Oil exhaust and power vent

I have had problems with exhaust fumes building up in my mechanical room which are then pulled into the ductwork and sent thru the house. I have had this issue since the initial installation six years ago and two technicians have looked at the unit and found nothing wrong. I service the unit myself every year and do not have a problem with an oil smell……..this is clearly an exhaust smell. Sometimes it is worse than others………in fact sometimes it isn’t even there and other times it is very strong in the mechanical room and it is not related to windy conditions. I have a power vent but I do not use outside air for combustion because the mechanical room 13 x 16’ is connected with an open doorway to a 26 x 50’ basement. My oil furnace was ordered with an extra larger blower (12 x 12 instead of the standard 12 x 10) and when it comes on it will pull the basement door shut if it is ajar. I’m wondering if the negative pressure created in my basement is the issue which could allow outside air to push back into the furnace after the power vent shuts down………but if so, I don’t understand how the fumes can get out of the combustion chamber. The view port is closed tightly. My power vent is a TJERNLUND PRODUCTS, Side Shot Model SS1. Thanks in advance for any help you can give.

Greetings LL welcome to the Forum.

I think your problem has created more questions for me than answers, but, let me just gab a bit.

You checked your Flue Gas mix/Temp, should that Door to the Basement room be close or open, seems like with negative pressure like that, it'd make a big difference.

On your return, is the building old enough to have Plenum, or a Duct, does it return form another area, which a door could be left open, drawing fumes in from there?

Just where does your combustion air come from, seems like when you operated the Power vent, it would exasperate the problem, making more negative pressure in the room !

How about a Toilet that's close, or a Floor Drain that the trap has dried up on, or occasionally dry, maybe it's sucking in some sewer fumes?

Maybe the exhaust stack is cracked or got a loose joint, seal from where it exits back into the room, where the negative pressure is sucking some gas back in ?

That's about as good as I can do right now, but, all that negative pressure sure has me concerned.

Have a good Day !
S.W.

Thanks SW.

I don't have the tools needed to check the exhaust mix and I don't believe either of the technicians did either...I think I need to get a real technician with power vent experience and combustion analysis tools, although it was hard to find anyone that worked on oil last time I tried.....everyone was experienced in gas. Anyway, everything is ducted, the door I mentioned is the door upstairs that leads down to the basement and it is always closed. The combustion air comes from the basement space which consist of the 13 x 16 mechanical room and 26 x 50 basement. Definitely not sulphur like smell from drains. I'm concerned about the negative pressure also but I don't understand why the problem is not more consistent.

LL,

Just to make sure you understand, I'm just as clueless now, as when I read your first post !!
But like I said, we're just gabbing now.

YES, you need to get someone who can check those gasses for you, with the door open and closed! It's got to make a difference in the analysis, and one way or another (open or closed) you're burning fuel you don't need to be.

You said that the circulatory system was closed (ducted). so, where's the negative pressure coming from !?
I can't believe that you got SO much draw from your Furnace (burner) that it's powerful enough to pull a door closed.
Is that where the NegPres is coming from !?

Given you mentioned "oil", you must be in the North somewhere, and what I'm about to say may be ridiculous but....

You got to get that Negative Pressure settled somehow, and if I were you, I'd put a Fresh Air Duct to the outside, with Filters and Dampers, where you could control how much it drew in.

Now for the ridiculous part....
Outside air in Houston Texas, is NOT like it is in New York or somewhere up there !
We never hardly ever go below a +32°f around here, but when you get in the single digit area, I might be telling you to destroy your whole basement, or the piping in it anyway.

And, that'd be a pacifier, if you got some controlled Fresh into the area, you probably wouldn't smell the fumes, and get a much more controlled burn on it too.

My mind keeps going back to the same thing, and that's the NegPres, resolve that, and I think you resolve everything.

Have a good Day !
S.W.

I'm in the Mid-Atlantic region.......I also think fresh air for combustion would be a good idea. It is the extra large blower that is creating the negative pressure not the power vent or the burner. One technician even thought the blower might be pulling some exhaust out of the draft intake on the piping leading to the power vent. I did notice that the view port doesn't have a spring to keep it tightly closed so I taped it shut and I'm keeping an eye on it to see if that helps.
Have a nice day!

Livnlearn