The low-water cutoff switch is a very important safety feature on a boiler. It automatically stops the flame in the boiler if the water level inside drops too low.
Water keeps the casing of the boiler cool while the flame is running. If the water level is too low, the casing will overheat, and this can cause the casing to crack or warp. Worse, a boiler can explode if water comes into contact with the red-hot casing. The water will immediately flash into steam and generate a tremendous amount of pressure, resulting in an explosion.
While the low-water cutoff switch is a vital safety feature on your boiler, it can quickly become an annoyance when it starts tripping all the time, turning the boiler off. If your boiler keeps turning off because the low-water cutoff switch keeps activating, read on to learn what can cause it and how you can fix it.
Leak in Your Boiler System
The simplest reason why a low-water cutoff switch can trip all the time is a leak in your boiler. You'll need to check all of the radiators in your home and the pipes leading to them for leaks. If you can't see the pipes, look for signs of a hidden leak, like water stains on your floor, walls, or ceiling. You'll need to replace any pipes or radiators that are leaking.
You also need to check the pressure relief valve on your boiler to see if condensation is forming on it. The pressure relief valve opens if the pressure in the boiler gets too high, allowing steam to escape and reducing the pressure in your boiler's pipes. The steam will come out of the valve as water vapor, which will form condensation on the valve or on the walls next to it. If the valve is stuck open and constantly releasing steam, you'll need to have it replaced by a boiler repair service.
A cracked heat exchanger can also cause your boiler to lose water. The boiler's heat exchanger is where the air warmed by the boiler's fire heats up the water in the boiler. A crack in the heat exchanger will cause water to drip down into the fire, turning it into steam. To find out if your heat exchanger is leaking, look for steam coming out of your home's chimney. Your chimney is connected to your boiler's exhaust flue, so any steam that's generated from a leak in the heat exchanger will exit from it.
Leak in the Low-Water Cutoff Switch's Float
A low-water cutoff switch works by monitoring the water level in the boiler using a hollow float. If the float drops too low, it signals that there's a low water level in the boiler, and the low-water cutoff switch activates. Floats can sometimes develop a pinhole leak due to corrosion, which allows them to slowly fill with water. This will cause the float to sink, tripping the low-water cutoff switch even though the water level in the boiler is normal. You'll need to replace the float in order to stop the low-water cutoff switch from activating.
Faulty Low-Water Cutoff Switch
Your low-water cutoff switch may simply be too sensitive. Turbulence in the boiler that causes the float to bob up and down may activate the low-water cutoff switch, turning off the flame in your boiler. You can fix the problem by replacing your low-water cutoff switch with one that functions normally.
If you need help finding a leak in your boiler system or replacing your faulty low-water cutoff switch, call a boiler repair service in your area. They'll test your low-water cutoff switch and check your boiler, radiators, and pipes for signs of a leak. Fixing your low-cutoff switch will allow you to use your boiler again without worrying about having to constantly reset it.