Does a Bad Nozzle Cause Soot in Oil Furnaces?

Function

• An oil spray nozzle has three functions. It breaks the oil up into very fine droplets, thus speeding up the vaporization process. It’s responsible for delivering a steady, predetermined amount of fuel to the combustion chamber, and it’s designed to deliver the fuel in an even spray pattern and at an angle best suited for the burner that it’s installed in. Inspect your nozzle by detaching the oil supply line from burner. Let the fuel run into a glass container and examine it for water or particles. If you see either, your oil spray nozzle is probably clogged.

Symptoms

• In addition to the appearance of soot, other symptoms indicate a problem with your oil burner nozzle. If the oil droplets being delivered by the oil spray nozzle aren’t fine enough, they crack and produce “shooting stars” along with the soot and coke that covers the boiler floor and heating surfaces. A soot test will show yellowish-brown spots caused by the unburnt oil. Other symptoms may include a furnace that doesn’t light or one that runs rough.

Life Span

• The life span of an oil spray nozzle depends on how often you run your furnace, how clean the oil is, how much dirt is present, and whether there’s a filter on your nozzle and your pump. Heat radiation from linings can also shorten the life span of your nozzle by causing coke to build up on the tip. Most oil furnace technicians recommend having the nozzle changed every year.

Prevention

• It’s not uncommon for rust to form inside your fuel tank. Using an in-line oil filter helps keep your nozzle from becoming plugged by removing extra dirt and rust from your oil. Place the filter as close as you can to the oil burner. Follow your burner manufacturer’s instructions when replacing the oil spray nozzle; choose a nozzle and spray pattern recommended by the manufacturer. Match the nozzle size to the design load.

Cleaning

• Cleaning a nozzle is difficult to do without damaging it because it’s hard to scrape the deposits that collect around the opening. In addition, it’s hard to see if the cone slots are clean unless you use a microscope to look. Cleaning a nozzle takes a lot of time and effort. A new nozzle costs less than $5 in 2011. It’s more economical to purchase a new nozzle than to clean an old one.

Replacement

• An oil burner nozzle should be handled carefully so it doesn’t become damaged before it’s installed. Keep it in its container until you’re ready to install it. Don’t touch the filter or strainer with dirty hands. Don't install it with a dirty tool or take the nozzle apart before installing it. Flush the nozzle line and adapter with a pint of oil, or use compressed air to remove dirt from the line before you install it. Don’t blow into the nozzle because that could contaminate it.