Professional Member*
Just had this problem presented to me from a student and thought I would share the story and see if anyone would like to comment on a solution, or what is causing the problem.
The homeowner has a fireplace insert, more like a wood stove. It doesn't have any type of blower. The homeowner uses it all winter long. I guess they think it is saving them fuel but it is not a sealed unit and gets all its combustion air from the living space.
Last fall the HVAC contractor took out their standard vented furnace and water heater and installed a 90% furnace and electric water heater. The furnace and water heater were in a separate tile liner in the same chimney with the fireplace.
Ever since they stopped using the fireplace this spring or at starting using it less, they are getting constant smells in the house and the fireplace chimney is drawing into the house. This didn't use to be a problem. When they turned on their A/C the spillage and smells got worse. They do sometimes use the fireplace when the A/C is running but that's personal preference.
To date the contractor added some outside make-up air to the duct system, tried to reduce the return air in the room and increase the supply air and the problem hasn't improved. It is an older 2-story house that is loose. Tightening the house is not an option at this time.
As an HVAC contractor, being told they caused the problem, what would you do? Hearthman, I know you understand this better than myself, but let's see if anyone else wants to think this out and figure out why this is a problem now and what could be done to alleviate the problem.
Don't use the fireplace, leave all the windows in that room open and tightening the house are not options. This is certainly not your normal summer A/C problem.
captain CO
AOP Committee/Professional Member*
Keep the fire inside the fireplace.
Professional Member*
Lock top chimney cap or line it first option being much cheaper
For some reason I learn more with my mouth shut
Regular Guest
At this point I have more questions before I could state with confidence an answer. I'll have to watch this and see if we are thinking alike.
Professional Member
sounds like the chimney/liners are damaged. also with the damp spring we have had, the odors are gonna stick around more.
Professional Member
A 90% furnace is not supposed to be in a chimney. It needs to be direct vented. That will solve all his problems. Not only condensation, but odors will result in a chimney vented 90% furnace.
Professional Member
good call, but I'm guessing they no longer use the chimney that that the old furnace and water heater were in.Originally Posted by oil lp man
but maybe your right, those "contractors" can be real winners =/
Professional Member*
The old furnace and water heater were vented into a separate liner which is no longer in use. The 90% furnace and electric water heater do not use the old liner. Sorry, I did not explain that clearly.
captain CO
Professional Member
Sorry. I had a few brews when I answered the question the first time.
It sounds like the chimney liner is oversized now that the old furnace and vented water heater is removed. I would have a first class chimney inspection to make sure the liner is intact and appropriately sized.
I would think the colder air in the house with the AC running would make the draft up the chimney worse. That might explain the worsening odors when the AC is running.
Professional Member
Just to throw it out there to clairfy with the way it was explain would a negative pressure in the house be a cause and what I mean by that is that instead of air venting or escaping out air is getting stucked back in someway that the chimney odors/gases would come back in home? just a question. Interesting stuff
Professional Member
Yes. Leaky AC supply ducts in the attic allowing too much air removed by the return air from living space.
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