IRIS P520 Instructions for use

FLAME MONITORING SYSTEM
MODEL P520 SIGNAL PROCESSOR
APPLICATION MANUAL

IRIS MODEL P520 APPLICATION MANUAL
Page 2
TABLE OF CONTENTS
Model P520 ------------------------------------------------4
WIRING AND INSTALLATION------------------------4
FIGURE 1 - TERMINAL WIRING OF REAR PCB4
CARD FRAMES ------------------------------------------4
WIRING THE REAR PC BOARD --------------------5
FIGURE 2 - WIRING VIEWING HEAD -------------6
FIGURE 3 - WIRING AND ASSEMBLY
VIEWING HEAD ---------------------------------------7
OPTIONAL LTA ADAPTER----------------------------7
WIRING OF VIEWING HEAD-------------------------8
POWER SUPPLY ----------------------------------------9
FIGURE 4 - POWER SUPPLY TABLE ------------9
FIGURE 5 - 19” HALF-CARD FRAME WITH
STANDOFFS--------------------------------------------9
FACTORY STOCKED POWER SUPPLIES ------ 10
REDUNDANT POWER SUPPLIES---------------- 10
SELF-CHECKING FUNCTION --------------------- 10
REMOTE I/O MODULE------------------------------- 11
FIGURE 6 - REMOTE I/O MODULE -------------- 11
FIGURE 7 - IRIS P520 I/O MODULE
SCHEMATIC--------------------------------------------- 12
FIGURE 8 - FIELD WIRING TO I/O MODULE------- 13
FIGURE 9 - I/O MODULE SHOWING
SELF-CHECKING & FLAME RELAY
CONTACTS ------------------------------------------- 14
APPROVALS -------------------------------------------- 15
POWERING UP THE P520-------------------------- 15
SET POINTS -------------------------------------------- 16
FIGURE 10 - SET POINTS -------------------------- 16
CHANGING SET POINTS --------------------------- 16
FLAME FAILURE RESPONSE
TIME (F.F.R.T.)--------------------------------------- 16
4-20mA REMOTE OUTPUT------------------------- 17
FIGURE 11 -REMOTE METER ANALOG OUT-
PUT------------------------------------------------------ 17
INSTALLATION OF VIEWING HEAD------------- 17
FIGURE 12 - VIEWING HEAD
CROSS-REFERENCE TABLE ------------------- 18
SIGHTING OF THE VIEWING HEAD------------- 18
MULTIBURNER REQUIREMENTS --------------- 19
FIGURE 13 - CUTOFF FREQUENCIES --------- 19
MULTIPLE VIEWING HEADS ---------------------- 19
DETERMINING SIGHT PIPE SIZE---------------- 20
SELECTING THE PIPE------------------------------- 20
MOUNTING HOLE------------------------------------- 20
MOUNTING OF SIGHT PIPE ----------------------- 20
INSTALLING THE VIEWING HEAD--------------- 20
PURGE AIR---------------------------------------------- 20
SET UP AND ADJUSTMENT PROCEDURES - 20
SIGHTING ADJUSTMENT--------------------------- 21
INITIAL SET UP ---------------------------------------- 21
ADJUSTING SET POINTS -------------------------- 22
TROUBLESHOOTING GUIDE --------------------- 23
NOISE INTERFERENCE AND GROUNDING------- 23
S506 VIEWING HEAD -------------------------------- 24
S506 SELF-CHECKING VIEWING HEAD------- 25
S509 VIEWING HEAD -------------------------------- 25
S511 VIEWING HEAD -------------------------------- 26
S512 VIEWING HEAD -------------------------------- 26
ORIFICING----------------------------------------------- 28
FIGURE 14 - ORIFICING: SIGNAL-REDUCING
CHARACTERISTICS OF DISCS ---------------- 28
SIGNAL SOURCES ----------------------------------- 28
ANGLE OF VIEW OF VIEWING HEAD ---------- 29
FIGURE 15 - VIEWING HEAD: ANGLE OF VIEW
- DISTANCE AND DIAMETER ------------------- 30
APPLICATION OF IRIS VIEWING HEADS ----- 30
LOW NOx APPLICATIONS-------------------------- 31
APPLICATION OF P520 ----------------------------- 31
USING A PLC WITH IRIS FLAME MONITOR ------ 31
FIGURE 16 - VIEWING HEAD APPLICATION
TABLES ------------------------------------------------ 32
FIGURE 16 - VIEWING HEAD APPLICATION
TABLES Cont’d.-------------------------------------- 33
BASIC BURNER START CIRCUIT ---------------- 34
FIGURE17-BASIC BURNERSTART CIRCUIT------- 35
MODULE COMMUNICATIONS -------------------- 36
MODBUS COMMUNICATION ---------------------- 36
COMMUNICATING WITH
MODICON PLC -------------------------------------- 37
COMMUNICATION WITH HUMAN-
INTERFACE HOST COMPUTER --------------- 37
RS-232 to RS-422 CONVERSION----------------- 37
SETTING ADDRESSES------------------------------ 37
TECHNICAL HELP------------------------------------- 38
FIGURE 18 - SPECIFICATIONS------------------- 39
FIGURE 19 - MODEL P520 SIDE VIEW --------- 40
FIGURE 20 - S5XX VIEWING
HEAD DIMENSIONS ------------------------------- 40
FIGURE 21 - 4 MODEL P520s FRONT AND
REAR VIEW MOUNTED IN FACF -------------- 41
FIGURE 22 - IR VIEWING HEAD LOCATION -------- 42
FIGURE 23 - UV VIEWING HEAD
LOCATION -------------------------------------------- 42
FIGURE 24 - OPPOSED FIRED VIEWING HEAD
SIGHTING --------------------------------------------- 43
FIGURE 25 - VIEWING HEAD MOUNTING. ------- 43
INDEX ----------------------------------------------------- 44

