Part number 550-141-825/1211
24
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WTGO
OIL-FIRED NATURAL DRAFT WATER BOILER — SERIES 3 — Boiler Manual
SERVICE TECHNICIAN ONLY — read and follow completely.
General wiring requirements
Electric shock hazard. Can cause severe personal
injury or death if power source, including service
switch on boiler, is not disconnected before install-
ing or servicing.
• Installations must follow these codes:
• National Electrical Code, ANSI/NFPA 70, latest edition
and any additional national, state or local codes.
• In Canada, CSA C22.1 Canadian Electrical Code Part 1
and any local codes.
• Wiring must be N.E.C. Class 1. 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 an-
ticipator, set heat anticipator in thermostat to match power
requirements of equipment connected to it. Boiler wiring
diagrams give setting for standard equipment.
Zone Valve Wiring
4- wire zone valves may be connected directly to the boiler
control.
Connect wiring
Junction box (furnished)
• Junction box houses electrical connections for all boiler
components.
• “P” boilers have harnesses furnished.
• “A” boilers 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 equipment
ground wire to green wire with wire nut.
• Service switch (15 amp) is provided with boiler. “A” 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 harness incorporates a disconnect plug, providing a
convenient way to disconnect wiring when burner mounting
door is opened.
• All “P” boilers have a power disconnect plug installed on
burner.
• On “A” boilers, mount the plug (provided in water trim
carton) on the burner housing as shown in Figure 17. For
Carlin burners, screw burner plug into threaded conduit
coupling, then mount this assembly to the burner housing
using the chase nipple. Route wires through housing and
make connections in burner junction box as shown in boiler
wiring diagram.
High temperature limit
• To comply with ASME, UL 726 or Canadian requirements,
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 26.
DO NOT connect directly from 3-wire
zone valves to the T-T terminals on the
boiler
. When using 3-wire zone valves, install
an isolation relay. Connect the zone valve end
switch wires to the isolation relay coil. Connect
the isolation relay contact across the boiler
T-T terminals. Failure to comply can result in
damage to boiler components or cause unre-
liable operation, resulting in possible severe
property damage.
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