Gremcat wrote:The internal chimney deal that goes above the fire and back down? I cleaned it when I resealed. Surprised the service guy that cleaned and lit it didn't. I will get the gauge and look into the other thing. All three chimneys have caps that are the same height. I couldn't figure out how the basement smelled like smoke from upstairs fireplace. I was worried about a leak between the two liners but the cleaner said it was them both being the same height and capped.
He is probably right. If your getting a smoke smell in the basement area when only using the upstairs fireplace, the chimney for the basement stove is down drafting the smoke/fumes from the upstairs fireplace. Your units require a certain amount of makeup air and If you don't provide it, it will pull it from anywhere it can. That is usually the largest opening which is that second flue.
You can try removing the chimney caps and put an extension on the upstairs flue pipe. You can do something as simple as setting a section of clay pipe over the existing upper floor flue. This will allow the smoke generated to exhaust higher than the basement flue which will hopefully stop the basement chimney from pulling the smoke down. However that doesn't solve the problem of that second flue pulling a downdraft to satisfy the makeup air needs of the house when burning the upstairs unit.
Easiest and probably the most effective is open a window near the upstairs unit or in the basment area. Your house is gonna get makeup air from somewhere and pulling it down a chimney is not the most desirable way to do that. If opening a window solves the problem then you can start a project of supplying outside air vent for the upstairs and downstairs units.
Congratulations for buying a "tight" house to save on heating costs.
Remember the old saying "no good deed goes unpunished."