Boiler not producing heat

Symptoms

• Radiators or baseboards stay cold throughout the house
• Boiler may be silent or running without producing heat
• Pressure gauge may read low

Likely causes

• CommonLow system water pressureMost boilers need pressure in a specific range (often 12–15 psi) to circulate and heat properly.
• CommonThermostat not calling for heatA dead thermostat or wrong setting stops the boiler from ever starting.
• CommonPilot light out or ignition failureLike a furnace, a boiler needs successful ignition to produce heat.
• PossibleFailed circulator pumpThe boiler may fire but heat won't reach radiators if the pump isn't circulating water.
• PossibleAir trapped in the systemAir pockets can block water flow to some or all radiators.

What to do

1. Check the thermostat is set to Heat and calling for a temperature above room temperature.
2. Look at the boiler's pressure gauge; if it's below the manufacturer's minimum (often around 12 psi), it may need refilling.
3. Check that the pilot light is lit, or listen for normal ignition sounds on an electronic-ignition unit.
4. Listen for the circulator pump running; a silent pump when the boiler is firing suggests it's failed.
5. If pressure is low, locate the feed valve and slowly add water per the manufacturer's instructions, watching the gauge closely.
6. If pressure, ignition, and pump all seem fine but there's still no heat, call a technician rather than guessing further.

Tools and parts

• Flashlight

When to call a pro

Call a heating technician if pressure, thermostat, and pilot checks don't restore heat, especially for circulator pump or air-bleeding issues.

Safety