We are working on an addition to our home. On the electrical drawing we put that we were adding a smoke detector to the family room. The inspector stamped on there "smoke detectors each level each bedroom interconnected battery back-up" He then wrote "if the addition is over 25% of the largest floor, min of one each level." We started to run the wiring today and then got to thinking....
We already have interconnected battery backup units on each floor of the house, including the main floor which is where the addition is. Does another one then NEED to be added and to be interconnected also? Or does the one on that floor already count, and we can just add a battery operated unit (combo carbon monoxide) as we planned?
First off, this is a building code issue, not an electrical isue. Luckily most electricians know this area of the code.
that being said, every area is different as to actual specs.
I can safely assume he will allow the existing units to be used to interconnect with the new ones. It would be crazy not to.
Make SURE that the old units are compatable with whatever new ones you get.
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.