6.2  D system, DHP-L
With a DHP-L in a D system, the heat pump can produce both heat-
ing and hot water with the compressor and an external auxiliary 
heater (oil boiler, electric boiler, district heating or similar) that is 
located after the exchange valve replaces the integrated auxiliary 
heater to produce heat.
The cables for the integrated auxiliary heater must be disconnect-
ed, which means that the heat pump cannot carry out peak heat 
charging (legionella function). Peak heat charging must take place 
with an electric heating element that is integrated in the water 
heater or with an electric heating element on the supply line to the 
water heater.
The heat pump control computer also controls an additional shunt.
DHP-L, connection diagram D system
General connection diagram DHP-L, D system.Figure 47: 
Position  Name
1   Supply line
2   Return line
3   Safety valve cold water (9 bar) (included in delivery)
4   Safety valve expansion heating system
5   Expansion heating system
6   Strainer (part of the delivery)
7   Flexible hoses (part of the delivery)
8   Vacuum valve
9   Non-return valve
10  Shut-off valve
11  Cold water
12  Hot water
13  Heat pump (part of the delivery)
14  Water heater
15  External auxiliary heater
16  Circulation pump
17  Non-return valve
18  Moved supply line sensor (included in heat pump)
19  Auxiliary shunt
20  Safety valve for temperature and pressure (mounted only on cer-
tain models, see chapter 6)
6.3  VLD system, DHP-A, -AL
A VLD system is largely similar to a VL system, but with an external 
auxiliary heater (often a boiler that is fired with solid fuel) in combi-
nation with a DHP-A or DHP-AL.
DHP-A’s integrated exchange valve is replaced by an exchange 
valve that is located after the external auxiliary heater so that both 
the heat pump and the auxiliary heater can produce heat and hot 
water. The integrated exchange valve is disengaged with the flow 
direction locked towards the heating system. 
Production of heating and hot water cannot occur at the same time 
because the exchange valve for heating/hot water is positioned 
after the auxiliary heater. The integrated auxiliary heater carries 
out peak heating charging (legionella function) in those operating 
modes that permit auxiliary heat.
The heat pump’s control computer controls the external additional 
heater via an output (283) on the defrosting card (factory installed 
in DHP-A or DHP-AL). The heat pump control computer also con-
trols an additional shunt.
DHP-A, connection diagram VLD system
General connection diagram DHP-A, VLD system.Figure 48: 
Position  Name
1   Supply line
2   Return line
3   Safety valve cold water (9 bar) (included in delivery)
4   Safety valve expansion heating system
5   Expansion heating system
6   Strainer (part of the delivery)
7   Flexible hoses (part of the delivery)
8   Vacuum valve
9   Non-return valve
10  Shut-off valve
11  Non-return valve
12  Shut-off valve
13  Hot water
14  Cold water
15  Heat pump (part of the delivery)
16  External auxiliary heater
17  Circulation pump
18  Non-return valve
19  Moved supply line sensor (included in heat pump)
20  Auxiliary shunt
21  External exchange valve
22  Safety valve for temperature and pressure (mounted only on cer-
tain models, see chapter 6)