Smoke siphoning thru Water Heater Flue

[knute_m]

Smoke frequently siphons down my gas water heater flue when either the wood furnace and/or woodstove are burning -- which is pretty constant this time of year.

My masonry/stone chimney has three flues -- one for my combination wood/gas furnace, one for my wood stove, and one for my gas water heater. The flues are about 18-inches apart at the top. It's about 35-feet from the top of the chimney to where furnace and water heater connect into their respective flues in the basement, and about 24 feet from the woodstove to the top.

Both the furnace (a Yukon Husky gas/wood furnace) and the woodstove (a high efficiency Quadra-fire) are pretty clean burning.

I get temporary releif if I run hot water long enough for the water heater to start, thus getting the air current in the flue going up rather than down.

Does anybody have any ideas how to prevent this? It's darn smokey in my basement tonight. It is about 12 degrees outside and snowing. I'm burning both the furnace and woodstove.

Thanks,
Knute

 

[kenmac]

If your water (I guess nat gas ,propane) isn't vented into the same flue as your wood heater. I wouldn't have any idea as to why this would be happening unless you have a leak in the flue seams ( the one the w.h vents into & the 1 wood heater vents into) To solve the problem , you could run vent pipe for the w.h. through the flue that the w.h. is vented into (all the way out the roof ) & install a vent cap . provided ,the w.h. is vented into that flue by itself. Does this smoke come out around the draft hood or draft diverter on top of the w.h. ?

 

[hockeyhead]

first thing I'd do is crack a window or vent in the basement, sounds like your home is sealed too tight, you are drawing air for you wood furnace and stove from down your hot water tank flute . They manufacture air make-up systems for such condition, do a search. contact your Quadra-fire dealer. I have a fireplace insert from them, works good, they do have a system that will draw outside air for the combustion required, I want to say your furnace manufacture does also

 

[kenmac]

This was my 1 st thought ,but he would have to have a neg. pressure in this area & this would cause flue gassess to be pulled down the w.h. vent all the time. Is your furnace , wood header using up all the air in your basement or the room where they are located. If so you will have to introduce outside air to that area to offset the neg. pressure

 

[eanjay]

Whenever wood stoves and other heaters come together in a 'common' chimney, the the wood stove should be the lowest connection inserted in the flue. This is so that gases from the other devices don't come back at you through the wood stove.

If the smoke from the wood stove is coming back down to the basement, it would seem that you are not maintaining a warm enough stack temp. to provide an 'up-draft'. This is why the hot water heater seems to improve things. Cold air is forcing the smoke down. Try increasing the wood stove rate of burn to improve this.

EanJay

 

[Highbeam]

It sounds like you have a proper chimney with an independent flue for each appliance all the way to the top. Great. Now you are sucking smoke through a gas appliance flue all the way down from the chimney cap and into the basement. That's some serious suckage and enough to make a coed......... I digress, it is amazing that your situation allows for this. Are you absolutely certain that smoke is actually coming out of the gas appliance flue backwards and not just a backdraft situation on your quad? Did you see the smoke come down?

Crack a window. If that fixes it then it is time to look for a more proper ventilation solution to equalize the pressures.

Quite a sucky situation... Be sure your CO detectors are working and in the right places to protect youwhile you sleep.

 

[Egon]

As others have stated, you may need some air make up in what I would assume is the furnace room. [ I'm assuming this room contains the furnace and hot water heater ]

There are commercial units for make up air but a simple one is to bring a pipe into the house from outside and end it in an open topped 5 gallon bucket. If there is low pressure air will enter. If not no cold air enters as it is stopped by the 5 gallon bucket.

 

[knute_m]

Thanks for all the replies -- and giving me something more to think about. This is only our 2nd winter in this house.

And yes, all three flues are separate in the chimney. The furnace flue is about 24 inches higher than the gas flue. They are the two outside flues. The woodstove flue is in the middle, both in location and height. The massive chimney is half inside, and half outside the house. This time of year, it would take more heat than I could generate to warm the outside sufficiently (It was 8 degrees F this morning when I went out to plow the driveway.) But, we generally run the wood flues at 400 to 600 degrees F where they enter the masonry.

The Quadra-Fire receives outside air, and it is on a different floor from the furnace and water heater. Great little wood burner. This is our first season with it. It is amazing how much heat it eeks out of a piece of wood, with virtually no smoke. (QUADRA-FIRE: Products - Wood Fireplace Stoves)

But, your comments changed my thinking. I think I see the problem. My Yukon Husky (Wood Furnace by Yukon-Eagle) uses an 8-inch flue pipe with a barometric damper.

The barometric damper is about level with the top of the water heater, and about 3-1/2 feet away. When the wind blows, or when the thermostatically controlled damper on the furnace closes down, the 8-inch barometric damper opens to pull room air up the furnace chimney so that the furnance burn rate remains relatively constant. I'm guessing it is getting its air from the water heater flue.

The flue on the water heater is shaped like a funnel, and sits on spacers about an inch above the water heater -- so it is essentially wide open all the time.

So, I guess I've got to find a way to feed air to the barometric damper. For right now I've set the barometric damper so that it doesn't open quite as easily -- not my most favorite idea.

I think I am going to try Egon's idea of a pipe and bucket. I just have to figure out how to get to the outside.

And yes, we do have CO2 and smoke detectors on each floor.

Thanks again for all your suggestions.

Knute

 

[dmccarty]

We did something similar to what Egon suggested. I have read various opinions about bringing in make up air. Some for and some against. My FIL has a pipe running under his slab to the front of the fireplace. When the fire is running you can feel the air rushing from the vent into the fireplace.

When we built the house we had a 6 inch pipe put under the slab that ends at the hearth right behind the wood stove. The pipe has a 90 degree bend to get to the top of the hearth. The stove can be connected to the pipe but it was a PITA to do so. The connection just let the air into the space under the stove with the ash pan. I just left our pipe unconnected and it works fine.

When the stove is running you can feel the air being pulled into the house if you put your hand over the pipe opening. On the outside of the pipe I took a cap, drilled a bunch of holes and then put in a couple layers of screen to keep bugs out. Works fine. If there is no fire the pipe does not draft and no air comes into the house.

Egon's solution would very likely work if makeup air is the problem.

Later,
Dan