Russ,
These valves usually come with a mnfrs. data sheet giving the options for various circuit control layouts, with wire colors to stepper motor and relay feeds and outputs shown.
Usually, the valve is opened by a signal from a programmer, time clock, switch or programmable thermostat. Upon being fully open, a relay in the valve closes, ( and often there is a NC set of contacts available too), which gives an independant signal which you can use to fire up a boiler or furnace, run water circulators etc.. This independance of signal is vital if you have multiple zone heating or domestic hot-water heating + central heating etc, because you don't want to backfeed other programmers or thermostats upstream.
I have used this sequence;
Programmer signal to valve, and to the water circulator. That's safe, the water is circulating when the valve is open. Relevant valve relay signal taken to the boiler [furnace] firing sequence through a thermostat, so when the boiler/furnace shuts down, [ie. satisfied], the circulator continues to run using residual heat.
I know this sounds obvious, but in complex set-ups, make a sketch of the circuit showing the wire colors and identifying the valves etc., and keep it for reference. You'll be back to fit replacements in the future.
And if an old dolt like me can do it, anyone can!
Alan
