Poor Heating & Limited Hot Water – Cylinder Temperature Probe Fault

Poor Heating & Limited Hot Water – Cylinder Temperature Probe Fault

The Problem

A homeowner reported that their hot water supply was inconsistent, and the heating performance wasn’t as expected.

Despite the system running regularly, the house wasn’t heating properly, and hot water behaviour didn’t seem right.

What I Found

During a review of the system, it became clear that the issue was related to how the hot water temperature was being measured.

• The cylinder temperature probe had come loose from its pocket

• The system was reading a lower temperature (around 38°C)

• In reality, the stored water was significantly hotter

Because of this:

• The heat pump believed the hot water was never reaching target temperature

• It continued heating hot water for extended periods (up to the 90-minute limit)

• Heating cycles were shortened, reducing overall heating performance

This imbalance meant the system was prioritising hot water unnecessarily, leaving the heating underperforming.

What I Changed

The fix itself was simple:

• Guided the homeowner to correctly reposition the temperature probe into the cylinder pocket

Once the probe was reading accurately, the system could respond properly.

I also:

• Reviewed and optimised the system settings

• Enabled weather compensation instead of fixed flow temperature

The Outcome

With the temperature probe correctly positioned, the system was able to properly detect when hot water had reached the required temperature.

This allowed:

• Hot water cycles to complete correctly

• Heating to run as intended

• Overall system balance to be restored

The homeowner experienced improved heating performance and a more consistent hot water supply.