Honeywell Fire-Lite Alarms ACC-25/50 Instruction Manual page 44

Installation
Backbox = 4.75" (12.07 cm)
with Door = 4.8" (12.19 cm)
Backbox = 26.0" (66.04 cm)
with Door = 26.17" (66.48 cm)
44
Backbox = 15.5" (39.37 cm)
with Door = 15.78" (40.08 cm)
Figure 3.3 ACC-25/50 Series Backbox and Battery Box
Audio Command Center Series Manual — P/N 51889:E1 6/8/2010
Backbox Installation
Backbox = 4.22"
(10.71 cm)
with Door = 4.8"
(12.19 cm)