Smoke Coming From motor area of Oil Furnace


  #1  
Old 10-13-02, 08:46 AM
jrrepairman
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Unhappy Smoke emitting from oil burner after shut down

Hi,

Did a search for "smoke AND oil burner" but didn't get any hits so I'm looking for help.

Having a problem with smoke backing up and coming out of motor area in my motherís oil burner.
Hereís what is happening:

I serviced the oil burner this year (thanks to everybodyís help here), also replace the two electrodes for the gun and adjusted them according to the manufactureís specs.

Oil burner fires up nice and runs great, then:

Right before shut down smoke begins coming from the holes where you can look into the motor and also seeps out from under the large black cap that covers the gun area. This happens for about 10 seconds, then:

The oil burner sort of back fires and shuts down, at the same time the smoke stops.

Hummmmm,

It appears the oil burner is somehow sucking chimney smoke back down and it can only escape through the above mentioned areas.

Iíve noticed this smell last year for the first time and when I questioned the service man (last yearís service man) he said not to worry about it because that happens after servicing the burner and it will eventually go away. But after taking the cover off and checking out the shut down process it appears to me that it IS a problem, although it does seem minor.

I ruled out a faulty motor because Iím sure it would certainly be blowing smoke during itís entire operation if it was about to burn up. I am certain that right before shut down somehow a small quantity of smoke is being sucked back out of the chimney through the pipe OR smoke still remaining inside the burner area is being sucked out and escaping wherever it can.

Does anyone know what is happening? And, is this something which I should be concerned about, other than the minor annoyance of the smoke smell in the basement which lasts for a few minutes. It doesnít emit a lot of smoke, just enough to make in annoying.

Hummmmmmmmmm,

Further developments, two days later:

Could it be the serviceman was right when he said the smoke would stop, because it seems to have ceased. I've watched the last three fire ups and shut downs and NO smoke.

Also, the backfire I mentioned isn't a backfire; it's the sheet metal sides of the furnace either popping out or contracting in just as shut down is completed.

By the way, what are those makings on the side of the motor ranging between 2,3,6,8, and 0 which have a mounted ring with a pointer on it; is that something like the timing on a car to TUNE the motor?

jrrepairman
 

Last edited by jrrepairman; 10-14-02 at 06:15 AM.
  #2  
Old 10-17-02, 12:31 PM
jrrepairman
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More developments

Gee, the smoke is still coming out. After further observation this is what happens:

The motor runs and the furnace burns, runs very smooth; then, the motor stops and the furnace continues to function (I guess itís burning of the excess oil?) then before the furnace completely shuts down the smoke starts seeping out. This is intermittent however, I timed it as long as 45 seconds and as short as 10 seconds; sometimes it doesnít emit smoke at all????????? Finally, the furnace starts again, I guess itís doing something like circulating the air. Oh Yeah, this is a FORCED AIR furnace; all the heat comes out through one large 3 x 3 hole in the hallway area.

These are two theories I have:

The nozzle is SOMETIMES over spraying onto the rim of the hole into the burner area and this oil is being burned of AFTER the first shut down.

OR

The amount and length of smoke seems to depend on the period of time BETWEEN start ups. I was doing some plaster work around the hallway so I shut down the furnace but FORGOT to turn the thermostat back up, after turning it up the furnace ran for a good while; thatís when I got the 45 second length of smoke. I didnít notice this before but I hung around my momís house to observe the start ups and it sure does look like it depends on the start up intervals; I deliberately increase the thermostat a few times to get some start ups and it DIDNíT smoke.

