Viessmann Vitotronic SPS Service Instructions Manual page 30

Configuring the system
System parameters
Parameters:
■ "Parameter heating properties"
"Maximum differential secondary to cylinder"
–
At a value of 0, the set output is reduced as soon
as the condenser return temperature has reached
the set buffer temperature (to within approx. 3 °C).
If, when charging the heating water buffer cylinder,
a large spread arises between the buffer tempera-
ture and the heat pump secondary temperature,
this value must be increased to prevent the set
output from being reduced too early.
■ "Use of therm. energy f. cooling (dual fuel op.)"
– "Re-cooling set to cylinders"
Here you can specify whether the cylinders (buffer
cylinder and DHW cylinder) are used for re-cooling.
(Dual fuel operation)
– "Re-cooling set to DHW cylinder"
Can be enabled separately, since it is not possible
in every system and because efficiency is reduced
at high temperatures.
"Set val. reduction HW buff cyl for re-cooling"
–
This value specifies by how many °C the set cylin-
der temperature of the buffer cylinder is reduced if
it is heated via the re-cooling function. This makes
it possible to ensure that efficiency is not too heav-
ily reduced in dual fuel operation. (The higher the
temperature differential between the primary and
secondary sides, the lower the efficiency)
– "Set value reduction DHW cylinder for re-cool-
ing"
As for the parameter "Set val. reduction HW buff
cyl for re-cooling", but in relation to the DHW cyl-
inder
– "Switching threshold cyl for re-cooling"
If both cylinders are enabled for re-cooling, the cyl-
inder with the lower temperature will always be
heated. The switching threshold is determined with
this value. At the standard setting of 1 °C, switch-
ing occurs only once the differential is greater than
1 °C. By increasing the switching threshold, the
frequency of switching is reduced.
"Options DHW heating"
■
These starting options apply in addition to the stand-
ard operating mode that is set through the system
visualisation. They cause DHW cylinder heating to
start without the heating start threshold having been
reached. Heating of the DHW cylinder does not start
following these events only if the stop threshold has
already been reached.
– "DHW cyl htg start after power supply utility
enable"
With this function, heating of the DHW cylinder is
started as soon as the power supply utility enable
signal becomes active again following a power-
OFF period.
– "DHW cylinder heating start after fixed time"
Heating of the DHW cylinder always starts at the
set start time.
30
(cont.)
■ "Options natural cooling"
– "Interval test natural cooling possible"
Interval following which the system will test
whether the temperature of the refrigeration source
has fallen far enough again, after natural cooling
has been stopped due to too high a source tem-
perature.
– "Prim. circuit adv. runtime f. nat. cooling test
possible"
The advance runtime must be set such that follow-
ing the advance runtime, the source temperature
can be measured by the temperature sensor in the
evaporator. Once the advance runtime has
expired, the temperature in the primary circuit must
be stable.
– "Minimum differential for natural cooling
demand"
Natural cooling is enabled only once this tempera-
ture differential has been reached.
"Stop threshold natural cooling"
–
If the differential between source and cooling cir-
cuit is too small, no cooling capacity will be availa-
ble. For this reason, natural cooling will be blocked
at the temperature threshold set here. (Factory set-
ting: 0.5 °C)
"Options cooling control"
■
– Output control down to 0 %
When a cooling demand is present, the heat pump
can be prevented from starting if, due to the previ-
ous operating mode, the evaporator is very cold
and the cooling stop temperature has already been
exceeded. To prevent this happening, the set out-
put as the stop threshold is approached should be
set back to no lower than 10 %. If the cooling func-
tion should be started and stopped only according
to the specification of the external set value, the
output control must be run until 0 %.
Buttons:
■ "Back"
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