If you're familiar with gas or electric heating systems, you may be slightly confused with some of the terminology surrounding oil-burning furnaces. While heating oil systems generally work similarly to their electric and gas counterparts, there are also some noticeable differences. In particular, the oil burner is a separate component attached to the outside of the furnace.
Well-maintained burners can last for many years. However, keeping these systems in operation requires periodic inspections, maintenance, and repair. One component that may occasionally cause problems is the primary control, which directs the operation of the burner. Keep reading to learn three things you should know about your primary control, the problems it can experience, and what kind of heating repairs will fix them.
1. The Primary Control is a Critical Safety Device
Primary controls serve a similar role to the flame sensor in natural gas furnaces and boilers. The primary control monitors the burner's flame at all times, ensuring that it remains lit for as long as the burner should be operating. As with a gas burner, an unlit oil burner can create a dangerous situation if the valve continues to spray fuel into the combustion chamber.
Unlike natural gas furnaces, modern oil burners typically utilize a more advanced flame sensing technology called cadmium cell devices or cad cells. As a result, replacing or diagnosing a faulty primary control in an oil burner is often more complicated than dealing with a faulty flame sensor in a natural gas furnace.
2. Wiring Issues May Seem Like Primary Control Issues
Oil burner primary controls generally require more complex wiring connections than the flame sensors found on natural gas furnaces. A primary control requires wiring to the oil valve, igniter, and burner motor, as well as wiring at line voltage for the relay. Issues with wiring to the primary control unit can often appear with similar symptoms to primary control failures.
For example, a stuck relay or faulty ground may prevent the primary control from igniting the burner and running the motor. An experienced HVAC technician will check the wiring on your primary control to confirm that each terminal is receiving and sending the proper voltage. This step is necessary to avoid needlessly replacing the primary control unit when experiencing problems.
3. Repeated Resets Can Be Dangerous
All primary control units feature a reset button that you can use to attempt to restart the burner when the primary control safety trips. However, you should never repeatedly press the reset button if the burner won't start. In some cases, the primary control may have engaged a lockout due to a safety issue, and attempting to override the safety can be counterproductive or dangerous.
If your burner stops working, it's best to contact an HVAC contractor rather than repeatedly attempting to reset the primary control. An expert can properly diagnose the issue and solve the underlying problem, allowing your burner to run safely.