IRIS MODEL P520 APPLICATION MANUAL
Page 3
FIGURE 1 - TERMINAL WIRING OF REAR PCB -----------------------------------------------------------------4
FIGURE 2 - WIRING VIEWING HEAD -------------------------------------------------------------------------------6
FIGURE 3 - WIRING AND ASSEMBLY VIEWING HEAD -------------------------------------------------------7
FIGURE 4 - POWER SUPPLY TABLE ------------------------------------------------------------------------------9
FIGURE 5 - 19” HALF-CARD FRAME WITH STANDOFFS ----------------------------------------------------9
FIGURE 6 - REMOTE I/O MODULE -------------------------------------------------------------------------------- 11
FIGURE 7 - IRIS P520 I/O MODULE SCHEMATIC------------------------------------------------------------- 12
FIGURE 8 - FIELD WIRING TO I/O MODULE ------------------------------------------------------------------- 13
FIGURE 9 - I/O MODULE SHOWING SELF-CHECKING & FLAME RELAYCONTACTS ------------ 14
FIGURE 10 - SET POINTS -------------------------------------------------------------------------------------------- 16
FIGURE 11 -REMOTE METER ANALOG OUTPUT------------------------------------------------------------ 17
FIGURE 12 - VIEWING HEAD CROSS-REFERENCE TABLE ---------------------------------------------- 18
FIGURE 13 - CUTOFF FREQUENCIES --------------------------------------------------------------------------- 19
FIGURE 14 - ORIFICING: SIGNAL-REDUCING CHARACTERISTICS OF DISCS -------------------- 28
FIGURE 15 - VIEWING HEAD: ANGLE OF VIEW - DISTANCE AND DIAMETER--------------------- 30
FIGURE 16 - VIEWING HEAD APPLICATION TABLES-------------------------------------------------- 32, 33
FIGURE 17 - BASIC BURNER START CIRCUIT---------------------------------------------------------------- 35
FIGURE 18 - SPECIFICATIONS------------------------------------------------------------------------------------- 39
FIGURE 19 - MODEL P520 SIDE VIEW --------------------------------------------------------------------------- 40
FIGURE 20 - S5XX VIEWING HEAD DIMENSIONS ----------------------------------------------------------- 40
FIGURE 21 - 4 MODEL P520s FRONT AND REAR VIEW MOUNTED IN FACF----------------------- 41
FIGURE 22 - IR VIEWING HEAD LOCATION-------------------------------------------------------------------- 42
FIGURE 23 - UV VIEWING HEAD LOCATION ------------------------------------------------------------------ 42
FIGURE 24 - OPPOSED FIRED VIEWING HEAD SIGHTING----------------------------------------------- 43
FIGURE 25 - VIEWING HEAD MOUNTING ---------------------------------------------------------------------- 43
FIGURE INDEX

IRIS MODEL P520 APPLICATION MANUAL
Page 4
Model P520
The P520 is a Signal Processor used with the IRIS
Model 5xx- or 55x-series Viewing Heads. The P520
is a plug-in module, designed to conform to the DIN
41494 19-inch card frame system. It is designated as
3Uhigh and 21HPwide, or5.06 x 4.18inches, andits
length is 220mm (8.66 inches). A rear backplane PC
board (PCB) is required for termination.
WIRING AND INSTALLATION
Before wiring or installing the P520, we recommend that
you read the companion colour brochure describing the
hardware and the basic operation of this signal processor.
CARD FRAMES
The backplane card frame consists of a kit of parts
that will make up a 19-inch card frame. This kit
does not include the card guides that the module
slides into. Four card guides are required for each
P520module; therefore, atotal ofsixteen cardguides
would be required to mount four P520 modules. The
cardguides are packagedin quantities of10 perpack.
This rack also requires spacers for the top and bot-
tom of the rear backplane PCB, and the spacers are
available in packs of two.
FIGURE 1 - TERMINAL WIRING OF REAR PCB

IRIS MODEL P520 APPLICATION MANUAL
Page 5
The card frame kit does not include the card guides,
so these must be ordered separately - as with the
backplane type card frame. All card frames and ac-
cessories are available from the factory.
A half-card frame, or “half rack” (9.5 inches wide)
is available as an alternative to the 19-inch card
frame, and this half rack will mount two P520 mod-
ules. Again, the kit does not contain the card guides,
which must be ordered separately. As an option, the
cardframe can beassembled with thenecessary parts
ready for mounting (IRIS part numbers FACF, and
FACF-1/2).
WIRINGTHE REAR PC BOARD
A view of the rear backplane PCB is shown in Fig-
ure 1. The relay outputs are located on the nine-con-
tact terminal block (upper right).
RF C refers to the common terminal of the flame
relay, with ON being flame on, and OFF being flame
off. You will note that there are two sets of contacts
used for the flame relay.
SCC refersto thecommonterminal ofthe self-check-
ing relay. There is only one pair of contacts used
for the self-checking function. Here, the designa-
tion ON refers to the self-checking taking place in a
normal manner. OFF indicates a failure in the view-
ing head or processor resulting from
- the hardware (i.e. the shutter mechanism in
the viewing head, or the output relay itself);
- electronic components anywhere, or in-
ternal software in the P520; or
- the power to the unit is OFF – the most
likely condition
The horizontal set of six terminals (top left) is used
for the main power into this plug-in module (PWR
IN). Each designated terminal is a double terminal,
or pair, so that the wiring from the power supply can
be“daisy chained” from oneP520 to thenext without
having to twist wires together into one termination.
The pair designated BAT is for battery backup, if
used. Note the rectifier (to the left of this group of
terminals) used internally to prevent the 26 VDC
main power supply from feeding into the battery.
The backup battery, if used, should be 24 volts, to
ensure that the 26 VDC power feeding the P520 will
not feed back into the battery. In other words, no
current will flow from the battery as long as voltage
of the main power supply is above that of the bat-
tery. The negative side of the battery goes to the
GND terminal on the right.
Figure 1 shows how these terminals are connected
inside the P520. Note the two fuses marked F1 and
F2. F1 is the main power fuse for the signal proces-
sor as well as the viewing head(s), and is rated at .75
Amp. Fuse F2 feeds only to the viewing head(s),
and is rated at .25 Amp. Each viewing head draws
about 100mA, so this output can supply only two
viewing heads; so, if more than two viewing heads
arerequired, it willbe necessary toincreasethe value
of fuse F2. Consult the factory for details. On newer
units (those with NO, CAL, and YES in red letters
onthe frontpanel) these fusesare self-resettingtypes,
and will recover from an overload automatically af-
ter power is removed from the P520 for 10 seconds.
Justbelowthe six-pinPWRINterminals aretwo,five-
pin vertically-mounted viewing head terminals iden-
tified as V.H. A. and V.H. B. If only one viewing
head is used, you must wire to the V.H. A. terminals.
BelowtheV.H. A.terminalsare twoterminalsmarked
V.H. SEL (viewing head selector relay). Energizing
this connection with 26 VDC will cause the relay on
this PCB to switch to viewing head B.
Only the viewing head signal wire (SIG) and the sig-
nal ground wire (SIG GND) are switched with this
changeover relay; the 26 VDC and power ground
circuit is not disturbed. Make sure that the viewing
head signal wire and signal ground (braided shield
in the four-conductor cable) are both connected, be-
cause this ground connection is the only return path
for the signal and self-checking circuit. The 26 VDC
used to switch this relay can be connected without
regard to polarity. The two terminals marked V.H.
SEL go directly to the relay coil.
The two-pin terminal to the right of V.H. SEL des-
ignated CHAN SEL is used for selecting channel
A or channel B on the P520. Energizing this pair
of terminals causes the B channel to be selected.

