Chimney advice needed

[r0GuE]

Three years ago I bought a 50 year old ranch style house. The chimney was in fine shape with an 8” ceramic liner. At the top of the chimney are 4 brick pillars that support a cement slab that acts as a chimney cap. All of this was in good shape.

I had the old natural gas fired boiler style furnace replaced with a new one @ 136,000 BTU. The furnace has a 7” metal exhaust that runs to the wall in the basement and feeds into the chimney.

Three years later, my chimney (especially the 4 brick pillars and the cement slab) are falling apart. /forums/images/graemlins/mad.gif I had a chimney guy tell me that the exhaust gasses are filled with a hydrochloric acid and that this is causing the damage. He said the chimney should have been lined with a stainless steel liner and insulating pellets poured around that to fill the remaining gap. Because it was not, condensation is getting on the inside of the chimney and the acid is going to work on the mortar.

I’m not sure how the problem didn’t exist for 50 years and now it does. I think the old furnace was bigger so that might explain why I get condensation in my chimney now, but I still do not understand why the brick and cement parts above the chimney lasted for 50 years and fell apart in 3. They would have still been cold even though the chimney tube may have been kept warmer by the larger less efficient furnace.

Anyway, not I’m in a real bind. The chimney sweep guy tells me that the chimney is too small for a 7” liner. The furnace requires a 7” exhaust. All I can think to do is to replace the furnace again ($$$) and size the new one smaller. This would allow a 6” exhaust and it would run more often giving the chimney a more consistent heating.

I’m really hoping for some TBN expertise here. Thanks in advance for any help or advice.
/forums/images/graemlins/confused.gif

 

[RobS]

rOGuE, sorry to hear of your difficulties. Your furnace guy is right, the newer furnaces are harder on masonry due to much lower exhaust gas temps which lead to more condensation and less non-combustion air exiting with the exhaust.

I'm surprised they used your chimney at all. Around here almost all newer furnaces use PVC exhaust and exit right out the rim joist of the house (assuming basement). The furnaces have gotten so efficient that the exhaust gas temp is relatively low. There is a lot of condensation but they usually accomodate that with a specific drain line for it.

Come to think of it, our hot water heater even uses a PVC exhaust. The only things up through our roof are the plumbing vents.

You're probably out of luck with the chimney. I'd ask the guy about the PVC route /forums/images/graemlins/smile.gif

 

[thcri]

I don't know what your codes are but around here when changing an appliance with an old chimney like yours we have to put a liner in it. We don't have to do the pellet thing like another poster pointed out. Your flue gases are way cooler than the old appliance thus you have condensation. This is what is eating at your chimney. Call the guy back and tell him he did not complete the job and now your chimney is being destroyed. If you have a local inspector you may want to inform him also. Other than that, an attorney would be the next step if you want to take it that far. But the first thing is to get a liner in there.

murph

 

[beenthere]

I don't understand why the company that put the furnace in didn't go the pvc venting route. Maybe to keep the original cost down (but pay me later?).
Seems the chimney sweep guy also didn't have the best answer either (not sure why the pvc up through the chimney wouldn't work too, but it may be too long a run).
The last thing I would think of doing at the moment is replacing the furnace just to get a smaller flue pipe up the old chimney. Look to go the pvc route to vent the new furnace. How you do it, depends on if you can get some straight answers, and get the furnace guy by the ear (I know how difficult that is too).

 

[Hakim]

Sorry about your chimney troubles.

We had a furnace chimney and could not run a wood stove off the same chimney. So, to comply with code, we installed a "metalbestos" chimney for the wood stove. Worked like a charm.

The key point to metalbestos is, if you have to route it inside the house at all, along walls, thru roofs, etc, it does not get hot hardly at all. You only need an inch or two of clearance. I felt a lot safer, and the kids didn't get burned.

Metalbestos link There are other probably similar products, but Metalbestos is the best.

Metalbestos is recommended specifically for wood stoves, but I see no reason why it couldn't be used to vent a furnace. Ask the chimney guy. Or maybe a TBNer will know.

 

[r0GuE]

This is a pretty big furnace boiler and not all that efficient (82%?). Anyway, the outlet is 7" aluminum pipe. I do not think this is like those 96% jobs that can use a 3" PVC.

 

[Freds]

Exactly rogue. You never mentioned the efficiency and it's only the high efficiency models (98%) that use PVC for the flue exhaust. They are also limited in flue length and take into account how many turns it makes.

