I have a home with multiple zones with the valves mentioned in the question. The documentation (http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf) isn't clear about whether contact 3 is energized when the valve is manually operated or not, and I'd like to open one of them manually for an extended time.
I'm in an awkward spot; I have a zone valve that I suspect is faulty, and no immediate access to a meter to diagnose it. I'm going to be away for an extended time in very cold weather, and this zone includes a bathroom that I'm nervous about freezing without heat. I'd like to open the valve manually (using the lever made for this purpose), and have the zone receive water anytime another zone calls for heat, but not trigger the boiler itself. So far, experimental evidence is suggesting that it does not trigger the boiler, but I'd like confirmation. Note: this is a very small zone (a powder room and hallway) that's open to the kitchen, so I'm not concerned about wasting too much heat, as it will reduce the demand in the kitchen zone somewhat.