IRIS MODEL P520 APPLICATION MANUAL
Page 6
Polarity must be observed when wiring this connec-
tion (the positive terminal is on the top). This is an
isolated input, so two wires are required. Any DC
voltage from 7.5 to 30 may be used. The current
required will depend upon the voltage, because this
is a photocoupler interface circuit with a 3900 ohm
resistor feeding the LED light source.
For example: a 26 VDC voltage will result
in a current flow of 25/3900 = .0064 Amp.
If flame is being detected and the channels are
switched, the flame relay will remain energized for
one cycle regardless of the new set points, allowing
channel changes “on the fly,” so to speak. If the
new flame OFF set point is equal to or greater than
the current signal count, then the flame relay will
de-energize on the subsequent cycle.
The remaining two-pin terminal designated RE-
MOTE METER (to the left of the V.H. SEL termi-
nals) is for the remote meter connection. This out-
put is a current-driven signal that ranges from 0 to
20 mA for remote meters, and can be switched to a
range of 4 to 20 mA for DCS (distributed control
system) applications (refer to section 4-20mA RE-
MOTE OUTPUT). Connect the terminal marked
“positive” to the positive meter terminal. This cur-
rent signal can be used with a volt meter by feeding
the signal to a resistor connected to the ground. The
voltage developed across the resistor will follow
Ohm’s law V = IR.
For example: a 3-volt meter can be used
witha resistorof 3/.02= 150ohms,which
willresult ina full-scalereading of3volts
for a 20mA output.
The terminals called TX+, TX-, RX+, and RX- (at
the bottom of the PCB) are used for the serial com-
munication link. They are also in pairs to accom-
modate “daisy chaining,” but the pairs are arranged
fortwisted pairs insteadof adjacentredundancy. The
serial communication is achieved by using ASCII
character code transmission at 4800 through the RS-
232 com ports on the host computer. The P520 uses
RS-422 data transmission which is over two, twisted
pairs that are differentially transmitted and received,
allowing long wire runs to be used through noisy
environments. An RS-232 to RS-422 converter must
be used to communicate with the P520, and the connec-
tions are made to the terminals marked TX+, TX-, RX+
and RX-. The transmitting, twisted pair goes to the TX
terminals, and the receiving, twisted pair goes to the RX
terminals.
Note: the terms “transmit” and “receive”
used here with respect to the P520 will
be reversed with respect to the RS-232
connection on the host computer. Refer
to later sections in this manual for a de-
taileddescription ofthe softwareand how
it is to be used with the P520.
FIGURE 2 - WIRING VIEWING HEAD

IRIS MODEL P520 APPLICATION MANUAL
Page 7
IRIS CABLE
3 CONDUCTORS PLUS 1 COAX
3CONDUCTORS: 16 AWG 19 STRAND INSULATED WITH
CROSSED-LINKED-POLYETHYLENE .017 THK
COLORS: BLACK-RED-GREEN
1 COAX: 16 AWG 19 STRAND INSULATED WITH
CROSSED-LINKED-POLYETHYLENE .017 THK
COLOR WHITE36 AWG BRAIDED SHIELD 90% COVERAGE
WITH .012 THK JACKET COLOR BLACK
CABLED: POLYPROPYLENE FILLERS FOR ROUNDNESS
JACKET: CROSSED-LINKED-POLYETHYLENE
STRIP 3/8 TYPICAL
GROMMET
FLAT WASHER
CABLE ENTRY NUT
SHIELD *
CABLE
PREPARATION
1 3/4
(TYP)
CABLE
CABLE CLAMP
CONNECTOR WITH
REAR COVER REMOVED
INSULATE SHIELD WITH SHRINK
TUBING LEAVING 3/8 STICKING OUT
CONNECTOR JACKSCREW
FINAL ASSEMBLY
* CABLE IS SHOWN WITH SHIELD
ALREADY REMOVED FROM WHITE WIRE
Optional LTA Adapter
FIGURE 3 - WIRING AND ASSEMBLY VIEWING HEAD

