Notification Appliances and Notification Circuit Design
Domain 4 - Notification Appliances and Circuit Design
This domain tests audible and visible coverage, candela selection, synchronization, and the voltage-drop arithmetic that proves a notification circuit will actually work.
Audible requirements
- Public mode: 15 dBA above the average ambient sound level, or 5 dBA above the maximum ambient lasting 60 seconds or more, whichever is greater, measured 5 ft above the floor.
- Sleeping areas: 75 dBA at the pillow.
- Commercial sleeping areas generally require 520 Hz low-frequency sounders for the hearing-impaired occupant.
Visible requirements
- Mount 80–96 in. above finished floor to the top of the appliance, or per the listing.
- Candela rises with room size and ceiling height; small rooms and corridors commonly use 15 cd, larger open areas 30–110 cd per the manufacturer's spacing tables.
- Appliances within the same field of view must flash in synchronization.
Notification circuit design
- Class B: two wires plus an end-of-line resistor at the last device; an open disables everything beyond it.
- Class A: a return path keeps downstream appliances operating after an open.
- Voltage drop: V = I × R over the round-trip conductor length. The last appliance must see at least its listed minimum - for 24 V systems, commonly 85% of rating (20.4 V).
Worked example
A 2.0 A notification circuit on 200 ft one-way run of 14 AWG copper (2.58 Ω per 1,000 ft). Round trip = 400 ft → 1.03 Ω → drop = 2.1 V. 24 − 2.1 = 21.9 V, above 20.4 V, so the circuit passes. If it fell short, upsize to 12 AWG or split the circuit.
Traps
Forgetting the round trip; applying candela spacing from a different ceiling height; mixing synchronized and unsynchronized appliances on one circuit.