MG & SG Series Boilers – Installation and Service Manual
24
Wiring Diagrams Section 7
Simplified Wiring Instructions
IMPORTANT
• Disconnect power source to boiler before wiring zone control board.
• All wiring must comply with applicable codes, ordinances and regulations.
• The non-replaceable fuse on the board will be blown if 240 Vac is connected to the board or if the
24 Vac system is even momentarily shorted out.
A: Line Voltage Connections
Connect 120 Vac, 60 Hz, single phase power to terminals L1 (HOT) and L2 (NEUTRAL). Strip wire ends
to a maximum of 3/16" before inserting into terminal block. Tighten terminal screw clamps. Connect
ground wire to ground screw “G” on the boiler control panel.
B: Zones
Remove zone one plug-in terminal block. Connect 24 Vac thermostat leads to terminals TH1 and TH2 on
plug-in terminal block. Connect normally closed zone valve 24 Vac motor leads to terminals ZV1 and
ZV2. Connect zone valve “end switch” leads to terminals ES1 and ES2. Strip wire ends to a maximum of
3/16" before inserting into terminal block. Tighten terminal screw clamps. Re-insert plug-in terminal
block into mating connector on Zone Control Board. Repeat for zones 2, 3, and 4 as required.
C: Optional Second Pump
A second pump (120 Vac, 1/6 HP maximum) may be connected to terminals P1 (HOT) and P1C
(NEUTRAL).
D: Jumpers
Jumpers J1 and J2 are factory set for a multi-zone installation.
E: For Single zone Applications
Install jumper J2 and connect 24 Vac thermostat leads to terminals TH1 and TH2 on Zone 1 plug-in
terminal block.
Manufactured exclusively by
Allied Engineering Company
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