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14698_r00
depending on the availability of the SA room temperature probe, as
shown in the diagram of figure 6.
-10
0
10
20
30
40
50
60
70
80
90
100
110
19,8
20
20,2
20,4
20,6
20,8
21
21,2
21,4
21,6
21,8
22
22,2
Fig. 6 – Parameter-based modulation diagram
Based on the room temperature value, three conditions can occur:
1)
T
AMB
room temperature lower than (T
I
– d): in this case the
percentage of modulation power will always be equal to 100%
(max. heat demand) and the second EV2 valve stage will be
activated;
2)
T
AMB
room temperature between (T
I
– d) and T
I
: in this case the
percentage of modulation power will be calculated according to
the following formula:
100
*
d
T
-
T
=
P
AMB
I
%
3)
T
AMB
room temperature higher than T
I
: in this case the
modulation power will always be equal to zero (a condition
corresponding to the absence of heat demand).
The
thermal hysteresis parameter takes effect on the modulation
only in case the room temperature exceeds the T
I
set-point value
and then decreases. In these conditions the percentage of
modulation power will remain equal to zero (no heat demand) until
the T
AMB
room temperature will reach the threshold (T
I
- i), below
which the formula on point 2 will be respected again.
Contact room thermostat
In this case, the modulation power depends on the status of the
adjustment thermostat only, i.e.:
-
TA thermostat closed (ON): in this case the modulation power
will always be equal to 100% (max. heat demand) and the
EV2 second valve stage will be activated;
-
TA thermostat open (OFF): in this case the modulation power
will always be equal to zero (a condition corresponding to the
absence of heat demand).
-
Heating mode (FAN function)
The introduction of hot air into the environment is carried out by
means of a hot air blower (FAN). The operation of this type of load
is dependent upon different factors:
-
the operation status of the system (pre-purge time, first running
stage, …);
-
the heat exchanger (outlet) air temperature measured by
means of the SR heating circuit probe;
-
switch-on and switch-off delay times.
The FAN function begins when the system enters the first running
stage (RP1). As already described above, this phase of the cycle
enables a suitable heating of the exchanger: in fact, hot air can be
introduced into the environment only if its temperature is high
enough.
From the RP1 first running stage entering, the system guarantees
a waiting time (delay time on FAN activation) which is considered
to be necessary to enable an appropriate heating of the exchanger:
at the end of this time, hot air can be introduced into the
environment and the FAN hot air blower can therefore be
activated. If the heat exchanger temperature exceeds the T
V
(ventilation temperature) threshold during the switch-on delay time,
the activation of the FAN hot air blower will be anticipated, as the
system will have already reached suitable conditions for the
environment heating.
A similar operation is carried out during the heat exchanger cooling
phase: in case the control unit leaves the running status (due, for
example, to heat demand failure), the FAN hot air blower remains
activated at its max. speed for a time which can be set up on
request (post-purge time on FAN hot air blower); if before the end
of the cooling phase the temperature measured by the SR heating
circuit probe is lower than the T
SV
(ventilation-stop temperature)
threshold, the FAN hot air blower will be switched off and the post-
purge stage interrupted.
The device is prearranged for the (electrically parallel) connection
of two blowers.
-
Summer ventilation
This function enables to use the FAN hot air blower for summer
ventilation. The FAN blower can be activated even in case the
control unit is in lockout status.
!!!!
IMPORTANT NOTE
The summer ventilation function can be activated only if a BRAHMA
chronothermostat type ENCRONO GA1 is used. For further details please refer to
the data sheets of this device. If this remote adjuster is not available, summer
ventilation will have to be managed externally by supplying the FAN hot air blower
as described hereunder.
J6
FAN
1 2 3 4 5 6 7 8 9
LINE
Fuse
Switch
TC340
-
Manual reset limit temperature, switch-off temperature and
re-ignition temperature
The operation of the system also depends on three additional
temperature thresholds of the heat exchanger: the manual reset
limit temperature (T
L
), the burner switch-off temperature (T
OFF
) and
the re-ignition temperature (T
ON
).
The T
L
manual reset limit temperature is used in the versions
equipped with double NTC heating circuit probe (standard version)
and represents the threshold above which the control unit goes to
lockout. In the versions equipped with single NTC heating circuit
probe, this threshold corresponds to the contact safety thermostat
switch-on temperature: when the heat exchanger temperature
drops to acceptable values for a correct operation, the burner does
not restart automatically, but needs the manual reset of the control
unit by the user.
The T
OFF
burner switch-off temperature represents the threshold
above which the normal burner operation is stopped without
system lockout: in fact, the control unit will go to stand-by position,
while the FAN hot air blower will remain activated at its max. speed
to enable an appropriate cooling of the heat exchanger.
T
AMB
[°C]
P
[%]
OFF
MODULATION AREA
(T
I
– d)
(T
I
– i)
T
I