IRIS MODEL P520 APPLICATION MANUAL
Page 8
WIRING OF VIEWING HEAD
Wiring of the viewing head is made to the termi-
nals on the rear backplane PCB. These terminals
are described as follows:
TERM DESCRIPTION
+V 24 VDC power to viewing head
GND Power Ground
SC Self check/shutter drive signal to
viewing head
SIG Flame signal from viewing head
SIG GND Signal ground
Figure 2 shows a four-conductor cable to the view-
ing head. Note that the flame signal wire going to
terminal 7 on the M502 is shielded, and the shield is
terminated at both ends of the cable.
A source impedance resistor is required when using
the P522 module with a S550 viewing head. This
resistor should be 330W for viewing head cable runs
up to 500 feet, and it should be 150W for cable runs
500feet to 1000feet. The resistor shouldbe installed
across the SC and SIG GND terminals on the rear
backplane PCB. A 1/4 watt resistor is suitable.
Originally, specifications of the IRIS Model 500 in-
structed that a five-conductor cable be used, with
one wire shielded. However, the standard is now a
four-conductor cable, with one wire shielded. In
this case, the shield is used as the signal ground wire
that goes to terminal SIG GND on the P520 (termi-
nal 8 on the M502) and to pin 3 on the viewing head
plug. The shield should be a braided type for this
application –do not use a foil type shield– so that a
solidsignal groundis maintained. This signalground
shield is also the self-checking circuit return path.
Refer to Figures 2 and 3 for wiring details.
Connections of the IRIS cable to the viewing head
plug should be performed as follows:
After removing the plug from its packaging, take the
cable entry nut out of its housing. Remove rubber
grommetand flatsealing washer. Witha pairof long-
nosed pliers, remove the center ring only of the rub-
ber grommet.
1. Strip twoinches ofthe cable’souter cover
from the cable, removing any cellophane
wrap or filler material, and strip the in-
sulation from the shielded wire (if insu-
lated over shield) a full two inches, to
expose shield.
2. Slide the shield back until a bulge devel-
ops close to where the wire exits the
cable’s outer covering.
3. Carefullyspreadafewstrandsoftheshield
atthe bulge–making surenotto breakany
strands–tocreatean opening,andslipwire
out of shield through opening.
4. Carefully return shield to original shape
and length by pulling gently, then cover
withplasticshrinktubingtopreventshorts.
5. Slide nut (with threads toward the cable
end), the washer and the grommet onto
the cable approximately six inches.
6. Slip the cable through the bottom open-
ingofthe connector, makingsure that the
cable’s outer jacket is secure under the
cable clamp, and tighten the two screws
on the cable clamp.
7. Reassemble thegrommet, flatwasher and
cable entry nut, and tighten.
8. Before wiringtoconnector,strip eachwire
3/8 inch, as shown in assembly diagram.
9. Proceed to wire the connector. Refer to
Figure 2 for terminal locations.
– Connect the viewing head signal wire
WHT (the shielded wire) to terminal
No. 1 by inserting it into the opening,
then tightening the retaining screw.
– Connect the shutter drive signal wire
BLK to terminal No. 2.
– Connectthe signalground shield from
the WHT wire to terminal No. 3 with
shrink tubing.

IRIS MODEL P520 APPLICATION MANUAL
Page 9
– Connectthe 24VDC powerwire RED
to terminal No. 4.
– Connect the power ground wire GRN
to terminal No. 5.
– Assemblethebackoftheplugandinsert
jackscrew through the plug assembly.
The cable wiring at the other end going to the signal
processor is easier. The cable should be prepared in
a similar way to the plug end – particularly the shield
from the WHT wire. Make sure the shield doesn’t
touch the other terminals.
POWER SUPPLY
Careful consideration should be given to the power
supply used for the P520. 26 VDC is used to back
bias the “steering” rectifier, as shown in Figure 1, to
preventthe power from feedinginto the 24VDC sup-
ply. EachP520module drawsapproximately200mA,
andeach viewinghead drawsabout 100 mAof power
(26 VDC). Also, the amount of current drawn by the
P520 will depend upon other factors that can affect
thepeak current, suchas whether ornot thereis flame
being detected, the remote meter output is connected,
and serial communication is occurring.
The viewing head is powered through the P520 via a
.25A self-resetting fuse. In other words, the 26 VDC
power feeds into the P520 (through a .75A self-reset-
ting fuse) and feeds back out through a 250 mA fuse
to the viewing head, resulting in a current drain of
about300 mA foreachP520 (withoneviewing head).
This small amount of current means that one power
supply could support a number of P520 modules (the
disadvantage, of course, is that if the power supply
fails, all the P520 modules connected go off). The
self-resetting fuses change to high resistance when
their current ratings are exceeded, but recover to their
normal low resistance when power is removed.
STTAWNIYTICPACYLPPUSREWOP225PLEDOMSIRI
YTQW5.7W51W03W05W001
1XXXX
2XXX
3XXX
4XX
5X
6X
7X
8X
9X
01 X
FIGURE 4 - POWER SUPPLY TABLE
FIGURE 5 - 19” HALF-CARD FRAME WITH STANDOFFS

IRIS MODEL P520 APPLICATION MANUAL
Page 10
FACTORY STOCKED POWER
SUPPLIES
Power supplies are readily available from the fac-
tory for the P520 modules. The IRISPS030 power
supply will support up to three P520 modules with
one viewing head each. The 50-watt power supply
will power up to six or seven P520 modules with
one viewing head each (30 watt). The IRISPS050
power supply will support up to six P520 modules
with one viewing head each (50 watt). And the
IRISPS100 will power up to twelve P520 modules
with one viewing head each (100 watt). These
“switching type” power supplies are efficient and
very compact. To obtain the size and weight of the
power supplies, contact IRIS Systems Inc.
Each power supply can be either rail mounted or
panel mounted, and it is up to each end user to deter-
mine their installation preferences and requirements.
We recommend that not more than four P520 signal
processors be supported by one 26 VDC power sup-
ply. For instance, four P520 processors with one
viewing head each equals a total of 31.2 watts – a
relatively small power supply, particularly if an ef-
ficient, switching type is used.
Other possible combinations can be used; for in-
stance, the battery backup terminal could be used
for redundancy. However, care must be taken with
these redundant schemes to make sure that failure of
the primary power supply won’t affect the backup
power supply, as well.
REDUNDANT POWER SUPPLIES
It may be more economical to use larger-capacity
power supplies for applications using 12 or more
P520 signal processors.
For example: the 100-watt power supply
available from the factory can handle
twelveP520modules,each withoneview-
ing head. Should the power supply fail, a
redundant scheme utilizing two power
supplies with “steering” rectifiers to pre-
vent current from flowing into a failed
powersupply outputwouldprevent the12
flame monitors from being de-energized.
The positive output from each power supply is wired
to the anodes of the MBR 1545CT. This dual,
Schottky-type rectifier, rated for 15 Amps, will
present a low forward voltage drop for this applica-
tion. Both power supplies can be adjusted for 26V
output, and a low-voltage indicator light can be used
on the output of each power supply to monitor their
outputs.
Larger power supplies can be used with this redun-
dant wiring scheme if there are more than twelve
P520 modules in a system. Care should be taken
when wiring multiple P520s to ensure the selected
bus wires will carry the current. The rear PCB on
the P520 will accommodate a wire size up to
14AWG, allowing for relatively high currents.
SELF-CHECKING FUNCTION
Whenenergized, the self checkingfunction indicates
that both the P520 and the viewing head are func-
tioning properly. The software in the P520 activates
the self-checking relay only if there are less than 10
pulses coming in from the viewing head during each
darkperiod. To energizethis relay, thesoftware must
generate pulses –at a particular rate and with a spe-
cific duty cycle– to a self-checking circuit. If this
regular pattern is not maintained, or if any of the
circuitry fails, the relay will drop out. The blinking
LEDonthe front panellabelled SELF-CHECK O.K.
is evidence that voltage is applied to the coil of this
self-checking relay, because both are energized by
the same voltage. The difference is that the voltage
to the coil is applied steadily, while the voltage from
the relay to the LED is gated on and off by the soft-
ware in conjunction with the pulses counted during
the dark period.
Note that, with regard to the viewing head, the self
checking function still works the same way as with
the M502, A513 and D504 signal processors. For
instance, a runaway UV tube will cause a “lockout
condition” (more than 10 pulses counted during the
dark period). (Refer to section EXPLANATION
OF1-9, >10PULSES COUNTEDDURINGTHE
DARK PERIOD, in the Model 500 Signal Proces-
sor Application Manual.)

