Clean Cut Pump Question
Hi! I have a furnace with a Beckett burner with a PF20322 clean cut pump. I’ve been having an issue with afterdrip which causes some drops of oil from the bottom of the burner housing.
The burner is serviced regularly and has been running fine other than the drip. My technician took a look and concluded that the pump likely has a bad cutoff and suggested pump replacement to solve the afterdrip.
I’m trying to understand more about the clean cut pump and I was curious because I noticed that the solenoid valve stem is a replacement part offered by Beckett (21877U).
As I understand its operation, the energized solenoid causes the stem to block the return circuit within the pump, allowing pressure to build up, and it opens the return path when de-energized.
Could the stem be at fault if it’s somehow not retracting quickly or fully enough after power to the solenoid is cut?
I’d imagine most times the pump is just replaced but I was wondering what situation a technician might replace the valve stem instead of replacing the whole pump, considering it is offered as a replacement part.
Comments
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A bad solenoid doesn't cause after drip. There's an internal cutoff in the pump. The nozzle assembly will go to 0 psi after shutdown.
Is it an OEM burner? Is pitch on the air tube adjustable at the flange, or is it fixed? Carbon on the head? Combustion numbers?
I'd find the cause before replacing anything.
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I agree with @HVACNUT
. The first place I would look is the burner mounting flange. On some burners there is an adjustable flange and that is subject to having the incorrect pitch. This is the diagram for using the adjustable flange from the beckett instruction manual
See how the burner is pitched 2° towards the combustion chamber. When properly pitched, the after drip that may come from the nozzle on each shut down will drop into the chamber.
If someone uses that burner for support as they stood up from working on that burner, that adjustable flange will give way and perhaps have the incorrect pitch in the wrong direction. That will cause any accumulated after drip from each cycle to flow to the burner housing and eventually end up in the bottom of the housing and drip on the floor.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Trapped air inside the gun assembly. Air bubble is compressed when working/under pressure, expands on an off cycle thens you get the drip.. The drip, Bah Ha Ha!
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@BDR529, I have a slide from my class that illustrates your point.
In the top "Running" illustration the 100 PSI oil pressure has compressed the air bubble to a veery small volume inside the nozzle tube.
In the bottom "shut-down" illustration, the oil pressure drops to zero allowing the air bubble expand and force some oil out of the nozzle after the fuel pump's cut off valve closes.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Thanks, guys. It is the OEM burner that came installed in the furnace (just a couple years old). I will double check but I believe the flange is fixed. I didn’t see any carbon on the head either when we had the nozzle assembly out.
It’s strange because it seems like this developed throughout the season. No changes were made to the system since after the last service 6 months ago and definitely don’t recall seeing it immediately after the last service.
@EdTheHeaterMan thanks, it would seem based on the illustration that a tiny bit of air could allow the nozzle to continue to spray normally enough for the burner to run but cause the after drip. Is that right?
One thing I hadn’t tried is to perform a bleed through the pump because I’d assumed if it was running correctly then there was no air in the line and that any air would’ve eventually purged through normal operation but realize now that may not be the case.0 -
After spending six months chasing suction leaks, I completely agree. The burner would run but would constantly drip. It would drip even AFTER all the suction leaks were fixed and the bleeder reflected totally pure fuel flow.
The question that begs is whether the air bubble will clear itself with sufficient running time……………I have a suspicion that the size of that air bubble is relevant. Anytime you change a nozzle, the line is presumably full of air and the burner generally has no problem with it………….but………….it could be the situation that the drip generally goes into the CC with the correct pitch. In my situation, the furnace has no pitch on the outer shell………..where the burner is mounted.
I believe you mitigated this issue by your own technique to fill the nozzle line prior to installation. This may have merit although nobody does it.
It COULD be that your technique is REQUIRED for all burners that do NOT have the 2 degree pitch.
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The air bubble will be gone after a few starts and stops.
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……………provided you don't have ANY suction leaks……………otherwise it won't.
I could not get the drip to stop until there was absolutely no air going to the pump. It still took quite awhile for the drip to finally stop. Running it continuously clearly didn't work.
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When a burner has a small oil stain under the bottom of the burner housing, those are only two of the illustrations that appear in my mind's eye that can be the cause of the drip in that location. Another one is the fact that even after years of experience I have installed the retaining escutcheon nut for the nozzle assembly backwards. That prevents the flare nut from making a liquid tight seal on the nozzle assembly. You find that out immediately upon commissioning the oil burner after you make that mistake.
Once that oil sprays all over the place the fan sucks some of that oil into the burner housing. If the tech that made that mistake does not take the time to disassemble the burner to wipe the oil off of each fan blade and the interior of the burner housing, then that oil will continue to drip for some time after the tech leaves.
There are many other things that pop into my mind’s eye when I see that particular drip. And experience from hundreds of service calls per heating season, will dictate which one(s) will be the cause. And then direct me to the solution. Sometimes the pump seal is defective and there is no human error involved with drip. And sometimes the homeowner does not have enough money to purchase the new fuel pump that will solve that problem, so they elect to place an aluminum baking pan under the burner as the permanent solution.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
1 -
I think I have a better understanding of the after drip now thanks guys!
As I currently have heat and the drip is being caught by a container, I’m going to wait until a bit later in the season when I can dive in further. I’m thinking:
I have a pressure gauge, so first I plan to try to confirm whether the pump cutoff is at fault.I can try to take a look to see if there’s any oil around the pump seal.
For good measure, I’ll bleed the line or maybe even power bleed, to make sure there’s absolutely no air.
If it comes to it, I may pick up a vacuum gauge as well to try to diagnose whether there are any vacuum leaks in the pump or any in the suction line.
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I just found this discussion (Post) from 2024 where I go over proper nozzle care, and how I was taught to take care of nozzles and to properly install then in the oil burner nozzle adaptor. Take a close look at step #9
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
2
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