Burner Runs But No Heat?
Your oil burner is firing, you can hear it running—but the house stays cold. The problem is usually in the distribution system, not the burner itself.
Sound Familiar?
"Burner fires but radiators are cold"
The boiler water may be heating, but it's not circulating to your radiators. Check if the circulator pump is running.
"Some zones work, others don't"
This points to a zone valve problem—the valve controlling that area is stuck closed or has a failed motor.
"Radiator tops are cold, bottoms warm"
Air trapped in the radiator is preventing full circulation. You need to bleed the radiators.
"I hear the pump but no heat comes out"
The pump may be running but not moving water (failed impeller or coupler), or the aquastat settings are wrong.
Understanding Your Hydronic System
When your oil burner fires but you get no heat, the issue is typically in the distribution system—the components that move hot water from the boiler to your radiators and back.
Key components include: the circulator pump (moves water through pipes),zone valves (control flow to different areas), and theaquastat (tells the circulator when to run based on water temperature).
Common Causes & Repair Costs
What might be preventing heat distribution
| Cause | DIY? | Description | Cost |
|---|---|---|---|
Failed Circulator Pump Motor burned out, impeller jammed, or coupler broken | Pro | Motor burned out, impeller jammed, or coupler broken | $400-800 |
Stuck Zone Valve Valve motor failed or valve physically stuck closed | Pro | Valve motor failed or valve physically stuck closed | $250-450 |
Air Lock in System Air trapped in pipes preventing water circulation | Yes | Air trapped in pipes preventing water circulation | $0 Pro: $150-250 |
Low Water Pressure Pressure below 12 PSI prevents proper circulation | Yes | Pressure below 12 PSI prevents proper circulation | $0 Pro: $100-200 |
Faulty Aquastat Temperature controller not calling for circulator operation | Pro | Temperature controller not calling for circulator operation | $250-500 |
Thermostat Wiring Issue Break in wire from thermostat to zone valve | Pro | Break in wire from thermostat to zone valve | $150-300 |
Not sure what's wrong?
Our $199 diagnostic ($199 for new customers) identifies the exact issue.
What You Can Try First
Check Boiler Pressure
Look at the pressure gauge. Should read 12-15 PSI. If below 12, add water via the fill valve.
Bleed Your Radiators
Use a radiator key to open bleed valves. Start with the lowest floor and work up. Close when water flows.
Listen for the Circulator
Put your ear near the pump when the boiler is running. You should hear humming and feel warmth. No sound = possible failure.
Check Zone Valve Lights
Many zone valves have indicator lights. If a light isn't on when calling for heat, that valve may have failed.
Frequently Asked Questions
Frequently Asked Questions
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