Poor Draft - Chimney Height

eddie wrote:I was thinking of adding a foot or foot an a half of chimney height to try to improve draft. The height of the chimney is 30' to 35'.

Since (all other things being equal) draft is linear with respect to chimney height, if your chimney is 32.5 feet tall and you add one foot making it 33.5 feet tall, then your draft will improve by only about 3.1%. You probably wouldn't even be able to notice it on a manometer.

Adding 3-1/2 feet would gain you about 10% better draft.

30' of chimney should draft well. Whatever the problem is, it isn't the height of the chimney.

coaledsweat wrote:30' of chimney should draft well. Whatever the problem is, it isn't the height of the chimney.

It's highly likely due to the low pressure zone of the home being in the basement as others have already pointed out. Letting in some fresh air to raise (or perhaps more properly, normalize) the pressure in the basement is probably the easiest and most straight forward solution to improved draft in this case.

Yes, ifn you have 30 ft of chimney, then draft is not the problem.!!! When you look at an active coal bed, look for "dead spots". These are areas of the coal bed not burning. They will be dark areas lacking of blue flames and or red coals. If this is the case, which I highly suspect it is; then you need to poke very vigorously in order to break up & dislodge the ash. IE: open the ash pan door, give it 5 min, it should be hummin right along. Now look for "dead spots", Take your poker and rake it like you ,mean it. Ya ain't gonna hurt nothing because only ash is gonna fall through the grates. Note: close ash pan door before raking or shaking, otherwise dust will get ya. Now first poke and rake like hell, this will settle the suspended ash. Now with both doors closed shake until "entire" ashpan is illuminated.!! Ifn shadowed areas exist in ash pan then a more aggressive approach is necessary. Vacating ash is paramount for an even burn.
Jim

eddie wrote:My flue is 6" X 6" ... I was thinking of adding a foot or foot an a half of chimney height to try to improve draft.

Nope, no room in a 6X6 flue to add an insulated liner. Adding to the height MIGHT help but only because the rule of thumb is AT LEAST 2 feet above anything within 10 feet horizontally, and you don't have quite that clearance above the roof. I have found, when dumping my ash pan into a trash can in the yard, that air currents are really strange, and if I stand close to the can it doesn't much help whether I am upwind or downwind, the ashes swirl all around me. So you could be getting interference from the roof or trees or ??? close to the chimney.

6X6 is a smaller size flue, especially at lower draft times.

Could this be my problem. I start off with 6" dia. stove pipe, go into a 8" dia. thimble, then back to a 6" X 6" flue. I also use 2 90 degree elbows, one at the stove exhaust and one going into the 6" to 8" enlarger at start of thimble. Thanks for all the help!

eddie wrote:I got poor draft. My chimney opening is 1' 2" above the peak of my roof. Will adding another foot improve my draft much?

If you are getting poor draft presently it could be because its warm outside. Did you see (and measure) poor draft during the winter season? If you were measuring it with a manometer, what sort of draft are you considering poor?

eddie wrote:Could this be my problem. I start off with 6" dia. stove pipe, go into a 8" dia. thimble, then back to a 6" X 6" flue. I also use 2 90 degree elbows, one at the stove exhaust and one going into the 6" to 8" enlarger at start of thimble. Thanks for all the help!

The exhaust slows down when the pipe gets bigger around. Then it has to speed up when it gets back to the smaller size. This helps dump flyash in the thimble and choke off your draft. You should be able to slide a 6" thimble right into the 8", just make sure the end of it is even with the interior chimney wall. Even with a six inch flue, 30'+ is a lot of chimney. Your house may be too tight requiring a vent to make up air. You may have a basketball or racoon's nest in your chimney. Is this chimney taller than the rest of the home? A home with a bad case of "stack effect" will make a good chimney a corpse.

Eddie, do you have an outside cleanout door? You have more than enough height, something else is wrong.

I have no clean out door. I reach in from inside the basement to back of thimble and down to pull up soot whatever. So at the back of the thimble, the opening in the chimney goes down about a half foot
and I haven't tried to clean out further down. This half foot down opening couldn't possibly be the problem. As I said in the past, the chimney is 6" X 6" and about 30' high.

Are you having draft failures during warm weather? A manometer would be a big help.

Have you tried the extra secondary air trick to help the draft move along? It was suggested earlier in this thread.

I haven't tried secondary air that may help or be the solution. I have an oil burner and bought the chubby to burn coal for Dec. Jan. and Feb. by disconnecting the pipe to the thimble from oil burner and connect the chubby using stove pipe. 3 years ago I tried in Nov. and had trouble with draft with monoxide and sometimes smoke detector going off. So I would quit and use the oil burner. Every year I would try again varying things and get same result, apparently poor draft. I was going to hook up a manometer and get a better idea of what's going on. Thanks for the help.

eddie wrote:Could this be my problem. I start off with 6" dia. stove pipe, go into a 8" dia. thimble, then back to a 6" X 6" flue. I also use 2 90 degree elbows, one at the stove exhaust and one going into the 6" to 8" enlarger at start of thimble. Thanks for all the help!

Are you sure it's a 6x6 tile? would be hard to shove a 8" thimble into a 6" liner?

The 8" thimble touches the opening of the 6' X 6" flue. There is no liner in the chimney. The interior sides are brick. This chimney was built in 1975 for the oil burner installed in the basement.