Size of Flue of Chimney concerns

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ducker

Feeling the Heat
Apr 22, 2008
409
Leominster, MA
One installer for a Haman stove said if the flue is wider then 7x7" they will have to put in a liner as it's too large for a pellet stove. Why is this. Is this true? I've only heard one installer mention this to me when I have been discussing with different installers how I want to vent my pellet stove directly to my chimney replacing my wood burning stove.

So is there a real concern with venting a Harman P36 in to a 2 story chimney with a 8x8" flue?


And what would that problem/concern be?

Thanks!
 
It may have to do with improper draft. The large opening may cause an unwanted down draft. Where a pellet stove uses an exhaust fan to vent, the downdraft allowed by the large 8" * 8" opening may create smoke in the house. You are better off with a 3" or 4" liner to create a good updraft. If the power ever went out while stove is going, you are now relying solely on the updraft of the chimney flue to vent the smoke of the stove until the fire goes out. The chimney kits come with a plate for the top of the flue to restrict any downdraft. The kits are pricy at around $400 for a 25’ 3” stainless but you could buy the parts individually and save some money.
 
oh geesh... yea they figured something like an additional $1100 to line the chimney... Anyone else out there that can confirm this possibly of a backdraft in the flue?
 
I would use your own noggin to make such a decision.Personally I would chance it and if it was a problem....then spend all that money.And if it isn't a problem,then you will feel pretty good about your reasoning.Thing is,usually when the power goes out is when there is a storm and this is when you find these things out-'tween whats right and wrong.....but then again sometimes it wouldn't have made a difference anyways! My pellet goes to large stainless stovepipe,I think it is 6 or 7 inch-been so long...but it works grrrrreat!
 
So it's not like it isn't something they can add later.

Well the fact that I'm looking to move within 3-5 years and would most likely want to take the stove with me; further makes me NOT want to drop another 1.1k in lining the chimney.

Thanks for the input :)

-Mike
 
Ducker, you may pay more for a latter date,I decided to have the stainless pipe added same date as the stove was installed. My chimney had the same size flue 7x8 and the installer mentioned he would have to charge more if he came back at a latter date. Only an addition of $400 for pipe plus the install of $350.00 I feel I got away with this resonable, and piece of mind.
 
oc4man said:
Ducker, you may pay more for a latter date,I decided to have the stainless pipe added same date as the stove was installed. My chimney had the same size flue 7x8 and the installer mentioned he would have to charge more if he came back at a latter date. Only an addition of $400 for pipe plus the install of $350.00 I feel I got away with this resonable, and piece of mind.
Click to expand...

so you were tabbed for 750 for the install of the liner... I was quoted another 1100... seems like these guys are very vague on the prices they hand out for quotes.

I've called one place and received 2 different prices for an install.. very frustrating.
 
No, the $350.00 was for the installation of the pellet stove only. When he checked the flue size he recomended to line it.The $400.00 was for the flexable stainless pipe and cap. So for the total $ 750.00 well worth it !
 
oc4man said:
No, the $350.00 was for the installation of the pellet stove only. When he checked the flue size he recomended to line it.The $400.00 was for the flexable stainless pipe and cap. So for the total $ 750.00 well worth it !
Click to expand...

yea.. well for an additional $350 over the price of the rest of the install - yes I'd do it. but when he said $1100 additional over the price of the stove/install/parts just for the lining... geesh.
 
First of all, what is called an 8x8 flue is usually about 7" square in the inside, so that part is a little vague.

Pellets stoves are forced draft - they do not rely on natural draft of the chimney.

A smaller liner will heat up quicker...even with forced draft...than a larger and cooler one, so lining is always a good idea.
 
Webmaster said:
First of all, what is called an 8x8 flue is usually about 7" square in the inside, so that part is a little vague.

Pellets stoves are forced draft - they do not rely on natural draft of the chimney.

A smaller liner will heat up quicker...even with forced draft...than a larger and cooler one, so lining is always a good idea.
Click to expand...

Ah, very interesting... But what will help with the liner heating up quicker, simply added draft for the exhaust?

I should of included how I derived my 8x8 flue... My chimney sweeping company wrote that on my paper work, that I have an 8x8 flue. If it's really 7x7, then I'm, as the installer stated "boarderline" they would rather a 6x6 or smaller flue, if I was not to install a pipe.

So all that being said, what is to be gained by adding a liner? The liner will heat up quicker, but why do I care about the temperature of my flue?

Again, it might be very obvious but I want to make sure I understand.

Thanks for replying.
 
I guess the key is back-draft smoke coming back in to the house on cold and windy days. The installer did say it was border line but for the cleanliest and smoke free he thought it would be best to have it done.Knowing what I know now it would have been an easy install to line the flue but the price was right.
 
I just had a liner installed in my chimney. We have a two story house, and the pellet stove is on the first floor. The supplies for the lining were about $450. This does not include labor. The TOTAL labor for the stove install, including lining the chimney, was around $500 IIRC.
 
