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Electrical Safety–NFPA 99 Requirements

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1 Electrical Safety–NFPA 99 Requirements
April 2014 Created by: SSgt Hans Arcand

2 2012 NFPA - Testing Intervals
- Electrical safety tests must be performed when equipment is initially installed, and after any patient-care related repairs or modifications Electrical Safety Inspections Include: - Leakage Current (Fixed Equipment) - Touch Current (Portable Equipment) - Lead Leakage (All Leads Tested In Parallel) - Resistance Measurements (All Units) Reference NFPA 99, 2012, Section , Testing Intervals

3 Visual Inspection Visually inspect the power cord assy for signs of degradation…pay close attention to the means of grounding. -Power Cord Assy - Power Cord - Attachment Plug - Cord Strain Relief - Look for cuts, knicks, abrasions, tears or possible separation of the power cord assy, and its contents. - Visual electrical safety inspections do not have to be formally documented, BUT they will be completed on all scheduled AND unscheduled maintenance work orders. BE OBSERVANT!!! Reference NFPA 99, 2012, Section , Physical Integrity

4 Power cord Resistance - Power Cord Resistance Tolerances - NFPA Ohms – Maximum Permissible Limit Within a Healthcare Facility (1)The cord shall be flexed at its connection to the attachment plug or connector. (2)The cord shall be flexed at its connection to the strain relief on the chassis. - IEC Detachable Power Cord Ohm Non-Detachable Power Cord Ohms - Polarity tests are recommended on initial equipment assembly and power cord repairs. Reference NFPA 99, 2012, Section , Resistance

5 Leakage Current testing – Fixed Equip
- Leakage current refers to the current that is felt on the grounding conductor of FIXED/PERMANENTLY-WIRED EQUIPMENT - Leakage tests shall be performed in the ‘ON’ and ‘OFF’ positions to simulate real- world patient-care situations - Leakage current shall not exceed 10mA through the grounding conductor of permanently-wired equipment, while grounds are lifted. - No annual requirement for performing electrical safety tests on fixed/ permanently- wired equipment. Reference NFPA 99, 2012, Section , Fixed Equipment

6 Touch current - Previously known as chassis leakage, chassis touch, or leakage current - Refers to the leakage current through the chassis/housing of portable equipment - Touch current limits - Cord-connected equipment/normal polarity/ground intact- 100uA - Cord-connected equipment/normal polarity/ground disconnected - 500uA - When multiple devices are connected together and more than one power cord supplies power, the devices shall be separated into groups according to their power supply cord, and the leakage current shall be measured independently for each group as an assembly. If the collective leakage current of connected devices exceeds 500uA, efforts to reduce the leakage current must be made. (e.g. separating equipment/appliances, additional power supplies) Reference NFPA 99, 2012, Section , Touch Current Limits

7 Lead leakage testing - Leads should be tested in parallel (all connected) - The testing of individual leads is no longer required, per NFPA 99, 2012 rev. - Lead Leakage is performed with the plug connected normally and the device ON - Limits -100uA/Ground Connected -500uA/Ground Open Reference NFPA 99, 2012, Section , Testing Intervals

8 NFPA Testing diagrams 2-Wire Resistance Measurement -Two-Wire Resistance Technique. A known current is fed through the unknown resistance. A high-input-impedance voltmeter measures the voltage drop across the resistance, R, and R is calculated as voltage divided by impedance, V/I. This technique measures the lead resistance in series with the unknown resistance. When the unknown resistance is a ground wire (less than 0.15 ohm), the lead resistance is appreciable. This is accounted for by shorting the lead wires together and “zeroing” the voltmeter. The actual resistance, in effect, subtracts out the lead wire resistance. In order for this technique to be reasonably accurate for measuring ground wires, an active high-impedance millivoltmeter has to be used. Reference NFPA 99, 2012, Section A10.3.2, Resistance

9 NFPA Testing diagrams 4-Wire Resistance Measurement Four-Wire Resistance Technique. This technique is very similar to the two-wire resistance technique. The difference is that the known current is fed to the resistance to be measured through a pair of leads separate from the pair of leads to the voltmeter. The voltmeter is measuring the true voltage across the resistance to be measured, regardless of the resistance of the measuring leads. This method eliminates the need for zeroing out the measuring lead resistance. Reference NFPA 99, 2012, Section A10.3.2, Resistance

