Advice
What Size Combi Boiler Do I Need?
Correct sizing is the foundation of efficiency and comfort.
Combi boiler 'size' refers to its heat output (in BTU/h or kW) and its hot water flow rate. The correct size comes from a heat-loss calculation based on your home's size, insulation, windows and climate — not from simply matching the old unit.
An oversized boiler short-cycles and wastes fuel; an undersized one struggles on cold days. Proper sizing is where good installers earn their keep.
What affects sizing
- Home square footage and ceiling heights
- Insulation and window quality
- Number of bathrooms / simultaneous hot water demand
- Climate and exposure (e.g. higher-elevation Coquitlam)
- Radiator or radiant-floor system volume
Why bigger isn't better
An oversized boiler reaches temperature too fast, then cycles on and off repeatedly — increasing wear and reducing efficiency. We size to a measured heat loss so your boiler runs longer, gentler cycles at peak efficiency.
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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