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Black Soot from oil burning furnace

Posted by mom2fiveplantluva (My Page) on
Tue, Apr 5, 11 at 15:25

my furnace is not connected to my fireplace.... the exhaust blows thru a vent directly outside.... I came home from work Friday to find black soot blowing from the exhaust, completely covering the side of my home. It is NOT puffing back into the house at all, all of the soot is going outdoors. I freaked & called the fire department who inspected & said to call a furnace company. I called a local place who sent someone out to clean but said after what is supposedly a thorough cleaning " Still can't get a clean burn".

My house was built in 1988 and this is the original furnace.

Upon some google'ing I have found that it could be a broken (cracked) heat exchanger...I would've thought the guy sent to clean it would've noticed and mentioned that.

If worse comes to worse, I may need to replace entire furnace. If so, I am thinking of getting an electric furnace ( sick of getting oil deliveries and at the rate oil is rising, oil isn't cheaper than electricity anymore) ...but I will cross that bridge when I get there....

I purchased a CO detector today band since we are at 60 degrees for the next few days, I can go without turning on the furnace....

in the mean time, SUGGESTIONS??

Follow-Up Postings:

RE: Black Soot from oil burning furnace

If your heat exchanger was cracked, you'd be getting soot INSIDE your house. You're lucky.

Soot can be caused mainly by not enough air supply to mix with the fuel oil. Cleaning properly usually fixes that problem. With the modern burners, oil burns with zero smoke.

It's pretty easy to get a no-smoke burn, so I wonder why the tech made that comment.

Sometimes lint or animal hair can block the air supply at the burner. Maybe a bad nozzle. Does your air supply come from outside, along with the exhaust pipe? If so, maybe a bird nest, or other critter built a nest over the inlet.

Check along the lines of improper air supply.

Oil may be high, but I still think it's cheaper than electric. A heat pump might be a better choice.

RE: Black Soot from oil burning furnace

The tech was likely trying to sell you a new furnace and is probably not trustworthy. Any tech who knows what he's doing can get a 0 smoke burn EASILY from modern oil-fired equiptment.

RE: Black Soot from oil burning furnace

A complete cleaning of the burner assembly is needed. The burner blower is a "squirrel cage" type and may be covered in lint. It needs cleaning. That blower may be loose on the shaft and not turning full speed. The burner electrodes need to be cleaned (with solvents) so that they glisten like your china plates. A new nozzle of the PROPER type and size should be installed. The pump pressure needs to be checked. It is rare to find a technician who really understands oil furnaces. Get the book "Domestic and Commercial Oil Burners" by Charles Burkhardt, McGraw-Hill.
Often discounted on eBay and

RE: Black Soot from oil burning furnace

So apparently, the tech didnt do a "good" cleaning... and needs to come back out for a more thorough $75/hour cleaning

RE: Black Soot from oil burning furnace

His boss will call it a callback and you might not be charged. Something was missed along the way.

RE: Black Soot from oil burning furnace

final analysis: even after "good" was a bad nozzle on the burner ( this is relatively new burner- was replaced 2 years ago)
"Supervisor" didn't charge to repair


RE: Black Soot from oil burning furnace

It's rare that a new nozzle is bad, but it happens. Many technicians don't know that a nozzle MUST ONLY be handled by the outer brass hexagon edge. Oil from your skin, much less soot, will contaminate the filter and especially the orifice, making a new nozzle worthless.

Another point of trouble is that the nozzles are tightened too tightly in the nozzle holder. They a tightened "finger tight" and just a little more. Maybe 3 foot pounds of torque.

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