Is it CAN use 4" vent, or MUST use 4"?

[Madcodger]

We have two pellet stoves vented with 4" pipe and they work great (one freestanding running straight out to a vertical rise and the other an insert running 30' up a chimney). Our success with them has my neighbor now interested in pellets. Like us they have a heat pump (ours used remarkably little these days!) but two years ago they spent major $ on a new wood stove insert and chimney liner (inside existing masonry chimney) for a finished basement. They both work and have a small child so a wood stove does little more than provide some weekend basement heat because they can't tend it during the day and it takes too long to heat things up at night.

The question they (and I) have is, can they just replace the wood stove and use an adapter to connect to the bottom of the existing wood stove liner (presumably 8" and only 2 years old), or do they need to replace the entire liner? We often talk about the need to use 4" instead of 3" pipe for long vertical runs, but is it possible to go TOO large for a pellet stove? Figured I'd start a thread to discuss this specifically and have the experts weigh in... Thanks!

 

[Defiant]

I have done this in existing 6" wood stove liners with no issues, I am sure if they have an 8" liner there still would be no problems, just my .02.

 

[SmokeyTheBear]

The larger the flue gets the more difficult it becomes for the combustion blower to purge cold air in the flue. The length of the flue also comes into play. Some stove manuals will warn you about the size of the flue.

One can always read the manual for the stove and/or give it a shot.

The down sides are poor drafting, possible back pressure caused heat build up at the combustion blower (leads to the combustion blower thermaling off, loss of vacuum, and then stove shutdown, could also result in seals giving way), and faster ash build up inside the lower portions of the venting system. As with all drafting situations involving exhaust gases that cool down past a certain temperature creosote deposition.

 

[stoveguy2esw]

check with the manufacturer, with my stoves i'd say no for the reason mentioned above , other manufacturers may be ok with that large a liner, but get it from the horses mouth first hand

 

[briansol]

Check with your town hall too. Here, it is illegal to re-use exhaust of any kind for a new install. new exhaust piping must be installed at the same time.