BIO · Edition 09.22
EN-7
➔
A minimum air excess of 20% (lambda=1.2) should
be set in a cold furnace for initial adjustment since
the air volume falls as the temperature rises.
➔
Fine adjustment should be carried out at max.
furnace temperature and at as high a capacity
demand as possible.
5.3 Notes on the flow rate curve
➔
If the gas density in the operating state differs from
that reflected in the flow rate curve, convert the
pressures according to the local operating state.
pB = pM .
B
δ
➔
δM: Gas density reflected in the flow rate curve
in kg/m3(lb/ft3)
➔ δB: Gas density in operating state in kg/m3(lb/ft3)
➔pM: Gas pressure reflected in the flow rate curve
➔pB: Gas pressure in operating state
5.4 Burners without gas measuring orifice
1 Read the gas pressure pgas and air pressure pair
from the enclosed flow rate curve for cold air on
the basis of the calculated flow ratesQ.
[mbar (inch WC)]
[m3/h (ft3/h)]
pgas pair
pair
pgas
Qair
Qgas
➔
Note possible capacity changes due to positive
or negative pressures in the furnace/combustion
chamber. Add positive pressures or subtract neg-
ative pressures.
➔As not all the effects caused by the equipment are
known, setting the burner using the pressure values
is only approximate. It is possible to set the burner
precisely by measuring the flow rates or flue gas.
5.5 Burners with gas measuring orifice
1 Read the differential pressureΔpgas and air pres-
surep
air
from the flow rate curve for cold air on the
basis of the calculated flow rates.
[mbar (inch WC)]
[m3/h (ft3/h)]
Δpgas pair
pair
pgas
Qair
Qgas
pgas
∆pair
➔Note possible capacity changes (air) due to pres-
sure loss in the furnace/combustion chamber. Add
positive pressures or subtract negative pressures.
➔
The differential gas pressure Δp
gas
measured on
the integrated gas measuring orifice is independent
of the furnace chamber pressure.
WARNING
– If reducing fittings or manual valves with internal
thread are installed, Δpgas on the integrated gas
measuring orifice is reduced.
➔Reducing fitting with internal and external thread:
deviation from the flow rate curves may occur when
the cross-section of the reducing fitting differs from
that of the threaded gas connectionGA or when
a manual valve is screwed directly into the burner.
➔
Reducing nipple with external thread at both ends:
no deviation from the flow rate curves occurs.
➔
Ensure an undisturbed flow to the measuring orifice!
➔As not all the effects caused by the equipment are
known, setting the burner using the pressure values
is only approximate. It is possible to set the burner
precisely by measuring the flow rates or flue gas.
5.6 Restrictors
➔
The air volume required for the low-fire rate at a
given air pressure is determined by the ignition
position of a butterfly valve, a bypass hole in the air
valve or an external bypass with restrictor.
➔
Burners as from construction stage E (see type
label) are equipped with gas flow adjustment to
replace the restrictor in the gas pipe.
5.7 Hot air compensation
➔
The combustion air pressure p
air
must be increased
in hot air operating mode (lambda=constant).
0 50 100 150 200 250 300 350 400 450 500 550
100
150
200
300
250
Air temperature [°C]
Air pressure p
air
➔The gas pressure is increased by 5–10mbar.
➔The total burner capacity Pgas rises as the air tem-
perature increases.
0 50 100 150 200 250 300 350 400 450 500 550 600
100
110
120
Air temerature [°C]
Total capacity Ptot [%]
