Oil furnance wont stay running black smoke from chimney

[BETHANY PIER]

Hi everyone

So here's the problem... I hAVE A mclain p-wtgo-4 oil furnace....it's emitting very black smoke from chimney and won't stay on. We have replaced oil filter and nozzle taken the furnace apart cleaned it and the. Burn chamber...bled the line i have Also located cad sensor and cleaned that bc it was complelty black....furnace kicks in stays in for about 5 min turns off and then back on for another few min and stays off....any ideas on what to do now I'm at my wits end

 

[Smooky]

Maybe it is not getting enough air?

http://www.weil-mclain.com/sites/default/files/field-file/wtgo-manual_1.pdf

 

[Sponsor]

 

[BETHANY PIER]

Ive adjusted the air intake it was set at 5 _scale was 1 closed -10 very open nothing changed I tried all the levels nothing changed

 

[DonL]

Ive adjusted the air intake it was set at 5 _scale was 1 closed -10 very open nothing changed I tried all the levels nothing changed

Is the nozzle pressure correct ? Is the fuel good ?

It could be a spark misfire, If the fuel pressure is good.

Good Luck.

 

[Dana]

Are you sure it was the correct size & pattern nozzle?

It's possible/likely that the flue is partially blocked by a bird nest or an asphyxiated raccoon or something. When that happens the blocked vent sensor will turn off the burner when flue spillage is detected, and only re-fire after several minutes have passed. See page 27 of the manual.

Even if you're able to get it running semi-normally with your debugging efforts, since you've monkeyed with both the nozzle and the air mixture control it's time to hire a burner tech with the proper combustion analyzer tools to re-tune it.

Also, it's a boiler (it heats up water), not a furnace (which heats up air), and it would be a pretty big one for most houses under 8,000 square feet. (It has enough output to keep my ~2400' antique 1920s house nice & toasty down to about -160F out door temps.) At 145,000 BTU/hr out it is probably way oversized for your space heating load and running less efficiently, well below the nameplate AFUE due to it's very low average duty cycle. If it is getting on in years (more than 15 years old) it's not unreasonable to think about scheduling it for early retirement, and install something more right-sized for your actual loads. If it's more than 25 year old it's not likely to be hitting anywhere near it's nameplate combustion efficiency due to corrosion on both the fire side and water side of the heat exchanger plates, and it's gone a reasonable lifecycle. Fixing the burner problems and with regular maintenance it can probably go an other 30 years, but that's not really the "right" thing to do unless you're a real short-termer hoping to sell in the next handful of years.

 

[JStoner80]

I have the same issue but it only happens once it gets warm and the furnace is no longer used for heating, just for hot water. This is year 3 of this issue, it failed again today for the first time this season. We've had almost every single part replaced in the furnace but it's still not fixed. Researching hot water heaters now ...

 

[Tom Sawyer]

If you don't have combustion analyzing equipment, you're wasting your time. Everything you do is nothing but hit or miss guesswork.