Installation manual

installation manual TWIN 80 EN
22
3.5. Gas/Air Ratio
(1). Venturi-screw – Full load adjustment
Turn the venturi screw anti-clockwise to increase
the CO
2
value,
clockwise to decrease it
.
(2). Gas control screw – Low load adjustment
Turn the screw anti-clockwise to decrease
the CO
2
value on low
load, clockwise to increase
it.
(3). Cover screw
3.5.1. Pre-adjustment to be done in voltage-free
condition:
- LPG GAS – Turn venturi-screw clockwise 3
completely down on its seat.
Then turn the venturi-screw anti-clockwise 4 for
1/2 complete turns.
- N
ATURAL GAS – Turn venturi-screw clockwise 3
completely down on its seat.
Then turn the venturi-screw anti-clockwise 4 for 3
complete turns.
With a callipers vernier the distance between venturi-screw (1)
and the Top of the venturi-stud (1) has to be measured to find
the rough setting of the venturi-screw for full load, and
depending of the used gas type.
The exact adjustment of the setting has to be made using the
CO
2
analysing method as described below.
3.5.2. Final Gas/Air adjustment (CO
2
analysing)
The gas controls are set in the factory to the type of gas to be
used. This type of gas is stated on the packaging and on the
identification plate. To check the settings, you have to make a
flue gas analysis.
Note that each unit has to be set according to the same
procedure individually.
Proceed as follows:
Remove the rubber plug (L) or (r) from the flue tube concerned.
It is not necessary to set the units in a certain order. Fit the
measurement probe of a flue gas analyser (CO
2
meter) in the
measurement opening of the flue tube canal concerned.
Adjusting full load
Make sure there is sufficient heat dissipation through the
heating.
Activate the chimney sweeper function on full load.
Read the CO
2
value on the
analyser. If the value does not
correspond with the value in the
"CO
2
setting" table, carefully
adjust the venturi-screw (1). Turn
the venturi-screw anti-clockwise
to increase the CO
2
value,
clockwise to decrease
it.
Adjusting low load
Activate the chimney sweeper function on low load
Read the CO
2
value on the
analyser. If the value does not
correspond with the value in the
"CO
2
setting" table, carefully
adjust the gas control adjusting
screw (2). To do this, temporarily
remove the cap (3) with the aid of
a Torx-screw driver. Turn the
screw anti-clockwise to decrease
the CO
2
value on low load, clockwise to increase it.
CO
2
setting full load low load
Natural gas
(G20, G25)
8,8 % CO
2
8,2 % CO
2
PRE- ADJUSTMENT MEASUREMENT:
Distance between Venturi-screw (1) and the Top of the
venturi-stud to be about:
9 12 mm for natural gas G25
9 14 mm for natural gas G20
9 16 mm for LPG gas G31
(L)
rubber plug
Left unit
(r)
rubber plug
right unit