Heating Water Buffer Cylinder; Switching On The Compressor - Viessmann VITOTRONIC 200 Service Instructions Manual

Function description
2-stage refrigerant circuit

Switching on the compressor

The refrigerant circuit controller always switches on the
compressor that was not running most recently. This
ensures that the runtimes of the two compressors
remain balanced.
When the heat demand is low, only one compressor is
in operation.
Switching on with 1 direct heating circuit without

heating water buffer cylinder

With high output heat pumps, we recommend always
using a heating water buffer cylinder in the secondary
circuit flow.
In special cases, a direct heating circuit can also be
supplied without a heating water buffer cylinder.
If all of the following conditions are met, compressor 1
starts:
■ A heat demand is present. The secondary circuit
return temperature undershoots the set value by 2 K.
The blocking time of 20 min since the last compres-
■
sor was started has expired.
■ The blocking time of 5 min since stopping the most
recently started compressor has expired.
If the heat demand still exists 20 min after compressor
1 was started, compressor 2 also starts.
Switching on with heating water buffer cylinder or
DHW cylinder
The compressors are switched on under the following
conditions:
A heat demand is present. The set temperature of
■
the relevant consumer is undershot by the corre-
sponding start hysteresis:
– Heating water buffer cylinder: "Hysteresis tem-
perature heating buffer cylinder 7203"
– DHW cylinder: "Hysteresis DHW temperature
heat pump 6007"
The blocking times (20 min/5 min) have expired: See
■
previous chapter.
Switching off the compressor
Switching off with 1 direct heating circuit without
heating water buffer cylinder
If the secondary circuit return temperature exceeds the
set value by the stop hysteresis, first compressor 2
and then, after a short delay, compressor 1 switch off.
28
[6]
(cont.)
The compressors start according to the following sys-
tem, depending on the output integral I
System for compressor demand
Output integral I
I 0.5 times the "Start
>
L
threshold 730E"
I "Start threshold 730E"
>
L
Compressor 1: The compressor started first
1
Compressor 2: The compressor started last
2
I Output integral: The integral of the duration and
L
extent of the deviation between the set and actual
return temperature in the secondary circuit
For further information on the output integral: See
page 121.
Switching off with heating water buffer cylinder or
DHW cylinder
If the stop conditions for the relevant consumer have
been reached, the compressors switch off, depending
on the output integral I
:
L
Compressor
L
1
ON
ON
.
L
2
OFF
ON