I.R.I.S. FLAME MONITORING SYSTEM P522 - Manual (Page 10)

IRIS MODEL P522 APPLICATION MANUAL
Page 10
modules in a system. Care should be taken when wir-
ing multiple P522s to ensure the selected bus wires
will carry the current. The plug-in terminals on the
P522 will accommodate a wire size up to 14AWG,
allowing for relatively high currents. Note that, if the
power wiring (26 VDC) is “daisy chained” by using
the terminal pairs provided, the pairs are “jumpered”
by copper traces on the mother board; so, if the plug
is pulled out, the jumpered connection is broken.
SELF-CHECKING FUNCTION
When energized, the self checking function indicates
that both the P522 and the viewing head are func-
tioning properly. The software in the P522 activates
the self-checking relay only if there are less than 10
pulses coming in from the viewing head during each
dark period. To energize this relay, the software 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
LED on the front panel labelled 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
OF 1-9, > 10 PULSES COUNTED DURING THE
DARK PERIOD, in the Model 500 Signal Proces-
sor Application Manual.)
A runaway UV tube or any component failure, in-
cluding the shutter, will cause a lockout condition that
will de-energize the flame relay. The LOCKOUT light
on the P522 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.
APPROVALS
The P522 and viewing heads have Factory Mutual (FM)
Approval for Combustion Safety; Canadian Standards
Association (CSA) Certification, and National Recog-
nized Testing Laboratories (NRTL) Listing.
POWERING UP THE P522
Once the power is connected (26 VDC) to the plug-in
connector, the P522 will be operational. There is no
ON/OFF switch on the P522; 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
input at the plug-in connector is de-energized). Make
sure the voltage is 24 to 26 VDC. The P522 will be
reset when the power is turned on; however, the power
must be a step function (i.e., the power must be ap-
plied abruptly) for this reset to work properly.
The P522 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
P522 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.
This internal circuit monitors the 26 VDC power
feeding the P522, and when the voltage drops to
about 19 volts, the processor shuts down, the pro-
gram stops running, and the self-checking function
ceases (the self-checking relay de-energizes). The