Danfoss DHP-AT, Installation Manual

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Defrosting
The heat pump has an automatic defrosting function that will start when required. The control system decides defrosting program de-
pending on data collected from the temperature sensors. As an option, defrosting can also be activated manually by the user.
Auto defrosting
Auto defrosting is active when the air temperature is below 15°C and no failure is detected in the coil temperature sensor. In heating
operation, when the coil temperature reaches the value set in Menu 04, the defrost starts and the compressor runs for the defrost cycle
setting time in Menu 03. Accumulated running time will be cleared after the defrosting has stopped and a new cycle starts the next time
defrosting is required.
Defrosting stops when the coil temp is more than the defrost stop temperature in Menu 05 or when the defrost time reaches the maxi-
mum setting specified in Menu 06.
Manual defrosting
When the air temperature is below 15°C and the compressor has run for more than 10 minutes, manual defrosting can be activated
using the key pad on the control unit. Manual defrosting should only be initiated when the automatic defrosting function is not suffi-
cient (heavy icing on the outdoor unit).
To start a manual defrosting cycle, press and simultaneously for 5 seconds. If all defrost conditions are fulfilled, the defrost
symbol will be displayed in the information window. An air temperature below 15°C is required and the compressor must run for at
least 10 minutes.
N
If the defrost symbol disappears almost immediately, the defrosting criteria are not met and defrosting will
not start.
The defrosting sequence will stop when the defrost time setting or the defrost stop temperature has been reached. The symbol will
then disappear from the information window.
The defrosting sequence is as follows:
▪
Send out defrost signal and show symbol on operator panel.
▪
The three-way valve remains in the current position determined by the current active operation mode.
▪
Power on the 4-way valve switch.
▪
Stop the fan.
▪
The compressor is still running.
▪
The water pump runs as normal.
▪
The internal electrical heater starts according to the setting in Menu 15 (if it is 0=Auto).
▪
Drain heater is turned on, but controlled by its own conditions.
When the defrosting stop conditions have been met, the heat pump will perform the following sequence:
▪
Defrost signal ends and the symbol on the operator panel will disappear.
▪
The compressor is still running.
▪
The fan starts.
▪
The 4-way valve switch is powered off after 30 seconds
▪
The three-way valve starts again if the domestic hot water function is active.
▪
Accumulated defrosting running time is cleared
▪
The heat pump goes back to normal heating
Timer defrosting (special condition, faulty coil sensor)
If the coil temperature sensor for the heat exchanger fails, and the air temperature is below the value set in Menu 05 , then a timer
controlled defrosting cycle will start.
Installation Guide DHP-AT
VMGFI302 Danfoss Heating Solutions
14