This is a class 2 power limited nurse call system. I have an existing 3 gang back box for a station where I intend on mounting a 1 gang station on each side. Typically I would just cut a ring in. This is a non fire rated wall. I'm hearing that I must put a box in with some flex to the 3 gang. Can you direct me to the code that dictates this. This is in a California hospital under the OSHPD jurisdiction enforcing the California Electrical Code. Thank You.