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X Wiring
1) Line Voltage (120 VAC) Connections (Fig 10.1) – The line voltage connections are located in the junction box
on the right side of the vestibule:
• Black – Line voltage “hot”
• White – “Neutral” for boiler and circulators
• Red – “Heating” circulator “hot”
• Blue – “Indirect Water Heater “ circulator “hot”
• Green – Ground connection
2) Maximum circulator continuous current draw is 2A. When Piping Method #1 is used, it may be desirable to
use the boiler to directly control the primary circulator in addition to the secondary circulator. If this is done,
control both heating circulators using a relay with a 120VAC coil, such as a Honeywell R4222, as shown in
Figure 10.3. Select a relay with a contact rating in excess of the combined draw of the two circulators.
3) Low Voltage Connections (Fig 10.1) – These connections are screw terminals located on the terminal strip
next to the junction box on the left:
• Terminals 1 and 2 – “Heating” thermostat connections
• Terminals 3 and 4 – “External Limit Control” connections
• Terminals 5 and 6 – “Outdoor Reset Sensor” connections
• Terminals 7 and 8 – “Domestic Indirect Water Heater” thermostat connections
• Terminal 9 – “Flame Signal Reading”
• Heat anticipator setting for the thermostat connection is 0.1 A when thermostat is connected directly to
terminals 1 and 2.
4) If the outdoor sensor is connected to terminals 5 and 6, the boiler will adjust the target space heating set point
supply water temperature downwards as the outdoor air temperature increases. If used, this sensor should be
located on the outside of the structure in an area where it will sense the average air temperature around the
house. Avoid placing this sensor in areas where it may be covered with ice or snow. In general, locations
where the sensor will pick up direct radiation from the sun should also be avoided. Avoid placing the sensor
near potential sources of electrical noise such as transformers, power lines, and fluorescent lighting. Wire the
sensor to the boiler using 22 gauge or larger wire. As with the sensor, the sensor wiring should be routed away
from sources of electrical noise. Where it is impossible to avoid such noise sources, wire the sensor using a
2 conductor, UL Type CM, AWM Style 2092, 300Volt 60°C shielded cable. Connect one end of the shielding
on this cable to ground.
WARNING
All wiring and grounding must be done in accordance with the authority having jurisdiction or, in
the absence of such requirements, with the National Electrical Code (ANSI/NFPA 70).
CAUTION
• WHEN MAKING LOW VOLTAGE CONNECTIONS, MAKE SURE THAT NO
EXTERNAL POWER SOURCE IS PRESENT IN THE THERMOSTAT OR LIMIT
CIRCUITS. IF SUCH A POWER SOURCE IS PRESENT, IT COULD DESTROY
THE BOILER’S MICROPROCESSOR CONTROL (MCBA). ONE EXAMPLE OF
AN EXTERNAL POWER SOURCE THAT COULD BE INADVERTENTLY CON-
NECTED TO THE LOW VOLTAGE CONNECTIONS IS A TRANSFORMER IN
OLD THERMOSTAT WIRING.