Viessmann C3HA, Installation And Service Instructions For Contractors

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Oil/gas boilers as auxiliary heat sources
See system version 3.
The auxiliary heat source is controlled
via the set flow temperature for the heat-
ing circuits. It is enabled via terminal
QX4 on Vitotwin 300-W at the external
hook-up for the boiler and heating circuit
control unit. It is only enabled if the out-
put of Vitotwin 300-W exceeds the value
set in coding address 3691 (delivered
condition 80 %) or the actual flow tem-
perature falls sharply.
The auxiliary heat source can be locked
in a selected outside temperature range
via codes 3700 and 3701 (delivered con-
dition "- - -", auxiliary heat source always
enabled or no restriction).
The auxiliary heat source can be started
with a time delay on demand via code
3723 (delivered condition "- - -", function
switched off).
If the type of auxiliary heat source has
been selected via code 3750, this is dis-
played accordingly.
If economy mode is switched on, the
auxiliary heat source is locked in the
delivered condition (code 3702). ■ Starting criterion:
If the actual flow temperature on the
common flow temperature sensor
(common flow sensor B10) falls below
the set flow temperature by
the
"Switching diff on" , the diverter
valve (terminal QX2) switches and
passes through the boiler. The auxili-
ary heat source burner is enabled if the
"Switching integral" (code 3720) is
reached.
When the auxiliary heat source is ena-
bled, the set flow temperature for
Vitotwin 300-W is increased by 10 K
(code 3690), so that this is not
switched off or modulated.
■ Shutdown criterion:
Burner enable will be blocked if the
actual flow temperature on the com-
mon flow temperature sensor (com-
mon flow sensor B10) rises above the
set flow temperature by the
"Switch-
ing diff off" (code 3722). The diverter
valve is switched once the run-on time
has elapsed.
Auxiliary heating source and DHW
heating
The auxiliary heat source is only enabled
for DHW heating if the Vitotwin 300-W
cannot be operated (code 3692), e.g. as
a result of a fault.
Solid fuel boiler as auxiliary heat source
See system version 4.
The additional buffer cylinder is connec-
ted via the Vitosolic (ΔT-control). Code 5982 must be selected as "Supp
burner block" and code 5891 as "DHW
ctrl elem Q3" .
Function description
Boiler temperature control
(cont.)
5618 294 GB
Service