Line Isolation Monitors (LIM)
What is a Line Isolation Monitor (LIM)?
Isolated power systems maintain continuity of essential power to critical equipment in the event of a line-to-ground fault.
The Line Isolation Monitor (LIM) system is the core component of the Isolated Power Panel. The LIM is continuously monitoring the Total Hazard Current (THC) of all equipment powered by the panel. In the event of a line-to-ground fault an audible and visual signal will notify the medical staff of a potentially hazardous condition but the patient is still protected.
How does a Line Isolation Monitor Work?
The LIM is continuously measuring the electrical current within the operating room. If the current reaches a dangerous level, the monitor alarms, notifying caregivers of a surge in electric current. In the event of one line-to-ground fault, the Isolated Power Panel for hospitals provides uninterrupted power and also eliminates the danger of electrical shock. This allows the procedure to continue while keeping patients and caregivers safe
Isolated Power is required in category 1 critical care hospital operating rooms and other “wet procedure locations” because if a fault were to occur, the electric current will flow through the path of least resistance. In a “wet procedure location,” patients are vulnerable, critical electrical equipment is often used, and fluids are present. This combination creates a dangerous environment should an electrical fault occur.

SafeDetec LIM
SafeDetec® has been developed using advanced filtering and measurement techniques to accommodate and adapt to current and future equipment.
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Mark V LIM
Digital technology with on-board status display, event logging and communication capabilities.
Learn MoreProduct Downloads
- Plus Series Model Numbering Guide
- Plus Series Isolated Power Specifications
- Plus Series Isolated Power Systems Installation and Operation Manual
- Isolated Power Product Catalog
NFPA 99 Healthcare Facility Code Requirements:
All Isolated Power Systems and Line Isolation Monitors (LIM) are designed in compliance with NFPA 99 Healthcare Facility Code:
- 6.3.2.6.3.1 – "In addition to the usual control and protective devices, each Isolated Power System shall be provided with an approved, continually operating Line Isolation Monitors that indicates possible leakage or fault currents from either isolated conductor to ground."
Special protection against electric shock is required by NFPA 99 Healthcare Facility Code and NEC (2014 Edition) to be installed in all “wet procedure locations”. Isolated Power Systems are the preferred method of achieving this protection where power interruption cannot be tolerated.
Do you need to update your current LIM system? Click here for Line Isolation Monitors retrofitting and installation services.