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blast tube question

MARK_21
MARK_21 Member Posts: 19
Just a quick question-I notice on my hot air unit Its a Rheem with a becket gun-- when i tilt the transformer back with the unit off i notice oil had dribbled out of the nozzel and tried to drip down into the fan cage... What would cause this..New pump new nozzle everything just about new.. I cleaned everything and fired everything back up and all works great but in about 2 weeks i will see oil drip from the bottom of the gun assy just under the cage fan...

It cleans up fast but whats causing this? Thanks!

The oil doesnt drip into the chamber! It seems to dribble out the nozzel and go back....

Comments

  • Leo
    Leo Member Posts: 770
    re Blast Tube

    Is the system brushed and vacumned yearly? What is the overfire draft, within specs? Is the house excessively tight, the blower or power venter if you have one could pull the house into a vacumn. Is the blower speed too fast, or too little return air or both, this could pull the basement into a vacumn. Another thing to check is the copper line from the pump to nozzle assembly, the little flared end at the nozzle assembly can leak allowing the oil to be drawn into the area you describe.

    Hope this helps,

    Leo
  • Bob Cat_4
    Bob Cat_4 Member Posts: 2
    Its never easy

    To pin point a problem like this is never easy but the most important thing is the nozzel. You say its new, was it replaced with the correct nozzel (you have to check manafacture literature.)Then there is always the possibility you got a bad nozzel. Or its possible the nozzel adaptor is cracked.

    Next you have to ask if the electrodes are set correctly. improper setting of the electrodes produce incomplete combustion resulting in unburned fuel, hence the mess.

    Make sure the draw assembly is in the correct position. ( this is the front to back location of the nozzel in the tube again refer to MFG for distances. If it is too far back in the tube sometimes it sprayes onto the wall of the tube.

    But above all IF YOU DON'T KNOW WHAT YOUR DOING call a service company and save youself a headache. Most of the situations I describer require a combustion test to be completed after adjustments. When ever you adjust a burner you change the charateristics of the flame.

    good luck,

    BOB Cat
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    all

    great answers, guys. I've encountered this many, many times as a service tech..

    I would also check the pitch on the tube..should be toward the chamber, and the drip hole needs to be open in the end cone..could be carboned over and plugged. Sometimes when the air tube is replaced and a universal flange is used, the installer must ensure the tube is set on the right angle on the flange and locked down. I've seen flanges installed upside down, and the pitch backwards due to the setscrews angled wrong.

    Take a close look at the pump seal. A minute leak will result in a mist of oil being drawn into the fan housing, and the air tube, giving the impression of drip back as well. Look closely at the various plugs on the pump for leaks too. I dry everything thoroughly off and spend some time watching what happens when the burner runs..

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  • john_35
    john_35 Member Posts: 29
    oil drip

    What you're experiencing is "off-cycle drip". Delevan makes a special nozzle screen/strainer with a check valve in it that's supposed to prevent it. You have to unscrew the existing screen on the back of the nozzle and replace it with the new one. Hold the hex part of the nozzle with a 5/8" wrench and grip the screen with a pliers and unscrew it.

    Having said all that I can't swear to the effectiveness of this product. "Off-cycle drip" is caused by heat reflection from the ceramic fiber combustion chamber on shut down. The oil in the nozzle line expands and when it drips out into the tube the heat radiating from the chamber will actually push the oil uphill and out into the housing below the squirrel cage. This is unfortunately a common problem with Beckett oil burners(sorry). They've tried to lessen the effect by putting a steel rod in the tube of the drawer assembly(that's what you hear rattling when you hold the assembly while you change the nozzle).It's also meant to take up space that would be occupied by air after your service tech changes the nozzle(allowing the oil to drain out). Riello and Carlin both have a much smaller diameter tube and (here's the key) they either offer a soleniod cut-off device or in Riello's case integrate it into the design of the burner.

    You can purchase an after-market oil valve that mounts between the discharge of the fuel pump and the drawer assembly. They come with or without delay-on-start features which is helpful if you have rough starting problems. I would also recommend a control that incorporates a post-purge feature to allow the chamber to cool down before the cycle ends. The solenoid valve works because it gives you positive shut-off (like a ball valve as opposed to a stop'n'waste) and that causes a vacuum to develop in the tube which keeps the oil from expanding as much.

    All the things mentioned by the first three posts are also possible. If you've been thru all that and still have the puddle coming back then you know it's what I think it is.
    You said it was a Rheem right? The one with the 4 or 5" flue pipe, right? It probably originally came with a Wayne burner.
  • rob
    rob Member Posts: 64
    Off-cycle drip

    Have seen this occasionally on Rheem and EK systems.
    Usually can help by applying a thin bead of hightemp silicone on the lower mating area of the air tube and motor housing. from about 9 o'clock to 3 o'clock in a circular motion to form a little "dam" that the air flow will push out next firing cycle. Check the blower off timing and deltaT across the htex. This will perhaps reduce radiant heat which is overheating nozzle. Also try Beckett @
    1800 OILBURN, they are always a big help.
  • john_35
    john_35 Member Posts: 29
    silicone trick

    That's right I forgot about that little trick with the bead of silicone. Probably the cheapest n easiest fix! Just make sure the area is clean and dry or the silicone won't stick.
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    drips

    My first thought would be to check to see if you are getting air into the fuel line. If it is, the nozzle will keep on dripping and also cause you sooting problems. Next step would be to check the nozzle line adapter for a bad shoulder. Firedragon sells a tool for reconditioning the face of the adapter. The only other two things I can think of are the fuel pump seal leak, or the nozzle spraying on to the end cone, as allready mentioned by the other guys.
    LOL, Rick in Alaska
  • Big Ed
    Big Ed Member Posts: 1,117
    The Drip

    This has been a problem of the mini pumps since day one . The mini pump's shut off has slight lag. I add a nipple to the bottom of the housing to lift up and maintain the inward downward pitch. If you set it with just the flange all you need is someone comming by after you leave leaning on and it will pitch back again. Adding a electrical oil solenoid after the pump is another approach.... Now air could be another problem so please don't get confused .If the oil lines are sucking in air you will also get a drip ,but you will notice the after burn .With the mini pump drip you will not notice anything until it drips back into the housing and out the bottom weep hole. The old burners had a problem with their large nozzle assembly oil tube.The air would pocket inside and under pressure it will compress the bubble of air and once the burner shut off , the bubble will expand back to it's original size forcing some of the oil out through the nozzle.We use to fill the large tubes up with pieces of cut metal wire hanger to make the inside of the tube smaller which helped force out the trapped air with the now faster moving oil. Beckett added the disk to the back of the nozzle adpter and notch the top to do the same thing...
  • sootmonkey
    sootmonkey Member Posts: 158
    drip

    make sure the burner is clean. remove the motor, pump, pump coupling, both air bands, nozzle asmmy., and air cone. clean out any dirt, oil, dryer lint, pet hair, saw dust, bats, mice, old bolts, and wire nuts. make sure that you at least brush the burner fan. sometimes better to take it out to the van and spray it clean. take your tourch and burn the carbon off the burner head. check the z demention. put it all back together. some good ideas have already been posted.
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Check pump cutoff

    Came across a job with a bad pump cutoff that caused this same problem. I would check this first.

    John
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