Enviro Omega- 3" or 4" exhaust?

[izula]

Hello all-

I've got an Enviro Omega coming on Wednesday! Woohoo! It was an adventure trying to locate one... In all of my research, I recall there being a graph that indicated whether a 3" or 4" exhaust was required based on elevation and BTUs or something of the sort. Does anyone have a link or a direction that I can follow to find the information again? I'll be installing it myself (perfectly comfortable doing this - I'm a general contractor and a mechanical engineer) and so I'd like to do the install properly in terms of combustion exhaust flow, etc.
Thanks!

 

[DiggerJim]

Generally if you have 15' of effective vent length you need to go to 4" pipe. Effective vent length is the sum of the running length + allowances for elbows & credit for vertical runs --- so a 90 degree elbow (or T) counts as 5 feet, a 45 degree elbow counts as 3 feet, a horizontal run is equal to 1 foot per foot of run and a vertical run of vent is equal to 1/2 foot per foot of actual vertical run.

To get your effective vent length:
A. Multiply the # of 90 degree elbows by 5
B. Multiply the # of 45 degree elbows by 3
C. Multiply the # of horizontal feet by 1
D. Multiply the # of vertical feet by 1/2
E. Add A thru D
F. If E is 15' or larger, use 4" pipe
G. Use 4" anyway, it will give you better draft and isn't that much more expensive.

 

[terryjd98]

To get your effective vent length:
A. Multiply the # of 90 degree elbows by 5
B. Multiply the # of 45 degree elbows by 3
C. Multiply the # of horizontal feet by 1
D. Multiply the # of vertical feet by 1/2
E. Add A thru D
F. If E is 15' or larger, use 4" pipe
G. Use 4" anyway, it will give you better draft and isn't that much more expensive. [/quote]

I am planning on just doing a streight run right from the back of the stove to the outside. Total distance would be around 3 feet by the time I get through the stone wall. Would you still recommend going to 4 inch pipe or would 3 inch be ok? Hard to see going to 4 inch would make any difference in that short of run but I know nothing about pipe venting and what size should be used for enough dratt.
That looks like a good formula to follow for an install. Just in my case I am going to have a short run.

 

[DiggerJim]

I am planning on just doing a streight run right from the back of the stove to the outside. Total distance would be around 3 feet by the time I get through the stone wall. Would you still recommend going to 4 inch pipe or would 3 inch be ok? Hard to see going to 4 inch would make any difference in that short of run but I know nothing about pipe venting and what size should be used for enough dratt.
That looks like a good formula to follow for an install. Just in my case I am going to have a short run.

A straight run of 3" would be fine. However, if you're prone to power outages you might want to consider a vertical (5') section outside to create a draft in the event the power goes out and the stove's combustion fan stops and the pellets have to burn out on their own - otherwise you may get smoky feedback. You may also get siding sooting from the fly ash from the straight vent but shouldn't with the vertical run - although there are lots of folks who go straight without backsplash, just make sure the prevailing winds won't drive the exhaust back against the house. With a 3', Tee and 5' vertical you should have no problems with 3" vent piping.

 

[izula]

G. Use 4" anyway, it will give you better draft and isn't that much more expensive.

4" it is. Thank you very much!

 

[terryjd98]

quote]A straight run of 3" would be fine. However, if you're prone to power outages you might want to consider a vertical (5') section outside to create a draft in the event the power goes out and the stove's combustion fan stops and the pellets have to burn out on their own - otherwise you may get smoky feedback. You may also get siding sooting from the fly ash from the straight vent but shouldn't with the vertical run - although there are lots of folks who go straight without backsplash, just make sure the prevailing winds won't drive the exhaust back against the house. With a 3', Tee and 5' vertical you should have no problems with 3" vent piping.[/quote]

I am planning on hooking up a UPS to the stove that will let it keep going if the power goes out. A cheaper UPS would give about 15 min of power so I would have time to shut the stove down right and then put a battery back up on it or a generator if it looked like a long blackout. Also a UPS will keep a steady voltage going to stove if on a battery back up or a generator or even Hydro if they have a brown out. From what I have read they work well and will sure help stop any damage to a stove or electronics of anykind.
We get the odd black out here, maybe a couple a year that last more then a few hours if a bad storm other then that we are pretty lucky. The prevailing winds run right down the side of the house where the pipe is going. If I was putting the stove on the north west back wall then I would be worried about soot. House is out in the open pretty well and we always get a good wind if any wind at all, nice in the summer but sure shows the cracks in the old house in the winter.
Thanks for the help. just made the install eaiser and cheaper.
Terry