AFTER DRIP QUESTION

Jim Davis

I have never found any device, OSV, Solenoid, Check valve etc that will stop after-drip. Finding the cause of the after drip and correcting it, is the onlu way and this is done with a CO(carbon Monoxide) test. Having tested thousands of oil burners I found a sequence of CO readings that determine if the drip is caused by air, poor nozzle pattern, drawer position, excess heat on the tube etc. A CO meter in the flue needs to measure the CO spike at Start-up, the CO during the Run cycle and the spike at Shut-down. If CO is above 100ppm at Start-up & Shut-down but not running it is air in the line. A two line oil system will cause this to occur indefinitely. If the CO is only above 100ppm at Shut-down it can be caused by positioning of the drawer assembly. If the CO at Shut-Down is low but then after 1-2 minutes starts to rise, this would be caused by the heat of the chamber coming back into the tube. There are several more senario's depending on how high the CO levels go above 100ppm at any given time.

BOB WILLARD

After drip on Beckett burner in hot air unit?

I have a question about after drip-when my burner shuts down. I understand you will always get a few drops of oil after the unit shuts down-and there is a little hole in the front of the blast tube at the bottom-I would assume that any after drip from the nozzle would go out that hole into the Combustion chamber.. My question is--When i flip open the Transformer and look down below the nozzle tube and electrodes--I see oil (After drip) thats not moving foward out of the front of the blast tube--Why?

The nozzle is new and tight (Tried 3) The nozzle adaptor is new and tight-The nozzle tube is NEW-The furnace is level-The beckett burner bolts to the front of the furnace with 3 nuts-So i couldnt even pitch the burner-when you tighen the 3 bolts the burner sits flush with the rest of the unit!
Plus if i pitch the burner--The flame wont be centered in teh combustion chamber...

I even installed the delavan nozzle adaptor-Stops after drip-This problem i have ONLY HAPPENS WHEN THE UNIT SHUTS DOWN--its seems like the hot chamber is drawing a drop or two of oil out of the nozzle-and its dripping back instead of foward...

Does anyone have any ideas? Thanks so much!!!!!

Climate Creator

I seem to remember...

Working on an aero water heater that did this, and it turned out to be that the tube was not cooling off properly and the heat from the chamber was warming the oil in the nozzle assembly and expanding it. How is the draft in this unit? Is there something new that has happened recently with this unit that has caused this change maybe?

CC

BOB WILLARD

Draft is fine..Nothing has changed!

Climate Creator

Well then

Install a cut-off

cc

Steve Eayrs

Agree with the oil cutoff, and also there should be a small hole in the bottom of the burner tube, just below the nozzle assembly, so the nozzle drip can run into the combustion chamber instead of backwards down the burner tube. It could be plugged. On most applications the burner tube should be slightly sloped towards the combustion chamber. Did someone recently replace the burner tube, or pull the burner for some reason, and re-install it wrong.??

Steve

BOB WILLARD

DRIP

I have installed a OSV and a Oil delay valve.. I also have a delavan nozzle shut off device on the nozzle.. The tube does have that little hole under the nozzle and its clean!

There is no way to pitch the tube because it mounts flush to the furnace..If i try to pitch the burner the flame will not be centered in the CC.....

Thanks for all your help...

J.C.A._3

O.K. Enough already!

With a few furnace manufacturers , that are no longer in business, the solution was to put a couple of washers on the SIDE bolts, leave the top bolt free of them and get a thicker "universal gasket".

Sometimes it was tough to find these gaskets, but now-a-days, if you have a Riello or Buderus dealer in the area, ask for one of theirs. You can also try to fill the gap at the bottom with kaowool rope or hard kaowool board ,shaped to fit. If youve got a OEM flange,(no choices, this is how it goes...." ,you can also try changing to a "universal flange" with oblong mounting holes and adjusting the set screws in the tube mount so you get a pitch to the chamber.

If you have any further questions, email me . I've been seeing this for so long,WE should be able to come to a fix. BTW, have you made sure that there isn't a pump seal leak, and the fan is putting the oil in the tube? Another possibility is a weeping fuel unit gasket.(sometimes they don't get tightened all around, and if you use something other than OEM gaskets, they seem to leak more. The air being moved by the fan CAN pull this "drip" into the air gate/band and fool you too.

