, the air handler ran non stop for the next month until the installer made it back. Our three hygrometers throughout the home never got below 45 percent, bathroom/kitchen always stayed 5 % higher. The building science I read says that when below 0 degrees F one should drop the interior humdity to as low as 20% short term to reduce condensation on windows etc.. Our structure has been up for a season already, (we were heating with electric radiant heaters to get by for a year) if moisture of curing concrete, drywall, paint etc. was in the home and trying to dry out, I suspect humidity would be staggering in a tight structure....The installer shrugs, seems interested, says, "it'll be interesting, we've never installed in a tight superinsulated place like this" So he is looking into dehumidifier option.

Yes, interesting. I guess that's how we learn. The good news is, the installer wants an ICF house now.

I've never been apart of a water to water/hot deck/chilled water system like this and am learning a lot, so is the installer. One thing I learned is I'd better have all the chilled water lines to the air handler insulated perfectly to keep condensation from becoming a problem in the summer! I'm wondering how warm we can keep the water to do the job...