For wiring, refer to the diagram page 3 (3.2.5 Viewing head
connector wiring).
➔ Ensure that the viewing head signal wire and the signal ground
(braided shield in the four conductor cable) are both connect-
ed, since this ground connection is the only return path for the
signal and self checking circuit.
Important: Install the source impedance matching resistor on the
signal processor between the terminals marked SC and SIG GND.
The required resistor is 330 Ohm, 1/4 Watt if the distance
between the signal processor and the viewing head is less than
500 feet (150 meters). For a distance greater than 500 feet (150
meters), but less than 1000 feet (300 meters), a 150 Ohm, 1/4
Watt resistor is required. For distances greater than 1000 feet (300
meters), contact your local Honeywell distributor or the factory for
guidance.
3.2.5 Viewing head connector wiring
S256BE Connector
3.2.6 Remote Meter
The terminals located at the bottom of the signal processor des-
ignated RMT METER (to the left of the CHAN SEL terminals) are
for the remote meter connection. This output is a current-driven
signal that ranges from 0 to 20mA for remote meters, and can be
switched to a range of 4 to 20mA (refer to the GAIN SET button).
The current signal can be used with an external volt meter by
connecting a resistor across the analog output terminals marked
GND and +RMT. For full scale deflection of 10 volts, use a 500
Ohm, 1/2 Watt resistor.
3.2.7 Modbus transmission to PC
The P222 signal processor uses RS422 data transmission over
two, twisted wire pairs. The four terminals labeled +TX, -TX, +RX,
and -RX are used for the serial communication link. Serial commu-
nication is achieved by using Modbus RTU.
RS422 converter is required to communicate via the USB com-
munication port on the host computer.
➔ The terms "transmit" and "receive" used here with respect to
the P222 will be reversed with respect to the RS422 to USB
converter.
3.2.8 Channel select
A second set of configuration parameters can be stored and used
in circumstances where flame characteristics and/or configuration
needs require a second set of parameters. The CHAN SEL termi-
nals are located at the bottom of the signal processor.
To set channel B configuration parameters press and hold the "B"
button until it begins to flash quickly (the P222 is now in B channel
adjust mode and all configurations for viewing head gain, time
settings and flame off level can now be adjusted.
➔ Whenever Channel A or Channel B parameters are being ad-
justed the appropriate channel light will flash quickly.
➔ The B Channel is not active until selected by closing the con-
tacts between the terminals marked B and +. The + terminal
must be con- nected to the +24V OUT terminal located on top
of the signal processor, next to the incom- ing power supply. A
Modbus register is also available for switching Channel A and B
control via an external computer.
3.2.9 Manual Mode
Manual mode is entered by pressing the AUTO/MAN button on
front of the signal processor. Additionally, manual mode is entered
if the flame signal is absent for a period equal to the longest delay
(relays de-energized). In manual mode, (HAnd), the Signal proces-
Signal Processor
Shrink Tubing
Connection
Shield
SIG
GND
White
SIG
Black
SC
Red
+V
Green
GND
M35683
sor will not automatically respond (energize the relays) after a loss
of flame until manually acknowledged (cleared).
Manual mode is indicated by the AUTO ON (yellow LED) being off.
If the flame signal is absent for a period equal to the longest delay
(relays de-energized) the processor will enter the Manual Mode
Tripped state (AUTO ON yellow led flashing), which requires a user
RESET. In this mode the relays will not be energized if the flame
is detected unless the manual mode is cleared by either a remote
switch on the MAN CLEAR Terminal to Ground, or by pressing the
RESET button on front of the signal processor. Note that pressing
the RESET button in the Manual Mode Tripped state, will toggle
between Tripped and back to ready states (indicated by the yellow
LED flashing or off). The user must also select the Auto mode
via the AUTO/MAN button for the signal processor to return to it
automatic state.
3.2.10 Wiring the Viewing Head
The viewing head wiring terminals are located on the lower right
side of the P222 signal processor. The terminal descriptions are
noted at page 3 (3.2.11 Terminal description).
page 3 (3.2.5 Viewing head connector wiring) shows a
four-conductor cable connected to the viewing head plug.
➔ The "WATCHDOG III" Flame Monitoring System requires the
use of one of the available ASY55XBE-series cable accesso-
ries.
➔ A source impedance resistor is required at the signal proces-
sor between the SC and SIG GND terminals for proper signal
transmission. For resistor value and wiring instructions, refer to
the Viewing Head Connections section.
3.2.11 terminal description
terminal
GND
+V
+24VDC Power to Viewing Head
SC
Self-Check signal to Viewing Head
SIG
Flame Signal from Viewing Head
SIG GND
3.3 s256Be Connection
1 Thread the connector onto the S256BE ¼ turn beyond finger
tight.
2 The cable at the signal processor end should be prepared as
shown in the wiring diagram page 2 (3.2.3 Terminal
labeling), making sure that the shield does not touch the other
adjacent terminals.
3.4 Viewing Head Location
1 Locate and mount the S256BE viewing head in the location
that provides a clear view of the flame and also provides easy
access.
➔ As the S256BE viewing head uses the UVTron tube, it is not
affected by sun light.
However, the following guidelines will help in satisfactory opera-
tion:
1 Limit elevation of the S256BE to 45 degrees or less. This will
prevent debris from falling onto the lens assembly.
2 Make sure line of sight is clear and not obstructed by a build-
ing or activities that are typical in an industrial plant, such as
road transportation.
3 If the site is dusty, air pressure may be required to ensure a
clear view. Install an air connection on the S256BE hood.
3.5 Viewing Head Aiming
At the back of the S256BE viewing head is a digital display, which
shows the two most significant digits of the UV signal value shown
on the P222 signal processor display.
Aim the S256BE using its telescope hood to align the viewing
head to the target flame area. Note that both elevation and hori-
zontal position adjustment are necessary.
Adjust the elevation and/or lateral movement to obtain the maxi-
mum signal. Refer to the Configuring the P222 section.
EN-3
Description
Power Ground
Signal Ground
