Viessmann Vitocrossal 300 Service Instructions For Contractors page 44

Commissioning, inspection, maintenance
Further details regarding the individual steps
In the case of absolute priority, heating
circuit pumps eQ/rR/tR are switched off
and mixers rT/tT are closed. With mod-
ulating priority control of the heating cir-
cuits with mixer, heating circuit pumps
rR/tR remain on, and mixers rT/tT
close far enough to enable the boiler
water temperature set for cylinder heat-
ing to be reached. In this case, DHW cyl-
inder qP or qR and heating circuit with
mixer rP and tP are heated simultane-
ously.
DHW heating by the solar thermal
system
Solar circuit pump wE starts and DHW
cylinder qR is heated up, if the tempera-
ture differential between collector tem-
perature sensor wQ and cylinder temper-
ature sensor qT exceeds the start tem-
perature differential.
Pump wE is stopped according to the fol-
lowing criteria:
■ The actual temperature drops below
the stop temperature differential
■ Exceeding the electronic temperature
limit (up to 90 °C) set in the solar con-
trol module (type SM1) wZ
■ The temperature selected at high limit
safety cut-out qZ (if installed) is
reached
Function/system components
Operation with LPG
System only with two heating circuits with mixer (with-
out unregulated heating circuit)
44
Demands for the auxiliary function are
met by circulation pump wR.
Suppression of reheating of the DHW
cylinder by the boiler in conjunction
with solar control module (type SM1)
Reheating suppression takes place in
two stages.
Reheating DHW cylinder qR by boiler
1 is suppressed as soon as DHW cyl-
inder qR is heated by collectors wP. For
this, the set cylinder temperature for
reheating is reduced by boiler 1. Sup-
pression remains active for a certain time
after solar circuit pump wE has been
switched off.
In the case of uninterrupted heating by
collectors wP (> 2 h) boiler 1 will only
reheat, if the set cylinder temperature
(coding address "67") selected at boiler
circuit control unit 2 is not achieved.
In control unit 2, coding address "67"
defaults a third set DHW temperature
(setting range 10 to 95 °C). This value
must be below the first set DHW temper-
ature.
DHW cylinder qR will only be heated by
boiler 1 when this set value is no longer
achieved by the solar thermal system.
Adjust Delivered con-
(cont.)
Code
dition
82:1
00:8 00:10
00:7
82:0
00:9