Let us know how you make out . We all want to know!. Chris

BOB WILLARD

AFTER DRIP

Wont that cause the flame to hit a different part of the combustion chamber? The chamber is stationary so -if you pitch the burner assy-in any direction wont the flame be off center? Thanks so much for your help!

J.C.A._3

Depends ....

Is the flame hitting the bottom of the chamber now? If your using a "hollow" fire, firing at max. rate for the unit, my guess is you've still got some "squirm room". The patterns of nozzles are as steady as the fuel their being fed.

If it seems to be striking the bottom, try a SS, or semi-solid (same spray pattern) nozzle, Makes the fire a little tighter and may keep it from hitting bottom. Might be a bit noisier, but a fine firing unit is better than a foul firing one.

Again, I would make sure all criteria of the manufacturer are being met first. A phone call to the furnace maker and or the burner manufacturer may shed a bit of light on the situation. Sometimes things change, and if this is the case, they will have the latest updates or suggestions as to your particular problem. Chris

BOB WILLARD

DRIP

Ok thanks so much!!

Steve Eayrs

Jim, Sounds like an interesting test. I have never heard of someone usng CO test, as you have described, but it makes sense to me.


It seems to me that if the drip is because the oil expands because of overheating then there is way too much heat flowing backwards, from the combustion chamber around the nozzle assembly. In fact I would question the draft, and look to see if there is a neg. air pressure problem, not enough combustion air, or a plugged heat exchanger.
I think this has to be the main reason for transformers melting down too. At least thats what I suspect when we find one melted down.
Is my logic logical???

Steve

kk_2

Does the primary control

have a post-purge mode?

If it's caused by heat after the burner shuts off, post-purge could cool it off enough to stop it from happening.

The newer primary controls pre-purge (turn the burner motor on for some number of seconds before turning the oil valve on) and post-purge (turning off the oil valve and then letting the motor continue running for some number of seconds or minutes.)

Examples of controls that can do this are the Honeywell 7184 and the Carlin 60200.

Jim Davis

CO-Oil

It took me about 5 years to make any sense out of the CO readings I measured on oil. They are totally different than any other fuel. I first got interested in CO testing oil when I found an oil furnace making zero smoke making over 5000ppm of CO back in 1983. Once again, if the CO readings at shutdown start rising 30-60 seconds after the burner shuts off and keep rising heat is the problem. If not it is one of the other problems.

jim sokolovic

Interesting indeed!

But if any one of these problems are causing an after-drip, wouldn't you always see a consequent high CO level at that time, regardless of the cause? Is there something different about each after-drip condition that causes CO in some cases, but not in others (at shutdown)?

Jim Davis

Each problem is different reading

The start-up and run CO readings change with the specific problem. The level of CO at shutdown also has variation. Together they sort and distinguish each problem. Except in the case of underfiring, most CO on oil is caused by the oil droplets hitting hot surfaces and fuming. I have an explanation of this in one of the manuals I use in class and I am working on a new diagnostic cheat sheet just for oil.

Mad Dog

I Agree - a slight pitch

foward helps. Mad Dog

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jim sokolovic

Thanks for the explanation, Jim...

I'm having a hard time picturing each shutoff cycle producing the same after-drip condition and consequent CO level, though. And then there is the way different combustion analyzers display the reading (response time to see highest level, time to clear, etc.). I thought this type of stuff could only be predictable during steady-state operation. I'll have to experiment someday to see!

BOB WILLARD

DRIP

my drip happens when the burner shuts down-draft is good everything is clean and new...To me it looks like a draw from the hot chamber--and the nozzle and tube are set correctly....Strange stuff...

Climate Creator

Pitch

If you want to pitch the tube downward (assuming unit is level) with a Beckett burner without a welded flange you can loosen the allens that hold the tube and pitch it then re tighten. No messing with washers. But I agree with having some post purge, thats what I did to fix that water heater, it was power vented so I just increased the post purge time, no more drip.

CC