When is Electric Shock Protection Required and When Should Isolation Power be Utilized?| August 7, 2017
Patient and personnel safety is critical in the design of operating rooms and other procedure rooms within hospitals and healthcare applications, especially when considering the electrical systems to be installed within these areas. Utilizing isolated power systems and ground fault protection are key design features to protect patients and personnel by mitigating shock hazards within these spaces. An understanding of these systems and the procedures performed in the areas being evaluated are important in selecting the appropriate form of mitigation to ensure the safety and health of patients and personnel.
What Is Isolated Power?
Isolated power (IP) systems consist of an isolation transformer, isolation monitoring and panelboard manufactured within a single enclosure where the neutral (ungrounded circuit conductor) on the secondary side has no direct bond ground or intentional reference to earth. The systems ungrounded neutral conductor provides the return path for single line to ground faults, protecting patients and personnel against electric shock. Since there is no intentional ground on IP system, the neutral conductor will carry the majority of the fault current, significantly reducing the amount of current that may flow through a person or other conductive materials within the space.
Patients are further protected by IP systems during critical care procedures by ensuring that a single line-to-ground fault does not interrupt power to critical systems. Critical systems include task illumination, equipment and receptacles serving areas and functions related to patient care where loss of power would be harmful to the patients and or staff. Isolation panelboards monitor and alarm when “leakage current” is detected which occurs with any line connection (short circuit) to “ground”. When a single line to ground short circuit is detected the line isolation monitor predicts potential current flow if a second short were to develop and alarms if the amount is hazardous. This allows the procedure to continue in the event of a short circuit and ensures the patients and staff are protected from a serious shock or harm from the procedure not being completed properly due to shutdown of power.
What Is Ground Fault Protection?
Most people are familiar with ground fault protection since it can be found in any bathroom or kitchen utilizing ground fault protection (GFCI) receptacles, which can be identified by the presence of a test and reset button on the device. The National Electrical Code (NEC) Article 100 defines a ground fault circuit interrupter (GFCI) as “a device intended for the protection of personnel that functions to de-energize a circuit within an established period of time when a current to ground exceeds the values established for a Class A device” (4-6mA). GFCI devices monitor the current flowing to the load and the current returning on the neutral conductor. If the return current does not equal the load current within a 5mA sensitivity the device is designed to trip (i.e. open or de-energize the circuit). What this means is that in order to protect patients and personnel, power is disabled to the electrical circuit in order to eliminate the shock hazards. This is acceptable when the safety of patients and staff is not harmed due to loss of power.
When Is Isolated Power or Ground Fault Protection Required?
In order to determine if isolated power or ground fault protection is required, a risk assessment must be conducted in accordance with NFPA 99 to determine the Risk Category of the procedures performed within the room. NFPA 99 (Health Care Facilities Code) requires that wet location patient care areas be provided with “special protection against electric shock”. It further establishes two ways to provide the protection, which includes Isolated Power or Ground Fault Current Isolation. IP and GFCI are used in different applications and a firm understanding of the procedures to be performed in the room are necessary to determine which form of protection is applicable. When it is required to maintain power while also protecting against electric shock hazards, IP is the best method, however, when power is less or not critical to maintain for patient safety, GFCI is an economical solution.
NFPA 99 defines (4) different Categories which would dictate when to use one form of protection or the other. Categories 1 and 2 consist of systems that if power is lost could cause serious injury or death, which are the categories that would require Isolation Power to ensure power is not lost. Categories 3 and 4 consist of systems where a loss of power is less detrimental and may cause mild discomfort or have no adverse effects at all, these categories can utilize GFCI protection as loss of power is not a critical issue.
What Classifies a Room as “Wet” and Changes to Operating Room Wet Classification
NFPA 99 (Section 3.3.171) classifies a wet procedure location as “The area in a patient care space 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.” Based upon this definition, the 2012 edition of NFPA 99 revised the classification of OR’s such that they are always considered wet areas unless determined to be dry after conducting a risk assessment. Although previous versions of NFPA 99 indicated that wet procedure locations required special protection against electric shock, they did not automatically define all OR’s as wet. This change was included in Chapter 6 (Section 126.96.36.199.8.4) which states the following: “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 shift requires that the health care governing body now prove through a risk assessment that the operating room is dry rather than proving that it is wet.
One thing to point out here is the risk assessment is conducted by the health care governing body, meaning, although the engineer will provide input, the hazard category is not determined by the engineer. The final determination of the hazard category is provided by the health care governing body since they understand the procedures performed within their hospital the most.
Therefore, at the start of the process of designing a new operating room or renovating an existing operating room the conversation should be started with the client to determine if the OR is a wet location based upon the risk assessments. If a risk assessment cannot be completed during the design, or it is determined the OR is a wet location, an isolation panelboard shall be provided to serve the OR(s) to meet the requirements of NFPA 99 188.8.131.52.8.7.