HVAC Residential Market / Furnaces

Oil Furnaces Require Special Care

Regular Maintenance Can Maximize Efficiency and Increase Longevity

December 2, 2013
Trans

Many homeowners recently fired up their oil furnaces for the first time this season. If they’ve invested in proper service and maintenance, chances are high that their equipment will keep them comfortably warm all winter long. Hopefully all homeowners are aware that regular maintenance is essential for proper and safe operation of oil furnaces, said Al Breda, service manager, Sippin Energy Products, Monroe, Conn., and president of Oil and Energy Service Professionals (OESP).

“As long as I can remember, fuel oil suppliers have made it clear to their customers that an annual maintenance visit is required,” said Breda. “I am still of the opinion that an annual tune-up is necessary. Maybe not for the same reasons as 30 years ago, as older oil furnaces had to be cleaned once a year because oil burners were not tuned-up with today’s precision adjustments. Although times have changed, and a well-running oil furnace should have little or no soot accumulation, the furnace should be inspected for safety, as well as checked to be sure it is set up for maximum efficiency.”

Safe And Sound

While annual maintenance can keep oil furnaces operating at maximum efficiency, regular service can also increase the lifespan of the system, said Damon Whorton, service manager, Trame Mechanical Inc., Dayton, Ohio. “Oil-fired equipment, if serviced annually, will last years longer than similar equipment that burns other available marketed fuels, mainly because heavier-duty materials are used to manufacture oil-fired furnaces.”

Routine annual maintenance on oil-fired furnaces should start with an inspection of the heat exchanger, which involves removing the clean-out access plates in order to gain access to the flue passages, said Breda. “There should be virtually no accumulation of debris in a well-operating furnace, but it is very important to remove all of the combustion products, even though there may not be much accumulation.”

Do not wait to clean the flue passages until there is a danger of restricting flue gases, cautioned Breda, as this will not only reduce efficiency due to accumulated debris, but the debris can retain moisture in a damp basement, which will most certainly accelerate the degradation of the heat exchanger.

After inspecting and cleaning (if necessary) the heat exchanger, inspect the blower compartment and air filter system, noted Breda. “Blowers need to be checked and lubricated, and the belts need to be inspected (if applicable). Air filters and evaporator coils also need to be cleaned so that the furnace can operate efficiently. Make sure airflow is not restricted, as this can not only result in a lack of heat in the home, it can cause the heat exchanger to overheat, leading to a premature failure and potential threats to health or property.”

The oil-handling parts are next, said Breda, and this typically involves replacing the fuel filter, as well as cleaning or replacing the fuel unit strainer and replacing the fuel unit strainer gasket. “Remove the drawer assembly (or nozzle assembly) from the burner housing, remove the nozzle, and take note of the nozzle specifications. It is best to remove the igniters/electrodes, then clean and inspect for cracks in the porcelain. If there is any question, replace the igniter or the porcelain insulator. Remember, there is a lot of voltage going through the electrodes that is looking for a ground before getting to the spark tips.”

It is especially important to replace the nozzle with one that meets the specifications on the furnace’s rating plate, emphasized Breda. “Do not take for granted that the previous technician installed the correct nozzle, as any size and style of nozzle will screw right into the same nozzle adapter. Don’t leave this to chance. Reinstall the igniters on the drawer assembly and set the electrode gap to the manufacturer’s specification. All oil burners do not have the same spark gap settings, and improperly setting the spark gap may lead to a delayed ignition or no ignition.”

After changing the filter and strainer, prime the burner and check the fuel unit pressure. This is also very important, explained Breda, because the nozzle firing rate is expecting a pressure of 100 psig. As the fuel unit pressure increases, the nozzle will deliver more oil per hour, and it is possible to exceed the furnace rating if a maximum fire nozzle is installed.

