Advice
How a Combi Boiler Works
The technology behind the most popular boiler type in modern homes.
A combi (combination) boiler provides both central heating and domestic hot water from a single, compact wall-hung unit — no separate hot water cylinder or cold-water tank required. When you turn on a hot tap, the boiler heats water instantly as it flows through; when your thermostat calls for heat, the same boiler warms water for your radiators or radiant loops.
This dual function is what makes combi boilers so space-efficient and popular in Greater Vancouver condos, townhomes and detached houses alike.
Key components
- Gas burner and heat exchanger
- Diverter (3-way) valve that switches between heating and hot water
- Circulation pump
- Expansion vessel and pressure relief valve
- Flow sensor and temperature sensors
- Control board (PCB)
Why homeowners choose combis
Combi boilers save space, deliver hot water on demand without waiting for a tank to reheat, are highly efficient (95% AFUE for condensing models), and qualify for FortisBC/CleanBC rebates. They're an excellent fit for most BC homes.
This is not a DIY repair
Combi boilers are gas-fired appliances regulated under the BC Safety Standards Act. Opening the unit, touching the gas valve, or working on the flue without a valid BC gas-fitter licence is both unsafe and illegal. Diagnosing the fault is helpful — fixing it should always be left to a certified technician.
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