Oil burner nozzle question

Old 11-17-15, 05:52 PM
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Oil burner nozzle question

Hi everyone,
How does one determine the proper size oil burner nozzle?
I only ask because my oil service guy (who was a tech for an oil company for many years before he went out on his own) told me that many oil companies instruct their techs to install larger than needed nozzles to effectively waste more oil, and thereby make more money for the oil company.
When my wife and I purchased our current home it had a 1 gph nozzle. We he found that he laughed and said that the "oil company was at it again". He switched it to a .75 nozzle and there were no problems at all last winter. Any thoughts on this?


Last edited by Zack1978; 11-17-15 at 06:45 PM.
Old 11-18-15, 07:45 AM
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Hi, no expert here, but I think there are nozzle size and spray angle recommendations from the boiler manufacturer. You may find them in the owner's manual. If different burners were available for your boiler, there will probably be different specs for each different burner. The idea of the oil company installing a larger nozzle to sell you more oil is an interesting idea but, in my opinion, unlikely.
What sometimes happens is that the service person doesn't have the correct nozzle on the truck and substitutes. Or the last seviceman substituted and the latest one went back to the recommended nozzle. After saying all that, sometimes a smaller nozzle can be substituted if the boiler is oversized and good combustion readings can be obtained with the smaller nozzle and combustion testing. Oil pump pressure may also have an influence on the nozzle size. All in all, lots of variables for a good service person to figure out. Steve
Old 11-18-15, 08:18 AM
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The idea of the oil company installing a larger nozzle to sell you more oil is an interesting idea but, in my opinion, unlikely.
Agreed. They make plenty on selling the oil and the service contracts. They don't need to pad their sales numbers by causing customers to burn more oil.

In general, the burner should have the nozzle spec'd by the manufacturer installed.

There ARE exceptions to this rule though, but it sorta sounds to me as if your guy might have a chip on his shoulder, and somewhat of a 'know-it-all' type...

IF it's an older boiler that was originally shipped with the oil pump pressure set to 100 PSI, an improvement can usually be made by upping the pressure to 140 and installing an appropriately sized smaller nozzle. The FIRING RATE will remain the same because the higher pressure causes the nozzle to provide the same quantity as a bigger nozzle at the lower pressure. The result is slightly better combustion because of the smaller droplet size.

An oversized boiler can often be DOWN FIRED, but WITHIN LIMITS. The physical size of the combustion chamber dictates these limits. DOWN FIRE TOO MUCH and you end up with WORSE combustion. I wouldn't count on being able to down fire more than 10% or so. Fuel savings gained from down firing is hard to quantify, and it's NOT proportional to the amount of down firing.

In other words, do NOT expect a 25% fuel saving by going from the 1.0 to the 0.75 nozzle. In fact, you would be lucky to see even FIVE percent... IF THAT... you might scarcely notice a difference even.

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