IRIS MODEL P520 APPLICATION MANUAL
Page 11
A runaway UV tube or any component failure, in-
cludingthe shutter,will causea lockoutcondition that
willde-energizetheflamerelay. The LOCKOUTlight
on the P520 will indicate this condition, requiring a
reset to return to normal flame monitoring mode. A
reset can be achieved only if the lockout condition
has been corrected, and can be performed from the
front panel (by pressing the RESET button), or re-
motely through the serial communication.
REMOTE I/O MODULE
An input/output (I/O) module is available for imple-
menting the basic functions described in the previ-
ous section. It will also help facilitate the field wir-
ing in applications where it is impractical to wire to
the rear PCB of the P520.
For example: in a standard NEMA 12
wall-mounted or free standing enclosure,
a card frame cannot be mounted unless
rack-mounting rails or rack-mounting
angles are installed. In this instance,
where there is only one relay panel, the
standard card frame can be reversed and
mounted directly to the panel.
FIGURE 6 - REMOTE I/O MODULE

IRIS MODEL P520 APPLICATION MANUAL
Page 12
FIGURE 7 - IRIS P520 I/O MODULE SCHEMATIC

IRIS MODEL P520 APPLICATION MANUAL
Page 13
TO
NEXT
BNR
+26VDC POWER SUPPLY
REMOTE FLAME
METER
(0-20 OR 4-20mA) STP
(STOP)
SW
FLAME
ON
FLAME
OFF
OPEN
BNR V.
FROM PLC
BNR
VALVE
OPEN
PILOT V.
FROM PLC
PILOT
VALVE
NOTE:
SERIAL TRANSMISSION
TERMINALS TX & RX
NOT SHOWN IN THIS DWG
ISOLATED
CONTACT
CLOSE
ON NO
FUEL TRIP
STR
(START)
SW
FIGURE 8 - FIELD WIRING TO I/O MODULE

IRIS MODEL P520 APPLICATION MANUAL
Page 14
Figure 5 illustrates a half-card frame (19-inch)
mounted to a panel with four, male-female 10-32
standoffs. Any number of P520 modules can be
mounted this way, using the standard 19-inch card
frames.
A rear I/O PCB is used at the rear of the card frame
to terminate each P520 A ribbon cable is then used
to connect the I/O module, which can be mounted
anywhere on the panel. The rear I/O PCB incorpo-
rates a viewing-head switching relay and the ribbon
cable receptacle.
The I/O module is illustrated in Figures 6 & 9, and
the wiring schematic of this module is provided in
Figures 7, 8, & 9. The I/O module provides a mas-
ter relay (load relay) with two sets of form A con-
tacts rated to 15 Amps, and is designated as M2 in
the schematic.
SC
+V
VH
SEL
CH
GND
+V
SIG
GND
SIG
GND
SC
SIG
GND
SIG
SEL
TX+
TX-
TX+
TX-
RX-
RX+
RX-
RX+
FLAME RELAY
SELF-CHECKING
RELAY
V
FOLLOW THE
FLAME RELAY
RM
RM
STR
STP
JUMPER TO
MAKE RM
(
OPTIONAL
)
RF
RC
P520
RELAYS
OFF
MFT
OFF
ON
COM
GND
COM
ON
J1
IRIS P520 I/O MODULE
MASTER
RELAY
RELAY
RELAY
RF
SELF-
CHECK B
V.H.
BAT
+26
+
MTR
P520
34
A
V.H.
1
FIGURE 9 - I/O MODULE SHOWING SELF-CHECKING & FLAME RELAY CONTACTS

