Considering running OAK up flue?

I have a Harman P35i insert in my fireplace. 4" exhaust is routed up thru the flue to the top of the chimney where it has a rain cap mounted in the center of the 13" by 17" flashing/covering.

What I would like to do is run my 4 inch OAK line up the flue and attach it at the top 13" by 17" covering, but the existing one seems designed for a single inlet/exhaust line. It's a Duravent product and the existing hole is mounted directly in the center of the flashing/covering.

Question is: is there any kind of flashing/covering with a dual inlet/outlet that I could utilize for this application? Currently my OAK is routed down the cleanout and into the basement. The basement is not heated and gets quite cool in the winter due (in some part) to the OAK line terminating in the basement pulling in cold air from the outside (I think).

There's been a lot written about OAK vs no OAK, OAK not required, etc. Personally I don't like pulling the cold air into the house, I'd like to route this OAK up the flue so it can pull outside air from outside, and the most direct route is straight up the flue - app 15 total linear feet in my single story ranch.

Besides fabricating my own covering, is anyone aware of a product I can pull off the shelf and install my exhaust line on one side and my OAK line on the other side?

 

Interesting post, I have the same situation. I would think that it should be the same brand as the venting that is already installed. I know that Selkirk and DuraVent make concentric kits.

 

yes.

I have an oak up my flue for the insert. Running a cap Scott williamson makes which is a 2-story cap. Exhaust on the top floor, intake on the bottom floor with a seperator to keep the exhaust from getting sucked in.

not sure if he sells them standalone... i had him come out to do the full oak install.
Pellet Stove Installation, Pellet Stove Cleaning and Pellet Stove Repair: Serving CT, ME, MA, NH and VT

 

I had forgotten about Scott.....or has he been on the site under a new name? Smart guy that would be a real asset to the forum.

 

You might consider this option. I routed my OAK down the fireplace clean out as you did but changed the 3" metal pipe coming out of my P61I to a 4" where it transitioned at the clean out. I then removed a 1/2 brick in two rows vertically on the rear of the chimney where it was certain to be in the clean out pit. it is only single thickness of brick in this area. Using a covered dryer vent with the flapper removed and a screen installed completed the installation. clear RTV attached the dryer duct. Works perfect! i believe in OAK's.

 

Good option. My insert is in a dble sided fireplace in center of the room. I think my simplest approach in the straightest line is right up the flue. I just need to find a different chimney cap to hold both the stainless exhaust and the flex intake line and keep the rain and critters out.

I was considering just cutting a circular hole in the existing cap, notching it, and attaching the intake/oak to some kind of collar and cap and siliconing all around it. Itd probably help if I had a picture and didnt sit behind a keyboard all day so I could actually get it done before winter.

 

If you use a collinear chimney cap then make sure it is stainless steel . There are many aluminum collinear caps only certified for gas appliances. Since the SS collinear caps are so expensive I prefer the stainless steel 4" diam flue liner and the aluminum 3" diameter (That is what the Harman frame has for fresh air connection) Olympia part # KA335 for the fresh air intake. If you cut the 13x13 top plates and seal them with high temp silicone to seal them up, both liners will easily fit in one flue. Make sure the flue top is higher than the fresh air top and there cannot be any stone top over this flue.

 

If it were me I'd knock a hole through the masonry in your basement and run 4" solid dryer pipe to the outside of the house. Same idea artc mentioned just an interior FP. Seems much easier and cheaper. Unless you have a finished basement that is.
Doesn't woodstock stoves utilize a pipe within a pipe style installation? I'm not familiar with pellet stoves, just cruzin through

 

Do not use any dryer venting ever. No. just no. Not even for the OAK. if you lose power, there is potential for hot exhaust gases to back track up the intake and it needs to be up to fire rated code just like the exhaust.

 

I would suggest (maybe you considered this?), using the Harman intake kit below your current liner retainer/cap, running 5 or 6 feet of intake pipe through your blockoff plate and not pulling the intake air 20 or 30 feet down from the top through a 3' intake line...I tend to worry about restricted air intake when you're pulling it that far.

I wouldnt use the dryer vent exterior cowl for an intake, but for intake air, its fine to use the aluminum flexible dryer vent as an air conduit. The nice thing about the install I mentioned is that the flexible pipe is nowhere near the exhaust exit

 

The one disadvantage of that installation is the chimney top is sealed up from the flue top plate. That is one big air restriction!
Therefore I like the 3 inch open flue top with no restriction.

Also we have done at least 6 installs with the 2 liners up 25 feet with no problems. The first ones done 2 years ago so there is proof of concept here too.

 

Hi Dexter
The rigid venting is good for your installs but any rigid venting is not recommended for chimneys because water can get in. Also going to the top with a nice rain cap for the chimney oak with flex assures no leaks.

 

you need to check out the air intake kit, Don. The intake kit assembles below the top kit, allowing intake air to enter the annular space between the chimney wall and the liner....also gives more separation from flue gas than a 3" vent thru the cover. The part number is 1-00-674104. See page 16 of the installation manual: http://downloads.hearthnhome.com/installManuals/ACC52i_I.pdf

 

Hi LW
That is interesting, but fresh air is still coming down a dirty chimney and you have to be a Harman dealer to get that part. So coming into a 2" fresh air stove pipe with a 3" inch pipe is plenty. The way you do it is a very good alternative! Certainly nothing wrong with it.

 

FWIW I tried to install an OAK on my P68 last year the way LW described (just go a little way up the fireplace flue) but it did not work out for me. It's for the very reason Don described, the top of the flue is sealed up tight so no gasses or ash can come back down, so there's also no way to get fresh air to come down either. I tried drilling a couple holes up at the top to let some air in, but it still wasn't enough - the stove ran terrible and there was smoke in the hopper. At that point I just gave up and scrapped the whole idea. Over the course of this little adventure, I talked to several local installer guys. All but one of them acted like I was crazy for wanting to install an OAK, and did everything they could to talk me out of it. They didn't even know the specifics of my situation, they are just plain dead set against the OAK idea in general and there was nothing I could say to convince them otherwise. These are guys that do this every day for a living, I don't get it! The only one that would do the job wanted to charge me ~$1,000 for it. Yes, you read right. Thinking this was not meant to happen.

 

Dex, what's your take on Selkirk vs. Duravent? I like the idea of the Selkirk where the flue and OAK are in the same pipe, with the flue pre-heating the OAK air. When I had the P43 installed, I asked the stove shop guy about using Selkirk instead of Duravent for this very reason, but he was not on board with it. He didn't get into specifics but said he doesn't like to use Selkirk in general, hinting it is not of the same build / quality standard as Duravent. Anything to it, or do you think this was just a personal preference thing?

 

well, to make the outside air thing work, it should go without saying that you need to have an INLET for the fresh air as well. Where is the fresh air going to come from if you have no inlet for outside air to enter?

 

well, a dirty chimney? We don't install into dirty chimneys...should be cleaned prior to the liner/stove install.... why would you put a liner into an existing chimney with creosote which can still combust? And I am a Harman dealer....I can get the part . Most of the Harman intakes are 3", so, your intake pipe needs also to be a minimum of 3" as well....if you restrict intake air too much, you get a dirty, lousy burn. So, with that in regard, don't make your intake pipe too long...will also restrict your airflow.

 

Like I said, I drilled holes at the top to let fresh air in. It didn't work. I really wish one of you guys lived closer to me, I would gladly pay you to do a proper OAK install for me. Just not $1,000.