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4.3
BOILER CALIBRATION
The boiler must always be calibrated while set on heating.
"∆p air" ADJUSTMENT
To measure "∆p air" simply con-
nect a differential pressure
gauge with a decimal or Pascal
scale to the positive and nega-
tive tap, observing the symbols
( Drawing 1 ).
Sequence of operations:
1) Turn the heating power con-
trol trimmer clockwise as
far as it will go ( B – Drawing
2 ) with the fan at its top
speed.
2) Attempt to achieve the "∆p
air" values given in the table
by adjusting the MAX trim-
mer on the fan board
( Drawing 3 ):
∆p air max.
Dewy
25
Natural gas (G20) 49,5
Propane (G31)
49,5
3) Turn the heating power con-
trol trimmer anti-clockwise
as far as it will go ( B –
Drawing 2 ) with the fan at
its top speed.
4) Attempt to achieve the "∆p
air" values shown in the
table using the "MIN" trim-
mer on the fan board
( Drawing 3 ):
∆p air min.
Dewy
25
Natural gas (G20)
7, 1
Propane (G31)
7, 1
Upon completion of the calibration procedure, check CO
or below the values indicated in the table is found, it will be necessary to correct it:
CO
(Natural gas)
2
"MIN" output
"MAX" output
– Use the OFFSET screw ( 2 – Drawing 6 ) to correct CO
– Use the capacity step to correct CO
ATTENTION:
– On PROPANE – G31 boilers
it is a good idea to check
that the position of the GPL
bridge on the control board
is correct.
– Diaphragm code 6028640
( Drawing 7 ) is assembled
on the "Dewy 25" model
functioning on PROPANE –
G31 only.
Drawing 1
Drawing 2
B
30
63,8
68,4
MIN. MAX
"∆p air"
adjustment
Drawing 3
30
8,4
9,2
values using a combustion analyser. If a difference which is more than 0.2 above
2
"Dewy 25"
CO
(Propane)
2
9,3
10,2
8,9
10,0
at "MIN" output.
2
at "MAX" output ( 1 – Drawing 6 ).
2
Drawing 7
"∆p air-gas" ADJUSTMENT
To measure "∆p air-gas", simply
connect the positive tap of the
differential pressure gauge to
the gas tap and the negative
tap to the corresponding tap on
the boiler ( Drawing 4 )
Always adjust gas pressure
with the fan at its top speed.
Sequence of operations:
1) Turn the heating power con-
trol trimmer anti-clockwise
as far as it will go ( B –
Drawing 5 ) with the fan at
its top speed.
2) Open the gas capacity step
( 1 – Drawing 6 ) all the way
so that the notch is in a hori-
zontal position.
3) Adjust the gas valve OFFSET regulation ( 2 – Drawing 6 ), aiming
to achieve the "∆p air- gas" shown in the table:
Capacity step open
Dewy
Natural gas (G20)
Propane (G31)
4) Using the capacity step ( 1 – Drawing 6 ), attempt to achieve the
"∆p air-gas" shown in the table:
Capacity step regulated
Dewy
Natural gas (G20)
Propane (G31)
"Dewy 30"
CO
(Natural gas)
CO
(Propane)
2
2
9,0
10, 1
9, 1
10,3
– If the fan control board code
8260501 is replaced on
"Dewy" models running on
PROPANE – G31 it is very
important to remember to
cut the specified resistance
( Drawing 8 ).
Drawing 4
Drawing 5
B
1
2
Drawing 6
25
30
7,3
7,0
8, 1
10, 1
25
30
5,3
6,3
4,4
9,0
Drawing 8
Fig. 26
IT
ES
PT
GB
97
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