To provide a margin of safety for the consumer, regulatory agencies usually require that a product exhibit a line voltage leakage current of less than 0.5mA. With some products equipped with 3-prong plugs and warning stickers, the permissible leakage current may be as high as 0.75mA, but the typical limit is 0.5mA. Since hipot tests are usually required for 100% of the units in a production line, and since hipot tests are more stringent, line voltage leakage tests are normally specified as design or type tests and not as production line tests. Line voltage leakage tests are typically required on all medical products as a production test.
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Line voltage leakage test are conducted with a circuit similar to that shown in Figure 17, measuring the leakage current under various fault conditions such as “no ground” or with line and neutral connections reversed. Voltage is applied first with normal line and neutral connections, followed by a test with the connections reversed, and then with no ground.
The measurement of leakage current is a requirement for type testing of any mains powered product. A compliance laboratory or National Recognized Test Lab (NRTL) normally performs the type testing on a sample of products during the design phase. Once the type testing is complete generally no further leakage testing is required on a production basis with the exception of medial products. Leakage current measurements are routinely performed on the production line for medical products for safety reasons.
10.1.2
Experimental or research apparatus built to order or under development shall be used under qualified supervision and shall have a degree of safety that is equivalent to that described herein or that has been deemed acceptable by the facility.
10.2.2.1.1
All cord-connected electrically powered appliances that are not double insulated and are used in the patient care vicinity shall be provided with a three-wire power cord and a three-pin grounding -type plug
10.2.2.1.2
Double-insulated appliances shall be permitted to have two conductor cords and shall be rated as Class II devices.10.2.2.3.1
Appliances supplied by other than 120-V single-phase systems shall use the grounding -type plug (cap) appropriate for the particular power system.10.2.2.3.2
The grounding prong of the plug shall be the first to be connected to, and the last to be disconnected from, the receptacle
10.2.2.3.3
If screw terminals are used, the stranded conductor shall be twisted to prevent stray strands, hut the bundle shall not be tinned after twisting.
10.2.2.3.4
If the conductor is not twisted, it shall be attached by an approved terminal lug.
10.2.2.3.5
The power cord conductors shall be arranged so that the conductors are not under tension in the plug
10.2.2.3.6
The grounding conductor shall be the last one to disconnect when a failure of the plug 's strain relief allows the energized conductors to be disrupted.
10.2.2.3.7 Strain Relief
Strain relief shall be provided.
10.2.2.3.7.1
The strain relief shall not cause thinning of the conductor insulation.
10.2.2.3.7.2
The strain relief of replaceable plugs shall be capable of being disassembled.
10.2.2.3.7.3
Plugs shall be permitted to be integrally molded onto the cord jacket if the design is listed for the purpose.10.2.2.3.8 Testing
The wiring of each cord assembly shall be tested for continuity and polarity at the time of manufacture, when assembled into an appliance , and when repaired.
10.2.3.1.1
The flexible cord, including the grounding conductor, shall be of a type suitable for the particular application; shall be listed for use at a voltage equal to or greater than the rated power line voltage of the appliance ; and shall have an ampacity , as given in Table 400.5(A) of NFPA 70, National Electrical Code, equal to or greater than the current rating of the device.
10.2.3.1.2
"Hard Service" (SO, ST, or STO), 'Junior Hard Service" (SJO, SJT, or SJTO), or equivalent listed flexible cord shall be used, except where an appliance with a cord of another designation has been listed for the purpose.
10.2.3.2.1
Each electric appliance shall be provided with a grounding conductor in its power cord.
10.2.3.2.2
The grounding conductor shall be not smaller than 18 AWG.
10.2.3.2.3
The grounding conductor of cords longer than 4.6 m (15 ft) shall be not smaller than 16 AWG.
10.2.3.2.4*
grounding conductor in the power cord shall not be required for double-insulated appliances , but a functional ground conductor (functional earth conductor) shall be permitted.10.2.3.3.1
A detachable power cord shall be permitted if an accidental disconnection would not present an unacceptable hazard or if a mechanism that reliably prevents inadvertent disconnection is used.
10.2.3.3.2
Separable power cord sets shall be designed so that the grounding conductor is the first to be connected and the last to be disconnected.
10.2.3.3.3
The cord set to the appliance shall be listed for the purpose.
10.2.3.4.1
Power cords, regardless of whether intended for use on grounded or isolated power systems , shall be connected in accordance with the conventions of a grounded system.
