Venting a Pellet Stove in Existing Chimney?

[westcliffe01]

I looked for examples of exterior soot on the internet and it was the best one I found in a quick search. There are far worse examples. What can happen is that depending on the direction of the prevailing wind, the direct vent flue may be in a positive or negative pressure zone. If in a positive pressure zone, the amount of combustion air will be REDUCED, thus the stove will burn rich and create soot.

Most stoves have a damper on the air inlet which can be adjusted to balance the installation, but when venting through a wall the immediate wind direction is going to have a major impact. A vertical chimney with a proper cap is hardly influenced at all by wind direction, when maintaining the 2/10 rule. My vertical double wall chimney was about 24' straight up and out near the peak of the roof, so I had to close the intake damper a lot to compensate for the additional draft.

I will say that I have seen considerably worse examples that the picture I found yesterday. If the flue is on a low pressure side, I think the effect will not be quite so bad, but you have the risk of the suction holding any particulate close to the wall of the house, so I really don't know which is better... Vertical out the roof works perfect, even if it costs a bit more, that is my advice...

Wow Westcliffe! Is that from the corn?

My pellet only stove is in the basement, goes up thru the ceiling and out the side of the house (chimney box for upstairs fireplace). I have not had any sooting issues on the outside in at least 8 years. Also, mine vents to the north side so it is into the prevailing wind.

That has to be from corn...I have heard that it is a little dirtier burning.

 

[rgs03833]

Below is a screen shot of the manual (Harman pellet stove) regarding a chimney install. The chimney is in good condition with the clay tile liner, so according to the manufacturer an install without a liner should be OK. The stove dealer recommends a liner, as well as some of the posters here, so I'm still not sure which direction to head in regarding going into the chimney.
My alternative install would be about 72" of pipe at a 45 deg angle from the house wall to clear from under a porch roof and would be cheaper than the chimney liner.

Look at the last line on the Manual.

" Be sure to design the venting so that it can be easily cleaned. "

I would NOT cut cost because it will $ave you a lot of money and time in the future.

Your Alternative sound GOOD+++ to me if you can do it and get a good Cap. Imagine paying someone cleaning your Chimney every year or even two. The good side to this method because I have one. I get my tall Ladder in the Summer, open the 45 deg angle on the bottom and turn it toward the grass and Brush and HOSE the sucker down from up top. LOL... It was Easy Cleaning, hehehe, and money stayed in my Pocket!

 

[Lola4231]

I ran a corn/pellet stove for 2 seasons. Despite what is said regarding these stoves being "direct vent" if you do that it will leave a nice big sooty mark on your wall, which most people will find unsightly.

The flue temperature on these stoves is a lot lower than a wood stove, probably too low to draft properly in a large masonry flue. A pellet stove will never provide enough heat in my opinion to warm a masonry flue adequately.

If you go with the liner down the masonry flue it is a much better situation. Much less thermal mass, no interruption from the stove all the way to the chimney cap, so the combustion blower can do its job in venting the flue gases. The vertical rise will also mean that if you have a power outage, the stove will safely vent and not spill smoke into the house. Smoke damage was quite common with pellet stoves when they came out and is one of the reasons why proper vertical flues are recommended.

I have the same setup, instructions stated pipe outside of home should be longer than what you are showing, hence the black on your house. My pipe is out about 16" from the house and never had one mark of black on my house or anywhere else. Your pipe is too short.

 

[westcliffe01]

That is not a photo from my install. I went with a 24' straight up double wall 4" vent so I had more draft than needed. However, the situation that is shown in the picture is not at all uncommon. "direct vent" systems are a complete double wall package supplied by the factory UL certified. Building inspectors will not allow anything different. Geometrically, there tends to be little difference between direct vent systems for propane, natural gas and pellet stoves when viewed from the outside.