I have a Bosch LP installed at the driver rear underneath the radiator vented out on the outside of the radiator. Of my MCI seven right now I'm just using it for hot water. And it is working great. I believe it is a 125. It is a 3.7 gpm I will have to dig out the pictures. It was a tight squeeze. As for the water lines freezing. I'm staying in the South, Houston and Tucson.
But I didn't have a rope light underneath it for winter temperatures of about 32° and had no problem. I would recommend a good heat tape or colder areas. If you get calculations on how to use for heat in the living area. Please keep me informed.
I know this unit uses a Hydro switch. I believe it is a turban, rotating inside the tube as water passes by and generates a spark. This one uses no electricity, from an outside source.
Good luck, Ron