To get consistent, reliable operation from a commercial oil-fired boiler, it must be monitored and serviced on a regular basis. The best boiler will turn into a hunk of metal or become a dangerous vessel if it doesn’t get the attention it needs. Two boiler experts provided their ideas on the frequency and requirements for servicing commercial boilers.


How often should an oil boiler be serviced? Peter Desens, corporate technical service manager for ECR International, Utica, NY, said, “The end user should continually monitor their heating system. For oil-fired equipment, it is an industry standard to have a service person maintain the equipment annually. This will ensure the equipment is operating at peak performance.”

According to Glenn Stanton, manager of training, Burnham Hydronics, Lancaster, PA, “The frequency of boiler/burner required service would vary in accordance with the size and complexity of the equipment installed. A full annual service is the minimum interval. Many building owners purchase service contracts with boiler/burner service companies whereby a monthly check is standard. These monthly checks make sense in that ‘an ounce of prevention is worth a pound of cure.’”

What checks should the end user make? What checks should only a qualified technician or contractor make?

“End user tests should be limited to simple maintenance procedures such as checking for water or oil leaks on the boiler or system, occasional blow down of a steam system, and weekly blow down of a low water cutoff device on a steam boiler if equipped with float-type cutoff,” said Stanton. “A qualified contractor, for reasons of liability, should perform all other maintenance procedures.”

“The end user should always be aware of any changes in the operation of the system or equipment, i.e., a zone that is not heating like it used to, or the boiler sounding different, or spotting water leaks,” Desens said. “The entire system should be serviced only by an experienced service person, annually or anytime the end user notices something is wrong.”

A standard published by the American Society of Mechanical Engineers (ASME) International, “Controls and Safety Devices for Automatically Fired Boilers” (CSD-1), provides a list of requirements for boiler maintenance and testing. It includes a schedule of daily, weekly, monthly, semi-annual, annual, and as-required checks/tests. For example, on a low-pressure boiler, a boiler operator should check the low water fuel cutoff device and alarm weekly. A service technician should test the high limit and operating temperature or steam pressure controls annually.

The Burnham V9 Series boiler features a cast-iron sectional design to ease assembly. (Courtesy of Burnham Corp.)


Elaborating on the important ser-vice checks and test procedures that a tech should carry out, Stanton said, “A complete combustion analysis should be performed at least on an annual basis after the boiler and burner has been properly cleaned. A smoke test and flue gas temperature test should be performed in the breeching while the system is up to proper operating temperature (warm chimney).

“Over fire and breech draft tests should also be performed to properly establish draft through the boiler and breeching. A CO2 or O2 combustion analyzer should be used to determine the CO2 or O2 percentage content in the flue gases at the breeching. Having gathered all of this data, combustion efficiency can then be determined.”

To keep the system clean, “At least once a year, a complete boiler/burner cleaning should be performed,” stated Stanton. “This should include removing the cleanout plates between the sections (if equipped), flue canopy, and burner. Brushing the cast iron sections with a properly sized flue brush should be done first while vacuuming out any carbon or soot. Extreme care should be taken to not damage any refractory devices such as target walls or combustion chambers with the brush or vacuum cleaner.

“Reinstall cleanout plates and canopy and sealer to ensure gaskets are sealing properly. Finally, remove oil nozzle(s) and replace with properly sized nozzle(s) with correct spray pattern. Adjust ignition electrode gap per specifications, and remove, clean, or replace fuel filter screen. Properly set up the burner to specifications and perform a complete combustion analysis (as outlined above).”

Noted Desens, “The entire system and heating equipment should be checked for problems during annual service. On a forced water system, all components should be checked to be sure they are operating properly, i.e., air eliminator, zone controls. With a steam system, the water may need to be drained and replaced with fresh water. All components must also be checked for proper operation.”


Pay attention to boiler water. “An occasional drip or leak from a hot water or steam system can add up to quite a bit of makeup water being introduced into a heating system over a period of time,” Stanton said. “Exorbitant amounts of fresh oxygenated water being introduced into a cast iron heating boiler for an extended period of time can cause internal corrosion of the boiler vessel and related devices and fittings.

“Check the pH or condition of the boiler and system water. Most manufacturers will state in their respective installation manuals the proper pH to maintain in the system or boiler. If leaks in the system were encountered during the annual check, then the pH may have been altered somewhat. Consult a water specialist on the best way to address an adverse water condition to return it to manufacturer’s specified levels. Always comply with the boiler manufacturer’s specifications for pH of system water.”

As to the fuel system, “There are many fuel system checks that may be required,” declared Stanton. “A vacuum test of the oil transmission lines on an annual basis is a good way to determine if there may be any sludge buildup in the pipes. Regular oil filter changes are a must with varying frequencies based on equipment size. For equipment using heavy oil, a quarterly check of the preheater is a good idea. For systems with an oil transfer pump or storage vessel, a check every three months is good insurance.”

“Clean oil is the main concern,” emphasized Desens. “Always replace filters annually. If there is evidence from the old filter that the tank is dirty, it may need to be cleaned or replaced.”


What electrical system checks should be made? “Testing of secondary safety high limit devices should be performed on an annual basis,” Stanton said.

“On water boilers, set the manual reset high temperature limit control to a setting just below that of the operating temperature control. Operate the boiler and check to see if the manual reset control locks out when the respective control setting is reached. Readjust the setting to a temperature above the operating control when the test is complete.

“On steam boilers, perform the same test with the manual reset pressure limit control by setting it below the operating pressure control setting. Operate the steam boiler briefly to ensure that the manual reset function operates as desired. Return the manual reset settings to where they originally were set prior to the test.”

He added, “Testing of manual reset low water cutoff devices should also be performed to ensure their proper operation. To perform this test, shut off any makeup water devices to the boiler and install a temporary jumper on the operating low water cutoff device (probe or float type) terminals and drain water from the boiler until it reaches the minimum water level line of the boiler. (Do not allow the water level to drop below the lowest permissible water level of the boiler.)

“Continue to slowly drain water until the manual reset low water cutoff device activates and shuts the burner off. Add water very slowly to return the boiler water level to its normal level. And remember to remove the jumper from the operating low water cutoff device.”

For more information, visit the following websites:

  • American Society of Mechanical Engineers:
  • Burnham Hydronics:
  • ECR International:
  • Publication date: 12/16/2002