Always smoke in the house

[bill.mackinnon]

New to the forum. I hope someone can help me. I'll lay out my situation with as many details as I can.
Small, single story house. Wood/oil combo furnace in basement. Outside chimney on west end of house (wind almost always from west). Chimney only a foot or so from roof. Trees close to house at west end. Basement door and window almost always open to outside air.

Unless the fire is raging and the weather is clear, I'm always getting smoke in the house. It comes out the loading door when I load, (usually) and comes out the chimney and crawls around the house, looking for a way in. I even smell smoke coming out of the registers sometimes (I assume it gets in the house and is being recycled by the cold air ducts.

I'm going to try a chimney extender but I'm not convinced that is all my problem. I think I must have negative pressure in the house, but my basement is usually open except in the coldest weather. I probably have inadequate cold air return but I don't know if I can fix that.

Any advice is appreciated.

 

[heaterman]

You probably identified the problem in your last sentence. If the blower on the furnace can't get enough air through the return ducts, the basement is going to go into a negative pressure situation where your chimney can "reverse" and you'll pull smoke into the house. This needs to be corrected now if not sooner as it can lead to CO in your house. That will ruin your day..........that is, if you wake up.

 

[maple1]

Chimney only a foot from the roof throws a flag here.

 

[brenndatomu]

Yup, chimney needs to be 2' taller than anything else within 10' and 3' taller than where it passes through (past) the roof. How tall is the chimney, overall? Just out of curiosity, what kind of furnace do you have? Also, why is the basement door/window usually open? I wonder if that could be helping to set up a "chimney effect" on the whole house, cold air in the bottom, warm air rises and pulls right out the top?
Is there a barometic damper on the flue pipe? Those can need a lot of outside make up air, cracked window near the furnace could be good for that...
Man, I'm having trouble understanding how too small return air ducts could pull a neg pressure on the house?! Too small ducts would pull neg pressure on the furnace blower box and maybe the first few feet of duct, but after that, nah?! Besides that, a centrifugal fan (blower) won't pull much "vacuum" and will "self balance", in other words, they can only "put out" as much as they can "suck in"
If you wanna test the too small duct theory, I'd block part (not too much, don't wanna overheat the firebox!) of the filter with some plywood, that would relieve any "neg pressure" on the ductwork itself and the house.
I bet extending the chimney works for you.

 

[heaterman]

May not be the case here but usually "too small" equates to a duct system that may be partially done, leaky, maybe not even fully connected to the furnace. In those cases the blower can easily cause a negative pressure in the basement. It's just the first thing I would check for reasons of safety seeing as how smoke is getting in the house somewhere.

 

[arbutus]

What type of chimney?
Double wall with solid insulation, triple wall air insulation, masonry ... ?
We struggled with a triple wall air insulated chimney for several years. Negative pressure caused by heavy wind from the right direction and a very leaky house would draw smoke down the air spaces in the chimney.

You can fabricate an outdoor air inlet and plumb it near the furnace with dryer vent parts or 3" pvc or similar.

 

[brenndatomu]

May not be the case here but usually "too small" equates to a duct system that may be partially done, leaky, maybe not even fully connected to the furnace. In those cases the blower can easily cause a negative pressure in the basement. It's just the first thing I would check for reasons of safety seeing as how smoke is getting in the house somewhere.

Ah, OK, that makes sense. Thanks

 

[bill.mackinnon]

The chimney is about 14 feet high. It is masonry. Wind is always from the west, so it blows the smoke along the length of the house. I do not have a barometric damper on the system.

About fabricating an outdoor air inlet: Are you talking about an extra source of cold air to the cold air plenum?

 

[heaterman]

If your house is fairly tight it's sometimes a good idea to run a 4 or 6" pipe right from outside into the return duct or plenum for ventilation and to prevent any negative pressure situations from developing in the house.
Note that I said if your house is fairly tight......if it's like mine you don't have to worry about it.

