18
of
27
Option 34.5 - Calculating and entering the flow values manually LV3
If the flow values are to be calculated manually, the procedure below must be followed.
Enter Adjust Ratio Mode with oxygen trim
disabled
as outlined above.
1. Select the high fire position. This will cause the display to show A(n), where n is the number of the
high fire profile point.
2. Wait until the oxygen reading has stabilized, the value can be viewed using the engineer’s key.
3. Record the
excess air
value at location x in the table. For single fuel profiles, this value may be found
using the Engineer’s Key parameter EK48 (provided the hydrocarbon ratio has been entered into the
appropriate option parameter (35.1 - 35.4) for this fuel). For multiple fuel profiles,
Refer to NOTE
under section Options 35.1 to 35.4
.
4. Select the profile position immediately below high fire. This will cause the display to show A(n -1).
5. Wait until the oxygen reading has stabilized and record the
excess air
value at location a
1
in the table
6. Move air dampers 1 and 2 (if fitted)
up
until they stop, so that they are at the set point immediately
above the current position.
Do not press enter.
7. Wait until the oxygen reading has stabilized, then record the
excess air
value at location b
1
in the
table, relating to the current profile position
8. Repeat the above for all other profile positions including low fire (profile position A3), recording each
time the values at locations a and b in the table. When extra air is added at P3, the time taken before
the flue oxygen reading starts to increase should be measured and entered into option parameter
30.7.
9. After completing the table for all Excess Air values a and b, complete the Excess Air + 100 column, by
adding 100 (i.e. y = x + 100, c = a + 100 and d = b + 100.
10.Complete the Ratio column by dividing c by d (i.e. e = c/d).
11.Complete the Airflow column by multiplying e by the previous value of f (i.e. f
x
= e
x
f
x-1
).
12.If the system will be applying trim to the fuel, the fuel flow column must be completed. This is
achieved by multiplying the airflow at each point by the ratio of excess air + 100 at high fire divided by
the excess air + 100 at the actual point (i.e. g
x
= f
x
(y/c
x
)).
Example of table completed for A10 (high fire) to A8. In practice, the table must be filled out down to A3
(low fire).
Profile
position
Excess Air
Ex. Air + 100
y = x + 100
c = a + 100
d = b + 100
Ratio
Airflow
Fuel flow
High fire
= A
10
x
10
y
110
----------------
99.9%
99.9%
1 = A
9
a
1
b
1
8
33
c
1
d
1
108
133
e
1
= c
1
/d
1
0.812
f
1
= e
1
(99.9)
81.1%
g
1
= f
1
(y/c
1
)
82.6%
Summary of Contents for NEXUS NX6100 series
Page 3: ...3 of 27...
Page 4: ...4 of 27...
