LINE ISOLATION MONITORING AND TESTING
The NFPA 99 is a standard that is built for healthcare facilities within the United States and Canada. All healthcare facilities are required to inspect and test all their Line Isolation Monitors (LIM). Unless the facility has deemed the operating rooms, by means of a risk assessment, are a non-wet procedure environment.
HOW OFTEN SHOULD ISOLATED POWER PANELS BE TESTED?
Isolated Power, according to the NFPA 99 requires all LIMs to be tested and documented at least once every 12 months (every month for older, analog designs). The model of the LIM determines the testing frequency necessary. For example, LIMs that have an analog meter the testing is monthly. If the LIM does not have self-test features, then testing is monthly. For LIMs with digital meters and self-testing features the testing is annually.
These tests shall be documented, this is to show in the event of an audit, that the system is functioning properly.

The LIM circuit shall be tested at intervals of not more than 1 month by actuating the LIM test switch. For a LIM circuit with automated self-test and self-calibration capabilities, this test shall be performed at intervals of not more than 12 months. Actuation of the test switch shall activate both visual and audible alarm indicators. – NFPA 99
NFPA 99 Code also requires that LIMs are tested after any “repair or renovation” to the system using external fault loads.
The line isolation monitor (LIM) circuit shall be tested after installation, and prior to being placed in service, by successively grounding each line of the energized distribution system through a resistor whose value is 200 x V (ohms, where V equals measured line voltage.) The visual and audible alarms shall be activated. – NFPA 99
Line isolation monitors are the watchdogs of an isolated power system. It is very important that they function correctly for the facility to remain NFPA compliant. The NFPA code requires that hospitals and healthcare facilities test all line isolation monitors.
IN NEED OF LINE ISOLATION MONITORING?


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