Propane Fireplace Co-Axial Venting Adapters

[sbarshie]

I'm in the process of helping replace an old wood fireplace heatilator with a new propane free standing unit for a family member. I would like to use DuraVent DirectVent Pro 4x6 Co-axial to Co-linear 3x4 Adapter to route the exhaust and combustion air through an old Heatilator wood fire place. Since the new stove is not an insert, it's free standing I'd like to use a one foot section of horizontal co-axial pipe connecting the new propane fire place through a wall thimble into a vertical 90 and attach the co-linear adapter. This would then continue with co-linear pipe upwards 15' through the old damper and clay tile chimney to the co-linear adapter termination on the roof.

I'm reading that almost everyone uses these adapters directly on the heating unit but I see that they are rated for stoves (free standing). I can't determine from any of any literature if they can be used on any length of co-axial pipe before a masonry wall thimble or must always be attached to a fire place insert. In my circumstance the old heatilator is remaining and being closed in with masonary and a pass through thimble. The thimble will be centered in the remaining heatilator firebox with the adapter facing straight up the chimney.

This application would be a tremendous monetary saver and seems to be allowed. Can anyone confirm my understanding of the limitations on use for these adapters.
The square box in the middle is the adapter I'm talking about. And an example of the stove is below also.

DuraVent Direct Vent Pro Masonry Fireplace Adapter Kit​

 

[fitter30]

Call tech number and email in the manual. Didn't see a btu rating 4" corrugated.

DirectVent Standard Co-Axial to CoLinear Adapter (4"X6 5/8")

Use the DirectVent Standard Co-Axial to Co-Linear Adapter (4" x 6 5/8") for stoves with 4” x 6 5/8” co-axial outlets.

lindemannchimneysupply.com

 

[Jackfre]

While it can be a difficult job, I think you would be happier removing the old Heatilator box. I did this at my daughter’s place and two years ago did the same with our Majestic box. Once you get into it you will curse me for suggesting it, but it is a better job all the way around. I bought a set of HF metal shears and they make short work of it. I did this at 75 so not quite as nimble as I once was. You have to be careful of the vent above as you cut, but with care it can be done.