IRIS MODEL P520 APPLICATION MANUAL
Page 15
A field wiring diagram is provided in Figure 8.
Note that a “safe-start-check” circuit is used, requir-
ing an auxiliarytimer (see section BASICBURNER
START CIRCUIT). The same sequence of opera-
tions prevails, except that the RM contact is now
part of this I/O module (M1 and M2 in the sche-
matic). Refer to section The sequence of opera-
tions for BASIC BURNER START CIRCUIT).
Note on the module schematic (Figure 9) that the
RM relay can be converted to follow the
by installing a jumper from 26 VDC to the top of
the start switch (solder a bus wire between the pads
marked J1). This would be done for applications
not requiring a master relay, and where the RF con-
tacts must switch higher currents.
Figure 9 illustrates the relationship of the P520 in-
ternal relays with respect to the actual terminals on
the I/O module. Essentially, the P520 self-checking
relay and flame relay contacts are repeated on the I/O
module by using another set of relays. This is done
so that load currents will not have to be carried by
the ribbon cable which is composed of relatively
small-gauge wire. As mentioned before, the jumper
J1 can be used to make more flame relay contacts
available, assuming you are not going to use the
master relay for the “safe-start-check” function de-
scribed previously.
APPROVALS
TheP520andviewingheadshaveFactoryMutual(FM)
ApprovalforCombustionSafety; Canadian Standards
Association (CSA) Certification, and National Recog-
nized Testing Laboratories (NRTL) Listing.
POWERING UP THE P520
Once the power is connected (26 VDC) to the plug-in
connector, the P520 will be operational. There is no
ON/OFF switch on the P520; the moment it is pow-
ered on, it will reset and start up. The self-checking
light will start blinking, and one of the channel LEDs
(A or B) will light (A will be ON if the channel select
inputat theplug-in connector isde-energized). Make
sure the voltage is 24 to 26 VDC. The P520 will be
resetwhenthepower isturnedon; however,the power
must be a step function (i.e., the power must be ap-
plied abruptly) for this reset to work properly.
The P520 has been designed to deal with any fore-
seeable power failure or anomaly.
For example: if the power goes off while
you are in the process of storing a set
point (either from the front panel or from
the remote, host computer), the internal
power monitor circuit will signal the
P520 processor to complete the store
function before shutting down in an or-
derly manner. This prevents bogus num-
bers from being stored and protects ex-
isting data in the EEPROM (Electrically
Erasable Programmable Read Only
Memory) from corruption, and is facili-
tated by a special internal power supply
that holds a charge (like a battery) just
long enough to allow the processor to do
its job before going dead.
Thisinternal circuitmonitorsthe 26VDCpower feed-
ing the P520, and when the voltage drops to about 19
volts, the processor shuts down, the program stops
running, and the self-checking function ceases (the
self-checking relay de-energizes). The blinking,
SELF-CHECK O.K. light on the front panel will go
out, and the flame relay will de-energize. Please note
that the S509 and S512 viewing heads will shut down
atabout17.0 volts; theseheadshave theirownpower-
monitoringcapability,andwill shutdownontheirown
independent of the signal processor.
When the power feeding the P520 exceeds 19 volts,
the processor starts the program again. The SELF-
CHECK O.K. light will start blinking, and the self-
check relay will energize. If flame is present and a
S509 or S512 viewing head is being used, the flame
signal will not come back on until the power reaches
21.5 volts. This can cause a lockout condition if the
viewinghead turnson duringthe darkperiod (defined
bythe periodic self-checksignal goingto the viewing
head each second), requiring a manual reset of the
P520. There is a 20 per cent probability that a lock-
out will occur because of the duty cycle of the self-
check function (200 mSEC on and 800 mSEC off).
The other viewing heads (the S506, S511) do not in-

IRIS MODEL P520 APPLICATION MANUAL
Page 16
corporate the power-monitoring shutdown function,
and will not cause a lockout condition.
Thesedesign precautions ensure thatthere will never
bean unsafesituation createdby abnormalline power
(115 VAC) conditions. The 26 VDC power is very
unlikely to come on gradually, but, if this did occur,
the P520 would not get a proper reset. So, there is
another function in the processor (used in the P520),
implemented by circuitry and software, that causes
the P520 to appear dead (i.e., the front panel will be
dark) and to stay this way until the power is recycled
in an abrupt manner, initiating the reset.
SET POINTS
Thereare 10 set pointsstored in memoryin the P520,
divided into two equal sets, A and B.
To see what the current set points are, simply push
thedesired button. Forinstance, todetermine thecur-
rent FLAME ON set point, press the FLAME ON
button. The set point will be displayed on the readout
for about four seconds, then return to normal (like-
wise for all set points). The set points displayed will
be for the channel that is active, which is indicated by
a steady illumination of push-button A or B.
To see the other channel set points, first select the
channel (A or B), then press the desired set point
button.
Forexample: if channel Ais already ON,
indicating it is functional, and B is
pressed, A will go out and B will pro-
ceed to blink slowly, indicating that fur-
ther action is required. If A is already
ON and A is pressed, it will stay steady
ON and start to blink rapidly after a set
point button is pressed.
In all cases, A or B will rapidly blink after the set
point is selected. This action alerts the user that the
current display is no longer that of the flame signal,
and further action is required.
The fact that A or B is already on has nothing to do
with the process of viewing the current set points,
except that you do not have to select the channel if it
is already on. The steady illumination of A or B
indicates which channel is functionally active, and
is selected at the rear PCB marked CHAN SEL.
At any time, you can press the reset button causing
the P520 to go back to its normal operating condi-
tion. The reset button is also used for resetting the
lockout condition as explained in the section SELF-
CHECKING FUNCTION.
CHANGING SET POINTS
Changing any of the five set points is easy. Simply
bring up the desired set point and change it using the
UPor DOWNarrow buttons. Whenthe desirednum-
ber is displayed, press the STORE button. When
the set point is stored, four dashes are displayed
momentarily,indicating thatthe selected numberwas
stored into the EEPROM. Illogical settings cannot
be made; so, if four “E’s” are displayed when push-
ing STORE P.B., then an error was made when se-
lecting the set points. For instance, selecting aflame
out set point that is equal to or greater than the flame
on set point will result in this error indication.
Aswell,thesetpointscan beselectedremotelythrough
the serial communication port using a host computer –
explained in greater detail later in this manual.
FLAME FAILURE RESPONSE TIME
(F.F.R.T.)
The flame failure response time, or F.F.R.T., is de-
fined as the time it takes for the flame relay to de-
energize after the flame signal (from the viewing
head) drops out. This time delay is programmable
TNIOPTESYALPSIDREBMUN
NOEMALFREBMUNTIGID49992-1000
FFOEMALFREBMUNTIGID49992-0000
TESNIAGREBMUNTIGID299-00
.T.R.F.FREBMUNTIGID13RO2,1
NOYALEDEMITREBMUNTIGID13RO2,1,0
FIGURE 10 - SET POINTS

