Crown Boiler TWZ175 - Manual (Page 23)

21
Wiring Variations
1) Multiple Circulator Zones – Figure 20 shows wiring for two or more circulator zones using Honeywell R845As. One
R845A is required for each circulator zone. Circulator terminals “C1” and “C2” on the L7248 are not used. A DPST
Honeywell RA832A may be substituted in place of the R845A using the “X” and “X” terminals in place of the “5” and
“6” terminals on a R845A.
A call for heat from any thermostat will energize the DPST relay in that zone’s R845A. When this relay is energized,
electrical continuity is created between terminals 3 and 4, energizing the circulator for that zone. At the same time,
electrical continuity is created between terminals 5 and 6 on the R845A, creating a current path from terminal “T” to “T”
on the L7248 or L7224. Assuming that the supply water temperature is below the high limit setting, the normal ignition
sequence will be initiated.
2) Multiple Zones using Zone Valves – Figure 21 shows wiring for multiple zones using Honeywell V8043F zone valves.
This wiring diagram may be used for other 24-volt zone valves as long as they are equipped with end switches. Do not
attempt to use the transformer on the L7248 or L7224 to power the zone valves; use a separate transformer. Up to five
V8043Fs may be powered by one 48VA transformer, such as the Honeywell AT87A.
A call for heat from a given thermostat will result in the application of 24 volts across the TH and TR terminals on the
corresponding zone valve, energizing the zone valve motor. The zone valve opens and the end switch contacts are then
made. The end switches are connected in parallel with each other and to the “T” and “T” thermostat connections so that
any zone valve that opens will also start the circulator and fire the boiler (assuming the high limit is not open). Zone
valve terminal TH/TR has no internal connection on the zone valve; it is merely a “binding post” used to connect two or
more wires.
FIGurE 19: WIrInG DIaGraM, sInGlE HEatInG ZOnE OnlY