Why use different nozzle?

ChrisJ

I'm posting this simply out of curiosity and hope I don't upset anyone. 

Heres what I'm wondering....

You have a burner mounted in a boiler whos draft is regulated by a barometric damper.  The boiler manufacturer recommends a specific nozzle for that setup as well as preliminary adjustments for air and what not.  The fuel pressure is as specified, the draft is set as specified and the air is fine tuned for the best burn.



Being the draft is regulated by the barometric damper, the boiler manufacturer SHOULD know the exact conditions this burner will be operating being fuel pressure is constant and you tune air for the best burn.  <strong>Why would anyone use a different nozzle than specified?</strong>   Wouldn't the manufacturer know what works best in that specific system?





Again, not trying to upset anyone, I'm simply curious.

Steamhead

Normally

you would follow the manufacturer's specs. But there can be exceptions, such as



1. Where fuel quality is questionable, often the recommended solution is to use a nozzle with a smaller gallons-per-hour (GPH) rating, and raise the pump pressure, to produce better atomization. In this case, the spray angle (degrees) and pattern (hollow, solid, semi) generally stays the same. The smaller nozzle size and higher pump pressure are coordinated to keep the same actual firing rate. The standard pump pressure used to be 100 PSI, now many new boilers have burners set at 140-200 PSI or even higher;



2. If a unit is oversized, sometimes a smaller nozzle can be used to make it short-cycle less. When doing this, a tech MUST use a digital combustion analyzer to make sure the combustion parameters such as stack temperature do not change enough to cause problems. Of course, the tech should use an analyzer on every job;



3. If the manufacturer specifies a certain brand of nozzle that is unavailable, the brand used to replace it might have different spray characteristics than the original. In this case a different spray angle or pattern might be needed. This sometimes happens when switching to or from Hago brand nozzles.



4. And last but not least, sometimes the manufacturer gets the specs wrong. Fortunately, most manufacturers have techs available by phone who can provide the latest specs.



When working on an older boiler that has been upgraded with a newer burner, most times there won't be a manufacturer's spec. In that case, the burner manufacturer will have some basic recommendations that the tech can use as a starting point.



HTH.............

Paul Fredricks_3

OR

You could have a tech like we did. He put "W" nozzles in everything because delevan calls them "Universal" nozzles. Boy, did that create problems.

ChasMan

Manufacturers

When manufacturer specs are wrong, they sometimes stick by them in the face of all evidence against them. I think they might be testing with Jet fuel or something.

ChrisJ

Specs being wrong

ChasMan,



I'm guessing you have seen it where the manufacture specified a completely wrong nozzle?

ChasMan

Specs being wrong

Completely wrong nozzle? Well, no, but not an ideal nozzle. The nozzle / fuel pressure will partially dictate the air setting for a given casting and that combination I have seen way out. It leaves you scratching your head is all I am saying. Then repeated phone calls and visits by company reps has them all scratching their heads yet the numbers remain published in the manuals. Pressure drops are ballpark guesses at best in the literature.

Jim Davis_3

oil nozzle

The problem with oil nozzles is there is no consistency in spray angle or pattern.  The only thing that is tested is there flow at 100# with the oil heated to 100 degrees.

A right nozzle that is bad won't work and a wrong nozzle the is good may work better.  Understanding the all flame retention burners have solid air patterns should make selecting a nozzle for them fairly simple.

Older burners had more of a semi-solid air pattern but certainly not hollow. 

Some can make any nozzle work but making them work right is another situation.

If you check universal nozzle chart cross references it is fairly apparent that no one can make up their mind on which to use.  In almost all cases the burner design has more to do with the nozzle selection than the equipment, especially with flame retention burners.

A burner can run with Zero smoke and be making thousands of parts per million of carbon monoxide.  Smoke testing alone does not determine if a nozzle is working properly.

earl burnermann

W nozzle only

Worked for a company that only used w nozzles.

ChrisJ

cold oil

So tuning an oil burner is as much an art as it is a science.



What about cold combustion chambers?  My previous boiler had a domestic hot water loop in it.  Due to a boiler like that running all summer long with a poor draft and short run times is any compensation usually made such as extra air?

Do these boilers tend to soot up more than one used strictly during the heating season?



Again, thank you all for the responses.  I appreciate you taking the time to respond.

Steamhead

Depending on the material used in the chamber

it may heat up fairly quickly. This is particularly true of the Kaowool chambers used in modern boilers and as retrofits. So the "cold" period in this case is pretty short.



Older chambers were made of heavy refractory, which may or may not have been in brick form. These took a while to warm up and stabilize, which would have affected the burner's operation.



With a tankless coil, the boiler never really cooled down unless it was completely shut off, so the burner would always fire into a warm refractory. The warm boiler would have also kept the draft going even during warm weather.



When setting up a burner, you have to take all these factors into account. One constant rule is you never leave a burner right on the cutting edge of clean combustion, where reducing the air any more will result in smoke. I was taught to find the point at which the burner just started to make a bit of smoke, open the air shutter just enough to get back to zero smoke, take a CO2 reading and then open the air shutter enough to lower the CO2 by one percent. This would add enough air to take care of any oil, air or draft irregularities throughout the heating season without making smoke or soot, and without excessively lowering the unit's efficiency. It has always worked well for me.



There are still those who say that a "trace" of smoke is fine. This may have been true 50 years ago, but any burner made since the 1980s or so (as well as some earlier ones) was designed to run with zero smoke. Since smoke and soot are two big reasons the oil industry is losing customers, those who tolerate them have their heads in the proverbial sand.

meplumber

Well said, Steamhead.

Oil burner setup is definitely an art.  The manufacturer's guidlines ("specs") are a starting point.  Sometimes it works, sometimes it doesn't.  The draft regulators can only compensate for so much.  The factory tests never account for a large, tall chimney or a short skinny chimney. 

Every installation is slightly and sometimes very different from the manufacturer's test.  That is why all must be setup with a Combustion Analyzer.  Deciding which nozzle to use is more about experience than anything.