IRIS MODEL P520 APPLICATION MANUAL
Page 17
from both the front panel of the P520 and a remote,
hostcomputer. Only three settingsare possible: one,
two and three seconds.
The maximum time delay is limited to three seconds
in compliance with the FM (Factory Mutual) limit
of the F.F.R.T. to not more than four seconds.
The P520 decision-making process occurs on a pe-
riodic basis, and the decision to start a F.F.R.T. time
delay before de-energizing the flame relay is initi-
ated every second in step with the sampling rate of
the flame signal. This means that the actual flame
out condition (i.e., drop-out of the flame signal from
the viewing head) will, in all probability, occur dur-
ing the sampling period that causes the actual
F.F.R.T. to be greater than the set time.
For example: suppose the signal from
the viewing head drops out immediately
after a sampling from the P520, and the
sampling perceives flame to be present.
If the F.F.R.T. set point is set for three
seconds, there will be an actual time de-
lay of nearly four seconds. In other
words,the actual F.F.R.T.will be thecur-
rent set-point time, plus an additional
amount of time not exceeding one sec-
ond, depending upon when the flame sig-
nal from the viewing head drops out.
4-20mA REMOTE OUTPUT
The standard remote meter output has a 0-20mA
range and is designed to drive remote meters, as ex-
plained earlier in this manual. You can convert this
output to a 4-20mA range, as follows:
Pressthefrontpanelpush-buttons(indicatedinthetable
below) while holding down both the Ýand ßbuttons.
Press all in each row together (i.e., three in the first
row, two in the second row, and three in the last row).
Doing this toggles the function back and forth be-
tween the 0-20mA and 4-20mA ranges.
The change will be verified by four dashes “- - - -”
and “4-20” momentarily displayed. If the module is
programmed for the 4-20mA range, “4-20” will be
displayed; toggling back to the 0-20mA range will
again cause four dashes to appear upon power-up of
the unit. The factory default settings are 4-20.
One thing to consider when feeding the 4-20mA sig-
nal to a remote computer or DCS, is that there is no
isolation between the P520 ground and the remote
system ground. If there is a ground potential differ-
ence between the two systems, then there could be
serious noise and performance problems. You will
not encounter this problem when using a remote
meter by itself, because it will not be tied into an-
other electrical system (will not be sharing grounds).
The bargraph reading on the front panel will not be
affected by this change to 4-20mA output. It will
remain the same as before (i.e., go to zero on no sig-
nal detected). The 4-20mA output will still perform
the same way on the high end (i.e., on a strong sig-
nal, it will saturate at the same level, slightly above
22mA).
Specifications for the analog current output signal
are provided in SPECIFICATIONS, Figure 18.
INSTALLATION OF VIEWING HEAD
Before beginning the actual installation, determine
thebest locationfor mountingthe viewinghead based
upon the following factors:
EMALF NO EMALF FFO TESNIAGTRFF LEDEMIT NO
XXX
XX
XXX
FIGURE 11 -REMOTE METER ANALOG
OUTPUT

IRIS MODEL P520 APPLICATION MANUAL
Page 18
VIEWING HEAD CROSS-REFERENCE
PRESSURE
The viewing head lens will withstand 5 psi. If the
lensassembly isexposedto greaterthan 5psi through
the sight pipe, then an isolation unit must be used.
An IRIS isolation unit with purge air entrance is
available as an accessory.
TEMPERATURE
The viewing head will withstand an ambient tem-
perature to 80°C (176°F). However, the case tem-
perature of the housing must not exceed 60°C
(140°F). Purge air will help reduce conducted heat
through the sight pipe to flange (a plastic nipple will
also help), but direct radiation can cause the hous-
ing case temperature to exceed limits. If the ambi-
ent heat (direct radiation) is excessive, then a fiber
optic extension should be used (please refer to the
IRIS Model 500 Fiber Optic System manual). This
system is composed of a viewing head, a fiber optic
assembly, and an amplifier module.
The model S5xx series of viewing heads have in
place a sensor for sensing the internal temperature
of the head. To access the reading of the viewing
head temperature, press the “Reset” and the “Down”
arrow key at the same time. The temperature read-
ing will be displayed in the four-digit readout. The
reading (indicated in °C) will disappear and the nor-
mal reading will continue after several seconds.
VIBRATION
Do not install the viewing head where it could be
subject to vibration. A vibrating viewing head
(flicker type) can simulate flame when viewing a
glowingbackground. Provide anantivibration mount
if excessive vibrations are present.
CLEARANCE
Make sure there will be sufficient room to remove
the housing for servicing (see Figure 20).
SIGHTING OFTHE VIEWING HEAD
In general, the sighting of the viewing head should
be parallel to the center line of the burner in the di-
rection of the burner flame. This applies to both the
UV type as well as the flicker type. Flicker type
detectors respond to the high frequency flicker of
the flame; so, in order to achieve maximum dis-
crimination between burners, the near portion of the
primary combustion zone should be favoured –
meaning the sight pipe should be mounted as close
as possible to the burner center line. The sight pipe
should be aimed at the root of the flame, which radi-
ates the most intense, high-frequency flicker energy.
Sighting along the flame rather than across it per-
mits the detector to view a greater depth of the flame
root, obtaining better response (see Figure 22).
When sighting for a UV viewing head, you must aim
for the UV zone, which is usually at the very first
partof theflame root. UVradiation frommost flames
is restricted to a narrow region: it starts very close
to the burner nozzle and does not extend out very far
from the burner nozzle. You may have to angle the
sighting inward toward the flame root, as shown in
Figure 23.
The effectiveness of the sighting will depend upon
both the type of viewing head as well as the fuel.
UV flame detection works fine on natural gas, but
will cause problems with fuels that either block or
absorb the UV signal.
Forexample: in a pulverizedcoal burner,
there can be unburned fuel at the burner
nozzle, creating a “skirt” that blocks the
UV radiation coming from the flame.
Heavy oil burners can also cause prob-
REBMUNDLOREBMUNWEN
605S605S
S2XRI905S
SGRI115S
SRI215S
FIGURE 12 - VIEWING HEAD CROSS-
REFERENCE TABLE