10.2.3.4.2
The circuit conductors in the cord shall be connected to the plug and the wiring in the appliance so that any of the following devices, when used in the primary circuit, are connected to the ungrounded conductor:
10.2.3.4.3
A second fuseholder or other overcurrent protective device provided in the appliance shall be permitted to be placed in the grounded side of the line.
10.2.3.5.1
Cord strain relief shall be provided at the attachment of the power cord to the appliance so that mechanical stress, either pull, twist, or bend, is not transmitted to internal connections.
10.2.3.5.2
Astrain relief molded onto the cord shall be bonded to the jacket and shall be of compatible material.
10.2.3.6 Multiple Outlet Connection
Two or more power receptacles supplied by a flexible cord shall be permitted to be used to supply power to plug -connected components of a movable equipment assembly that is rack-, table-, pedestal-, or cart-mounted, provided that all of the following conditions are met:
10.2.4.1
Three-prong to two-prong adapters shall not be permitted.
10.2.4.2
Adapters and extension cords meeting the requirements of 10.2.4.2.1 through 10.2.4.2.3 shall be permitted.
10.2.4.2.1
All adapters shall be listed for the purpose.
10.2.4.2.2
Attachment plugs and fittings shall be listed for the purpose.
10.2.4.2.3
The cabling shall comply with 10.2.3
10.3.1* Physical Integrity
The physical integrity of the power cord assembly composed of the power cord, attachment plug , and cord-strain relief shall be confirmed by visual inspection.
10.3.2.1
For appliances that are used in the patient care vicinity , the resistance between the appliance chassis, or any exposed conductive surface of the appliance , and the ground pin of the attachment plug shall be less than 0.50 ohm under the following conditions:
10.3.2.2
The requirement of 10.3.2.1 shall not apply to accessible metal parts that achieve separation from main parts by double insulation or metallic screening or that are unlikely to become energized (e.g., escutcheons or nameplates, small screws).
10.3.3.1.1
The requirements in 10.3.3.2 through 10.3.3.4 shall apply to all tests.
10.3.3.1.2
Tests shall be performed with the power switch ON and OFF.
10.3.3.2 Resistance Test
The resistance tests of 10.3.3.3 shall be conducted before undertaking any leakage current measurements.
10.3.4.1
Permanently wired appliances in the patient care vicinity shall be tested prior to installation while the equipment is temporarily insulated from ground.
10.3.4.2
The leakage current flowing through the ground conductor of the power supply connection to ground of permanently wired appliances installed in general or critical care areas shall not exceed 10.0 mA (ac or dc) with all grounds lifted.
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10.3.5.1* Touch Current Limits
The touch current for cord-connected equipment shall not exceed 100 pA with the ground wire intact (if a ground wire is provided) with normal polarity and shall not exceed 500 pA with the ground wire disconnected.
10.3.5.2
If multiple devices are connected together and one power cord supplies power, the leakage current shall be measured as an assembly.
10.3.5.3
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.
10.3.5.4.1
If the appliance has fixed redundant grounding (e.g., permanently fastened to the grounding system ), the touch leakage current test shall be conducted with the redundant grounding intact.
10.3.5.4.2
Test shall be made with Switch A in Figure 10.3.5.4 closed.
10.3.6.1
The leakage current between all patient leads connected together and ground shall be measured with the power plug connected normally and the device on.
10.3.6.2
An acceptable test configuration shall be as illustrated in Figure 10.3.5.4
10.3.6.3
The leakage current shall not exceed 100 µA for ground wire closed and 500 µA ac for ground wire open.
10.4.2.1
Nonpatient care—related electrical equipment, including facility- or patient-owned appliances that are used in the patient care vicinity and will, in normal use, contact patients, shall be visually inspected by the patient's care staff or other personnel.
10.4.2.2
Any equipment that appears not to be in proper working order or in a worn condition shall be removed from service or reported to the appropriate maintenance staff.
10.5.2.1.1
The facility shall establish policies and protocols for the type of test and intervals of testing for patient care-related electrical equipment.
10.5.2.1.2
All patient care—related electrical equipment used in patient care rooms shall be tested in accordance with 10.3.5.4 or 10.3.6 before being put into service for the first time and after any repair or modification that might have compromised electrical safety.
10.5.2.3.1
Adapters and extension cords meeting the requirements of 10.2.4 shall be permitted to be used.
10.5.2.3.2
Three-to-two-prong adapters shall not be permitted.
10.5.2.3.3
The wiring shall be tested for all of the following:
10.5.2.4 Devices Likely to Be Used During Defibrillation
Devices that are critical to patient safely and that are likely to be attached to the patient when a defibrillator is used (such as ECG monitors) shall be rated as "defibrillator proof."
