Posted by Harold Kestenholz - Hydronic Network on November 03, 2001 at 22:05:42:
In Reply to: Wiring a 3 wired taco zone valve posted by Richard Matson on November 03, 2001 at 19:13:14:
Terminals 1 and 2 take the transformer 24 volts to operate the zone valve motor. The white wire of the thermostat goes to terminal 1. The other wire of the heating thermostat (usually red) goes to the transformer.
Terminal 2 is connected to the other transformer terminal that does not have the white wire going to the thermostat.
Terminal 2 of the Taco zone valve also performs another duty. When the zone valve is open a switch closes between 2 and 3. This switch is used to operate the relay that starts the circulator and/or burner, so the burner and/or circulator relay T and T terminals go to terminals 2 and 3.
Every zone valve is wired the same and the thermostat anticipator set at .9A
The wiring diagram is actually on the box or the tag attached to the head of a new Taco zone valve.
It is easier to buy an Erie or Taco zone valve relay that can handle three or more zones and wire the zone valves and thermostats from there, although that would cost more money.