Boiler Not Heating Radiators in Greater Vancouver

A boiler that fires and runs but fails to deliver heat to the radiators is frustrating — the system is consuming gas but the home stays cold. This is typically a circulation or zone control problem, not a boiler fault.

What This Symptom Means

For radiators to heat, the boiler must fire, the circulator pump must move hot water through the system, and the zone valves must be open to the radiator circuit. A failure in any of these three links breaks heat delivery.

Common Causes

• Circulator pump failed — hot water not being moved through the system
• Zone valve stuck closed or failed — hot water not reaching that zone
• Air trapped in the system preventing water flow through radiators
• Low system pressure causing circulation problems
• Thermostat not calling for heat or calling at the wrong zone
• Circulator pump power interrupted at the relay or control board

What Homeowners Can Check Safely

• Feel the pipes near the boiler when it runs — if pipes closest to the boiler are hot but radiators are cold, circulation is the issue
• Check thermostat zone settings — confirm the zone calling for heat corresponds to the radiators that should be warm
• Check system pressure gauge

When to Call a Licensed Technician

Boiler systems involve pressurized hot water, gas, and electrical components. Do not attempt to open sealed components, adjust gas pressure, or bypass safety controls without professional diagnosis.

• Circulator pump testing — confirm pump is running and moving water
• Zone valve actuator testing and replacement
• System air bleeding and power flush if air lock is severe
• Circulator pump replacement
• Control board zone relay testing

Frequently Asked Questions

How do I know if my circulator pump is working?

With the boiler calling for heat, place your hand on the circulator pump body — it should feel warm to the touch and you should feel a faint vibration from the motor. If the pump is completely cold and silent while the boiler is firing, the pump is not running. A technician can test the pump electrically and determine if it needs replacement.

Can one failed zone valve stop all my radiators from heating?

It depends on the system design. In a single-zone system, a stuck-closed zone valve can block flow through the entire system. In multi-zone systems, only the zone served by the failed valve will be affected. If some radiators heat and others do not, the problem is likely zone-specific rather than a pump failure.

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