10.5.2.5* System Demonstration
Any system consisting of several electric appliances shall be demonstrated to comply with this code as a complete system.
10.5.2.6 Electrical Equipment Systems
Purchase contracts for electrical equipment systems, such as nurse call and signaling that consist of interconnected elements, shall require all of the following:
10.5.3.1
The manufacturer of the appliance shall furnish documents containing at least a technical description, instructions for use, and a means of contacting the manufacturer.
10.5.3.1.1
The documents specified in 10.5.3.1 shall include the following, where applicable:
10.5.3.1.2
Service manuals, instructions, and procedures provided by the manufacturer shall be considered in the development of a program for maintenance of equipment.
10.5.4.1 Electrical Equipment in Oxygen-Enriched Atmospheres
They shall have both of the following characteristics:
FIGURE 10.5.4.1(a) Resistance Circuits (L < 1 mH): Minimum Igniting Currents, Applicable to All Circuits Containing Cadmium, Zinc, or Magnesium.
FIGURE 10.5.4.1(b) Resistance Circuits (L < 1 mH): Minimum Igniting Currents, Applicable to Circuits Where Cadmium, Zinc, or Magnesium Can Be Excluded.
FIGURE 10.5.4.1(c) Inductance Circuits (L > 1 mH): Minimum Igniting Currents at 24 V, Applicable to All Circuits Containing Cadmium, Zinc, or Magnesium.
FIGURE 10.5.4.1(d) Inductance Circuits (L > 1 mH): Minimum Igniting Currents for Various Voltages, Applicable to All Circuits Containing Cadmium, Zinc, or Magnesium.
FIGURE 10.5.4.1(e) Inductance Circuits (L > 1 mH): Minimum Igniting Currents at 24 V, Applicable Only to Circuits Where Cadmium, Zinc, or Magnesium Can Be Excluded.
FIGURE 10.5.4.1(f) Capacitance Circuits Minimum Ignition Voltages. (The curves correspond to values of current-limiting resistance as indicated. The curve marked Sn is applicable only where cadmium, zinc, or magnesium can be excluded.)Appliances , or a part(s) of an appliance or a system (e.g., pillow speaker, remote control, pulse oximeter probe), to be used in the site of intentional expulsion shall comply with one of the following:10.5.4.2
When only the remote control or signal leads of a device are to be used in the site of intentional expulsion , only the control or signal leads shall be required to comply with 10.5.4.1
10.5.4.3
Subparagraphs 10.5.4.1 and 10.5.4.2 shall not apply to small (less than 2 W), hermetically sealed heating elements such as light bulbs.
10.5.4.4
Electrical equipment sold with the intent to be used in oxygen-enriched atmospheres shall be listed for use in oxygen-enriched atmospheres
10.5.4.6*
High-energy-delivering probes (such as defibrillator paddles) or other electrical devices that do not comply with 10.5.4.1 and 10.5.4.2 , that are deemed essential to the care of an individual patient, and that must be used within an administration site or within oxygen -delivery equipment shall be permitted.
10.5.5.1*
The laboratory shall establish policies and protocols for the type of test and intervals of testing for appliances
10.5.5.2*
The physical integrity of the power cord, attachment plug , and cord-strain relief shall be confirmed at least annually by visual inspection and other appropriate tests.
10.5.6.1.1
A permanent file of instruction and maintenance manuals shall be maintained and be accessible.
10.5.6.1.2
The file of manuals shall be in the custody of the engineering group responsible for the maintenance of the appliance
10.5.6.1.3
Duplicate instruction and maintenance manuals shall be available to the user.
10.5.6.1.4
Any safety labels and condensed operating instructions on an appliance shall be maintained in legible condition.
10.5.6.2.1
A record shall be maintained of the tests required by this chapter and associated repairs or modifications.
10.5.6.2.2
At a minimum, the record shall contain all of the following:
10.5.6.3 Test Logs
A log of test results and repairs shall be maintained and kept for a period of time in accordance with a health care facility's record retention policy.
10.5.8.1*
Personnel concerned for the application or maintenance of electric appliances shall be trained on the risks associated with their use.
10.5.8.1.1
The health care facilities shall provide programs of continuing education for its personnel.
10.5.8.1.2
Continuing education programs shall include periodic review of manufacturers' safety guidelines and usage requirements for electrosurgical units and similar appliances
10.5.8.2
Personnel involved in the use of energy-delivering devices including, but not limited to, electrosurgical, surgical laser, and fiberoptic devices shall receive periodic training in fire suppression.
10.5.8.3
Equipment shall be serviced by qualified personnel only.
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