Frequently Asked Questions

A little information about Isolated Power System
Isolated power systems are electrical systems that are used in operating rooms and other wet locations throughout many hospitals. This system provides for additional safety against hazardous ground fault hazard.

Section 3.3.89 of NFPA99 defines an Isolated Power System Testing Services as A system comprising an isolation transformer or its equivalent, a line isolation monitor, and its ungrounded circuit conductors.
The isolated power system incorporates the use of monitors, called Line Isolation Monitors. These are informally called LIMs by technicians in the field. The line isolation monitor replaces the circuit breaker. It will alarm, instead of tripping a circuit breaker, during most ground-fault occurrences.

Section 3.3.9 of NFPA99 defines a Line Isolation Monitor as A test instrument designed to continually check the balanced and unbalanced impedance from each line of an isolated circuit to ground and equipped with a built-in test circuit to exercise the alarm without adding to the leakage current hazard. In an isolated power circuit, a ground fault would result in an alarm, but power would not be interrupted.
Section of NFPA99 addresses isolated power with regard to Critical Care Areas and states Where used in locations such as critical care areas, isolated power panels shall be permitted in those locations.
Section 3.3.184 of NFPA99 defines a Wet Procedure Location as The area in a patient care room where a procedure is performed that is 'normally subject to wet conditions while patients are present', including standing fluids on the floor or drenching of the work area, either of which condition is intimate to the patient or staff.
Section of NFPA99 addresses Wet Procedure Locations.

Section of NFPA99 states Wet procedure locations shall be provided with special protection against electric shock.

Section of NFPA99 states Operating rooms shall be considered to be a wet procedure location, unless a risk assessment conducted by the health care governing body determines otherwise.

This is the most controversial section. A risk assessment by the health care governing body can in fact deem an operating room not to be a wet procedure location. This would be contingent on interpretation of the mopping of the floor which occurs between cases as "drenching", as defined in Section 3.3.89 above.

Section of NFPA99 states Operating rooms defined as wet procedure locations shall be protected by either isolated power or ground fault circuit interrupters.

Section of NFPA99 states "Operating rooms defined as wet procedure locations shall be protected by either isolated power or ground fault circuit interrupters.
Section of NFPA99 states The use of an isolated power system (IPS) shall be permitted as a protective means capable of limiting ground-fault current without power interruption. When installed, such a power system shall conform to the requirements of

Section of NFPA99 addresses Isolated Power

Section of NFPA99 states The system shall be permitted to be installed where it conforms to the performance requirements specified in
Section of NFPA99 addresses Line Isolation Monitors

Section of NFPA99 states The monitor shall be designed such that a green signal lamp, conspicuously visible in the area where the line isolation monitor is utilized, remains lighted when the system is adequately isolated from ground; and an adjacent red signal lamp and an audible warning signal (remote if desired) shall be energized when the total hazard current (consisting of possible resistive or capacitive leakage currents) from either isolated conductor to ground reaches a threshold value of 5.0 mA under normal line voltage conditions. The line isolation monitor shall not alarm for a fault hazard current of less than 3.7 mA.

This is interesting, as many of the Line Isolation Monitors still in use are older, often analog units that are set to alarm at only 2 mA. These units must be replaced immediately, as it is a violation of code to use them.
Section of NFPA99 addresses Performance Criteria and Testing for Isolated Power System Testing Servicess.

Section of NFPA99 Line Isolation Monitor Tests states 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 alarms shall be activated.
Section of NFPA99 addresses Maintenance and Testing of the Electrical System.

Section of NFPA99 states 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.
Section of NFPA99 addresses Record Keeping.

Section of NFPA99 states A record shall be maintained of the tests required by this chapter and associated repairs or modification.

Section of NFPA99 states "At a minimum, the record shall contain the date, the rooms or areas tested, and an indication of which items have met, or have failed to meet, the performance requirements of this chapter.

Section 6.3.4..2.2 of NFPA99 Isolated Power System Testing Services (Where Installed) states A permanent record shall be kept of the results of each of the tests.
Here are the reasons to keep or install Isolated Power in all Operating Rooms:
  • Reduced Shock Hazard
  • Continuity of Power
  • Line Noise Reduction, the transformer acts as an electrical filter.
  • Advance warning system of what their equipment condition is.
  • Reduced Fire Hazard
  • Extra level of protection will keep down liability claims.
Here are some reasons why you should contract with us for your isolated power system testing and recertification services:
  • We have been in the industry for over 40 years
  • We provide complete documentation of your isolated power system leakage readings and alarm threhold limits
  • We perform our inspection services in the evenings and/or on the weekends, so as not to disturb your surgery schedule
  • Our service documentation will keep you in compliance with NFPA99 and Joint Commission accreditation requirements
Isolated Power System provides service coverage in all 50 stated in the United States, plus Canada, and throughout Latin American and the Caribbean. We cover the entire Western Hemisphere.
We have experience servicing isolated power systems and line isolation monitors manufactured byt he following companies:
  • Amsco
  • Auth
  • Bender
  • Crouse Hinds
  • Edwards
  • Electromagnetic Industries (EMI)
  • Federal Pacific
  • Federal Pioneer
  • General Electric
  • Hevi-Duty
  • Hill-Rom
  • Hospital Systems
  • Isotrol
  • Measurement Engineering Limited (MEL)
  • Post Glover
  • Russell & Stoll
  • Square D
  • Grainger
  • Schneider
Yes. We can quote you on a new isolated power system installation, or an upgrade from your current system. Send us pictures of your current system to inquire.
Feel free to contact us using the email form below, or call us at (424) 204-2382. You will need to make sure we are registered as a vendor to work in your facility. Once you send us the quantities of isolated power systems/line isolation monitors in use in your facility, we will provide you with a quote. Once we have a purchase order, we can schedule service.
We offer a complete array of healthcare technology management services, including:
  • Medical Equipment Repair and Maintenance
  • Hospital Information Technology
  • In-service Education and Service Training

Get in touch





Contact Isolated Power System

8306 Wilshire Blvd.
Suite 777
Beverly Hills, CA 90211

Phone: (424) 204-2382

Email: info@isolatedpowersystem.com

How to get service

Please email us with the quantity of isolated power systems (line isolation monitors) used in your healthcare facility. We will send you a quote.

Popular Posts