Total Speaker Load
Load is the sum of all the speakers in the system. Each speaker is added together at it's top setting, 1/4 - 1/2 - 1 or 2W. For hallway speakers 1W is most common. In smaller rooms, 1/4 or 1/2 will usually be adequate. Total speaker load sets the system power, but it is a good idea to factor in some headroom for those areas that might need some extra output after the fact. Speakers can be tapped up if more volume is needed later. 20% headroom is a good figure.
# of Zones
In many structures a single speaker zone is all that is required. You may want to run multiple circuits for ease of wiring. In High Rise structures it is common to use at least 1 circuit per floor.
Class A or B
In single circuit systems, A or B is field selectable. In zoned systems it requires a port change or additional components. Please specify.
Are Phones Required?
If you need fire phones, you are into a higher level system. Consult factory for high rise applications.
Example: Typical Systems
18 speakers - 12 @1W, 6 @ 1/2W, single circuit Class B
Total Speaker Load - (12 x 1) + (6 x 0.5) = 15W / # of Zones - 1 / Class B
System Required - EVAX 25 - 25W single circuit
62 speakers - 32 @ 1W, 24 @ 1/2W, 6 @ 1/4W, 5 circuits Class B
Total Speaker Load - (32 x 1) + (24 x 0.5) + (6 x 0.25) = 45.5W / # of Zones - 5 / Class B
System Required - EVAX 50/8Z - 50W 8 circuits