External Heat Exchanger; Cylinder Priority Control; Cyclical Heating - Viessmann SDIO Installation And Service Instructions For Contractors

Function description – version with SM1
Version with SM1 and KM-BUS (solar DHW heating)
Different modes of operation can be achieved by
determining the thermostat start temperature (coding
address "24") and stop temperature (coding address
"25"):
■ Start temperature < stop temperature:
Thermostat function e.g. for reheating.
Output is switched on when the temperature at
sS
sensor falls below the start temperature.
/
Output is switched off when the temperature at
sS
sensor exceeds the stop temperature.
/
Start temperature > stop temperature:
■
Thermostat function e.g. for utilising excess heat.
Output is switched on when the temperature at
sS
sensor exceeds the start temperature.
/
Output is switched off when the temperature at
sS
sensor falls below the stop temperature.
/

External heat exchanger

Set code/parameter "20:7" or "20:8".
&
sF
/
%
Fig. 4

Cylinder priority control

Set code/parameter "20:9".
In systems with 2 DHW cylinders, it is possible to set
the order in which the DHW cylinders are heated. The
order is set in coding address "26".
For this, a distinction can be drawn between operation
with and without cyclical heating (see the following
chapter).

Cyclical heating

Set code/parameter "20:9".
In systems with 2 DHW cylinders:
If the DHW cylinder with priority cannot be heated, the
secondary cylinder is heated for a cyclical heating time
that can be set in coding address "27".
After this time has expired, the solar control unit
checks the rise in collector temperature during a cycli-
cal pause time that can be set in coding address "28".
26
sS
(cont.)
■ Code/parameter "20:7":
The cylinder is heated via an external heat
exchanger. Secondary pump
solar circuit pump sF .
■ Code/parameter "20:8":
If an additional temperature sensor
ondary pump starts if solar circuit pump
sS
ning and the required temperature differential
between sensors and
%
To enable priority control, the actual temperatures of
both DHW cylinders are compared with the actual col-
lector temperature. Output
dary cylinder is being heated.
Coding addresses "10", "11", "26".
As soon as the start conditions for the cylinder with pri-
ority are met, that cylinder is heated again. Otherwise,
the secondary cylinder continues to be heated.
Coding addresses "26", "27", "28".
starts in parallel with
sS
is used, sec-
/
is run-
sF
is present.
/
will be 'live' if the secon-
sS