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Connect wiring — general information
Part number 550-142-330/0421
26
SGO
OIL-FIRED NATURAL DRAFT STEAM BOILER — SERIES 4 — Boiler Manual
SERVICETECHNICIANONLY—readandfollowcompletely.
General wiring requirements
ELECTRIC SHOCK HAZARD – Can cause severe
personal injury or death if power source, includ-
ing service switch on boiler, is not disconnected
before installing or servicing.
Installations must follow these codes:
•National Electrical Code, ANSI/NFPA 70, – latest edi-
tion and any additional national, state or local codes.
• In Canada, CSA C22.1 Canadian Electrical Code Part
One – latest edition and any local codes.
•Wiring must be NEC Class 1 – latest edition. If original
wire as supplied with boiler must be replaced, type 105°C
wire or equivalent must be used. Supply wiring to boiler
and additional control wiring must be 14 gauge or heavier.
•Provide electrical ground at boiler as required
by codes.
Thermostat wiring
•Install thermostat on inside wall away from influences of
drafts, hot or cold water pipes, lighting fixtures, television,
sun rays or fireplaces.
•Follow instructions with thermostat. If it has a heat antici-
pator, set heat anticipator in thermostat to match power
requirements of equipment connected to it. Boiler wiring
diagrams give setting for standard equipment.
Junction box (furnished)
•Junction box houses electrical connections for all boiler
components.
•Packaged boilers have harnesses furnished.
•For Semi-packaged and Knocked-down boilers, trim kits
are furnished with burner and limit harnesses.
•All field-provided high voltage wiring must be sheathed in
flexible metal conduit.
•Connect incoming line voltage “HOT” wire to service
switch, and neutral wire to white wire. Field-install equip-
ment ground wire to green wire with wire nut.
•Service switch (15 amp) is provided with boiler.
For Semi-packaged and Knocked-down boilers —
install switch as shown.
•Some local codes may require an emergency shut-
off switch installed at a location away from boiler.
Follow local codes.
Burner wiring
•Burner wire harness incorporates a disconnect plug,
providing a convenient way to disconnect wiring
when burner mounting door is opened.
•All Packaged boilers have a power disconnect plug
installed on the service switch junction box.
•The burner is provided with a burner discon-
nect plug as shown in Figure 20, page 29, or Fig-
ure 23, page 31. For burners in which the disconnect
plug is not factory-wired, connect the threaded
conduit coupling of the disconnect plug wire har-
ness (P/N 591-391-850, included in steam trim
carton) to the burner housing and route the wires
to make all connections in burner junction box as
shown in boiler wiring diagram.
High temperature limit
•To comply with ASME, UL 726 or Canadian re-
quirements, an additional high temperature limit
is needed.
•Install the secondary control in the supply piping
between boiler and isolation valve.
•Set the control to a minimum of 20˚F above the set
point of the combination control.
•The maximum allowable set point is 220˚F.
•Wire the control as shown on page 28 (float-type
LWCO) or page 30 (probe-type LWCO).
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