What do you find to be the biggest challenge with underground conduit installation? Place reinforcing steel at all four corners, with four inches of concrete cover around conduits. Because all boxes are prone to collect water if you live in a wet area. Article 250 is a foundational pillar of the NEC; it should be studied in its entirety to make sure that both grounding and bonding are done properly. But if you dont receive helpful feedback, all hope isnt lost. How high up do the conduit pipes need be be from the bottom of the underground handhold to avoid flooding during rainstorm? 0000003210 00000 n The termination fittings are specifically listed for Classes I , Division 1 locations. 100, includes installations underground, in concrete slabs in direct contact with the earth, locations subject to saturation with water, and unprotected locations exposed to weather. 770.3). As outlined in Sec. ARTICLE 300 - General Requirements for Wiring Methods and Materials Part I. In these instances, first, check with your local jurisdiction in charge. Always contact your local building authority for complete and up to date code information. As a general recommendation, houses also should have a receptacle at each side of a deck or balcony, accessible from the ground. 3/4-inch Conduit: Up to 16 of the 12-gauge wires. In your case, your steel rebar has a copper ground loop at the very bottom of the system. Privacy Policy Anyone familiar with conduit relining as used in plumbing being used in electric conduit? Concrete works as well as its fluid, and itll flow around conduits filling almost all air gaps. This will maintain the undisturbed state of natural soils. trailer c. Cables or raceways installed using directional boring equipment must be approved by the authority having jurisdiction (AHJ) for this purpose. The article also explains how cables shall be arranged so as to prevent damage to the enclosed conductors. MINIMUM COVER REQUIREMENTS, 0 . This will maintain the current carrying capacity of your conductors. The underground system should only occupy one lane of travel when installed in . Your IP: Because travelling lower underground, the soil becomes more tightly packed trapping out air. Data transmission wires (telephone, internet, etc.) thick that provides equal or better protection against nail or screw penetration shall be permitted. Electrical grounding or Grounding originally began as a safety measure used to help prevent people from accidentally coming in contact with electrical hazards. Low-voltage light fixtures (aka: luminaires) must be no closer than 5 feet from the outside walls of pools, spas, or hot tubs. G) Provide the minimum separation for instrumentation conduits from power conduits as follows: H) Place caution tape at least 12-inches above underground installations, not concrete encased. d_pM[XM=@rvm@4[ n: Idaho: 016438 | Utah: 8340037-5502 | Wyoming: M-45175, National Electric Codes for Outdoor Wiring. The level of compaction needs to match the density of surrounding undisturbed soil. The inspector said I needed some sort of fitting to attach to the conduit of my underground service entrance that would absorb shock if the house should ever come off of its foundation. Becoming familiar with the proper use of these tables can help installers ensure proper grounding and bonding on their projects and, in turn, ensure the safety of those within the building. 0000003513 00000 n This is one reason to add expansion fittings on vertical risers, to allow for settling. This also doesnt imply that the sealing material provides a watertight seal, but only that it prevents moisture from entering the raceways. Aug 18, 2009. Extreme temperature swings cause conduit damage from expansion and contraction. Koosha started Engineer Calcs in 2020 to help people better understand the engineering and construction industry, and to discuss various science and engineering-related topics to make people think. Thanks for killing some nasty urban legend! Receptacles in damp locations (under protective covers, such as a porch roof) must be weather-resistant and have a weatherproof (weathertight) cover. Our system is ground mounted, and the wiring comes together in a junction box on the mounting structure where two strings of ten panels are wire nutted together connected to an underground run that's in conduit to the inverter. Also, the temperature swings underground are much slower. All conductors of the same circuit, including grounded conductors, shall be contained in the same raceway, cable, or trench. Homes must have at least one outdoor receptacle at the front and rear of the house. 0000002750 00000 n All Trenches must be a minimum of 36" deep. The applicable rules for outdoor cables and conduits include: This is not an NEC requirement, but it could save your life, not to mention prevent considerable trouble with your service providers. Youll find many other underground conduit installation case scenarios listed. Install a layer of rigid insulation above your conduit in the area youve excavated. 