If your flue gases are not hot enough to vent properly you might see about installing a power venter in the flue pipe. That would be cheaper than installing a separate flue outside and I would go with the chimney liner, too. If you do install a new flue out through a wall, gas furnace flue can typically be double wall pipe when it gets outside or up through the attic. If you still have the instructions there is alway a whole section on different ways to run the flue and where it should be in relation to roof lines and such.

Flue pipe for a wood burner should be triple wall pipe, also called "all fuel", in order to keep the low temp flue gasses (compared to middle efficeiency furnaces) hot enough to vent. The inner wall is typically stainless steel. That stuff is VERY pricey and normally only used when the flue is run into a colder environment like mentioned. Metalbestos is a good, common brand, but I never saw one as better than another. The joints are just different, so you need to stick with one brand and can't mix and match.

Good luck!

 

[MarkLeininger]

I installed a new furnace a few years ago and installed the stainless liner myself. It was cheap, something like $75 if I recall. It comes collapsed like a slinky and extends as you pull on it. It's double walled, but it's so thin you can't really tell.

I would knock the chimney cap off and work from the top. Tie a wire to the bottom of the liner and have the person in the basement pull it down into the basement. Then it mates with another piece that sticks out of the wall that your flue pipe gets inserted into. It comes with a little cap that attaches at the top of the chimney to keep out rain and birds.

I think I'd try it with 6" to see if it drafts properly. Either it drafts or it doesn't. If it does you're done, if it doesn't you only lost $75 and some of your time. You have to get that decaying cap off anyway. You might try adding a power vent if it doesn't draft. I'd put a carbon monoxide detector in the basement anyway, it's good insurance even with the best installation in case something goes wrong. Don't put it right by the furnace or you can get some false alarms, but put it 10 feet away or so. Good luck.

 

[PineRidge]

If you do decide to go the route of the stainless chimney liner use caution when stretching or expanding the liner. We had more than a few technicians pull spiral liners apart by stretching them beyond their limits.

Sometimes even making the bend at the bottom of the chimney liner where the liner needs to make a 90 degree bend to enter the basement can create a problem.

 

[Youare]

I have an 8" square tiled chimney that was used for a woodstove for close to 30 years. The tiles were starting to show some signs or decay, wood stove smoke has some nasty stuff in it also.

The solution I used was a 20 gauge 316 stainless steel liner that was not flexible. The tee which connects the horizontal to vertical pipe attaches in a manner where you don't have to make a hole in the chimney.

I installed the whole business in less than two hours by myself, could have been quicker with someone else on the roof and one person in the basement to direct the lowering operation.

Randy

 

[r0GuE]

I believe that the flexible ones are actually aluminum and the solid ones can be either. The cost of the solid stainless pipe is pretty high, but ti sounds like the way to go. Hope I can get a 7" run in there. /forums/images/graemlins/frown.gif

 

[r0GuE]

</font><font color="blue" class="small">( The solution I used was a 20 gauge 316 stainless steel liner that was not flexible. Randy )</font>

Where did you get this pipe, and how much did it cost?
Thanks,

 

[PineRidge]

Here is a link to the flexible stainless chimney liners that I mentioned. stainless liners

 

[r0GuE]

Thank you so much for the link. This is going to be quite helpfull. I will call them on Monday. Local chimney swweeps want to line it with hard line at around $2500 and now is just not a good time for that huge expense. /forums/images/graemlins/frown.gif

At the same time, I was loosing alot of sleep. I was told that flexi liner is all aluminum and wouldn't last in the acid. Well now that I see stainless flexi liner, I can figure it would have to last for much longer than 6 months. Did it seem hard to install. I'm afraid it would tear on the morter edges between the ceramic pipes.

 

[PineRidge]

Rogue I think you would be hard pressed to damage the stainless liners. It's the aluminum ones that tend to damage more easily. If you install one of these it should take care of your condensing problems if it is properly sized. Condensation problems can do lots of damage as it eventually breaks the mortar down.

 

[Egon]

We installed a wood burning fireplace insert last fall. It uses a flexible stainless steel liner. 30 feet cost about $550. Can.

One fellow installed it by himself by lowering it down from the top.

Our chimney flue is larger than 8 inches.

The liner is flexible in that it bends but does not really accordion.

Had the installation done by certified personnel for insurance purposes.

Egon /forums/images/graemlins/grin.gif