Jotul c450 air inlet vs insulating the firebox

[nate0918]

Questions regarding the install of my insert:

I've been reading debates about whether to insulate around the firebox of a wood burning insert when in a masonry chimney but what I haven't found addressed was how to deal with the air inlet. If you insulate around the firebox, I assume that you must run a dedicated air inlet pipe so that the stove can receive air otherwise the inlet would be blocked off? My fireplace is in the basement with an interior chimney, no path to outside air unless I bore a hole in the chimney wall in the back that leads to a bedroom closet(ok with me)...

For running the electrical, I do not want to run the cord out the front but the receptacle for the blower cord is supposed to be installed in a knockout hole under the ash lip in the front of the unit(see pic). I would rather keep the cord hidden underneath the ash lip and run it to the back of the fireplace to an outlet(soon to be installed). Outlet would be turned on and off with a switch near the fireplace. I would have to wire the cord directly to the blower leads and skip the included receptacle. Electrical code seems nonexistent when rewiring inside the appliance, I've asked electricians this before. I have no warranty to consider. I suppose I could use a 90deg power cable and route the cord right back under the suround. Thoughts?

 

[nate0918]

 

[Bad LP]

I know what I did is frowned upon but I know for a fact it’s safe and it’s not going anywhere.
Even if something went completely sideways any fire is 100% contained in concrete and EMT.
Your table top candle is more of a threat that 99% of the people just accept as OK.

 

[mellow]

OAK is on the back, you can run a dedicated air line to it from outside, or leave a space and let it get air that is leaked in from around your surround.

Pictures of my old 450 in my insulated fireplace: https://www.hearth.com/talk/threads/got-the-itch-again-jotul-c450-kennebec.120801/

 

[EbS-P]

I don’t have any good reason to insulate around an insert in an interior chimney. Concentrate on a good insulated blockoff plate. Same goes for OAK not exiting the building envelope.

 

[nate0918]

Thanks for the input, I would think that if the blockoff plate seal is solid then any heat radiated to the chimney brick would eventually make it in the house anyway. For the insulation above the plate, what thickness? 10, 12 inches? I was thinking of grabbing some unfaced rockwool and fasten it to the top of the plate. Can you enlighten me on the OAK acronym? I can guess that the first words are Outside Air, but I'm lost on the "K". If I run the intake line to outside the chimney wall into the same room, how much hp will I gain from this, 5-10? I'm joking but if it does provide a benefit then it would be fine with me. What do you think of the electrical? I would rather not bust out the knockouts... I appreciate everyone's help, I'm really stoked to get this thing hooked up.

 

[EbS-P]

K= kit.

 

[begreen]

How much gap will there be between the back of the stove and the fireplace? If it is >2" then consider lining the back with 1" micore board, same for the sides.

 

[nate0918]

I should have about 5.5" of clearance. That should give me room for that board and run the OAK. I was thinking of running it out the rear-right side of the fireplace and underneath some built-in cabinets next to the fireplace. That should let me hide the inlet in the toe-kick.

 

[begreen]

That should give me room for that board and run the OAK. I was thinking of running it out the rear-right side of the fireplace and underneath some built-in cabinets next to the fireplace. That should let me hide the inlet in the toe-kick.

Is the OAK necessary? I don't recall it being an issue with this insert and thought it was optional but could be wrong. With that large a gap won't it pull air from the front of the insert?

 

[nate0918]

From the Jotul manual "If appropriate, use 3" noncombustible duct to connect an outside air inlet to the air inlet collar at the back of the firebox". Sounds like Jotul is tiptoeing around local regs. I am not a fireplace expert, but I would say I know enough about thermodynamics to be dangerous. The air intake located inside the back of the fireplace means that the insert will be sucking in hot air, which will contain less oxygen than cold air because the air is less dense and starving the combustion process. Also, since the intake is in the rear, the air has to get sucked around the insert and squeak through the crevices around the firebox and surround. Is the oxygen density differential plus the restriction of the surround enough to make a noticeable difference? Probably not enough for me to care, that's why the stove has a damper...

 

[mellow]

You are overthinking the OAK, it is for tight houses where combustion air needs to come from outside the building envelope. Most do not need it but if you have a super tight house it is recommended. Others have added it to stop a cold draft on the floor in front of the insert but it will not add to your BTU output.

As for the damper, the insert should not have one attached to it, maybe you are thinking of the primary air lever?

 

[nate0918]

Got it, thanks. My 1950 house is definitely not air tight. I am sure that I got my terminology wrong, in my HVAC days the air damper was the valve that controlled air flow into the device or room or whatever. Opening the valve allowed air in, closing the valve "dampened" or restricted the air flow. There I go again, overthinking things. How about the electrical? I'm going to assume that I am on my own on that...