No an insert needs to be installed in a working fireplace. And all of the insert manufacturers require that fireplace to be ul listed dont they? And on almost all fireplace instructions doesnt it say if you install any component or modify the fireplace in any way you have voided the ul listing?Doesn't the insert's UL testing then supercede, especially if the insert manufacture has it tested for ZC use?
I am not saying there will always be a safety issue I am saying if inserts were not tested in a given fireplace we have no idea if there is a safety issue.I'm still not understanding where you think there is a safety issue.
Yes but the insert will be at temp for much longer periods of time than that fireplace was designed for with much less airflow through the box which could easily allow for more heat transfer.The insert sides are much lower temp than an open fire
Yes if it is insulated but you and I both know many homeowners and installers dont do that then agian you have temps for much more extended periods of time leading to more heat transfer.the liner is insulated thus providing more protection than the original chimney
The you have the issue that many of the zc units were not installed with proper clearances to begin with and many are at or past their expected life span already. There are just to many unknowns for it to be worth the risk for me. And if you do it you will still have the drafty old zc unit there sucking heat out of the house.