Troubleshooting Oil Boilers

an oil boiler with pipes attached

Oil boilers are one of the most efficient for residential heating. The boiler basically consists of a burner and fuel tank. Once the burner has heated to the desired level, it transfers the heat into the boiler to heat the water. This produces steam which is then distributed throughout the house via a network of pipes, vents, and radiators. Oil burners tend to be more efficient and reliable than the electric type. However, even oil-fueled boilers do develop problems from time to time. Below is a guide to help you troubleshoot.

1. Oil Boiler Doesn’t Start

First thing you want to do is check your tank for availability of oil. You may have run out and not realized. If you’ve run out of oil, arrange for delivery from your oil supplier. It is also possible that the circuit breaker has tripped. Press the “Reset” button to fire up the boiler again. This is usually a square red button on the side of the burner. It should start after a couple of tries. However, if it fails, you could check the fuse. Replace the fuse if it appears to have blown. If the boiler still doesn’t start, check the motor on the burner assembly as it may have burned out. Should this be the case, arrange for a replacement.

2. Boiler Starts but Doesn’t Heat


A clogged burner nozzle may be responsible for this. The nozzle has an extremely tiny opening that could get clogged with mineral deposits or dirt. Change the nozzle and see if the boiler will heat. It is also possible that your fuel may be contaminated with dirt and water. As oil is being pumped into the tank you’ll need to shut the furnace off for about an hour. This will allow dirt to settle at the bottom of the tank. You should also ensure that the tank is topped off with fuel. This will keep the sediments at the bottom from being disturbed as much as infrequent fill-ups do. To check for presence of water in the tank, apply some water-sensitive paste onto a long stick. Dip into the tank. If it indicates water, you’ll have to drain the tank and inspect it for cracks. Arrange to repair all cracks.

3. Boiler Produces Smoke and Soot

This may be traced to a clogged flue pipe or cracked heat exchanger. Check the flue pipe, especially where it connects to the chimney. Clear any dirt and debris that may have clogged the pipe. Check the gaskets around the inspection door. If they are warped or you detect cracks, this allows heat and smoke to escape from the furnace. You need to replace faulty gaskets.

4. Insufficient Heat from the Registers

The problem could be a dirty air filter. Trace the air filter and check if it is clogged. A build-up of flint on the filter impedes air flow. It is possible that your fan belt may have broken. This needs to be replaced. If the fan belt is in good condition, check the supply air fan. It may have burned out and needs to be replaced. If your clothes dryer is close to the boiler, it is best to change its location. Dryers produce a lot of airborne lint which could contribute to a build-up of lint in your boiler air filter.