After seeing your chimney description, I'm guessing that getting it extended up is going to help you out a bunch. As was stated above, code is 2' above anything within 10' horizontally. Does you chimney have any type of liner in it?

 

[STIHLY DAN]

Are the return ducts in the basement? !4 ft is kind of short for a chimney, many stoves want 15 min. Is the wood dry? Wet wood is smoky and lazy too.

 

[bill.mackinnon]

The return ducts are in the basement. The wood is not as dry as it should be. It was cut in the springtime.

 

[Fred61]

You also mentioned that you have trees on the west side of your house and that the wind prevails from that direction. It's not unusual for the wind to blow downward after being pushed upward by trees. Depending upon whether they are evergreens or deciduous, you could see a change when the leaves are completely off the deciduous trees. This can sometimes be corrected by a chimney cap although there has been much evidence provided above to conclude that you may have several forces working against you, ie wet wood, combustion air supply, reduced draft from short chimney, negative pressure, etc, etc.

 

[maple1]

PIctures.

 

[STIHLY DAN]

Biggest of the problems are the wet wood combined with basement return. Get that return out of the basement, and add a supply to the basement. That would be a huge help.

 

[bill.mackinnon]

I'm not sure what the alternative to basement returns is. The return registers are in the house, but the ducts run through the basement.

 

[brenndatomu]

I think there may have been some confusion about that. If return ducts pull out of the house, then that is fine. Are there any supply or returns that do vent to the basement directly?
What kind of a furnace are you running bill?

 

[bill.mackinnon]

I think there may have been some confusion about that. If return ducts pull out of the house, then that is fine. Are there any supply or returns that do vent to the basement directly?
What kind of a furnace are you running bill?

No supply or return in the basement. I can't recall the brand of furnace. I'll look when I go down.

 

[brenndatomu]

After thinking about this a bit, it doesn't sound like this is a new install, so, if it didn't do this before, maybe there is a new problem. All the things mentioned before could be contributing to the problem, but, I wonder if the firebox and/or the secondary heat exchanger may have cracked? That would give you a smoke smell in the house all the time. Dangerous, could be giving you some bad fumes too!

 

[bill.mackinnon]

The install is a few years old. It has always done this. I don't know if it is worse, or if we are just less tolerant of it.

 

[brenndatomu]

Oh, OK, that's good, it's probably just one or more of the previously discussed items then. Less catastrophic for sure! Still wouldn't hurt to have that checked out though, to make sure there is no leaks from the firebox/heat exchanger.

 

[bill.mackinnon]

Yeah, it has been on my mind. It's a monster job to tear it down but if extending the chimney and piping some outside air to the cold air plenum doesn't fix it, I'll have to have a look.

 

[brenndatomu]

Regarding your earlier statement, your nose (or at least mine did) does get more intolerant of wood smoke in the house after a while, especially after an "incident" or two!

 

[bill.mackinnon]

you know what really got me? Going a way for a few days, and opening the suitcase and smelling the smoke on the clothes.

 

[hobbyheater]

There is an simple test you can do to determine if the heat exchanger is cracked or burnt through .
Let the wood fire go out , and turn the oil thermostat all the way down so the oil burner will not come on .
Let the house temperature drop to 60 degrees , this should give all the duct work throughout the house time lose any possible trapped fumes.
Turn the oil thermostat up to 70 degrees , so the oil burner fires continuously .
Go to the floor heat vent (register) nearest to the furnace and if there is any immediate hint of oil smoke fumes , you have a crack or pinholes in the heat exchanger.
No immediate fumes the problem is elsewhere.


This is a 35 year old combination furnace.


Side profile of the heat exchanger removed from the housing.


The top of the wood burning chamber is almost burnt through, possible pin holes .


Top of the oil burner section severely cracked .

 

[brenndatomu]

you know what really got me? Going a way for a few days, and opening the suitcase and smelling the smoke on the clothes.

Man, that stinks! No pun intended, well... maybe it was.