3 inch or 4 inch vent pipe for a Harman P35I insert

[dsksta46]

I was talking to the local Harman dealer about the P35I insert. We were discussing the size of the vent pipe. They only order inserts with the four inch pipe outlet. I told him I had a Whitfield Quest insert ( about 30,000 btu output and parts NLA to repair it ) that worked just fine with three inch vent pipe about 15 feet of stainless flex pipe attached to a five foot piece of Duravent pipe attached to a bracket to help hold the flex pipe. No outside air intake. The chimney is capped were the vent pipe exits to keep water out ( masonry lined chimney ). The damper plate was removed and resealed where the vent pipe passes through.

My question is if the three inch vent pipe worked for the Whitfield why would I need to increase to four inch for the Harman.

 

[jackman]

I would follow the installation manual. If it's installed differently than the guidelines it would probably fail a building inspection.

 

[Nadoniac]

I was talking to the local Harman dealer about the P35I insert. We were discussing the size of the vent pipe. They only order inserts with the four inch pipe outlet. I told him I had a Whitfield Quest insert ( about 30,000 btu output and parts NLA to repair it ) that worked just fine with three inch vent pipe about 15 feet of stainless flex pipe attached to a five foot piece of Duravent pipe attached to a bracket to help hold the flex pipe. No outside air intake. The chimney is capped were the vent pipe exits to keep water out ( masonry lined chimney ). The damper plate was removed and resealed where the vent pipe passes through.

My question is if the three inch vent pipe worked for the Whitfield why would I need to increase to four inch for the Harman.

I have that stove and run a 3" liner through a chimney that is approximately 20' high. My draft readings show that it is well within the Harman specification. I am also running an outside air pipe. Without the outside air i also met the specs for draft. Hope this helps!

 

[CapeMayDan]

I was talking to the local Harman dealer about the P35I insert. We were discussing the size of the vent pipe. They only order inserts with the four inch pipe outlet. I told him I had a Whitfield Quest insert ( about 30,000 btu output and parts NLA to repair it ) that worked just fine with three inch vent pipe about 15 feet of stainless flex pipe attached to a five foot piece of Duravent pipe attached to a bracket to help hold the flex pipe. No outside air intake. The chimney is capped were the vent pipe exits to keep water out ( masonry lined chimney ). The damper plate was removed and resealed where the vent pipe passes through.

My question is if the three inch vent pipe worked for the Whitfield why would I need to increase to four inch for the Harman.

Hello, just took a look at the installation manual. The P35I comes with the 4" vent as standard. There is a part which you could order for a 3" vent 20' max. As long as your existing vent and masonry chimney are OK, I don't know why you couldn't use it.
Check out page 12. Here is a link--> http://downloads.hearthnhome.com/installManuals/P35i.pdf .
JMO: You can't go wrong with 4".

Good luck with your new Harman.
Dan

 

[dsksta46]

Thank you to all that have replied so quickly. I forgot about the draft test. I do not think I have anything to loose. Install the stove fire it up put the draft meter on it and see what happens. If it is with in specs I'm good to go if not I replace the three inch pipe with four inch. I would like to know how much of a difference between three inch and four inch on the draft meter reading.

 

[CapeMayDan]

Thank you to all that have replied so quickly. I forgot about the draft test. I do not think I have anything to loose. Install the stove fire it up put the draft meter on it and see what happens. If it is with in specs I'm good to go if not I replace the three inch pipe with four inch. I would like to know how much of a difference between three inch and four inch on the draft meter reading.

I can't help with meter readings. I just wanted to say that the stove comes with a 4" vent standard which is going to give you the optimum performance. While 3" will probably be OK, 4" is going to give you that optimum performance.There is also the benefit of longer intervals between cleaning.

Dan