Anyone have a clue, because I sure donít????????????

jrrepairman
 
  #3  
Old 10-17-02, 04:00 PM
Nominal
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Things to check

Check with manufacturer about the size and spray pattern of the nozzle. ie .75 gph and 80 degree hollow,solid, semi, etc. Then replace the nozzle. They are cheap. Also at same time ask about depth of the firing assembly. Assembly may not be far enough in chase, and therefore oil is being oversprayed in chase area. Lastly, I believe the oil pumps have check-valves that hold the oil in the tube going to the nozzle. These check valves should prevent oil from dripping or running out after shutdown. The check valves could be bad. Short of works like holding your finger on the end of a straw with liquid in it. One way you may test the check valves is: Is there any hesitation of firing. After the furnance is shut off for awhile, does the furnance fire as soon as the unit is called for heat, or does the burner turn on and a few seconds later it fires? This would tell you that the pump is having to fill the tube with oil again. Hope this helps
 
  #4  
Old 10-17-02, 05:11 PM
jrrepairman
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Thanks Nominal

Well, weíve been using the same nozzle since the furnace was installed; but Iíll pick up a nozzle that doesnít have as wide a spray angle and see if that stops it. Will getting a shorter spray radius conflict with the operation of the furnace, Iím sure the manufacture recommends this particular nozzle for a reason. But reading the manual I did notice that various nozzles were mentioned, but that was only for the type gun (assembly) used. Itís also a possibility that I purchased nozzles that were not correctly set up, Iím sure these nozzles have some sort of plus/minus tolerance; so Iím thinking that altering the spray radius would not hurt the operation of the furnace. Am I correct???????????

After that Iíll try the check valves. You know I thought about dripping oil but shrugged it off because I figured it would be smoking ALL the time; but reading your suggestion this now seems very logical since according to your description of check valves they WOULD NOT drip until shut down, and this REALLY appears to be whatís happening.

About the assembly not being far enough in, that seems to be beyond my capabilities; but since this problem just began last year and I canít see any reason why this distance could change on itís own; meaning that the gun is secured in the SAME position by two fittings. Is it possible for this distance to change without being disturbed???????? Is it possible for DIFFERENT nozzle manufactures to make them to different tolerances; meaning, is it possible that I may have purchased nozzles that are SHORTER than the nozzles I previously was installing?????? Meaning, letís say I purchased a nozzle that is ĺ inch long and the original nozzle was 13/16 or 7/8 inch long, that would mean the nozzle would in fact be 1/16 to 1/8 farther back from the hole it is supposed to spray through and would most likely cause oil to spray on the outer walls. Is this possible or are these nozzles manufactured to STRICK tolerances?

jrrepairman
 
  #5  
Old 10-20-02, 12:10 PM
Ed Imeduc's Avatar
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oil smoke

?????????????? When you worked on this burner and took the nozzle set up out of the burner. Did you put it back at the same set up for the in and out of the nozzle so the oil dont hit the cone head????Id look at this before I change the angle of the nozzle.
The angle of the nozzle that you have is used for the size and shape of the fire box only.The out put for how much heat you need ED
 
  #6  
Old 10-21-02, 06:26 PM
bigjohn
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Listen to what Ed is saying. The spray angle of the nozzle matches the shape of the combustion chamber. If you change to a different spray angle, you could cause the fire to impinge on the combustion chamber surface and burn a hole thru it, ruining the furnace. I would check to make sure the nozzle is tightened down prorperly and that the oil supply tube that the nozzle is attached to is also tight.
 
  #7  
Old 10-22-02, 12:14 PM
jrrepairman
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Problem Solved

Well,

I took "nominals" info to my local plumbing/heating supply shop and there is a guru there who did this:

Gave me a "stone" for the back of my nozzle that had a "check valve" built into it; he also said that the nozzle I installed may have been defective, so I installed this new stone in a new nozzle and the smoke stopped.

I went back today to thank him and purchased a "new" pump since he said that it is most likely getting weak and most likely is the "REAL" problem, even though that installing this check valve stone cures the problem 90 percent of the time. I also purchased another nozzle and "smart stone" (with check value built in) for when the pump failure occurs; then I'll install the entire works. Or, better yet; next summer I'll just install the new pump and get it over with.

Thanks for your replies, another HAPPY customer of Doityourself.com

jrrepairman
 
  #8  
Old 10-22-02, 02:27 PM
Ed Imeduc's Avatar
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oil burner

Look around jrr you should be able to find a rebuilt on the pump.
The pump should read about 100 psi when running. good luck ED
 
  #9  
Old 11-08-02, 04:28 PM
purger406
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what you experienced is poor pump cut-off yes you should replace the pump and change the pump coupling. i mean you have the pump off .....change the coupling as well.
 
 

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