Technicians should verify a vacuum is being held on single-pipe oil suction piping when the pump is off, said Whorton, because if it can’t hold a vacuum, this may indicate a leak in the piping. “With maintenance finished, fire up the unit and do a combustion analysis, as well as check the stack temperature. You should also perform a smoke test.”

Make sure that the smoke test (done in the flue pipe) is no more than a 0+ (trace), said Breda. “Anything else and you shouldn’t even consider going any further on the combustion efficiency test. With the smoke rating adjusted properly, test overfire draft, breech draft, stack temperature, net stack temperature, and CO2, which will result in the combustion efficiency of the unit.”

One final step that is often overlooked is the heat exchanger test, noted Breda. With the results of the combustion analyzer in hand, check to see if CO2 or draft readings change when the blower is cycled on and off. “Any variation at all indicates a breech in the heat exchanger, and the source needs to be discovered before the furnace should be allowed to run, or else red-tagged and disabled,” he said.

Fixing Problems

Maintaining and servicing oil-fired furnaces is fairly easy, noted Whorton, and while procedures do not change much from one manufacturer to the next, it is definitely easier to work on older equipment. “Even though newer models have all the bells and whistles to help diagnose, they are normally less accessible for cleaning, viewing the flame, and setting up burners. Parts are jammed closer together, making for a smaller package, which makes it more difficult to access for repairs.”

When a furnace is not operating properly, Whorton often finds that poor installation is the culprit.

“Whenever there are problems with the oil burner, they always seem to relate to oil line installation, oil pump, and coupling issues. I rely on my oil pump gauges to observe oil pressure and vacuum in order to diagnose these issues, then take corrective action such as installing the return line plug, replacing the coupler, fixing the leaking pipe connector, adding an oil buster pump, etc.”

Lack of proper maintenance can also cause problems, such as oil flame failure lockouts, he added. “If I was not the last person to service the equipment, I start with the yearly maintenance requirements in order to track down oil burner flame failures. If I was the last to service the equipment, I can eliminate some of the maintenance-related requirements during troubleshooting.”

To troubleshoot fuel supply problems, cap off the nozzle line from the fuel unit to see if there is any fuel pressure going to the nozzle when the unit is reset, said Breda. “A steady reading of over 100 psig indicates that the issue is not in the fuel lines or fuel unit and points upstream to the oil burner or nozzle. If the gauge does not read any pressure or a varying pressure, then the issue is the fuel unit or is related to the fuel supply (make sure the pump coupling is tight first).”

According to the newest edition of Farmers’ Almanac, most of the U.S. will experience below-normal temperatures and above-normal snowfall this winter. So now is a good time to remind homeowners that their oil furnaces need yearly maintenance to ensure they make it through the chilly months ahead.

SIDEBAR: The Head Scratcher

Every contractor eventually comes across a service or installation problem that proves to be a real head-scratcher. For Al Breda, service manager, Sippin Energy Products, Monroe, Conn., and president of Oil and Energy Service Professionals (OESP), that problem came when he installed a properly sized furnace in place of an oversized furnace in an older home. “We removed an oil furnace installed in the 1950s for a couple who lived there for decades. The new furnace matched the heat load, which was about 60 percent of the old furnace, and the new direct drive motor was matched for the ductwork. The temperature rise of the system was right on target, too. We even threw in a new digital thermostat.”

Since installing the new furnace, Breda and his crew have visited the home at least 12 times due to complaints from the elderly couple such as the house wasn’t warm enough, the air was too cold, and the thermostat was off calibration.

“We even got calls that the furnace was not running, just because they could not hear it or feel the rumble from the old blower that used to vibrate when the system turned on.”

With each callback, Breda would adjust the fan and limits, firing rates, and multiple thermostats, and every time he left, he was confident that the customers would be happy. Then, a week or two later, he would get a call with another complaint.

The issue was finally resolved at the end of the first winter when the homeowners found that they saved almost 40 percent in energy costs, thanks to the new furnace. There have been no maintenance calls placed since.

Publication date: 12/2/2013 

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