How to Adjust Flame on a Fuel Oil Furnace?

While some suggest the best way to adjust flame on a fuel oil furnace is to use your phone – and immediately call an HVAC professional to do it – others with DIY attitudes want to know how it’s done.  It can be done with only one special tool – a $5 tool readily available for HVAC supply stores – that is required in order to properly position and gap the ignition electrodes.  Here’s an overview of how to adjust the flame on a fuel oil furnace.

Gap the Electrodes and Position Them Properly

If this step has been recently completed, you may be able to proceed directly to the flame-adjusting process.  Your manual will provide directions on the exact specifications you need to meet.  The purpose of gapping and positioning the electrodes is so that they conform to the spray pattern and angle of the atomized fuel oil, producing complete ignition and maximum efficiency.  This step simply isn’t possible to do correctly without the correct tool, so secure that ahead of time.  Once you have done this step with each electrode, wipe everything down to remove the sticky tar created by combusted fuel oil. You are now ready to adjust the flame on the fuel oil furnace.

Adjust the Fuel Oil Furnace Flame

Re-install the burner with its adjusted igniters back into the furnace and fire it up.  It should start quickly, without any explosive sounds that indicate improperly adjusted igniters.  The following steps describe how to adjust the flame on a fuel oil furnace.

1. While viewing the flame through the inspection port, turn down the air volume until the flame starts to fail and smoke.  It will be a very dull yellow in color at this point. If, upon inspection, the flame is already dull and smoky, proceed to step 2.

2. Increase air flow until flame stops smoking and becomes a bright yellow.  So you know what you’re looking at, continue to turn up the air flow until the flame’s “flower” shows blue highlights.  This is a sign the flame is too oxygen-rich and too hot.  At this level, the burning is inefficient because too much heat is being created to adequately  transfer it through the heat exchanger, and too much of it is lost up the flue.

3. Turn the air flow back down until the flame is vibrant yellow again, without blue tinges or any smoke whatsoever.  This is what the flame should look like when it is properly adjusted.

4. Close the inspection port and listen to the furnace.  If it runs smoothly, you are good to go.  If you hear any slight shuddering, it is still too rich.  Turn down the air until the furnace runs smoothly.

At this point your efforts at adjusting the flame on the fuel oil furnace are a success!  Your furnace should be running at the maximum efficiency it is capable of.