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Burning smell in the morning from hot air oil furnace

Zenwriter
Zenwriter Member Posts: 7
Hi, I have forced hot air oil heat with a whole house humidifier(in New York). Recently I had a failed blower motor replaced.

At the time, the motor wouldn't start and it seemed like the furnace shut off after getting too hot. Water had leaked everywhere from the humidifier running with no blower. During the time when the blower motor was down but the system running, the furnace gave off an acrid, burning smell.

Now, after replacing the blower motor, the system seems to be running OK. But in the morning after the furnace has been on all night, the basement area around the furnace has the same burning acrid smell (but not up through the registers). Later in the day, the smell seems to have dissipated and I can barely notice it.

Any thoughts on the problem?

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 5,724
    With no blower motor working, your furnace when up to high limit and probably beyond. Hopefully there is no plastic condensate drain pan. You could've had something melt, or melt a little, giving you the smell.
    Leaking water indicates something melt or broke, or water could've leaked into the heat exchanger.
    Time to check to see if there was any damage.
    Was anything done to fix the humidifier leak?
    steve
    HVACNUT
  • SuperTech
    SuperTech Member Posts: 1,792
    It could be several things. When was the last time the furnace was cleaned and maintained? It could be a problem due to poor combustion or draft. The furnace could be running too hot from a bad fan and limit control, dirty blower wheel or air filter or improper fan speed. What model humidifier? That's odd that it leaked water everywhere instead of draining normally.  Post some pictures of your system, it might help identify the problem. 
    HVACNUT
  • Zenwriter
    Zenwriter Member Posts: 7
    Hi, thanks for the comments. The humidifier is Field Controls, and it's installed on the air return side (I was told it should be installed on the supply side). The recurring burnt smell is similar to the smell the system made when it overheated when the blower was down. Re: the water on the floor and in the system, it seemed like when the blower motor was trying to go on and the system was hot, the humidifier just kept feeding steam into the system and it had nowhere to go.
  • mattmia2
    mattmia2 Member Posts: 5,717
    you should measure the supply and return temp after it has been running a while and compare to the rise and max temp on the ratings plate.
    SuperTech
  • Zenwriter
    Zenwriter Member Posts: 7
    Here are some pix if the system, if that is helpful… Williamson, I think
  • Zenwriter
    Zenwriter Member Posts: 7
    Another pix
  • Zenwriter
    Zenwriter Member Posts: 7
    Pux
  • mattmia2
    mattmia2 Member Posts: 5,717
    That tape or its adhesive or that insulation all could have got hot enough to be burned a little when the high limit tripped. I'm not sure if some of that material is rated to be that close to the furnace or the vent.
  • pecmsg
    pecmsg Member Posts: 2,949
    Most oil fired equipment requires a transition between the oil furnace and evaporator coil raising it 6 to 8” above. It’s in the manual. 
    I’ll agree probably overheated components!
    EdTheHeaterManHVACNUT
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,318
    edited March 11
    Agree with @pecmsg

    Just a thought about the AC Evap. Coil. A plastic pan to collect the condensate may be damaged. Keep a close eye on the system the first warm day you use the AC this summer. You may want to test it for 24 hours, before it gets too hot. If that condensate pan is damaged, you will get water all over the heat exchanger for the entire summer (or until you notice the puddle on the floor). You might be buying a new heat exchanger next winter if the water damages the furnace this summer.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • MikeL_2
    MikeL_2 Member Posts: 376
        Even though CO is odorless, it's never a bad idea to make sure your detectors are up to date & working......
    mikeapolis
  • pecmsg
    pecmsg Member Posts: 2,949
    MikeL_2 said:

        Even though CO is odorless, it's never a bad idea to make sure your detectors are up to date & working......

    It's better to have a Low Level CO detector in the house to give you an early warning to an issue!
    mattmia2SuperTechmikeapolis
  • Zenwriter
    Zenwriter Member Posts: 7
    Hi, thank you to everyone who responded.

    If you were to look for a burned component, where would you start? Everything looks normal in the furnace area when I take the large door off...

    Would it entail removing the insulation above the furnace and looking into the area where the heat exchanger is?
  • HVACNUT
    HVACNUT Member Posts: 4,621
    You could take the door off the evaporator to check if the drain pan is cooked. 
    When was the last time it was serviced? Is there a combustion report? The odors you're describing could be burner and or draft related as previously mentioned. Get it checked if it hasn't been. 
    The humidifier should have a pressure switch proving fan operation. A high humidity limit is sometimes also used.

  • Zenwriter
    Zenwriter Member Posts: 7
    Thanks to everyone who answered. mattmia2 got it right, but it wasn't the furnace making the odor, it was the foil tape on the hot water heater exhaust. The smell was there in the morning because the system ran after I took a shower. I discovered it when the weather warmed and I turned off the furnace, but the smell was still there. Am replacing the tape with a high-heat approved version.
    mattmia2
  • pecmsg
    pecmsg Member Posts: 2,949
    Why is there tape on the exhaust piping? It's not needed!
    mattmia2HVACNUT
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,584
    Hi, Some inspectors in the West require taping the vent piping. Theory is it prevents any fumes from getting out... o:)

    Yours, Larry
  • mattmia2
    mattmia2 Member Posts: 5,717
    :(
  • HVACNUT
    HVACNUT Member Posts: 4,621
    I hate when I see foil tape on flue pipe. It doesn't play nice when you need to take it apart.