Is 4" neccesary?

[bmfox]

I will be installing a heatilator cab50 on an interior wall. The plan is 12" horizontal, tee and 15ft vertical. Can I use 3" or do I need 4"? Manaul recommends 4" over 15ft. Help me, thanks.

 

[Stoveman 77]

You will be fine if 15 feet if it over that then I would think about 4"

 

[mralias]

IMO your EVL based on your venting configuration in 13.5. Anything less than 15 EVL you can use a 3" pipe. Does not mean you have to use 3".

 

[Pellet-King]

I'm using 3" @20' vertical with no problems