I have a new heating system, It is an oil heated Weil Mclian Gold
Series with a Beckett Burner. The service guy replaced the original
nozzle (after one year) with a 1 gal/hour nozzle. The original was
Now the system fires up with a bang. Also, what is this with the pump
running for 30 seconds before it ignites ? Seems like a bad design.
Doesn't the combustion chamber fill up with un burned fuel and then
ignites? This is inherent in the design of these new systems; tey run
for 30 seconds before ingition and then when the shut down the pump
continue to run for 30 seconds. My old sysem didn't have this and
there was never any loud bang when the oild ignited.
Also, I dont recall the bang noticeable when the burner had the 1.25
Anyone have similar experiece?
Sounds like it is set up wrong. The burner often runs before the oil as a
pre-purge of the combustion chamber, then the ignition and fuel come on.
Same with the post purge. As for the nozzle size, the depends on what your
needs are as the burner can often accommodate a range of sizes. What you
need is a competent service tech.
Go stand by the furnace and see what made the bang. My gas furnace
also went bang, the bang being a metallic noise as in hitting the
sheet metal sides with a fist. The bang occured during start-up as
well as when the fan motor shut off and slowed down.
The cause was the squirrel cage fan that looked OK. So I took it out
to see if there was anything I could fix as well as use the
opportunity to clean up the insides. The shaft was deeply scoured.
The bronze bearings ovalled. I replaced the 3/4 inch shaft and
repaced the bearings. Worked fine for 15 years now.
In my earlier annual maintenance routine I had overtightened the fan
belt. It should be tensioned with just the weight of the hinge
mounted motor. The motor should be able to turn the fan without the
belt slipping. I also added grease to the dry bronze bearings and
periodically put in 10/30 motor oil to fix the squeaks and bangs.
They worked for a time then I would have to repeat the exercise and
tension the belt again. What happened was the heat had baked the
grease hard and instead of lubricating the shaft it became a binder
and an abrasive. That scoured the shaft and wore down the bearings.
Motor oil lube made the problem worse as now there was a slurry of
metal filings and oil to scour the metal. Tensioning the fan belt of
course added to the wear rate.
The OP apparently has a boiler (heats water), not a furnace (heats air),
so there isn't a big blower or noisy sheet metal, there are cast iron
Almost certainly when the previous tech changed the nozzle to reduce the
firing rate, he knocked the igniter electrodes out of alignment and this
is causing a delayed ignition. Checking and adjusting the electrodes
should fix the problem, and if it began immediately after the tech had
changed the nozzle it should really be a no charge fix.
I have to agree with that. I'd also want to ask the tech WHY he changed
the nozzle, and if he did, what are the angle specs of the old and the
new nozzle, too?
The ignitor electrodes of course do need to be checked, and specced
for the new fuel delivery rate. The fuel delivery rate may also need an
adjustment (psi adjustment).
If all the tech did was change the nozzle, and especially if he
frogged the electrodes, that's causing the bang. Since it sounds like a
good loud bank, I'll also guess that your'e using #1 fuel or or
kerosene(basically same thing) for fue. and not #2 oil. I say that
simply because if it's #2 oil it's less likely to ignite, period,
although it can still flash with a bang.
The "problem" is too much atomized fuel collecting in the chamber
which for some reason the ignitor can not ignite until the chamber gases
fill it enough to finally ignite it with a relatively soft but noisy
NOTE: Should the ignition fail more than about three times in a row,
and start on say the 4th try, there could be a pretty considerable
amount of fuel oil in the bottom of the chamber which, when ignited,
will burn very very hot, with a whooshing sound, and if it's at night,
probably show coming out of the chimney. If a pipe blows apart from it,
you have an exposed flame possibility.
This CAN be dangerous. Not IS, but CAN be! If the furnace starts
and runs OK though, then anything in the bottom has burned off and is
Anyway you can ask for one of their "better" technicians to come and
take a look at it? Quickly? You shouldn't wait too long. Worst case,
the bangs are creating a lot of soot, which will block the eye inside,
and the furnace will quit running completely once that happens. Doesn't
see fire after start, shuts off the fuel line; pops the little red
button. Beware restart attempts after that point.
Hmmm, mine makes the same sound, I always thought it was normal. I do
remember when my tech came out to clean it this year it was a little
more quiet for a couple of days but then went back to the banging at
Yes, the same setup and the sound definitely comes from the force of
air going through the vent to the chimney. My vent has a one way flap
that I assume is there to keep the cold air from coming back down the
chimney when the boiler is off. That's what makes the most noise.
That's a better definition. It's still something that's likely to
result from the late ignition though as the excess fuel ignites, causing
lots of pressure, and then quickly settles back to "normal", rapidly
decreasing the pressure and pulling the butterfly valve back with a
bang, after which it begins to function normally.
BTW, while I'm thinking of it, if you're trying to watch this happen
through the fireport, be careful; that first ignition could remove your
eyebrows and eyelashes quite promptly, as at least one tech I know could
tell you<g>. Mostly got his hair, but gave his forehead a sunburn;
fortunately he was looking downward.
For the guy wondering about #2 fuel oil; it simply has a higher temp
flash point and doesn't ignite as easily nor remain suspended in air
nearly as well. That's all it meant. If you think it's misinformation,
feel to correct it, but it is the case.
I have had this system fro two years now Last year when I was using
the factory installed 1.25 gal/hr nozzle the bang didnt seem to be a
problem. This season the tech droped it down to 1 gal hr and now I
get the bang I had him come back once because the burner was running
lousey it was loud and an oil odor. He replaced the nozzle with a
differnt style nozzle. I think it was hollow vs solid.
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