What Is a Heating Interface Unit (HIU)

Why Does It Matter in Your Luxury Apartment? 

Hidden in a cupboard or discreet riser, the Heating Interface Unit (HIU) is one of the most important – yet least understood – components in modern luxury apartments connected to a centralised energy system. It plays a critical role in delivering both instant hot water and space heating on demand. 

Let’s break down what it does, why it matters, and why regular servicing is essential. 

🌡️ What Does a Heating Interface Unit Do? 

Think of an HIU as your personal boiler – without the gas. It's your apartment’s gateway to the central plant system in the building. 

Here’s how it works: 

• Hot Water on Demand: The HIU instantly heats domestic water as it flows through a plate heat exchanger. This means you get hot water straight to your tap without a bulky cylinder. 

• Space Heating: It regulates the flow of hot water to your underfloor heating or radiators, allowing room-by-room temperature control. 

• Energy Metering: In many setups, it also tracks your individual energy usage, so you’re only billed for what you consume. 

🦠 Why Servicing Your HIU Matters – It's Not Just About Comfort 

While the HIU is largely hidden from view, neglecting it can lead to serious health, efficiency, and cost issues. 

🔥 1. Water Temperature Must Reach 50°C – or Higher 

To prevent Legionella bacteria from growing in your pipes, your domestic hot water must reach at least 50°C at the tap within 60 seconds. 

👉 If the HIU isn’t properly calibrated or if its plate heat exchanger is scaling up, water may not heat sufficiently – putting your household at real health risk. 

💷 2. Faulty Valves Waste Energy and Money 

HIUs rely on actuators and control valves to open and close precisely when needed. If these components start to stick, leak or fail: 

• Hot water may circulate unnecessarily 

• Heat could be wasted when no heating is requested 

• Your energy bills go up 

• The building’s overall system becomes less efficient 

🧠 3. Servicing Helps You Spot Issues Early 

Routine servicing by a trained technician ensures: 

• Valves are closing and opening correctly 

• Heat exchangers are clean and descaled 

• Sensors are accurate and responding 

• Safety and compliance checks (such as temperature output) 

🛠️ What’s Involved in Servicing a HIU? 

A proper HIU service typically includes: 

• Cleaning or replacing strainers and filters 

• Checking and adjusting domestic hot water temperature 

• Verifying correct operation of control valves and actuators 

• Testing sensors and thermostatic regulation 

• Pressure and flow checks 

🏠 Why It’s Especially Important in Luxury Apartments 

In high-end buildings, energy efficiency, safety, and silent operation are expected – not optional. A faulty HIU can: 

• Cause noisy heating circuits 

• Lead to longer wait times for hot water 

• Result in cold zones or overheating 

• Undermine the entire building’s energy performance 

💡 Summary: Why You Should Service Your HIU 

Risk / Issue	What Could Happen	Servicing Benefit
Legionella risk	Hot water not reaching 50°C	Check and adjust water temp output
Wasted energy	Valves not closing = heat loss	Test and recalibrate valves/actuators
Poor water pressure	Dirty strainers = weak hot water flow	Clean filters and check flow rates
High bills	Inefficiency from undetected faults	Optimise for accurate energy use
System strain	Building plant works harder than needed	Support central plant longevity

✅ Peace of Mind Through Planned Maintenance 

Your HIU is out of sight – but it should never be out of mind. Annual servicing ensures comfort, efficiency, and health protection in your home. 

📞 Call our team on 02 0369 50901 or email sales@maintainmyhome.uk The only maintenance company exclusively focused on luxury London apartments.