Wiring Guide

11
Sequence of Operation / Settings
• There is a demand by one of the t-stats which
sends power to the corresponding zone valve.
• When the zone valve opens, its end switch
contacts close and signal a demand to the RW
(TT) contacts on the single zone relay control.
• Relay #1 and relay #2 fire
• If the factory installed jumper has not been
removed, the NO terminal of relay #1 will
deliver the hot leg of 120 VAC thus firing the
pump.
• Relay #2 closes the TT contacts on the boiler
signally a demand.
• The Zone LED illuminates.
• When the last of the T-stats is satisfied, the
corresponding zone valves closes which
opens the end switch contacts.
• The relay contacts return to their normal
position turning off power to the system pump
and opening the RW (TT) contacts.
• The Zone LED turns off.
WARNING: NEVER CONNECT R & C DIRECTLY,
this will be a direct short on the 24 VAC supply
Description of terminals
= Ground
N = Neutral (Common leg of 120 VAC)
L = Line (live leg of 120 VAC)
C = Common terminal
NO = Normally Open terminal
NC = Normally Closed terminal
Note: There is a factory installed jumper between the 120
VAC line (L) and the common terminal of relay #1 (C).
Thermostat terminals
R = 24 VAC
W = Heat call
C = Common of 24 VAC