Proper flue pipe sizing

[MadMax31]

Just bought an Summers Heat 55-SHP10 and about to install. Venting up through roof, at a length of 15-18'.

Im fuzzy with the IOM, as it states anything over 15' run 4". I also read at the 15' mark INCREASE to 4".

Should I just run 4" the whole way?

Thanks

Max

 

[Ranger72]

I would run 4" the entire length. How are you venting, straight from the back of the stove, through the ceiling attic and roof?

 

[MadMax31]

I would run 4" the entire length. How are you venting, straight from the back of the stove, through the ceiling attic and roof?

Yes, tee at stove and straight out through celing, through attic and then roof... No elbows

 

[Ranger72]

I would still go 4" if your manual calls for 4" anything over 15'.

 

[Ranger72]

My insert has roughly 11' of 4" flex tube. No issues.

 

[MadMax31]

Thats good to here. I hate doing things twice....

 

[SmokeyTheBear]

Just bought an Summers Heat 55-SHP10 and about to install. Venting up through roof, at a length of 15-18'.

Im fuzzy with the IOM, as it states anything over 15' run 4". I also read at the 15' mark INCREASE to 4".

Should I just run 4" the whole way?

Thanks

Max

Do not join a larger diameter flue at some point after the so called x feet you are cruising for a very rude awakening depending upon how much of the larger diameter pipe you use will help determine when it will happen.

It is an awakening you don't want to deal with ever.

The same diameter all the way from the stove to the vent termination.

 

[SidecarFlip]

Do not join a larger diameter flue at some point after the so called x feet you are cruising for a very rude awakening depending upon how much of the larger diameter pipe you use will help determine when it will happen.

It is an awakening you don't want to deal with ever.

The same diameter all the way from the stove to the vent termination.

You need to explain your premise....

I'll microwave a popcorn and be right back......

 

[SmokeyTheBear]

Well have you ever lit a fuse. Say a pile of pellets up inside a drop chute. That is one possible outcome.

Back pressure caused by the weight of air in the larger piece of pipe will block what the stove is able to evacuate from the stove via the smaller piece of pipe. This causes a poor burn and pellet pile up in the burn pot which leads to pellets in the drop chute and finally to the auger flight. Now a little negative pressure in the room with the stove you can get smoke rolling out of the air wash and even the hopper. If the negative pressure is strong enough the pellets in the drop chute can torch of those in the auger flight which by the way in this case ends at the bottom of the hopper which may or may not have pellets in it.

ETA: Hey I got the yard all cleaned up from the snow and ice we had, you got that popcorn all scorched yet or is the house all gone?

 

[SidecarFlip]

Your theory don't hold water simply because 99% of solid fuel appliances all have their transition from their CA blower to a 3" diameter outlet, so, all start at 3" not 4". Conversely, the exhaust output is forced, not draft by convection, unless, there is a failure in the CA blower and the flue pipe then assumes a convection draft scenario at which time 4" is always better than 3" and pellet vent is insulated, double wall, for a couple reasons, one of those is to promote natural draft in case of component or electrical failure in the appliance itself.

I've been running a vent system comprising of a 3" diameter horizontal run 3 feet long into a 3-4 Cleanout Tee and vertically in 4" to a height just shy of 20 feet vertical. for 15 years (the entire vertical run is outside btw) with no adverse effects from the 3-4 transition. 4"-3" reduction, certainly. 3"-4" increase, never. Got my popcorn in hand......

 

[SKOAL MAN]

EPIC! I'm going to have to look up the meaning of all kinds of words before this thread is over!

 

[SmokeyTheBear]

Your theory don't hold water simply because 99% of solid fuel appliances all have their transition from their CA blower to a 3" diameter outlet, so, all start at 3" not 4". Conversely, the exhaust output is forced, not draft by convection, unless, there is a failure in the CA blower and the flue pipe then assumes a convection draft scenario at which time 4" is always better than 3" and pellet vent is insulated, double wall, for a couple reasons, one of those is to promote natural draft in case of component or electrical failure in the appliance itself.

I've been running a vent system comprising of a 3" diameter horizontal run 3 feet long into a 3-4 Cleanout Tee and vertically in 4" to a height just shy of 20 feet vertical. for 15 years (the entire vertical run is outside btw) with no adverse effects from the 3-4 transition. 4"-3" reduction, certainly. 3"-4" increase, never. Got my popcorn in hand......

But your 3" front end isn't at that magic number that the OP was talking of 15' which I will take to mean an EVL of 15 which unless you have a super duper exhaust blower is the maximum recommended length for 3" vent.

Your total vent system has an EVL of about 18 and I'll also wager that you clean your stack on a regular basis thus removing the ash that ends up in the bottom portion of your stack.

BTW no combustion blower failure is required.