Honeywell #V8043E1061, 3/4" Sweat Connection Zone Valve, normally closed, 8 Cv (24v)

Two-way on-off low voltage valves consist of an actuator and valve assembly for controlling the flow of hot water.
Type: Use this valve in closed loop hydronic systems that do not contain dissolved oxygen in system water, such as fresh water from frequent source of makeup water.

Features
Manual opener (on all models, except straight-through, normally open valves) for valve operation on power failure; valve returns to automatic position when power is restored.
All models may be installed without disassembling the valve.
Compact construction for easy installation.
Complete powerhead may be removed or replaced without breaking plumbing line connections or draining the system.
Actuator motor may be replaced without removing the valve body or draining the system.