Physical Wiring - Lochinvar Knight 81 Instructions Manual

7
Wiring Requirements
Note that when the System Supply Temperature and/or the Tank Temperature are provided by the BAS, they need to be
refreshed every few seconds. Th is is required in order to prevent unwanted fl uctuations in these temperatures. If these values are
not provided every few seconds (timeout is programmable), the boiler will revert to its own internal control. If neither of these
temperatures is provided by the BAS, but any of the other control signals are being provided, the BAS will still need to refresh
these inputs at least every 4 minutes.

Physical Wiring

RS-485 Communication Bus
• Maximum Length = 4000 feet
• Cable Specifi cation = 24 AWG / A,B (twisted pair) and GND Shielded, with characteristic Impedance = 120 ohm
• Maximum Load = 32 units (32 nodes)
NOTE: Cable must be terminated with 120 ohm impedance matching resistor on each end.
A + (positive)
B - (negative)
Figure 7-1_Terminal Strip Connections
LOUVER RELAY
LOUVER
PROVING SWITCH
COM
FLOW SWITCH
NO
TANK THERMOSTAT
ROOM THERMOSTAT 3
ROOM THERMOSTAT 2
ROOM THERMOSTAT 1
FROM
A
PREVIOUS
B
BOILER
SHIELD
LOW WATER
CUTOFF
Modbus Instructions
ModBus and BACnet Communication Instructions
SHIELD
SYSTEM PUMP
SPEED
CONTROL
BOILER
PUMP
WIRE AS
NEEDED
A B
NOTE:
CONNECTION BOARD SPLIT FOR
ILLUSTRATION PURPOSES
BUILDING
MANAGEMENT
SYSTEM
TO
A
NEXT
B
BOILER
TANK SENSOR
OUTDOOR SENSOR
SYSTEM SUPPLY SENSOR
17