Det-Tronics U7602B-P Unitized UV Flame Detector/Controller - Manual (Page 18)

MODIFICATIONS TO ELIMINATE
HIGH BACKGROUND UV FAULTS
In applications where high background UV radiation
causes the U7602 to produce a fault response, it may
be necessary to disable the high sensitivity signal.
While the module will continue to perform the auto-
matic optical integrity (oi) test and to produce a fault
indication in the event of low detector sensitivity, it is
important to note that this modification disables the
ability of the U7602 to respond to high sensitivity
symptoms that could indicate background UV, spuri-
ous detector response, or a faulty, over-sensitive
detector module. An over-sensitive detector module
can cause a system actuation when no fire exists.
To disable the U7602 high sensitivity signal line:
1. Remove U7602 input power.
2. Remove the controller housing (Figure 1).
3. Cut out the white wire that joins connection point
7 on the third circuit board down from the top as
indicated in Figure 20, and connection point 5 on
the fourth circuit board from the top as indicated
in Figure 21. Remove the wire.
4. Re-install the controller housing.
5. Restore U7602 input power.
Operating Mode Fire Relay Fault Relay LED Current Output 4 to 20 ma Output
(if equipped) (standard) (if equipped)
Normal open closed on 40 microamps 4 milliamperes
Reason and Corrective Action: U7602 was not reset after fire or fault condition, oi test, or background radia-
tion detected and problem corrected.
Normal closed closed off 40 microamps 4 milliamperes
Reason and Corrective Action: If there is no fire but the Fire relay contacts are closed and the system is oth-
erwise operating normally, remove power from the U7602. If the Fire relay contacts remain closed, their ratings
may have been exceeded and the contacts are welded shut. Ensure that devices connected to the relays do
not exceed relay ratings. Be especially careful of end-of-line-capacitor type fire panels as these connections
often exceed the U7602 relay contact rating. Replace the controller module and return the defective one to the
factory for repair.
Fault open open or opening on 80 microamps 6 milliamperes
and closing or cycling
intermittently 40 to 80 to 40
Reason and Corrective Action: An oi fault has occurred. The first step in correcting this problem is to clean
the viewing window and oi ring on the detector housing following the instructions in the "Maintenance" section.
Remove the oi ring and clean and inspect the underside for a pitted or corroded surface. If the reflective sur-
face has been damaged at all, replace the oi ring. Re-install the oi ring (making sure that the oi test lamp and
the split in the oi ring are not aligned) and perform an oi test using the procedure described in the "System
Startup Procedure/ oi Test" section. If the fault persists, replace the detector module.
Fault open open on 120 microamps 8 milliamperes
Reason and Corrective Action: Background radiation is being detected or the detector module is too sensi-
tive. Check for extraneous sources of UV radiation. If none are present, replace the detector module. If extra-
neous UV sources are present, try to eliminate them or try to reposition the detector/controller so that the extra-
neous UV sources are outside of its cone of vision, while its view of the hazardous area is maintained. If these
methods don't work, consider modifying the module to eliminate fault conditions due to high levels of back-
ground UV (per "Modifications to Eliminate High Background UV Faults" procedure), or replace the detector
module with the DE1888T2 model, which has a lower sensitivity and is designed for this type of application.
Fault open open on 160 microamps 10 milliamperes
Reason and Corrective Action: This fault indicates a malfunction in the high voltage circuitry (which supplies
the detector module) in the controller module. To isolate the source of the problem, perform the
"Troubleshooting" procedure described in detail in this manual.
Fault open open off 0 microamps 0 milliamperes
Reason and Corrective Action: Input power not applied to detector/controller or defective controller module.
Apply input power or replace defective controller module.
Table 3—Troubleshooting Guide
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