Wood Stove Retrofit into ZeroClearance

I have been attempting to find the correct wood burning stove for my application, but have received many different answers from a number of manufacturers and installers. I want to do this in a cost-effective and SAFE manner. Please help!

I have an existing zero-clearance fireplace in a wood framed chase, going two stories up. It has a 12” lined chimney. Inside, there is a real stove façade, bluestone hearth and wood mantle.

I am searching for a wood burning stove to retrofit into this fireplace, for the purpose of heating this part of the house.

I have had vendors tell me that they have inserts that will fit “inside “ of the existing fireplace after removing the glass doors. I would line the chimney with flex liner, and then connect the woodstove to the liner. They said it will require modification of the front face of the existing fireplace. Some on-line sites say this is NEVER a good idea, not safe, and the stoves don’t produce heat – most still goes right up the chimney.

Another vendor told me I could set a true (small) woodstove on the hearth and rear pipe it back into the chimney, once again, lined. They said I can cover the opening (after removing the glass doors) with a piece of metal that allows the black chimney to go through. They also said I would have to install an additional bluestone on the floor in front of the existing one.

Please, can I get some guidance?

I bought one of these from ChimneyHeaters.com . I installed and it works fine. Heats my 2000 square foot house. I have the pump connected to a UPS but I am not sure how long the pump will run if the electric goes out. I had it installed all winter and did not have to turn on my Electric heat once which saved me about 200 euro a month here in Romania.

The Electric is not stable here so I had to rush to take out the fire a couple of times because the water pump had stopped and the pressure valves were going off. The UPS will solve that but I dont know how long a UPS will keep my central pump going. I will attach a pic of what chimney heaters are in case you are not familiar with them. The pump is a Grundfos and has three speeds.

I bought one of these heat exchangers from ChimneyHeaters.com and it is Stainless Steel. The rest of the pipes in my house are Copper and some plastic. I get a tremendous amount of heat from this thing and I am worried that it will melt the copper or plastic tubing.

The heat coming out of the Chimney Heater is about 190f does anyone know if this is to hot for the copper or Plastic pipes in my House?