First start-up
Installation, use and maintenance manual – K18 Simplygas
43
5
5.4
DIRECT CONTROL OF DHW PRODUCTION
FROM THE K18 APPLIANCE
In order for the K18 appliance to directly manage the
DHW production, it is essential that the probe in the
DHW buffer tank (GHP'', Paragraph 5.3.5.2
p. 40) is cor-
rectly connected and configured.
5.4.1
DHW charge cycle management
In all DHW production service management modes, a charge cy-
cle is managed with the criteria detailed below.
5.4.1.1
Activation
The K18 appliance is activated for DHW production when the
temperature measured by the GHP'' probe is lower than the val-
ue of the active setpoint (parameter 227/237 according to the
status of the COM-DHW contact), reduced by the value of pa-
rameter 235 (differential for starting the DHW charge).
For example if parameter 227 is set to 55 °C and parameter 235
is set to 5 K, the K18 appliance will be activated for DHW produc-
tion, with COM-DHW contact closed, if the temperature meas-
ured by the GHP'' probe is lower than (55-5) = 50 °C.
Simultaneously with the activation of DHW production, the di-
verter valve is switched to the DHW position.
The DHW production service therefore always has pri-
ority over the space heating service.
5.4.1.2
Deactivation
The K18 appliance is switched off for DHW production when the
temperature measured by the GHP'' probe is higher than the val-
ue of the active setpoint (parameter 227/237 according to the
status of the COM-DHW contact).
For example, if parameter 227 is set to 55 °C, the K18 appliance
will be switched off for DHW production, with COM-DHW con-
tact closed, if the temperature measured by the GHP probe'' is
equal or higher than 55 °C.
At the end of the DHW charging cycle, the diverter valve is
switched to the heating position only when the heating service
is required.
5.4.2
DHW production service management modes
The methods available for the DHW production service managed
directly by the K18 appliance are the following (alternatives):
1. Fixed comfort setpoint 24 hours/day
2. Fixed comfort setpoint with the possibility to deactivate the
DHW request via external contact (comfort / OFF)
3. Fixed comfort setpoint or DHW buffer tank antifreeze pro-
tection via external contact (comfort / antifreeze)
4. Variable setpoint (comfort and reduced) according to pro-
gramming (with external timer)
5. Fixed setpoint with anti-legionella function (with external
timer)
5.4.2.1
Fixed comfort setpoint 24 hours/day
▶
COM-DHW contact: not connected
▶
Parameters to set: 237
This mode must be chosen when you want the DHW request to
be active continuously, with the aim of keeping the DHW buffer
tank at the temperature set in parameter 237 at all times.
The COM-DHW contact must be left open and parameter 237
must be set to the desired temperature value for DHW buffer
tank.
This is the most energy-intensive mode, as the system always
maintains the temperature in the DHW buffer tank around the
setpoint value set in parameter 237. More precisely, between the
value (parameter 237 - parameter 235) and the value (parameter
237).
The only way to deactivate the DHW request is to manually
change the value of parameter 237 to a lower value (or to the
value 0 if you want to deactivate the request completely).
5.4.2.2
Fixed comfort setpoint with the possibility to
deactivate the DHW request via external contact
(comfort / OFF)
▶
COM-DHW contact: connected to switch or daily/weekly
timer
▶
Parameters to set: 227 (leave or reset parameter 237 to 0)
This mode should be chosen when you want to have the possi-
bility to activate the DHW request only in the presence of a sig-
nal coming from a switch or timer.
In this case the COM-DHW contact must be connected to the
request signal from the external switch or timer (SELV NO volt-
age-free contact) and the required DHW setpoint must be set in
parameter 227; parameter 237 must be left at the default value
0.
The K18 appliance will be available for DHW production only
if required by the external switch or timer; under these condi-
tions it will keep the DHW buffer tank temperature around the
value set in parameter 227. More precisely, between the value
(parameter 227 - parameter 235) and the value (parameter 227).
Otherwise, DHW production will be switched off.
5.4.2.3
Fixed comfort setpoint or DHW buffer tank
antifreeze protection via external contact (comfort /
antifreeze)
▶
COM-DHW contact: connected to switch or daily/weekly
timer
▶
Parameters to set: 227, 237
This mode should be chosen when you want to have the possi-
bility to activate the DHW request only in the presence of a sig-
nal coming from a switch or timer, but keeping the DHW buffer
tank always protected from freezing.
In this case, the COM-DHW contact must be connected to the
request signal from the external switch or timer (SELV NO volt-
age-free contact) and both parameter 227, which represents the
value of the DHW buffer tank setpoint in case of active DHW ser-
vice request, and parameter 237, which corresponds to the DHW
buffer tank setpoint for its frost protection (recommended value
7÷10 °C), must be set appropriately.
Pay attention to the value of the differential (parameter
235) whose default is 5 °C, because before reactivation
of the DHW charge the temperature in the DHW buffer
tank can drop down to (parameter 237 - parameter
235). Therefore, if the value of parameter 237 is not high
enough and the value of parameter 235 is too high, there
is in fact no protection of the DHW buffer tank against
freezing.
The K18 appliance will keep the DHW buffer tank temperature
around the value of the comfort setpoint, set in parameter 227,
if required by the external switch or timer (COM-DHW contact
closed). Otherwise it will keep the DHW buffer tank temperature
around the value set in parameter 237 (which corresponds to
the DHW buffer tank setpoint for antifreeze protection).
5.4.2.4
Variable setpoint (comfort and reduced) according
to programming (with external timer)
▶
COM-DHW contact: connected to a daily/weekly timer
▶
Parameters to set: 227, 237
This mode must be chosen when you want to have the possi-
bility to activate the DHW request on two different setpoints in
