Unigas E115X, Installation Manual

Page: 13 / 116

PART II: NOTES FOR THE INSTALLER
13
Combustion head gas pressure curves
Combustion head gas pressure depends on gas flow and combustion chamber backpressure. When backpressure is subtracted, it
depends only on gas flow, provided combustion is properly adjusted, flue gases residual O2 percentage complies with “Recommended
combustion values” table and CO in the standard limits). During this stage, the combustion head, the gas butterfly valve and the
actuator are at the maximum opening. Refer to , showing the correct way to measure the gas pressure, considering the values of
pressure in combustion chamber, surveyed by means of the pressure gauge or taken from the boiler’s Technical specifications..
Measuring gas pressure in the combustion head
In order to measure the pressure in the combustion head, insert the
pressure gauge probes: one into the combustion chamber’s pressure outlet to get the pressure in the combustion chamber and the
other one into the butterfly valve’s pressure outlet of the burner. On the basis of the measured differential pressure, it is possible to get
the maximum flow rate: in the pressure - rate curves (showed on the next paragraph), it is easy to find out the burner’s output in Stm
3
/h
(quoted on the x axis) from the pressure measured in the combustion head (quoted on the y axis). The data obtained must be conside-
red when adjusting the gas flow rate.
How to read the burner “Performance curve”
To check if the burner is suitable for the boiler to which it must be install-
led, the following parameters are needed:

furnace input, in kW or kcal/h (kW = kcal/h/860);

backpressure (data are available on the boiler ID plate or in the
user’s manual).
Example:
Furnace input: 600kW
Backpressure: 4 mbar
In the “Performance curve” diagram, draw a vertical line matching the fur-
nace input value and an horizontal line matching the backpressure value.
The burner is suitable if the intersection point A is inside the performance
curve.
Data are referred to standard conditions: atmospheric pressure at 1013
mbar, ambient temperature at 15° C.
Checking the proper gas train size
To check the proper gas train size, it is necessary to the available gas pres-
sure value upstream the burner’s gas valve. Then subtract the backpressure.
The result is called
pgas. Draw a vertical line matching the furnace input
value (600kW, in the example), quoted on the x-axis, as far as intercepitng
the network pressure curve, according to the installed gas train (DN65, in the
example). From the interception point, draw an horizontal line as far as
matching, on the y-axis, the value of pressure necessary to get the reque-
sted furnace input. This value must be lower or equal to the
pgas value, cal-
culated before.
PART II: NOTES FOR THE INSTALLER
1
2
4
3
Note: the figure is indicative only.Key
1 Generator
2 Pressure outlet on the combustion chamber
3 Gas pressure outlet on the butterfly valve
4 Differential pressure gauge
Fig. 1
ATTENTION : the burned gas rate must be read at the
gas flow meter. when it is not possible, the user can
refers to the pressure-rate curves as general information
only.
Campo di lavoro bruciatori
Tipo P60 Mod. M-xx.x.IT.A.0.50 - M-.xx.x.IT.A.0.65
-1
0
1
2
3
4
5
6
7
8
100 200 300 400 500 600 700 800 900
Potenza kW
Contropressione in camera di
combustione mbar
A
ba
ckpr
essu
re in
combu
st
ion
cha
m
ber
(mbar
)
Power kW
0
5
10
15
20
25
100 200 300 400 500 600 700 800 900
Potenza / Output (kW)
Minima pressione gas in
rete / Minimum inlet gas
pressure (mbar)
Rp 2" (50)
DN65
Power kW
mi
nimum gas pressure
in
the net
work
mb
ar
DN65