10 NFPA Testing diagrams AC Current Method AC Current Method. This technique utilizes a step-down transformer of known voltage output to feed current through the ground wire and measure the current that flows. The impedance of the ground wire is then calculated by Ohm’s law. Reference NFPA 99, 2012, Section A10.3.2, Resistance

11 Leakage current tests -
NFPA Testing diagrams If the required performance is obtained by a meter with integral response-shaping properties, then that meter should have a constant input resistance of 1000 ohms. (A high-input-impedance meter can be used by shunting a 1000 ohm resistor across the meter’s input terminals.) If, however, the required frequency response is obtained by a network that precedes an otherwise flat-response meter, then the input impedance of the network should be ohms ±10 percent, over the frequency range from 0 to 1 MHz, and the frequency response of the network–meter combination should be substantially independent of the impedance of the signal source. For maximum chassis leakage current permitted (i.e., 300 μA) below 1 kHz, this network will yield the limiting current of 10 mA above 30 kHz. Reference NFPA 99, 2012, Section A10.3.3, Leakage Current Tests

12 2012 NFPA changes Reference NFPA 99, 2012, Section 10.3.6.3
The 2012 edition of NFPA 99 has eliminated the 2005 edition requirements for the leakage current tests between each patient lead and ground; the isolation test; and the tests of leakage current between any one lead and each other lead, non-isolated input, and isolated input. This decision was based on an effort to streamline regular testing requirements and to ensure that the effort expended in required testing provides a reasonable level of safety value. The remaining requirement for testing the leakage current between all patient leads connected together and ground, as well as the touch current tests, is considered to be sufficient to determine any failures in leakage current protection for patients connected to portable equipment. Reference NFPA 99, 2012, Section

13 Patient/non-patient owned electrical devices
- Electrical appliances/equipment in patient-care areas shall be visually inspected by patient care staff or other personnel - Non-patient care items must be in a clean, serviceable and working order, in order to be used in the healthcare facility - Equipment that is deemed unsafe, dirty or in unserviceable condition, shall be immediately removed from service - Non-patient care items, in patient care areas, are not required to meet the same electrical safety requirements, as defined throughout this training. - a few examples of these non-patient care items include: -computers, speakers, dvd players…etc Reference NFPA 99, 2012, Section , Portable Equipment in Patient Care Room.

14 Extension Cords - Only used in emergencies - No 3 to 2-prong connectors are allowed in healthcare facilities - Extension cords will be tested for: 1. Physical Integrity 2. Polarity 3. Continuity of grounding at the time of assembly

15 WHAT DOES THIS ALL MEAN? Electrical Safety Measurements (e.g., Touch Curent, Chassis Current, Grounding Resistance, Lead Leakage) will only be completed during INITIAL INSPECTION/ACCEPTANCE work orders, and ALL open-case REPAIRS. Visual Safety Inspections (e.g., inspection of power cord assy, strain reliefs, attachment plugs and chassis integrity) will be conducted during EVERY scheduled AND unscheduled maintenance activity. --Visual safety inspections are the new electrical safety standard, as outlined in NFPA 99, 2012 Edition.

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17 Set-up 232d For PCR/CL, external lead, the unit needs to be set to Case Leakage uA, EXT LEAD, w/ ground closed For CL through the Ground Conductor, the unit needs to be set to Case Leakage uA, GROUND CONDUCTOR, w/ ground open

18 Fluke 232D – Safety Analyzer
- Grounding resistance of the equipment power cord; - Leakage current from the equipment's chassis or ground wire; - Equipment load current; - Voltage gradient (mV) and intergrounding resistance (mOhms) using the external meter function; and - Power system AC voltages: • neutral to hot, • neutral to ground, and • hot to ground - Fault Conditions • neutral (open and closed) • ground (open and closed) • polarity (normal and reverse) An internal ground fault circuit interrupter (GFCI) protects both the operator and the equipment under test. If a hot line to ground fault condition exceeding 10 milliamperes occurs, line voltage is immediately removed from the test receptacle.

19 Fluke 232d cont’d - Leakage current tests referenced to power ground • on all patient electrodes; • on individual patient electrodes-RL, 'RA, LA, LL, and the Vl-6 set; and • between specified patient electrode pairs: right arm and left arm (RA-LA), right arm and right leg (RA-RL), and left arm and right leg (LA-RL). - Isolation of all patient electrodes from ground with 120 VAC applied by the analyzer. (The current-limited test voltage is applied to the patient electrodes only when a front panel push-button is depressed and held by the operator.)


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