1
®
DESCRIPTION
The Fireye NEXUS
™
Integrated Controller is a microprocessor based, Flame Safeguard and parallel
positioning combustion controller built into one compact, user configurable package. The system
consists of the Controller, Display, Wiring sub-panel, Temperature / Pressure Sensors, Servo-Motors
and ComFire Software.
The Flame Safeguard portion of the control package provides burner sequencing including safe start
check, proof of main valve closure, selectable main gas safety proving sequence, supervised pre-
purge, low fire starting position, pilot and main trials for ignition, main flame supervision, and post
purge. Safety event timings are provided to meet North American and CE Standards. Time proven
Fireye Flame Scanners and amplification circuits using UV, UV-Self Check and Infrared sensors,
provide fast reliable scanning of most commonly burned fuels. Ten user defined auxiliary inputs pro-
vide supervision of safety critical and non-safety critical inputs.
Control of up to four Channels using an independent Servo-Motor for each controlled element
allows precise positioning, accurate to 0.1
R
, of the fuel and air metering devices over the burner’s fir-
ing range. One of two fuel profiles can be selected for each fuel channel with up to 24 positions per
profile including; Closed, Purge, Ignition (Preferred Start™), Low Fire and an additional 20 interme-
diate points from low to high fire. Each individual servo-motor’s position and speed are verified and
lockout will occur should either of these parameters be exceeded.
Modulation control is provided via the pressure/temperature sensor’s input. The Fireye NX1025,
NX1030 or NX1040 sensors provide checking circuits for fail safe operation. PID setpoints are
available for the chosen modulation input, selectable up to two decimal points. Track modulation is
available for those applications requiring less precise control.
The NX550 Display allows commissioning and current status of the system through the use of its
tactile membrane keypad. Multi-function keys allow the commissioning engineer the ability to
access the various Ratio Modes and Option Select menus. The two line 20 character Vacuum Fluo-
rescent Display clearly illuminates the Control Variable, Firing Mode, Fuel Selected and Hours Run.
It further allows the Boiler Operator access to the Auto/Manual selector, Motor Data (servo posi-
tions) and other operational parameters such as System Sequence Position, Valve Proving Sequence
Status, Gas Pressure, Flame Signal, Modulation Rate and Setpoint, as necessary.
Multiple Boiler Sequencing is accomplished through an RS485 Communications bus using ComFire
software. Lead/Lag and Standby set points for up to ten (10) boilers can be configured.
NEX-1001/3.1
JULY 2003
NEXUS
INTEGRATED BURNER
CONTROL SYSTEM
