Heat Pump Freezing Up Repeatedly – Pipework & System Design Issue

Heat Pump Freezing Up Repeatedly – Pipework & System Design Issue

The Problem

A customer was experiencing frequent freezing issues with their heat pump during colder weather.

The problem had become so severe that they were having to go outside and manually defrost the unit themselves.

This isn’t normal behaviour for a correctly installed system.

What I Found

After reviewing the system design, a number of issues became clear:

• The primary pipework between the heat pump and cylinder was excessively long

• The pipework had been installed directly in the ground with little to no insulation

• A buffer tank had been added, despite the system already having a large water volume

The combination of long, uninsulated pipework and poor system design meant:

• Significant heat loss before energy even reached the house

• Reduced system efficiency

• Increased likelihood of freezing and defrost issues

• Unstable system operation in colder conditions

What I Changed

We discussed a range of options with the customer — from minimal changes through to a full system redesign.

The customer chose to go ahead with the best long-term solution.

I produced a full system design that could be passed directly to their installer, which included:

• Replacing the external pipework with pre-insulated (low-loss) pipework

• Removing the unnecessary buffer tank

• Adding a low loss header to improve system stability

• Recalculating system volume and confirming that the existing pipework provided sufficient water content without needing a buffer

All designs were clearly documented, and I also supported the installer during the work, including guidance on setup and commissioning once installed.

The Outcome

With the system redesigned and installed correctly:

• Freezing issues were eliminated

• The system operated reliably in cold weather

• Heat loss was significantly reduced

• Overall system performance and efficiency improved

The customer no longer needed to intervene manually, and the system was able to run as intended.