Heat Pump Cascade - Viessmann VITOTRONIC 200 Service Instructions Manual

2-stage refrigerant circuit
System for switching off the compressors
Output integral I
L
I < "Start threshold 730E"
L
I < 0.5 times the "Start
L
threshold 730E"
I = 0
L
Compressor 1: The compressor started first
1
2 Compressor 2: The compressor started last
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.

Heat pump cascade

Note
Heat pump cascades are not possible with compact
appliances and air/water heat pumps for indoor instal-
lation.
A heat pump cascade consists of a lead heat pump
and up to 4 lag heat pumps. Each lag heat pump has
1 heat pump control unit.
The lead heat pump regulates operation of the heat
pumps within the cascade. One or more heat pumps
are started as and when required.
Note
Heat pumps with differing output can be combined with
each other (not recommended for
Hydraulic connection versions
Type of hydraulic connection
Parallel at the secondary circuit and DHW cylinder flow:
Each lag heat pump has its own secondary pump and circulation
pump for cylinder heating, which are switched on by the lag heat
pump when there is a demand from the lead heat pump.
Each via its own 3-way diverter valve "central heating/DHW heat-
ing", in parallel, in the secondary circuit flow:
In addition, a further 3-way diverter valve is required in the return
of each heat pump.
: The secondary pump and 3-way diverter valve are integrated
in each indoor unit.
: For each heat pump, a 3-way diverter valve and a secondary
pump are integrated into the secondary circuit flow.
Changeover between central heating and DHW heating occurs in
line with the demand made by the lead heat pump to the relevant
lag heat pump.
[6]
(cont.)
Compressor
1 2
ON ON
OFF ON
OFF OFF
/
).
Output-dependent operation
To operate the heat pump cascade in output-depend-
ent mode, set "Output control strategy, cascade
700F" to "2".
The lead heat pump and lag heat pumps are switched
on and off in a manner that ensures optimum COP for
each heat pump.
Note
Output-dependent control is not possible with the
Vitocal 300-A, type AWO 302.B.
Air/water heat pumps
X
X
Function description
—
X
29