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No Heat

A boiler that will not fire has a short list of causes, and two of them you can establish in a minute without touching the appliance.

In brief

Four things are worth looking at before calling anybody: power reaching the boiler, what the thermostat is set to and whether it is calling for heat, the pressure gauge, and whether the boiler is showing a lockout. The gauge is the reading almost nobody takes.

BoilerBridge is a referral service, not a contractor. We connect homeowners with independent contractors. Contractors are required to hold whatever credential their state or municipality demands. Every state page sets out who licenses plumbers there and where to check, so you can confirm before work begins. We carry out no work, we sell no equipment, we do not set prices, and we never charge homeowners anything — the contractors in our network pay us when we route them a call.

Power and the service switch

A boiler is on its own circuit and usually has a switch beside it or at the top of the basement stairs — frequently one that looks like a light switch and gets treated as one. Check the breaker and check that switch before anything else.

The thermostat, and whether it is calling

Set the thermostat well above room temperature and listen. If nothing in the system responds, the fault may be the call for heat rather than the boiler. A thermostat with dead batteries is a boiler that will not fire, and it is not a boiler fault.

The pressure gauge

Every hydronic boiler has a gauge, and a system that has lost pressure will not circulate. What the reading means is a page of its own, because it is the single most useful number on the appliance and almost nobody knows what it should say.

A gauge reading zero is telling you something specific has happened, and repeatedly topping the system up without finding out why is how a small leak becomes an expensive one.

The reading that means stop

If the boiler has locked out and is showing a fault, do not keep resetting it. A lockout after a failed ignition is a safety control doing its job, and repeated resets put unburned fuel where it should not be.

One reset is reasonable. A second is a call.

And if there is any smell of fuel or exhaust

Leave, and call 911 and the fuel supplier from outside. A combustion appliance that is not venting properly is the situation this whole site is most concerned about, and it is not one to investigate from the basement.

Source: US Consumer Product Safety Commission, Carbon Monoxide Fact Sheet.

A boiler is not a furnace, and the person you want knows the difference.Tell us it is a boiler, tell us what the gauge reads if you can see it, and we will route you to somebody in your area who works on them. You are never charged. Boilers give this site its name and not its limits.

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