Central Heating System Types: Combi, System, and Conventional

Why System Type Matters

The type of central heating system in your home affects which boiler you can use, how your hot water is delivered, what space is required, and the overall cost of installation. Understanding the differences helps you make better decisions when replacing or upgrading.

Type 1: Combi Boiler System

How it works: A single boiler heats both your radiators and your hot water on demand. No hot water cylinder or cold water tank required.

Components: Boiler only (plus radiators, pipework, thermostat, and programmer)

Best for: Smaller homes, flats, 1–3 bedrooms, 1–2 bathrooms

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Type 2: System Boiler + Hot Water Cylinder (Sealed System)

How it works: The boiler heats your radiators and also heats water stored in an insulated hot water cylinder. No cold water tank in the loft — the system runs at mains pressure.

Components: Boiler + hot water cylinder (typically in an airing cupboard)

Best for: Larger homes, 3–5 bedrooms, multiple bathrooms

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Disadvantages:

Type 3: Regular (Conventional / Heat-Only) Boiler

How it works: The oldest system type. A boiler heats water stored in a hot water cylinder, and a separate cold water storage tank in the loft feeds both the cylinder and the heating system.

Components: Boiler + hot water cylinder + cold water storage tank in loft

Best for: Older properties; replacing like-for-like where the existing system is conventional

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Which Should You Choose?

If you're replacing an existing system, staying with the same type is usually the most cost-effective option unless there's a good reason to change. We can advise whether changing system type would benefit you.

Call Halo Heating on 01483 676108 for a free assessment and recommendation.