Airwell PAC HT 14-7 Handbuch Technische Daten - Seite 5
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Operating Diagram - Two-stage Cycle with Economiser and Partial Injection
3
High pressure
HP
C2
COND :
Condenser
ECO :
Economiser
LP :
Low pressure
HP :
High pressure
Operating cycle
The PAC HT operates on a two-stage compression cycle.
It uses two compressors :
-
the larger (C1) for the Low Pressure (LP) stage.
-
the smaller (C2) for the High Pressure (HP) stage.
The economiser (refer to above diagram) located at the condenser outlet,
receives some of the HP liquid (point 4) which, after expansion (point 7),
cools the main liquid circuit and generates cooled gas that is mixed with the
gas coming from the LP compressor (point 8).
This economiser has two functions :
-
Sub-cooling the liquid to increase the evaporator's and therefore the heat
pump performance, both in heating mode and in domestic hot water
production mode.
-
Generating cooled gas to cool the HP compressor suction side.
When the LP or the HP compressor operates on its own, its cycle is identical
to that of a traditional single compressor cycle.
7
5
4
8
2
Medium pressure
9
Injection expansion valve
Main expansion valve
6
Low pressure
1
LP
C1
Compressor operation
The action on the two 4-way cycle inversion valves V1 and V2 creates the
following operating modes :
-
C2 (HP) compressor on its own.
-
C1 (LP) compressor on its own,
-
C1 and C2 compressors together.
-
De-icing with the C1 compressor on its own.
When heating needs are low and the water outlet temperature required is
below 55 °C, the small compressor C2 operates on its own. The machine
runs in normal mode but at a reduced capacity within an outdoor temperature
range of +20 °C to 0 °C by producing hot water at temperatures between
+35 °C and +55 °C.
Within these same operating limits (outdoor temperatures and hot water
temperatures), the larger compressor C1 operates instead of the smaller one
when the heating needs are greater.
When the outdoor conditions are between +7 °C and -20 °C, the heat pump
switches to high capacity mode with both compressors operating in series to
produce hot water at temperatures between +50 °C and +65 °C.
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