Insert OAKers, your thoughts please

[notch]

Hi folks,
I'm getting ready to install an OAK on my Harman Accentra insert. I don't want to run it up the 25' flue, so I was planning to core a 3" or 4" hole through the back of my fireplace, which has an outside chimney. I have a couple questions I thought the folks who have OAKs installed this way could help with.

1. What size hole to core? I assume a 3.25" hole would be perfect for a 3" pipe, but is a 4" hole with silicone caulking around the pipe OK?

2. What do you use for piping from the frame stub to the outside? Pros and cons of flexible vs. rigid?

3. Is condensation an issue? If so, what can be done to minimize any negative effects? I have a lot of left-over Roxul insulation from the block-off plate install if that can help somehow.

4. Should the pipe be sloped or level? If sloped, up or down going from the stove to outside and the reason for direction of the slope?

5. What do you use for a inlet cover on brick and mortar chimney? I would prefer to avoid buying the $60 Harman part if a galvanized dryer hood with some 1/4 inch screen and the flap removed would suffice.

6. If I should ever want to remove the stove and restore the fireplace functionality, can refractive mortar be used to close the hole? I'm thinking that I could tightly stuff the hole with Roxul leaving 4 inches to fill with mortar on each end.

I appreciate your comments and suggestions. Thanks!

 

[PoolGuyinCT]

This is a subject I have my mind on not much info floating around.

I can only help with the masonry aspect. Hopefully this thread takes off.

1. Puncture chimney from the outside, when cutting stone brick or cementous material always from the side to be seen. Strictly for visual reason. The exit side of the drill and chip will be ugly, so you want that inside behind the stove.

2. Try to pop hole under a full brick, so it serves as a "lintel or bridge"

3. 4" is a big through wall mortar plug, I'd like to see brisk or stone instead for exterior watershed reasons.
Keep in mid, depending on construction, brick is most likely a veneer.

4. As far as refractory cements, if you skill level or masonry training is low spend the money. If materials are handy mix your own.

5. Cementous grouts and mortars sold in premixed tubs (peanut butter consistancy.) will fail, they are emulsions and never truly cure. Hgtv created the market with 20 minute shower installs..

 

[notch]

bump

 

[movemaine]

When I inquired about installing an OAK on my Accentra, I was told I just needed the special cap and the the OAK piping just needed to be up past the damper/insulation - that it didn't need to run all the way to the top, like the exhaust does. I would be real hesitant to punch a hole through the fireplace - the reason being is that you are going to decrease the integrity of the fireplace - as a former Realtor, I wouldn't do it. If you ever sell your home, buyers will have a real issue with a hole put through the brick.

 

[CtPaul]

I'm in the middle of installing an OAK on my Accentra insert. I am doing as movemaine described. I especially didn't want to drill thought the back of my fireplace. I have an old fieldstone fireplace and no clean out either.

Here's the thread with pics. https://www.hearth.com/talk/threads/the-oak-install-begins.103023/#post-1328660

 

[BradH70]

I installed an OAK for my M55 over Thanksgiving weekend and it took about a half a day. I did not core drill a hole, just used a Bosch hammer drill to make a 4" square hole through fireplace liner, concrete blocks then through the bricks on the exterior. It was a rough finish and my exterior bricks chipped around the edges (because I went from inside to exterior with the drill) so if you can use a core drill, it would be a better option.

For the OAK material I used a length of 3" rigid dryer vent and used a hose clamp to secure it to the fresh air inlet on the back of the stove. It is tight enough that it holds up the vent pipe and keeps it aligned with the hole in the back of the fire place. I can then just roll the stove back into the fireplace and the pipe goes into the hole.

Outside I used a 3" inlet vent hood with a built in mesh screen. After I push the stove in, I have to go outside and insert the vent hood through hole and slip it over the pipe coming out of the back of the stove. There are no fasteners or pipe clamps at this connection since I need to be able to take it apart every time I need to roll the stove out.

The hood I bought is nice and rugged, no cheapo thin metals used. Here is the link to the vent hood.

http://www.famcomfg.com/wall-vents/hooded-wall-vent-with-screen-painted.html

I have not notices and issues with condensation. My pipe is pretty level, but if you were to slope yours, I would recommend slopping it down so that any condensation that may accumulate will run away from the stove.

Next time I have the stove out I will take some pictures.

 

[PoolGuyinCT]

I installed an OAK for my M55 over Thanksgiving weekend and it took about a half a day. I did not core drill a hole, just used a Bosch hammer drill to make a 4" square hole through fireplace liner, concrete blocks then through the bricks on the exterior. It was a rough finish and my exterior bricks chipped around the edges (because I went from inside to exterior with the drill) so if you can use a core drill, it would be a better option.

For the OAK material I used a length of 3" rigid dryer vent and used a hose clamp to secure it to the fresh air inlet on the back of the stove. It is tight enough that it holds up the vent pipe and keeps it aligned with the hole in the back of the fire place. I can then just roll the stove back into the fireplace and the pipe goes into the hole.

Outside I used a 3" inlet vent hood with a built in mesh screen. After I push the stove in, I have to go outside and insert the vent hood through hole and slip it over the pipe coming out of the back of the stove. There are no fasteners or pipe clamps at this connection since I need to be able to take it apart every time I need to roll the stove out.

Your exterior bricks will chip/spawl even if using a true rotary core from the inside. Always penetrate from face side.

 

[PoolGuyinCT]

Brad, change in performance draft or pics?

 

[BradH70]

Brad, change in performance draft or pics?

I have noticed that the cold draft coming into the living room was eliminated and the house holds the temperature for a longer period of time = less calls for heat by the T-stat.

 

[fmsm]

smwilliamson is installing mine on Saturday for my P35i. I will try and take pictures and describe in detail his process.

 

[notch]

Is there a way to use the fireplace cleanout?

I had hoped to do this but my firebox is not very deep and the frame covers the cleanout door.

I am doing as movemaine described. I especially didn't want to drill thought the back of my fireplace.

I thought about doing this, but many folks with long flues like mine (25') reported poor stove performance after installing the OAK in this manner. I don't really want to drill a hole in my fireplace either, but it is the only way to install an OAK with a short run. If/when I sell the house I'll fix the hole.

BradH70, thanks for the good info.

fmsm, I look forward to your pics of a professional install.

 

[SXIPro]

I was told by my local Harman dealer that it is not possible to set up an OAK on my Invincible insert.

 

[JonSkow]

I'm not a very opinionated person, but, I will say the having a repaired hole in the back of the fireplace would drive me nuts if I was living there with out an insert.
Im my own house, my original thought was to use an OAK throught the ash trap. Turns out that under the ash trap door (to my surprise) it was completely filled with concrete. If you must vent to the outside and have access to the ash trap. I would drill into the ash trap compartment from outside. Notch, sounds like your plan is the only way to go.
I'm still running with no OAK and have been pretty satisfied, even though its only been a couple weeks.

 

[fmsm]

I find there is a cold draft along my floor across my kitchen when the stove is running, I'm thinking my back door is the culprit. With the OAK the draft should be eliminated.