baltur GI 1000 LX Mode D'emploi page 44

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DIFFERENTIAL AIR PRESSURE SWITCH WORKING
The air pressure switch works to ensure safe working of the equip-
ment (locking it off) if the air pressure is not at the expected level.
The pressure switch must therefore by adjusted to act by closing
the NO contact (normally open) when the air pressure in the burner
reaches a certain level. The connection circuit for the pressure
switch is self-controlling and so the NC contact (normally closed),
which should be closed when idle (with the fan off and therefore
no air pressure in the burner), must actually be in this state, if not
the control and command equipment will not go on (the burner
stays off). If the NO is not closed (normally open), where it should
be closed when working, (insufficient air pressure) the equipment
carries out its cycle but will not switch on the ignition transformer
ignition and the gas pilot will not go on, with the result that the
burner locks off.
Adjustment before switching on the burner:
set the pressure switch at minimum.
Adjustment after burner calibration:
connect a manometer to the positive (+) pressure intake and an-
other manometer at the negative pressure (-) intake of the pressure
switch. Check at what point in the modulation there is the smallest
pressure difference (∆p) and adjust the pressure switch at the half-
way point of this difference.
Example: positive value + 1.5 mbar, negative value - 0.5 mbar
difference +  mbar, calibration : = 1 mbar
GAS PRESSURE SWITCH WORKING
The minimum and maximum gas pressure control switches have the aim of preventing the burner from working
when the gas pressure goes outside the preset limits. The
specific working of the pressure switches naturally means
that the minimum pressure control switch uses the NO contact
(normally open) so that it is closed when the pressure switch
detects a pressure greater than that set. Similarly the maxi-
mum pressure switch uses the NC contact (normally closed)
so that it is closed when the pressure switch detects a pressure
below that set. The adjustment of the minimum and maximum
gas pressure switches must therefore take place when the
burner is being tested, according to the pressure found from
time to time. The pressure switches are electrically connected
in series, so the intervention (i.e. circuit opening) of any of
the pressure switches when the burner is working (flame on)
causes the burner to shut down immediately.
Adjustment before switching on the burner: adjust the mini-
mum pressure switch at the scale's minimum and adjust the
maximum pressure switch at the scale's maximum.
Adjustment after burner calibration: With the burner at its
maximum output, adjust the minimum pressure switch by in-
creasing the calibration until the burner switches off, read the
calibration setting on the adjustment ring nut and set this to
5 mbar less. With the burner off, adjust the maximum pressure
switch by reducing the calibration until the NC contact (normally
closed) opens. Read the value on the adjustment ring nut and
adjust this by increasing it by 5 mbar.
Note: the pressure switch will be for minimum pressure if there is only one of these mounted on the gas train.
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