I.R.I.S. FLAME MONITORING SYSTEM P522 - Manual (Page 17)

IRIS MODEL P522 APPLICATION MANUAL
Page 17
The above settings will be satisfactory for
most applications, but are used only as a
starting point. So many variables can
affect the readings that it is impossible
to catalogue all the settings, and each
viewing head has its own characteristics
for the different types of fuels and burn-
ers. We recommend that you become
knowledgeable about the characteristics
of the different viewing head models
available before applying them to a par-
ticular application. Detailed descriptions
of the viewing heads are provided in this
manual, and the VIEWING HEAD AP-
PLICATION TABLES (Figure 11) are
a useful summary of the viewing heads
and their response to different fuels.
B. The initial settings for the flicker type
viewing heads (S509, S511, S512) should
be as follows:
1. Set filter switch to LL position.
2. Gain potentiometers (POTS) full
clockwise (these are 25-turn potenti-
ometers – a slight clicking sound will
be heard when the POT is maximum
clockwise). There are two POTS on
the S509: one for the Si channel, and
one for the PbS channel. If the fuel is
natural gas, turn the Si channel off
(POT full counter clockwise). Refer
to section S509 VIEW HEAD.
C. There are no initial settings for the S506
UV viewing head. It is important that
this viewing head be properly aimed to
pick up the maximum signal, as described
in the previous section.
ADJUSTING SET POINTS
Before adjusting the set points, take readings with
the P522 on the two worst-case conditions described
(see section SETUP AND ADJUSTMENT PRO-
CEDURES). Write down the readings for the burner
ON and OFF (with other burners on) under low load
conditions, and then the readings for the burner ON
and OFF under high load conditions.
There must be a definitive ratio between the read-
ings for burner ON and burner OFF. This ratio can
be defined by using the lowest reading for burner
ON from both of the load conditions, and the high-
est reading for burner OFF from both of the load
conditions. If the readings are 2:1 or more (BNR
ON to BNR OFF) then there should be no problem
discriminating between burners.
A good balance for the set points would be:
ON
SET POINT
= .75A + .25B
OFF
SET POINT
= .25A + .75B
where A is the lowest burner ON reading, and B is
the highest burner OFF reading.
Actually, a smaller ratio will work, as long as the
lowest BNR ON reading and the highest BNR OFF
reading never deteriorates to the point the former is
equal to or less than the latter. In other words, A
must always be greater than B. Using a safety factor
of 2:1 will allow for flame signal changes that prob-
ably will occur over a period of time.
A. FOR FLICKER TYPE VIEWING
HEADS: If unable to achieve discrimi-
nation from background signals (for mod-
els S509, S511 and S512 viewing heads),
remove the viewing head housing from
the flange and place the filter switch to
the next highest position L. Reinstall the
viewing head and take another set of read-
ings. Note: the filter switch should be
moved only one position at a time for
each set of readings. Refer to section
MULTIBURNER REQUIREMENTS.
B. FOR THE S509 VIEWING HEAD: If
you are still unable to achieve satisfac-
tory flame OFF operation, remove the
viewing head and turn the Si channel off
by turning the Si POT at least 30 turns
counter clockwise. The signal level will
now be lower because only the PbS de-
tector is being used, so the set points must
be re-evaluated. If you are using an S511
viewing head and not achieving success-