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Line Isolation Monitor Testing

The line isolation monitor is a critical component of an isolated power system. The line isolation monitor continuously monitors the isolated power system’s impedance from all conductors to ground. Impedance includes both resistive and capacitive readings. This value is then used to calculate the Total Hazard Current (THC), which dictates what current could flow if a patient were to come in contact with a conductor to ground. The THC reading provides advanced warning of issues that are present in the system.

Since the line isolation monitor is on an isolated power system, power interruption is not necessary and critical processes may continue to run. Continuity of power is maintained on systems where interruption cannot be tolerated. A single ground fault condition will also not trip the main circuit breaker. Appropriate actions may be taken while the system remains online.

The basic principle behind the system is that while a patient is anesthetized during treatment, and if there were a fault in the line, the patient would essentially be electrocuted and you wouldn’t have any way of knowing without the LIM installed.

The NFPA 99 states that a line isolation monitor (LIM) circuit shall be tested after installation , and prior to being placed into service. After installation the NFPA 99 requires that the line isolation monitor and ground fault circuit interrupter (GFCI) tests be conducted at regular intervals.

Medical Testing Solutions, can supply you with the industry leading monitors while ensuring that they are installed and tested correctly.