Domestic Hot Water Heat Pump Service Manual
36
System start up with BT1 (Air Inlet Temp) at 3°C
After 60 minute operation the defrost countdown timer is activated
After a further 60 minutes, the DHW-HP enters defrost operation
The solenoid valve opens and because the BT1 temperature is <4°C the compressor stays on
and the fan stops operation
Defrost operation stops after a maximum time limit of 12 minutes or when BT2 (T Air Out),
evaporator temperature, becomes higher than the set point of D10 (Defrosting Temp Stop),
factory set to 4°C.
BT1 (Air Inlet Temp) raised to 4.2°C
After a further 60 minutes, the DHW-HP enters defrost operation
The solenoid valve opens and because the BT1 temperature is >4°C the compressor and fan
operate. The fan increases operation to Max Fan Speed, D3 (Fan Speed Max) set point.
Defrost operation stops after a maximum time limit of 12 minutes or when BT2 (T Air Out),
evaporator temperature, becomes higher than the set point of D10 (Defrosting Temp Stop),
factory set to 4°C.
7.15 Legionella operation
In order to prevent the possibility of legionella bacteria accumulating in the DHW-HP, a
pasteurisation, or anti-legionella cycle, should be performed weekly.
Using the installer menu set up parameters D13 to D15 (detailed below). It is possible to select the
day, temperature and to enable or disable the anti-legionella cycle.
The anti-legionella cycle is activated at midnight (00:00) on the day set (code D15) but the higher
temperature is not activated until the next compressor start operation (DHW demand condition).
Note:
i) If there is no DHW demand, and therefore no compressor start, within 24 hours of the anti-
legionella control becoming active the anti-legionella control is forced to start regardless of
the water temperature inside the DHW-HP
ii) When the DHW-HP is set in HOLIDAY mode the anti-legionella control operates on the
selected day and starts the heat pump at 00:00.
Code
Set point
name
Description
Range
Factory
setting
D13
Legionella
The legionella function can be activated. The legionella function does not
switch the heat pump on, but just continues the heat up cycle to a higher
temperature D14 (Legionella T). The legionella operation works only with
the heat pump until 60°C. The remaining temperature lift is accomplished
with the electric heater alone.
OFF/ON
OFF
D14
Legionella
Temp
The legionella temperature set point can be regulated.
60-65
60
D15
Legionella
date
The legionella week day can be set
Monday/
Sunday
Sunday
