Questions: Pellet Stove install into existing through-wall connection

[moerdogg]

I have purchased a Harman XXV to replace an old wood stove in our house. The wood stove did not have a sufficiently large hearth, and the chimney is slightly too short for a good draft. The chimney has an 8in flue liner, and per the Harman install manual that should work okay for the new stove.

My issue is on the inside of the house. The previous owner installed the wood stove and used what looks like an 8-inch wall thimble, pretty much identical to this. Only difference is it doesn't have the 13" long extension into the room, it's more like 3-4in. The dimensions are otherwise identical. The installation does not appear to have been done correctly (at least compared to the (broken link removed)). There was a galvanized pipe inserted maybe an inch or two, and sealed with high-temp RTV. You can see the pipe and thimble below:

I have 3in pellet pipe for the new stove. The hole is 23in above the hearth, while the new stove outlet in 8.75in. So I have a T with cleanout and stove adapter, into an 8in adjustable, into a 90 to head into an adapter to stove pipe.

My question is: what is the best (safest) way to connect the pellet stove to the chimney? I have seen pellet pipe adapters for 8in stove pipe. Should I get some 8in SS stove pipe and run it into the flue? On the other end connect to the pellet adapter? Or should I take down the existing thimble and put in some other adapter that is designed for this application? Or...?

 

[DAKSY]

In order to save your combustion blower, you may want to run a smaller liner, either 3 or 4" dia., depending on the height of your chimney from your pellet vent at the thimble, to the cap. 8" diameter is 50+ square inches in cross sectional area. Multiply THAT by the height & that's a LOT of air to push out. There are adapters available to "Clean up" the install behind your XXV, & you can switch to the liner just after the adapter...

 

[moerdogg]

I guess I misunderstood the problem with having a large vent area. I had heard that the low flow velocity would cause ash to drop out and require more-frequent cleanouts. So it is taxing for the combustor blower too?

Any recommendations for which adapter to use?

 

[DAKSY]

I guess I misunderstood the problem with having a large vent area. I had heard that the low flow velocity would cause ash to drop out and require more-frequent cleanouts. So it is taxing for the combustor blower too?

Any recommendations for which adapter to use?

It will put undue strain on it, yes. Use the adapter that is made for use with your brand of pellet vent. You can't go wrong that way...

 

[moerdogg]

Well, the place I bought the stove from just got in touch and mentioned that by MA law I have to line the chimney anyway. My day just got more expensive, but the install will be done correctly now.

 

[briansol]

Always do it right. People who hack usually end up with problems burning, poor flame, or worse, fires. Pay up and do it right, no question about it.

 

[rona]

It will put undue strain on it, yes. Use the adapter that is made for use with your brand of pellet vent. You can't go wrong that way...

How can you put undue strain on the combustion blower by venting into a 8 inch chimney versus a 3 or 4 inch pipe. Once the chimney is warm it shouldn't make any difference and considering the stove is running 24-7 this shouldn't be a issue.

 

[DAKSY]

How can you put undue strain on the combustion blower by venting into a 8 inch chimney versus a 3 or 4 inch pipe. Once the chimney is warm it shouldn't make any difference and considering the stove is running 24-7 this shouldn't be a issue.

Think about it. a 3 or 4 " column of air takes less energy to move than a 8" column of air. That's less strain at start up. That's less strain when the air pressure outside increases. If you can keep it running 24/7 & manage to do your monthly maintenance at the same time good for you.

 

[rona]

Think about it. a 3 or 4 " column of air takes less energy to move than a 8" column of air. That's less strain at start up. That's less strain when the air pressure outside increases. If you can keep it running 24/7 & manage to do your monthly maintenance at the same time good for you.

I have a 8 inch chimney 25 feet tall and been using it for 8 years same stove same combustion blower no problem. I also know 3 other people that are doing the same thing. That is 4 of us and we own 1 Quad AE, 2 Bixbys, and 1 Harman PC45. We all do our own maintenence. Hot air rises naturally regardless of pipe size so I see no extra strain once the chimney is warm and as far as cleaning goes 1/2 hour should be enough to clean any of the 3 stoves I mentioned. The chimneys get cleaned once a year either at the end of the season or prior to burning.
I do have a friend who installed the 4 inch special pipe in his chimney figuring it would make his stove work better but other then costing 800.00 more the stove ran the same. If I were burning corn I would buy special pipe but not for wood pellets.

 

[DAKSY]

I have a 8 inch chimney 25 feet tall and been using it for 8 years same stove same combustion blower no problem. I also know 3 other people that are doing the same thing. That is 4 of us and we own 1 Quad AE, 2 Bixbys, and 1 Harman PC45. We all do our own maintenence. Hot air rises naturally regardless of pipe size so I see no extra strain once the chimney is warm and as far as cleaning goes 1/2 hour should be enough to clean any of the 3 stoves I mentioned. The chimneys get cleaned once a year either at the end of the season or prior to burning.
I do have a friend who installed the 4 inch special pipe in his chimney figuring it would make his stove work better but other then costing 800.00 more the stove ran the same. If I were burning corn I would buy special pipe but not for wood pellets.

Whatever works for you. I was a certified pellet tech & in the training we were told to avoid what you're doing. If it works for you who am I to say you're wrong. I'm saying it's not recommended. End of story. Enjoy your pellet warmth.