Montpelier II install into existing ZC Selkirk/Warnock Harsey Model 640, questions

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New Member
Oct 30, 2023
Saranac Lake, NY
The title says it all. We picked up a 1/2 price Montpelier II this summer without realizing that it is not a ZC unit. We currently have a ZC Selkirk/Warnock Harsey model 640. The 640 is flush-mounted to the wall with some ugly kitchen-countertop style granite used as a hearth, trim surround and mantle. This is all mounted on an exterior wall within a huge faux chimney that also houses our oil-boiler chimney. We recently stopped using the boiler and it will be removed. I would like to mount the Montpelier 8 to 10 inches proud of the wall and build a false chimney up our wall, tying into the existing pre-fab stainless chimney with an angle kit.

The Montpelier *might* fit within the 640, but the 640 would likely need modification (based on my visual estimates only). The refractory "brick" sides and rear would likely need to be removed and the floor of the unit might need to be removed (the 640 has a blower kit below the floor of the unit). I would also source fire rated fiberglass insulation mat to wrap around the entire unit before walling in. There should be plenty of room within the "chimney" structure to leave lots of clearance around the unit, especially since I plan on moving the whole assembly into the interior of the house by 8-10 inches and custom building around it.

So, anybody ever do this? Or something very similar? Is it possible to tie into existing prefab chimney, or does that stuff need to be ordered to size? I know the stock answer to modifying the ZC 640 is a "no" ... but can it be done safely?

If this is simply not a viable option to place the Montpelier within the 640 are there prefabricated masonry boxes available at a reasonable price? I found some very expensive options, frankly they cost MORE than the Montpelier itself. I could always brick and mortar one, but I am looking for a faster and more foolproof install...I'm no mason (but I could figure it out with research). Looks don't matter, it will be behind a wall.

If you read this far...thank you. I will keep this thread updated with what I end up doing and look forward to some advice!
"Selkirk/Warnock Harsey model 640"
- Warnock Hersey is the testing lab, not the brand or model of the ZC. The fireplace's make & model needs to be identified to see if an insert is permitted to be installed in it. Modifying any ZC as described is definitely not allowed.
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No, changing out a prefab is not inexpensive. Start with identifying the current ZC.
Alright, so after falling off the face of the earth for a bit I am back. And I need to correct some major errors I made in my original post. The model name is Selkirk 640/ZC40. The manual link I posted earlier goes to some kids game... here is the actual link:

I have been researching ceramic fiber blankets (I mistakenly referred to them as a fiberglass blanket in original post). My thought is to build a simple box made from concrete-board and line it with ceramic fiber blanket. This box would go around the insert with a hole cut for the chimney. I would give a minimum 2 inches of clearance on all sides, but will probably choose to go more. I can't imagine the bottom of this unit gets very hot, as it houses a blower and an electrical cord. I also notice that the Montpellier is built with an inner firebox that maintains an airgap with an outer shell.
According to Vermont Castings customer care, the MONTPELIER II models from 2023 and earlier are approved for at least some installations into existing zero-clearance fireplaces.