Monday, October 24, 2011

How often should we test line isolation monitors (LIMs)?  Is monthly often enough for maintenance testing?

If you are being surveyed to the 2000 Life Safety Code, the 1999 version of NFPA 99 applies insofar as TJC accreditation is concerned.  I believe you will have to meet newer AHCA requirements for any new installations, but not for maintenance testing.

Newer versions of NFPA 99 changed the chapter numbering to 4.3.3.3.2 Line Isolation Monitor Tests, but the following excerpt is from NFPA 99-1999, which is a mandatory reference from the 2000 Life Safety Code.  The paragraph references are to the detailed construction and operational requirements for the LIM.

3-3.3.4 Isolated Power Systems.
3-3.3.4.1 Patient Care Areas. If installed, the isolated power system shall be tested in accordance with 3-3.3.4.2.
3-3.3.4.2 Line Isolation Monitor Tests. The proper functioning of each line isolation monitor (LIM) circuit shall be ensured by the following:

a) The 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 of 200 x V ohms, where V = measured line voltage. The visual and audible alarms [see 3-3.2.2.3(b)] shall be activated.

(b) The LIM circuit shall be tested at intervals of not more than 1 month by actuating the LIM test switch [see 3-3.2.2.3(f)]. 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.

(c) After any repair or renovation to an electrical distribution system and at intervals of not more than 6 months, the LIM circuit shall be tested in accordance with paragraph (a) above and only when the circuit is not otherwise in use. 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.

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