Why My Radiators Aren’t Heating Properly After Heat Pump Installation

Quick Summary

If your radiators aren’t heating properly after installing an air source heat pump, you’re not alone. Many UK homeowners face this issue post-installation. This blog explains the common causes and provides practical, actionable solutions:

• Identify why your radiators are underperforming

• Learn the most common air source heat pump UK problems

• Fix heat pump radiators UK efficiently with expert tips

Introduction: Heat Pump Radiator Not Hot

Many homeowners in the UK switch to air source heat pumps to reduce energy bills and lower their carbon footprint. But after installation, some notice their radiators aren’t getting hot enough, leaving rooms colder than expected.

This is often not a fault with the heat pump itself but a combination of system design, property insulation, and flow temperatures. Understanding the problem and knowing how to fix it can restore comfort while ensuring your heat pump operates efficiently.

At Air Source Company, we specialize in diagnosing and resolving these issues. Our guide below helps you understand why heat pump radiators are not hot and how to solve it.

Common Reasons Your Heat Pump Radiators Aren’t Hot

1. Incorrect Flow Temperature Settings

Heat pumps work differently than gas boilers. They operate at lower flow temperatures (35–55°C) rather than high temperatures (70–80°C). If your system is set incorrectly or your radiators are designed for high-temperature systems, they may feel underwhelming.

Solution: Adjust the flow temperature settings with your installer. Low-temperature radiators or underfloor heating can compensate for lower flow temperatures.

2. Radiator Size & Compatibility

Old radiators designed for gas boilers may not emit enough heat at lower temperatures.

Solution:

• Upgrade to larger or higher-output radiators for rooms that remain cold.

• Consider fan-assisted radiators in poorly insulated spaces.

3. Poor Pipework or Balancing

Incorrectly sized pipes or uneven water flow can cause some radiators to heat slower than others.

Solution:

• Ask your installer to balance the system so each radiator receives the correct flow.

• Ensure pipework matches heat pump specifications.

4. Insufficient Property Insulation

Older UK homes with poor insulation lose heat quickly. Even the most efficient heat pump struggles if walls, floors, or lofts are poorly insulated.

Solution:

• Improve loft insulation, cavity wall insulation, and draught-proofing.

• Consider secondary glazing or double-glazed windows for heat retention.

5. Air in Radiators

Air pockets trapped in radiators reduce water circulation, causing uneven heating or cold spots.

Solution:

• Bleed your radiators regularly after installation.

• Install automatic air vents if the system is prone to air accumulation.

• Ensure the system is correctly pressurized after bleeding.

6. Thermostat or Control Issues

Incorrect thermostat placement or faulty controls can affect performance.

Solution:

• Check thermostats are located away from heat sources or drafts.

• Upgrade to smart thermostats compatible with your heat pump.

• Ensure temperature settings and schedules align with your household needs.

Fix Heat Pump Radiators UK: Step-by-Step

1. Check your flow temperature – Confirm your heat pump is set to optimal low-temperature settings.

2. Assess radiator size – Upgrade any radiators that cannot emit enough heat.

3. Balance the system – Ensure all radiators get even water flow.

4. Improve insulation – Make your home heat-efficient to support the heat pump.

5. Bleed radiators – Remove trapped air for consistent performance.

6. Adjust controls – Ensure thermostats and timers are optimized.

➡️ Following these steps usually resolves most post-installation heating issues within a few hours to a couple of days, restoring comfort and efficiency.

FAQs

1. Why is my heat pump radiator not hot?

Common reasons include low flow temperature, undersized radiators, poor insulation, air in pipes, or unbalanced system flow.

2. Can old radiators work with a heat pump?

Yes, but some may need to be upsized or upgraded to emit enough heat at lower flow temperatures.

3. How can I fix heat pump radiators in the UK?

Check flow temperature, balance the system, bleed radiators, upgrade insulation, and ensure thermostats are correctly placed.

4. How long does it take to fix radiator issues after heat pump installation?

Most issues can be resolved in 1–3 days, depending on insulation upgrades or system adjustments.

5. Should I contact my installer if radiators aren’t heating?

Yes. Always contact your MCS-certified installer, as proper balancing, flow adjustment, and radiator upgrades require professional assessment.

6. Can insulation improve radiator performance?

Absolutely. Heat pumps work best in well-insulated homes. Improving loft, wall, and floor insulation helps radiators heat rooms evenly.

About Air Source Company

Air Source Company – UK’s Trusted Heat Pump Partner

We provide air source heat pump installations, radiator system assessments, EPC upgrades, and grant assistance across the UK. Our MCS-certified team ensures your system performs efficiently and grants are maximized.

📞 Experiencing radiator issues with your heat pump?

Contact Air Source Company today for a free inspection and expert fix.

Restore comfort, optimize energy efficiency, and keep your UK home warm with professional guidance.