How Does A Heating Oil System Work?

Written on: May 3, 2021

about oilheat systems new yorkToday’s new high-efficiency heating oil systems feature enhanced technology and control capabilities to provide optimal comfort while decreasing your fuel bills.

If you’re new to oilheat, you may not be aware of all of the components that make it work. Before we dive into that, however, let’s start with the basics: the difference between the two types of heating oil systems: boilers and furnaces.

If you have a hot water (hydronic) system, water circulates around your boiler’s combustion chamber. A circulator pumps the hot water through pipes to heat baseboards or radiators. Eventually, the water returns to the unit to begin the cycle again.

Steam boiler systems work similarly except they generate steam, which rises up to radiators (no circulators are needed). A low water cut-off shuts down the boiler if water levels drop too low, preventing boiler damage

On the other hand, a furnace is the heating unit in a warm air system (sometimes called a forced-air system). After the air is heated in the furnace, a blower forces it into a duct system and it is released through vents or registers on floors, walls, or ceilings.

A Matter Of Control

Regardless of whether you have an oil boiler or an oil furnace, a wide range of controls are used in the operation of heating oil systems. And these operating controls have become more accurate and sophisticated with the introduction of more technologically advanced equipment.

Let’s start with the device that gets all the gears in motion whenever your home needs heat.


The thermostat is the control that gets all of the other controls on a heating oil system going. When heat is needed, the thermostat starts the burner through the primary control and an electrical circuit.

Today, many people are using a smart thermostat in their oil-heated homes. A Wi-Fi-enabled thermostat allows you to view and change temperature settings from anywhere, thanks to your smartphone.

Limit Controls

Limit controls on heating oil systems regulate warm air, water temperature and pressure control. There are two categories: high limit/safety controls and low limit/operating controls

High limit/safety controls: These controls act as safeguards to prevent overheating. They will turn off the oil burner if temperatures become too high in the furnace or boiler, or if the pressure in a steam boiler rises to an unsafe level.

Low limit/operating controls: These controls start and stop the burner on a signal from the thermostat or aquastat (a device that controls water temperature).

Primary Controls

Primary controls monitor the oil burner’s flame. Solid-state controls and advanced microprocessor-based controls are very accurate. Primary controls also have a reset button that allows you to restart your oil burner (when the power comes back on after an outage, for example).

Additional protection circuits, such as the cad cell (cadmium sulfide photocell sensors) were added to oil heat systems in the early 1970s. A cad cell, which is usually mounted on the burner, uses its photocell “eye” to send a shutdown message to the primary control board if it cannot “see” the burner’s flame anymore.

Burner Power Switches

There are usually two switches that will cut off power to the oil burner. A red emergency switch is typically located at the top of the basement stairs. If the heating system is located in a utility room, look for the emergency switch near the room’s entrance. A second burner power switch is often found on or near the heating system.

You can read more about oil furnaces and oil boilers here.