Princess 29 in a 31"Hx28"W x18"D tapered firebox

[monokhrome]

Hi all,

I'm deep in the weeds of researching an insert install for an old, oddly sized fireplace. The shallow depth and narrow tapered back wall are presenting a challenge in terms of available insert options that do not require extreme removal of the original firebox brick on the left/right tapered walls while still being able to size the insert appropriately for a 2-story, 2,300sqft home with 8.25' ceilings. After a bunch of reading (forums and installation manual), measuring, and remeasuring, I have a few questions regarding install of a BK Princess 29 insert:

1) Is it safe/code compliant to remove some brick from the left/right walls to allow unit to be fully recessed with the faceplate/surround sitting flush? I would need to remove and "notch in" about 1" on the left and right walls at a depth of 11-7/8", which at this depth would expand the existing width from 24" out to 26" (25.25" required per manual). The face of the fireplace sits diagonal to the actual chimney, so I believe left/right walls are only supporting the bricks that extend out into the room and not the chimney itself.

2) Is there clean looking way to install the unit with only the top shroud attached? The unit's horizontal span of 35.5" fully covers width of the 28.25" wide firebox, but there's still a gap of 7-5/8" at the top (31" H firebox - 23-3/8" H insert).
2a) Does the unit overlapping the firebox's width by 3-5/8" inch on each side impact the fan's ability to function?
2b) Does the 7-5/8" gap pose an installation challenge for connecting the flue liner?

3) Do the decorative wood pillars pose any combustible risk or code compliance issues considering they are 15" diagonal from the left/right firebox door flanges?

4) The hearth only extends 12.25" from the door flange (23.25" D - 11" unit face to door flange). Is it correct that I would either need a fireproof mat or permanent hearth extension of at least 3.75" to meet the 16" required hearth extension depth? Are there any other modifications that allow the 16" depth to be lessened (like building a 5" tile platform for the unit to sit on)?

5) Does a 6" diameter 35' liner cause concern for being able to manage over-drafting?

6) Am I missing anything that would pose a risk/challenge/compliance issue for install?

 

[spudman99]

I am not an installer or experienced wood stove merchant. Just a handy homeowner who installed my own PI29 4 years ago. Please keep this in mind as you consider my comments.

1. I believe it would be safe to remove bricks. I removed a bunch off the smoke shelf to allow the 6" insulated liner to breech the firebox. Since the PI29 is a self contained unit, there is no fire hazard. What the brick removal will do is prohibit a return to a traditional fireplace in the future unless they are replaced to restore the proper fire barrier.

2. Yes. The side and top shrouds are basically just painted steel panels. If you find some metal shop around, you could have a custom panel created to fit your dimensions and still attach to the PI29. This would include the side panels if desired for a clean look.

2a. The overlap does not interfere in the fan operation. Fan is attached on the left side and draws air from both through the baffles on the 7" extension. Not a concern. Be aware that there is just a single fan on this product and I have been underwhelmed by the volume of air that is pushed out by the PI29, and the fan is a bit noisier since it has to run at higher cfm's. Would be great if Blaze King could increase the fan air volume, but I suspect the engineers already looked at that and the current configuration is the maximum.

2b. Your gap above should be sufficient to connect the liner to the appliance. Tight but enough to get hands into attach the collar and secure it as per instructions.

3. Technically they fall within the clearance zone and yes are at risk. Looks like you might have 3" or so each side as true clearance from the firebox. Thats tight, although I will say I find the temps off the side of the unit to not be that high. I stuffed some rockwool along the side of the PI29 and the firebox for air sealant and to absorb some of the heat. In your case, you might get away with it, but I would monitor temps with an IR device and be prepared to take some mitigation. Remember it is the continued exposure to higher heat that causes pyrolysis and that is a slow burn (pun intended). I am not advocating this, just a mention.

4. I would not be concerned with the floor in front. My brick hearth is only 10" deep in front. Well below recommended clearances. I put a small board with tiles on the rug below, and remove that during the summer. I have never had any coals, sparks or flamables during opening or loading. In my opinion you look good, but by strict interpretation you can augment with a temporary barrier.

5. I have a 30' liner and I have VERY high draft. I installed a manometer and it almost always runs at 0.15 or higher water column, well above the 0.08wc recommended levels. I did install a damper in the liner pipe, with a steel rod straight out front (I modified the connections) so I can slow down the draft if I desire. I can say that I am not sure there is much of a difference in the quality of the burn, or the burn time with or without the damper. I can get 12 hr burns with ease. Never have gotten more than 18 hrs. Remember that the fan needs to run most of the time to extract heat, so that will reduce burn times. The long ones advertised are for the free standing units that radiate heat, and probably not much at the end of the 24 hrs. I suspect that you will not be able to install a damper. The PI29 is still a wonderful appliance, allows me to load at 7am, burn, reload at 7pm, heat the room, rinse and repeat for months on end.

Thoughts: block off plate is almost a requirement for this high of a chimney. Added once the liner is in place. I insulated the interior of the fireplace behind the PI29 with rockwool, my chimney is exterior and that does help the burn time considerably. You MUST have DRY wood. If you are doing this project soon, get your wood now split and stacked. Under 20% moisture is needed for clean and successful burns.