IRIS MODEL P520 APPLICATION MANUAL
Page 19
lems with UV-type flame detection, par-
ticularly if the fuel has a high sulfur con-
tent, which will absorb the UV radiation.
MULTIBURNER REQUIREMENTS
Multiburner installations require discrimination.
This means that, in spite of the brightness of other
flames in the furnace, the flame relay must respond
only to the presence or absence of the flame pro-
duced by the burner that it is monitoring. Not every
viewing head can be positioned so that its line of
sight does not intercept flames from other burners –
a situation that occurs in multi-level, opposed fired
furnaces where the burners face each other.
Insuch cases, thesighting angle isset upas described
above, with the viewing head sighting along the
flame directly into the flame root. If an opposing or
adjacent burner flame falls within the line of sight of
the viewing head, it may be effectively tuned out by
setting the FLAME OFF set point high enough to
ignore this background. If discrimination cannot be
achieved by doing this, it is recommended that the
filter switch in the viewing head (except the S506
UV, which doesn’t have one) be switched to a higher
position. This reduces the low-frequency flicker
reaching the detector so that the set points can be
adjusted to affect flame discrimination. The four
cutoff frequencies are outlined in Figure 13.
Ahigher filterposition creates anarrower bandwidth,
causingan overallreduction intheflame signal; how-
ever, the ratio of flame ON to flame OFF may be im-
proved by properly setting this four-position filter.
Notethe readingson thefour-digitdisplay whenmak-
ing these adjustments. The four-digit number is an
absolute indication of signal strength, and is not af-
fected by changing the gain of the analog output.
MULTIPLE VIEWING HEADS
This system can accommodate the parallel operation
of two viewing heads with one signal processor. The
flamesignalswillbeadditive,possiblyrequiringalower
sensitivity setting. A word of caution about this type
ofoperation: theunwantedbackgroundwiththeburner
flame out will also be additive, possibly causing a dis-
crimination problem in multiburner applications.
Note: The55x-series viewing heads can-
not be wired in parallel.
Another variation is to switch the flame signal ON
and OFF from each viewing head.
For example: one viewing head can be
used for the igniter, and the other for the
main burner. While proving flame from
the igniter, the main burner signal circuit
can be opened, leaving only the igniter
viewingheadsignalto beread. And,when
proving flame from the main burner, the
igniter signal circuit can be broken.
We recommend that only the flame signal from each
viewing head be switched, leaving the other connec-
tions to the viewing head intact (the one exception
would be the S506 UV head). Both the flame signal
and shutter drive circuits should be switched so that
when the head is not being used, the shutter is not
switchedonandoff. This wasdoneinthe designofthe
rearmotherboard(seesectionWIRINGREARPCB).
Note that both the SIG and SIG GND circuits are
switched. However, this can cause a lockout condi-
tion if the transfer of the viewing heads is done dur-
ing the dark period. This problem can be avoided
by changing channels when switching heads (i.e.,
by wiring the two terminal blocks V.H. SEL and
CHAN SEL together in parallel). This will inform
theP520 thatthe viewing headsare beingtransferred,
and the pulses counted during the dark period will
be ignored.
&115S215S&055S255s
LLzH631zH61
LzH172zH42
MzH5013zH33
HzH6814zH25
5zH57
6zH001
7zH551
8zH512
FIGURE 13 - CUTOFF FREQUENCIES

IRIS MODEL P520 APPLICATION MANUAL
Page 20
DETERMINING SIGHT PIPE SIZE
In order to determine the proper sight pipe, it is im-
portant to understand how the viewing head “views”
the flame. The viewing head employs a plano-con-
vex lens in front of the photodetector that focuses
the flame radiation on the surface of the detector.
The active photodetector element is quite small, and
its diameter and the focal length of the lens deter-
mines the angle of view. For the S509 viewing head,
thisangle of view isabout 2.8 degrees. Forthe S512,
the angle is slightly less.
To understand what this means, imagine a circular
target of flame radiation, one inch in diameter, 24
inchesaway from the lens: thisis the maximumfield
of view the detector sees. In other words, a one-inch
diameter sight pipe two feet long will allow maxi-
mum signal to be detected. A two-inch diameter
sight pipe four feet long presents the same target.
Actually, a one-inch target three feet away causes
an immeasurable signal attenuation, so you can use
a two-inch diameter pipe up to six feet long, with no
signal attenuation.
The angle of view for the S511 viewing head is 1.1
degrees. This translates into a one-inch, circular tar-
get 52 inches away from the lens. In other words, a
one-inchdiameter sight pipefour feetlong (or, atwo-
inch diameter sight pipe eight feet long) will allow
maximum signal to be detected.
For a detailed explanation of how the angle of view
is derived, refer to section ANGLE OF VIEW OF
VIEWING HEAD.
If a long sight pipe is required, then we recommend
that a swivel mount be used to overcome any optical
misalignment that might be present (see Figure 25).
In this way, the flame signal can be optimized by
adjusting the viewing head to the target at the end of
the pipe.
SELECTING THE PIPE
We recommend a black iron pipe to provide reliable
flame sensing. The viewing head is tapped for a one-
inch national pipe thread (NPT) threaded pipe. Any
diametersighting-pipelargerthanone inchwillrequire
a reducer coupling or swivel mount (see Figure 25).
MOUNTING HOLE
Cut a hole for the sight pipe in the burner front
windbox at the selected location. The hole should
be large enough in diameter to allow adjustment of
the sighting angle. If register vanes interfere with
the desired line of sight, trim the interfering vanes to
ensure an unobstructed view of the flame.
MOUNTING OF SIGHT PIPE
After cutting the pipe to the desired length, thread
one end of the pipe to fit the viewing head flange or
required coupling (see Figure 25). Insert the other
end of the pipe into the mounting hole, align the pipe
tothe desired sightingangle, and tackweld it inplace
to allow further sighting adjustments. Make sure
the tack weld will support the weight of the detector
when it is installed. Once the final position has been
determined, weld the sight pipe in place.
INSTALLING THE VIEWING HEAD
The viewing-head flange screws directly onto a one-
inch NPT threaded pipe (see Figure 25). Use a cres-
cent wrench to tighten the flange onto the sight pipe.
PURGE AIR
Use a flexible air supply line, allowing reposition-
ing of the sight pipe until the permanent detector
position has been verified. A continuous flow of air
must be maintained in order to keep the head cool
and the sight pipe clean. We recommend that at least
three CFM at approximately eight inches of water
columnabove windboxpressure beprovided for each
viewing head. The air supply must be clean, free
from oil and water, and preferably cool.
SET UP AND ADJUSTMENT
PROCEDURES
Multiburner applications require the most care in
adjustments to ensure proper flame out operation
under worst-case conditions (refer to previous sec-
tion MULTIBURNER REQUIREMENTS).
These same procedures can be followed for single-
burner applications, even though the adjustment
refinements described here may not be necessary.