You need to be concerned about the temp of your flue, anytime you burn something you create water vapor, if the temp of the flue is to low the water vapor will condense in the flue. Flue gases by nature are rather acidic, and will eat away and damage the flue. Even though running a liner is more expensive it is the proper way to go. The company that is recommending the liner is really looking out for your best interests, there are also safety factors involved in proper flue sizing. I know on my stove the maximum flue size without a liner is 6x6. That why I went through the wall and up. If your stove is installed improperly it may give your insurance company a reason to not pay for house damage, even if the stove was not the cause. Insurance companies can be funny that way. If it were me I would have it done right the first time. Hope this helps.
 
Probably the main concern is whether the flue is cold enough to actually reverse and be working against your draft rather than for it. As you can imagine, it is a lot easier to heat a smaller round pipe than a large square masonry mass. If the chimney was interior to the house, you might be OK, but in terms of an exterior chimney in colder climates I have to agree with the sweeps and installers.
 
I`m vented into a 7" SS round (interior) insulated chimney used with my former wood stove. It drafts nicely but I would have to believe even an 8" SS round insulated interior chimney would still work nicely without having to install a liner. Square masonry chimneys especially those with large 8X8 flues on an outside wall are always more prone to draft and condensation problems.
That said , a properly sized flue has to be the ultimate way to go.
John
 
Pook said:
ducker said:
One installer for a Haman stove said if the flue is wider then 7x7" they will have to put in a liner as it's too large for a pellet stove. Why is this. Is this true? I've only heard one installer mention this to me when I have been discussing with different installers how I want to vent my pellet stove directly to my chimney replacing my wood burning stove.

So is there a real concern with venting a Harman P36 in to a 2 story chimney with a 8x8" flue?


And what would that problem/concern be?

Thanks!
Click to expand...
2 story! i bet its got adequate draft, if not too much!
guess i'd open chimny entrance,when chimny aint hot/cool by lack of fire & wind aint blowing, stick a lit match in it & watch.
Click to expand...

Well just give it a try. You can always install a liner later.
Of course you can do the math and see that venting a 9 sq inch stove pipe into a 64 sq inch chimney is quite a difference and stretching the possibility of it working / drafting properly but you seem intent on doing it . Let s know what happens.
John
 
The chimney is on the interior.

Right now I have my wood stove still connected to it. So I guess I could put a match in there and see... my guess is that I'm waiting to see what happens to the flame. if it angles towards the back of the wood stove, my draft is strong. Otherwise it isn't and I should seriously consider a liner.

I know when running my wood stove, the only times I had any problem with smoke in the house is when the chimney was cold and I was just starting a fire (and it's windy)... or it was extremely windy out. Things I'd imagine anyone would have problems with in regard to an older stove with a leaky gasket.


So much great info/data... so it sounds like the best way to go would be to line it. but at an additional $1100 for a liner on a chimney I won't be utilizing after about 5 years doesn't seem like the best way to go for me.


So I guess what my overall feeling is... If it's still doable, and isn't that damaging, I'd rather go with out the flue.
 
If you found this forum you are most likely smart enough to put the flex pipe in yourself. I just did mine on a two story and it was easy as long as you can get to the roof. The cap and plate that goes on the top of the flue is real easy to do with a little high temp silicon. I used the clear made by rutland. You could always try a short pipe off the stove into the flue and see how it works. The true test would be on windy days or rain. You could also get the stove going and then unplug it to simulate a power outage to see if the house is gonna fill with smoke. Better off knowing now rather than later. I still recomend investing the $400 bucks into the flex SS liner and cap and doing it yourself. Hell, if you lived close to me I would do the install for $100 as it is no big deal. You have to like going up on your roof though. Good luck!!!
 
haha... finding a forum is easy for me... building a PC from scratch; easy for me.

cleaning my gutters on top of my 2+ story house; not easy for me
looking down a 2+ story chimney and installing a liner.... totally not easy for me.

:)

Yes, a shame you weren't closer :)
No thanks!!
103boutelle.jpg
 
Ooooooooo....I'm not real thrilled about that roof....Yikes!!!!!! Little steep for me. You could always try from the inside up and just feed it up the flue.

PS: Your only about 52 miles north of me....not to bad.
 
ok... just to check back on this...

So what should I do.. I really not want to go the route of investing another $1000 for a pellet stove, but I really do want the pellet stove vs. a conventional wood burning stove.

I can't be 100% sure of the flue dimensions, and I'm not about to climb up on the roof to look down ;)

I'm tempted just to call the company in and have them do the install; I'm figuring if the chimney isn't proper, they installer would say something, or tell me I have to install the liner definately.

I guess, I'm just in an odd position, since I've heard both sides... I can do it with out the liner, or with it. If money wasn't a concern I'd be all for the liner and the precautions. But, that isn't the case.

Thanks for any final feedback!

-Mike
 
I`d give it a go without a liner.
Since the chimney is inside and assuming it contains a good ceramic flue you shouldn`t get into any trouble. The worst scenario being you`d find out whether or not you really need one.
You can always hire a chimney sweep to clean and inspect it and have him install the liner for you while the ladder is in place.
John
 
well shouldn't even a pellet stove's chimney be swept once a year or so anyways?!

I'm wondering how else I'd know if there was ever an issue with the flue corroding or whatnot.
 
Having one`s chimney cleaned and inspected probably holds the record for being the most overlooked and rarely accomplished task in home maintenance history. (Other than those folks who heat with a wood stove)
John
 
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