By Tom Secondino, Technical Sales Support Specialist for U.S. Boiler Company
We will open this month’s article by saying “ALWAYS CHECK FOR LEAKS ON ARRIVAL AND DEPARTURE!!”
Having said that, while oil burner technology has certainly advanced since the introduction of the power oil burner, some of the basic premises which are critical to clean and reliable operation have not. First and foremost is an ample supply of clean oil. While this appears to be a simple concept, it is one the tech support team deals with frequently.
Examining the oil delivery system
For clarity, it’s easiest to tackle this topic in stages. When on a no heat call, the issue may be related to one of several different systems, one of which is the oil delivery system. First, we want to check oil delivery to the nozzle assembly. Remove the nut on the high pressure (nozzle line) at the nozzle assembly. Divert the line into a container by either loosening the nut at the pump and spinning the line, or attaching a hose to either the nozzle line or nozzle line port on the pump. Reset the boiler and monitor the discharge from the oil line after any solenoids open (if present). If the oil discharge is solid and free of any air bubbles, the problem is likely elsewhere in the burner or heating unit. If the oil flow is sporadic, foamy, or non-existent, this is a good indication of a restriction in the oil system, failed or slipping pump coupling, or possibly an out of oil condition. If the burner motor runs but no oil is present at the nozzle line during ignition check for an empty oil tank, bad solenoid, broken or slipping pump coupling, air bound or restricted oil line, bad primary, or possibly a bad pump.
Once it is determined that the issue is related to the oil supply, we first need to analyze the type of system we have. Is the oil flow to the pump vacuum or gravity? If it’s a gravity system, check the oil level in the tank (also confirm the gauge is accurate – often the gauge will stick and indicate oil when the tank is actually empty). If the tank has adequate oil, move on to the filter. Remove the filter at the tank. Open the valve between the tank and filter. Oil should flow freely from the filter head. The higher the oil level in the tank, the more flow should be present at the filter head. A full tank with barely a trickle of flow at the filter indicates a restriction in the tank, tank valve, or filter head inlet. Take steps to resolve the issue if this is the case.
The next step is up to your personal preference, but this is a way to confirm all elements of the system are clear. I recommend installing a new filter but not purging the air at the filter. On a pump with a removable strainer, pull the pump cover. On a pump with no strainer, remove the oil line from the pump and drain into a container, or if not possible, attach a hose to the oil line and allow the hose to drain into a container. Turn on the oil valve at the tank and allow the air bubble from the filter to pass through the line and vent through the pump cover/oil line. Remember, gravity is working its magic here. The oil level in the tank must be higher than the discharge point. This becomes more of an issue on highboy style furnaces as the burner is at a higher elevation. If the oil flow at the pump is reduced excessively from the flow at the filter head, the oil line is restricted and must be cleared or replaced. Check with your service manager or insurance company on oil line protocol. Restrictions may apply to using CO2 charges to clear lines. Once the oil line is confirmed to be clear, re-assemble the system, installing a new or clean strainer and gasket where applicable. Purge the pump of any air using the bleed port. If the pump coupling is intact, solenoid (if present) is functional and energized during ignition, and the oil system is in order, the next step is replacing the pump if the issue persists.
Keep in mind that some pumps may not prime after being run dry when in a vacuum application and may require manual priming by filling the pump with oil using a pump style oil can and possibly using a push-pull pump to fill the oil line.
Two Pipe Systems
When dealing with a two pipe, or suction oil system, most of the above items are still relevant but we have a few more items to check. Air leaks can be problematic and can cause atomization issues as well as early pump failure. In addition to the items mentioned above, an important check is for air or restrictions. An “oil watcher” is a clear plastic tube with a vacuum gage attached and normally with 3/8” flare fittings; a male on one end and female on the other. 3/8” x 1/2” adaptors are normally included for larger oil lines. This tool can be used for checking air leaks or restrictions in the oil line, and when combined with a valve may also be used to check the pump, including the shaft seal, for leaks. With the burner running, check for excessive vacuum or air bubbles. Excessive vacuum can be caused by blockages, jammed check or foot valves, or undersized lines. Air can be introduced from leaking fittings or by outgassing. Under elevated vacuum, fuel oil will outgas and introduce air bubbles to the system. The old rule of thumb was 1” for every 1’ of vertical rise not offset by a corresponding drop at the boiler, and 1” for every 10’ of horizontal run for 3/8” oil line plus additional loss for filters, fittings, etc. Divide by half for ½” oil line.
After diagnosing the oil system and resolving any issues the final step is to replace the nozzle, service the electrode assembly and check the pump discharge pressure on the nozzle line. Confirm the nozzle line pressure meets the manufacturer’s specifications and that the pump cut off is holding after shut down. As always be careful with gelling in outside tanks in areas subject to low temperatures, and be sure to always wipe all lines/fittings dry and check all devices and fittings for oil leaks prior to leaving.
If the pump must be replaced, be sure the replacement unit meets the original specs. Most (if not all) pumps ship with the bypass plug OUT, and as such will install directly into a single line system. If you have a two line system and forget to install the bypass plug this is known in our multicultural industry as “No Bueno.” If you have a single pipe system and install the bypass plug, this is known as “Super-Extra No Bueno”, and will necessitate a return to the supply house for another pump, as the second you turn it on the pump seal will blow out. Always set the pump discharge pressure to the manufacturer’s specs for the heating unit.
Tools of the trade
As mentioned in the article some specialized tools will help expedite oil service. A standard pump type oil squirt gun helps to prime dry pumps. Removing the upper supply port plug/fire valve will allow the pump cover cavity to be filled to aid in priming. A push/pull gun is a versatile tool that helps to not only clear oil lines but also flush chemical through the lines and pull oil to the pump on vacuum systems with long pulls, among other things. An “oil watcher” is a clear tube with a vacuum gauge which allows the technician to see whether the oil has air prior to entering the pump while simultaneously indicating vacuum. Another handy tool is a “Kwik Check” pump test kit which tests running pump pressure and has a valve to allow an easy test of the pump cut-off. A CO2 blow out gun provides a quick means of clearing oil lines but may also result in ruptured oil lines. A push pull gun correctly applied in conjunction with appropriate solvent is more manageable in avoiding oil line failures due to excessive pressure.
The final step
After repairs are complete, ALWAYS CHECK FOR LEAKS!!!!
Remember the old adage, “Leaks take weeks.” They may also cost tens to hundreds of thousands of dollars to remediate if site contamination becomes an issue. Wipe every line and fitting dry as you complete a task and be sure it is still dry when you leave.
Finally, after performing these tests if you are unable to isolate the issue, please feel free to contact your local rep, or the friendly and highly skilled U.S. Boiler tech support team! Please feel free to contact us with comments on this article or suggestions for what you would like covered in future articles. You can contact me directly at firstname.lastname@example.org. Have a great summer and stay safe.