How do I know my wood boiler went out before the house gets cold?

What to measure

• Supply temperature. When the water leaving the boiler falls below a set point and stays there, the fire is out or nearly out. This is the main alarm.
• Return temperature. Supply minus return shows whether heat is being delivered at all.
• High limit. A boiler approaching boiling needs attention as quickly as one that has gone cold.
• Storage tank temperature, if you have storage. It tells you how many hours of heat are left, so you can decide whether to load tonight.
• Pump status. A hot boiler with a dead circulator will overheat while the house cools.

Why a delay matters

Supply temperature dips every time a cold zone opens. An alarm set at 140°F for 20 minutes ignores those dips and still catches a dead fire well before the house cools.

Outdoor boilers and freezing

An outdoor boiler that goes out in a cold snap is at risk itself, along with the underground lines. A low-temperature alert on the boiler water gives you time to light it or switch to backup heat.

We run this ourselves

Our own house in Bradford, Vermont is heated by wood boilers, a solar array and a gas backup burner feeding storage tanks. The panel we sell is the one that runs it. You can see the live system on our heating page.