hoot
Burning Hunk
Let's just have a conversation from an engineering point of view, aside from who allows what. This is not an argument.An insert is considered an accessory. They are not allowed by the manual for their specific fireplace. The only way around it would be to get majestic to give a written addendum to their manual.
Very few prefabs allow inserts and supposedly ul is rewriting the standard so none are allowed unless they are specifically tested and listed as a unit with every part specified.
Most superior fireplaces don't allow inserts either
This is just the thinking of what issues come up with an insert in a zc fireplace.
Most all inserts have secondary sheet metal with air space to draw room air around the bottom , up the back and out through the top.
This "baffling" greatly reduces the radiant heat out into a standard brick fireplace, designed to handle direct open fire heat. There is no open flame and hot coals exposed to the masonry with an insert installed.
So in a conventional masonry fireplace, adding an insert overwhelmingly reduces stress on the masonry due to the above and reduces stress on the chimney due to the liner.
A ZC is designed much the same as a masonry fireplace except without bricks. It is designed to burn open wood fires 24/7. Most have 8" flues. A 6" liner will go up that flue like a glove.
Because the ZC has the same requirements as a masonry fireplace, an insert will also greatly reduce stresses on the prefab unit.
Concerns are the combustibles of the framing inside a ZC install. BUT, a ZC is specifically designed to allow it being close which means alot of engineering went into keeping internal heat soak to a minimum.
With an insert in a ZC you have literally double the protection... the insert baffling, the space between the insert and the ZC refractory panels and the added baffling of the ZC behind the baffling.
I think the biggest concern is the weight of these inserts... some as much as 550lbs.
ZC bottoms are sheet metal fabrications with a refractory set on top.
Because a ZC is much much lighter than an insert, the supporting structure underneath may not be adequate.
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