LG Therma V 9kW – DHW Loop Not Triggering

Hello All,

I have a 9kW LG Therma V monobloc heat pump installed two years ago. I’ve hit aan issue where the unit has stopped engaging the DHW cycle, eventually falling back to the immersion heater after the programmed 30-minute delay.

The Symptoms:

• Space Cooling/Heating: Works perfectly.
• Cooling/Heating on - DHW call: When a DHW cycle is called, the outdoor unit remains in heating/cooling mode. The controller displays “Outdoor unit operation” and “Water pump operation.”
• Fallback: After the 30-minute delay, the internal immersion heater kicks in. The display then changes to “DHW heater operation” and “Water pump operation.”
• Cooling/Heating off - DHW call: When a DHW cycle is called, the outdoor unit remains idle. The controller displays “There is no monitoring information” for the first 30 minutes.
• Fallback: After the 30-minute delay, the internal immersion heater kicks in. The display then changes to “DHW heater operation”.

Operation:

• No Error Codes
• 3-Way Valve: Visually confirmed to be operating.
• DHW Tank Sensor: Correctly reporting tank temperature (39°C - 42°C), so the sensor appears functional.
• Flow rate: set to optimal and running between 11 and 31 lpm as needed.

I understand the only sensor for the DHW is the tank sensor. I am going to order a replacement, but it does seem odd that it reports the tank temperature but the unit does not see the input to trigger the DHW loop.

In the pics I just switched off from cooling mode, so the feed and return temps are residual from that. After a while the feed and return temps become equal.

Any advice is appreciated.

Thanks, Peter