Taco makes two variants of zone valves - one type for general hydronic use, and another type marketed especially for geothermal use.
What is the difference in valves that particularly suits them for one application or the other?
All the manufacturer's literature I can find (so far) basically reads identically for both products. But the geothermal variants are more expensive. Having looked at samples myself, I don't see any superficially obvious differences. The actual valve portions appear to be potentially identical; but there could be some differences in the actuators ether mechanically or electronically which would not be obvious.
(Perhaps other manufacturers have a similar offering, I just happen to be a little familiar with Taco's).
Assuming there are substantive differences, in a pinch could one be used in the "wrong" application successfully? (e.g., using a regular hydronic in a geothermal system, or vice-versa).
Note - both samples I've seen are normally closed, so apparently the answer is not that one is normally open.