Background

A recently renovated 4-bedroom detached property in Surrey was experiencing inconsistent indoor temperatures and higher-than-expected electricity bills. The homeowner reported that the house often felt overheated during mild weather and struggled to maintain comfort during colder evenings.

The heat pump had been professionally installed and commissioned, yet performance did not reflect the expected efficiency of a modern air source heat pump system.

Property & System Overview

• Property: 4-bedroom detached home

• Location: Surrey

• Heat Pump: 11kW Air Source Heat Pump

• Emitters: Radiators (mixed sizes)

• Control Strategy: Weather compensation enabled

• Observed Issue: Temperature instability and high energy use

Initial Observations

Weather compensation is designed to automatically adjust flow temperatures based on outdoor conditions. When correctly configured, it allows the system to run efficiently at lower flow temperatures during milder weather while gradually increasing output as temperatures drop.

However, incorrect curve settings can significantly reduce system efficiency and indoor comfort.

Technical Findings

Following a detailed system review, we identified several configuration issues:

1. Compensation Curve Too Aggressive
   The heating curve slope was set too steep, causing unnecessarily high flow temperatures during moderate outdoor conditions.

2. Incorrect Minimum Flow Temperature
   The base flow temperature was higher than required for the property’s heat loss profile.

3. Radiator Sizing Not Accounted For
   The curve had not been calibrated to match the emitter performance, leading to temperature overshoot.

4. Poor Curve Offset Adjustment
   Minor adjustments that could have stabilised comfort had not been fine-tuned during commissioning.

Impact on Performance

These configuration issues resulted in:

• Higher-than-necessary flow temperatures

• Increased electricity consumption

• Reduced seasonal efficiency

• Indoor overheating during mild weather

• Reduced comfort consistency

Although the system was technically operational, it was not running within its most efficient range.

Corrective Strategy

Our recommendations focused on optimisation rather than hardware modification:

• Recalibrate the weather compensation slope

• Reduce minimum flow temperature settings

• Adjust curve offset to improve comfort stability

• Align curve settings with emitter capacity

• Monitor performance across varying outdoor conditions

Outcome

After reconfiguration:

• Indoor temperatures became more stable

• Flow temperatures reduced during mild weather

• Energy consumption decreased

• Seasonal efficiency improved

• Overall system comfort increased

The system was capable of efficient performance once properly tuned to the property’s real-world heating demand.