Version With Sdio/Sm1A Electronics Module And Plusbus; Solar Dhw Heating; Variable Speed Solar Circuit Pump; Suppression Of Dhw Cylinder Reheating By The Heat Generator - Viessmann SDIO Installation And Service Instructions For Contractors

Function description – version with SDIO/SM1A

Version with SDIO/SM1A electronics module and PlusBus

Solar DHW heating

Note
Set or alter the functions described below in the
parameters in the "Solar" group.
The solar circuit pump is switched on according to the
following criteria, resulting in the DHW being heated:
The temperature differential between the collector
■
temperature and the cylinder temperature is greater
than the start temperature differential set in parame-
ter 1492.0.
■ The minimum collector temperature set in parameter
1126.0 is exceeded.

Variable speed solar circuit pump

Suitable pumps:
Pumps with PWM input (only use solar circuit pumps)

Suppression of DHW cylinder reheating by the heat generator

In systems with boilers
Reheating is suppressed in 2 stages:
Reheating of the DHW cylinder by the boiler is sup-
■
pressed as soon as the solar circuit pump starts up.
For this, half the suppression becomes effective in
stage 1 (example: Set DHW temperature of 50 °C
and set DHW temperature for solar reheating sup-
pression of 40 °C results in a reduced enabled set
value of 45 °C). If the DHW temperature falls below
the reduced enabled set value, the boiler carries out
reheating. After the solar circuit pump has been
switched off, suppression remains active for a certain
time.
■ In the case of uninterrupted heating by the collectors
( 2 h), full suppression is activated. The reduced set
>
DHW temperature now applies. If the DHW tempera-
ture falls below the reduced enabled set value, the
boiler carries out reheating. Reheating suppression
ends as soon as the solar circuit pump is switched
off.
The reduced set DHW temperature is specified by
parameter 1394.0 in the "DHW" group. This value
must be below the 1st set DHW temperature.

Maximum collector temperature

If the maximum collector temperature set in parameter
1126.1 is exceeded, the solar circuit pump is switched
off to protect the system components (emergency col-
lector shutdown).
28
The solar circuit pump is switched off if one of the fol-
lowing criteria is met:
■ The temperature differential between the cylinder
temperature and the collector temperature is smaller
than the stop temperature differential set in parame-
ter 1492.1.
The maximum cylinder temperature (set DHW tem-
■
perature) set in parameter 1125.0 is exceeded.
■ The maximum collector temperature set in parameter
1126.1 is exceeded.
■ The temperature set at the high limit safety cut-out is
exceeded.
Note
Recommendation: Run the solar circuit pump at max.
speed when venting the solar thermal system (see
actuator test).
Reheating by the boiler is suppressed if a sufficiently
high temperature for heating the heating circuits is
available in the multi mode heating water buffer cylin-
der. The temperature is dependent on the required
flow temperature of the heating circuits.
In systems with heat pumps
During solar DHW heating, the "Set DHW tempera-
ture" is reduced by 5 K.
The solar circuit pump will restart when the collector
temperature falls to 20 K below the set value.