47
®
Inverter (variable speed) drives
WARNING: If an inverter is connected to the Nexus PPC5000 fuel air ratio control system
it must be listed or component recognized by authorities who have jurisdiction for the spe-
cific purpose for which it is being used.
Wiring must comply with all applicable codes, ordinances and regulations.
Wiring, where required, must comply with NEC Class 1 (Line Voltage) wiring.
System configuration
The Nexus PPC5000 fuel air ratio control system uses a 4-20mA output on the IDB (isolated drive
board), AH221244 as a speed reference signal to the inverter. A matching 4-20mA input is used to
monitor a feedback signal from the inverter, representing the speed of the motor.
In addition to the 4-20mA signals, the inverter also requires a motor start signal that must be taken
from the burner controller. The ‘motor start’ signal must occur at the same time as the HI/LO INITI-
ATE (PC11) signal to the Nexus PPC5000 fuel air ratio control system for reliable operation. The
fault relay of the inverter must be connected into the stat circuit of the burner, so that if the relay
breaks the inverter will be shut down.
Since there are two input/output pairs on each IDB and up to two IDB’s may be fitted in the option slots, a
maximum of four inverters may be controlled from one unit.
BURNER
CONTROLLER
INVERTER
STAT CIRCUIT
FAN START
STAT CIRCUIT
FAULT RELAY
RUN/STOP
SPEED
REFERENCE
SPEED
FEEDBACK
MOTOR
4-20mA IN
4-20mA OUT
3000 IDB
OPTIONAL
SPEED
SENSOR
Alternative
speed
feedback
