the proper way to install the electric fireplace is to the remove the old box if possible if not the proper way to do it is to seal the cavity with foam boards and the gaps with  spray foam. If we remove the box and the inside is not insulated and drywalled it should be to prevent any cold drafts in the winter. Once cavity has been sealed best as possible unit can be installed. Obviously power is required for unit so should be done prior to sealing if not available. The power for this unit does not have to ran from fuse box if line can support it. If you plan to run heater for extended periods of time may be best to run on independent line for safety reason. Electric fireplaces can have 220 ran to them in most cases however is not a practical heater since gas is still cheaper and will be till heap pumps are available. For homes that do not want heat electric is better since heater can be turned off and flame can still be ran such as summer time. adding 2 other brands shortly please bare with us or call for info we have it all ready and willing to share. We offer honest opinions and stand behind our products. We are here to offer solutions and offer a satisfaction guarantee. We put our customers first and foremost and hope to serve you one day.