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Serving the South Puget Sound and Western Washington Areas Since 1976

Serving the South Puget Sound and Southwest Washington Areas Since 1976

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Sunset Air Blog

Why Won’t My Boiler Stay Lit?

Boiler heating is a great option for heating your home. It’s energy efficient, cost effective, and avoids a lot of the disadvantages that forced air systems possess. Just like any other system, however, your boiler is vulnerable to all sorts of possible problems. One of the most common problems is an inability to stay lit. Read on for an explanation of why this might be happening.

Pilot Light Issues

Most boilers use pilot lights as ignition sources. The pilot light is a flame that burns underneath your boiler 24 hours a day. This flame is used to actually light the burners that power the boiler when the heat is turned on. Pilot lights are notorious for going out seemingly without reason. It’s usually a simple affair to relight them, which often fixes the problem. If the pilot light is not staying lit, however, you likely have a problem with the thermocouple.

The thermocouple is a long metal wire that acts as a heat sensor for the pilot light. One end of this wire is installed close enough to the flame to be heated by it, while the other end is connected to the gas valve. When the thermocouple is heated by the pilot light, it creates an electrical current that travels to the gas valve and keeps it open. When the pilot light goes out, the electrical current stops and the gas valve closes. This is a safety measure to prevent gas from leaking into your home. A faulty thermocouple is one that can no longer keep the gas valve open for whatever reason, cutting off the supply of fuel to the pilot light and smothering it.


Kettling is another factor that may be contributing to your boiler not staying lit. Kettling is what happens when hard water, which contains a lot of minerals, flows through the boiler’s heat exchanger. Over the years, hard water can deposit its minerals in the heat exchanger until they eventually block the flow of water. This causes the boiler to shut itself down as a safety measure, to prevent the buildup of dangerous water pressure levels.

If your boiler is having problems, call Sunset Air. Our heating experts cover all of Olympia.

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