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14698_r00
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IMPORTANT NOTE
In order to further reduce irradiated interference and increase the immunity of the
control unit, it is strongly recommended to mount a wire-wound power resistor with
a value from 1k
Ω
to 4.7k
Ω
between the high voltage cables and the related
discharge electrodes.
CHECKING AT START-UP
Check the control system before the first start-up, after any
overhaul and after a long period of non-operation. Before any
ignition attempt make sure that the combustion chamber is free
from gas, then check the following:
−
if the start-up attempt occurs without gas supply, the control
system should go to lockout at the end of the safety time;
−
when stopping the gas flow while the control system is running,
the power supply to the gas valves should be interrupted within
1s, and the control system should proceed to lockout after a
recycling attempt (or more than one up to 10 depending on the
settings);
−
operating times and sequence should correspond to those
declared for the type of control unit you are using;
−
the level of the flame signal should be high enough (see Fig. 4);
−
the ignition probes should be adjusted in the most stable way
for a spark gap between 2-4 mm;
−
the intervention of limiters or safety devices should cause the
lockout or safety shutdown of the control unit according to the
type of application and the procedure provided for.
Microammeter
A
+
-
J2
I
ION
Fig. 4 – Flame signal measuring method
TC340(A-P) - OPERATION
The following description refers to the standard operating cycle of
BRAHMA control units type TC340A and TC340P. The operating
cycle can be modified both using the available options and
according to particular customer's requirements.
-
First start-up
At the first start-up, the device carries out a “
self-test” to verify that
all the conditions required at the beginning of the ignition cycle are
respected.
At the end of this stage, the system goes on checking the type of
heat demand used in the appliance (power-free contact or
OpenTherm™ connection to BRAHMA chronothermostat type
ENCRONO GA1 or to an additional TC340 unit): in this stage,
lasting about 30 seconds, the SL LED signal flashes with green
light indicating the stand-by status.
At the end of this diagnostic phase, the unit is ready to receive the
heat demand and start the ignition cycle.
-
Ignition cycle
The ignition and flame control cycle starts on receipt of the heat
demand, which can occur in three ways:
-
through a BRAHMA chronothermostat type ENCRONO GA1;
-
through a power-free contact with room thermostat function;
-
through an additional BRAHMA device type TC340 in case of
cascade systems.
The control unit starts the ignition cycle by checking the air
pressure switch status (fan-assisted version) or the number of
revolutions per minute of the EF burner motor (premix version). In
case no signal is detected, the system starts the EF fume extractor
at its max. speed; as soon as the air pressure switch goes to “air-
flow” position (fan-assisted version) or the necessary number of
revolutions per minute is reached (premix version), the pre-purge
time (TP) begins.
In premix applications, a few seconds before the beginning of the
safety time (about 3 seconds, customizable upon request), the
system reaches a stage of the pre-purge time in which the EF
combustion motor speed can be decreased (TP2): this function
enables to carry out the burner soft-start, if necessary, starting the
burner at an (adjustable) lower power than the first running stage
(RP1).
At the end of the pre-purge time the device is ready to perform the
safety time (TS) and activate the following:
-
the inbuilt ignition transformer;
-
the auxiliary electronic ignition transformer;
-
the EV1 first valve stage;
-
the modulator (if available) at the power level requested for
ignition.
If a flame signal is detected, the unit will go to running position; if
no flame signal is detected, the system will proceed to lockout due
to ignition failure at the end of the safety time.
-
First running stage (RP1)
At the end of the safety time and in case of flame signal detection,
the control unit goes to running position. According to a delay
customizable upon request (waiting time for modulation start t
RP1
),
the system ignores all modulating parameters giving max. power to
the appliance in order to ensure a suitable heating of the heat
exchanger; in this stage, in fan-assisted versions, the EV2 second
valve stage is kept operating and the current modulator is kept
supplied at max. power.
At the end of this time the device enters the second running stage,
where the burner combustion power depends on the modulating
parameters provided by the temperature adjustment system.
-
Second running stage (RP2)
In the second running stage the control unit can perform
temperature adjustment functions depending on the type of heat
demand used in the appliance, which can be:
-
an OpenTherm™ connection (to a BRAHMA chronothermostat
type ENCRONO GA1 or to an additional TC340 unit);
-
a contact room thermostat.
The behaviour of the control unit in the two above-mentioned
cases will be shortly described hereunder.
OpenTherm™ connection available
In this case, temperature adjustment will be carried out according
to four variables:
1)
room temperature (T
A
): which can be measured both through a
chronothermostat or through an SA room temperature probe (if
available);
