521LX/521LXT Installation Sheet
Digital Monitoring Products
3
Sensitivity Level Test Mode
Each smoke detector also includes a special sensitivity level test mode
activated by holding a magnet near the integral reed switch for more than
one second. See Figure 6. Once the routine starts, the alarm LED flashes
one to nine times, indicating actual sensitivity and whether or not service is
required. See the
521 Sensitivity Table
.
After the sequence of blinks, if the sensitivity is found to be within limits and
if all other tests pass, the detector goes into alarm until reset by the panel.
If the sensitivity is not within limits, or an unser viceable hardware fault is
detected, the alarm LED con tinues to flash once per second until the detector
is reset by the panel. If the sensitivity test is not within guidelines, take
action as recommended in the
521 Sensitivity Table
.
Approximate
Obscuration (% ft.)
Blinks
Indication
Action
Photo
1
Reset unit and re-run sensitivity test, if
indication remains the same, replace unit.
4.35
2
Detector is not sensitive enough.
Clean per instructions. Reset unit and re-run
sensitivity test, if indication remains the same,
replace unit.
3.85
3
3.60
4
Detector is within sensitivity
limits.
None
3.10
5
2.60
6
2.10
7
1.85
8
Detector is too sensitive.
Check to be sure optical block cover is snapped
down completely. Clean per instructions.
1.35
9
Table 1: 521 Sensitivity Table
Smoke Detector Dip Switches
If there are dip switches to the left of the screw terminals, they are factory preset and must not be changed.
Maintenance, Cleaning, and Sensitivity
The smoke detectors are designed for easy field service and maintenance. If a smoke detector drifts beyond its
approved sensitivity range for more than 24 hours or fails internal diagnostic tests during power-up, the unit
automatically indicates trouble by flashing its LED every second. Under normal conditions the LED flashes every nine
seconds. Therefore, a simple visual check of the LED status meets NFPA 72 field sensitivity testing requirements
without the need for external meters or ladders. In accordance with NFPA 72-7-3.2.1, smoke detector sensitivity
should be checked within one year after installation and every alternate year thereafter, in commercial installations,
or every three years in residential sites.
The photoelectric detector sensing chamber un snaps for easy field cleaning and service. Whenever the status LED
indicates cleaning is necessary, remove the photoelectric detector cap, snap off and throw away the optical block.
Then blow or brush off the optical block base and snap a new optical block chamber back in place (see Figure 5),
replace the cap and verify sensitivity with the Sensitivity Level Test.
Figure 6: Sensitivity
Testing the 521LX/521LXT
Reed
Switch
Magnet
