I am doing an update on an older home. The master bath has a ceiling exhaust fan that is old and noisy. Resolution is replacement with a combination exhaust fan and heater made by Panasonic. Question, I have the option of installing the box or assembly using rafters at either side of the assembly through the plaster attaching the fan housing with 4 bolts into the rafters. I will have to add a 4/4 on one side to make it happen but that will bring the rafters to the proper width on the box. That being said do I screw it through the plaster that has been cut out to allow the fan box to just slide into the hole including the plaster in the bolt path or do I cut the plaster back to the edges of the fan box allowing the flanges to rest on the rafters as an installation method? Sounds kinda complex but I do have the ability to do either at this point. Thanks

 

If you study the instructions - a magnifying glass would help, the flanges are against the rafters. You would cut the opening to the size of the flange and after attaching the box, caulk all around the flange / drywall meeting point.

 

Make sure your current circuit will handle the additional load of the heater.

 

Thanks guys, I had imagined that attachment to the rafters would be a way more secure method. The house is old enough that it is built with plaster and not drywall. As for the amperage and circuit it will be using the original 20a circuit the old wall heater used originally. It is a stand alone circuit. Thanks again