What kind of WSHP? Boiler/Chiller? A cooling tower @78dFwb is going to use a ton of power to chill water. An air cooled chiller is also gonna be taxed. A geothermal system is going to gobble it up easily, but with a design of 32dF winter, I'd be concerned about the "recovery time" for the ground (to cool down) (the newest buzz word in geothermal is ground recovery time... Usually from mfgrs that have recommended undersized loop fields.
I've been using Mitsubishi VRF systems in northern climes with design temps in the 90's in summer & well below 0dF in winter. We've had a number of them operating well into the low 20s & even mid teens before having to add aux heat. I've got 120 tons in an underground parking ramp using outdoor ambient most of the year & circulation parking ramp air to temper the units when the outdoor temps drop into the teens. It's working great with energy consumption on par with geothermal & 1/3 the upfront installed cost.
With a 100db 78wb summer design, I don't think there would be a VRF issue as most are nameplate rated at 95-100dF.
I was licensed by IGSPHA in the early 90's for loop field design & install, and I now believe it's dead tech. VRF is the future of this industry.
the question would be what happens to the vrf efficiency at such low ambients? i guess if it is 1/3 the price you can aford a bit of extra energy for a month a year!
Currently, most of major manufacturers design systems for lower temperatures.
In practice, I would always look at manufacturer's fine print about defrost cycles, as it will affect real feel of efficiency more than anything else, in practice, especially if thermal inertia of building is relatively low, as is in some commercial buildings.
Commercial building, however, often make good ground for three-pipe (recovery) systems, which are really good thing if designed and decided on with care.
I'm using 2 pipe heat recovery systems all over northern climes. much easier installation. Ball valves allow isolation of single head during service w/o dumping all the rfrg... longer line lengths & primarily soft copper preinsulated linesets. Integration of analog sensors (motion, Humidity, etc...)to trigger outputs gives many control options. Mitsubishi R series puts the 3 pipers to shame
