How To Troubleshoot An Oil Boiler Low Flow Cutoff Issue

If you have an oil boiler that suddenly stops working and you see a light on the low flow sensor attached to the top of the boiler, then water is not moving through the system like it should. When this issue is detected by the sensor, the boiler is shut down automatically. This is necessary to make sure that the boiler does not overheat when water stops moving through the system. It may be necessary to contact a boiler repair specialist when this happens. However, there are a few troubleshooting tasks you can try first to see if you can get the boiler to start working again.

Flush The Cutoff Valve

The low water cutoff sensor is a device that is attached to the top water pipe that leads out of the boiler. The sensor detects whether or not a good volume of water is moving through the pipe or not. Typically, the sensor is a switch that is opened when a valve or a ball inside the water pipe is forced upward as water passes through it. If water does not move through the pipe, then the valve or ball remains in a low position to indicate that water is not moving through the pipe. The switch on the sensor remains off and electricity is cut to the start button on the boiler so the system cannot be turned on.

Sometimes, water is flowing through the system correctly and the shutoff ball or valve becomes stuck and prevents it from moving upward. Sediment, rust, and general debris can cause this to happen. To see if this is the issue, you will need to flush the valve clean to remove any foreign debris. Most oil boiler systems will have a water supply pipe attached above the cutoff valve so that flushing can occur. Look for this pipe, an open spigot, and a knob to control water flow. Place a bucket underneath the spigot and turn on the water. Allow water to run until you see it coming out clean. Turn off the water at this time. Reset the boiler system by flipping the breaker attached to it. Look to see if the low flow sensor light turns off. If it does, then you can restart your boiler.

Check For Frozen Pipes

If it becomes incredibly cold in your area or if you notice that water does not come out of the water supply line used to flush the cutoff valve, then it is possible that the water supply line feeding your boiler is frozen. If the water lines run close to the outside foundation or if some of your other water pipes have frozen in the home, then this is likely the problem. Feel the water supply lines that provide your boiler with water to see if they feel ice cold. If so, then place a small electric space heater near the water line, use your hair dryer along the length of the pipe, or place a heating pad on it. 

Try to warm up the pipe for several hours. You may hear water running to the boiler after the ice melts. If you do not notice this, then look for a small device on the water supply line that indicates that it is a water feeder valve. Press the button on this valve to manually force water to fill the internal compartment in your boiler. You should hear water rushing when this happens and the low flow cutoff light should turn off soon afterwards. 

If you cannot seem to resolve the problem using these tips, then contact a heating company like Robinson Heating & Cooling Inc as soon as possible so your home can be filled with heat once again. 


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