Internal Electrical Heater; Freeze Protection - Danfoss DHP-AT User Manual

User Guide
Domestic hot water
The prioritized function is Domestic Hot Water (DHW). When the water temperature reaches the set point, the
heat pump automatically switches to house heating. The maximum water temperature for DHW is 55°C run-
ning on compressor only. If higher temperature is required, the DHW tank electrical heater is used to reach the
set point. Maximum DHW temperature is 60°C. (Default DHW temperature is 50°C)
Defrosting
The heat pump will calculate and process the best defrosting programme depending on data collected from
the temperature sensors.
During defrosting, components will start and stop at intervals (this is normal behaviour).
Defrosting can also be activated manually, this is only recommended when AUTO defrosting is not sufficient.
This usually happens in the temperature interval -5 to +5 °C and when outside air humidity is high. Under these
conditions can heavy icing occur.
Legionella prevention
DHW tank with built-in electrical heater
There is an automatic legionella prevention when the heat pump function is set to DHW. The automatic legion-
ella prevention runs at 00:00 every 7:th day of operation. The maximum water temperature for DHW is 55°C
running on compressor only. The water in the hot water tank will be heated to 65 °C for 15 minutes, using the
hot water tank electrical heater. This will kill any possible legionella bacteria inside the hot water tank.
DHW tank without built-in electrical heater
There is an automatic legionella prevention when the heat pump function is set to DHW. The automatic legion-
ella prevention runs at 00:00 every 7:th day of operation. The water in the hot water tank will be heated to 55 °C
for 3 hours then returns back to previous operating mode.
3.3

Internal electrical heater

The internal electrical heater is used in situations when the heating from the heat pump is insufficient due to
low air temperature or when the heat pump itself has stopped.
The electrical heater will start in the following conditions:
▪ The system discovers insufficient heating from the heat pump.
▪ The heat pump stops (for protection) due to a failure, and at the same time, the water temperature has
not reached the set point.
▪ The heat pump is in defrosting mode.
▪ During freezing protection, step 2.
▪ Manually started by user
3.4

Freeze protection

As long as there is power supplied to the heat pump, an automatic freeze protection function will prevent in-
side components from freezing.
When this protective function is triggered, the controller will display either "Err 18" or "Err 19" depending on
the temperature in the system, this is not a fault. The unit will automatically recover once the conditions in the
control system is met.
Danfoss Heating Solutions
DHP-AT
VUGFC302
9