83338 document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Get daily articles and news delivered to your email inbox, voltage drop calculation showing the effects of wire resistance on current, Electrical Conduit Guide With 10 Useful Tips, 22 Tips How to Study Engineering Subjects, 7 Must Know Mechanical Engineering Design Tips. Also, the backfill material should meet the following requirements: If the material excavated from the site meets these requirements, use it as backfill. Check out my voltage drop calculation showing the effects of wire resistance on current. The very reason the original GFCI circuit breaker tripped indicates that there is something wrong with the circuit, and the GFCI circuit breaker was providing . endstream endobj 15 0 obj<> endobj 17 0 obj<> endobj 18 0 obj<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 19 0 obj<> endobj 20 0 obj<> endobj 21 0 obj<> endobj 22 0 obj<> endobj 23 0 obj<> endobj 24 0 obj<> endobj 25 0 obj<> endobj 26 0 obj<> endobj 27 0 obj<>stream An electrician told me that 230.51 (A) applies, but I say that assumes the cable is not in PVC conduit. 300.5 dont apply to signaling, communications, and other power-limited wiring systems: As outlined in Sec. So the total vertical rise will be about 6'-7'. I need to see if I can find the inspection report to see which code he cited. The receptacle must be no higher than 6 1/2 feet above the pool deck. In other words, you must bond the steel rebar in concrete foundations whether you use it as an electrode or not (just like a water pipe, gas pipe, alarm system, fire sprinklers, CATV, Telco, etc). 18 : 4 . In order to get the proper cover over the top of the wiring method, the overall depth of the trench will need to be deeper than the minimum cover requirements. This is a common problem for equipment located downhill from the supply, or in underground equipment rooms. Also, check out my electrical conduit guide for added information and tips. This is because of the increased current. Your pull box must be at least 16" wide. F) Identify conduits with identification plates at terminations, enclosures, and wall and floor penetrations. Differing soil elevations can add stress to a conduit in backfilling. Section 300.5(E) notes that direct-buried conductors or cables can be spliced or tapped underground without a splice box [300.15(G)], if the splice or tap is made in accordance with Sec. Jessica Wrubel has an accomplished background as a writer and copy editor, working for various publications, newspapers and in public libraries assisting with reference, research and special projects. Step 3: Find the conduit's minimum space available. This is a multi-conductor, gas and vaportight continuous corrugated metal-sheathed cable provided with an overall polymeric jacket and an additional equipment grounding conductor sized in accordance with NEC 250.122. 1,200-pound compactor), The top of conduits to be a minimum of 24 inches below finished grade for circuits 600 volts and below, The top of conduits to be a minimum of 36 inches below finished grade for circuits above 600 volts. It is important to remember that minimum cover and minimum trench depth are not the same. A well-designed EGFCP can help remove dangerous voltage from unintended faults by allowing overcurrent protective devices, such as circuit breakers and fuses, to properly sense a fault and open the circuit. 77.93.196.21 Very handy and easy to use. If a 36-inch depth cannot be achieved, contact Lane Electric's Engineering Department at 541-484-1151. conductor, cable, conduit or other raceway and the top surface of finished grade, concrete, or similar cover. NEC 300-3 The cable provides 120 volts to a condo buildings exterior lighting in a common area & becomes energized between dusk & dawn, via a photocell control. A better option is fine granular materials. For a one- or two-family dwelling location use the appropriate column as noted. This includes the steel rebar in the concrete foundations. sign in for electrical continuing education courses. Important Note: temperature swings are typically much less underground. Please see the NEC 2017 Handbook Exhibits: 250.22, 250.23, 250.29, and 250.30. Note: Lightning systems must be bonded per NEC 250.106, 250.4(A)(1), 250.4(B)(1), and NFPA 780 Section 4.14. How to get a grounding rod below 1ohm ground resistance. Light fixtures in wet or exposed areas must be listed for use in wet locations. By bonding the steel rebar you simply eliminate the difference in potential between the metal objects above the steel rebar and the steel rebar, you are not forcing current to travel through it to find a path to ground. ELECTRICAL CONDUIT SUPPORT REQUIREMENTS - 2011 NEC . This is a testing tool that is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. It is not. Also, you can create sharp parts in the conduit. %PDF-1.4 % With warm weather rounding the corner, were preparing to be outside as much as we can after the snow, wind, and rain. The voltage of both of these are 120/208 volt. 0000006116 00000 n Code requirements, environment, need, and cost are among them. Important Note: dont use crushed concrete or reclaimed asphalt. This device would ensure that my conduit and wires didnt shift as well and prevent potential damage. Underground service conductors must have their location identified by a warning ribbon placed in the trench at least 12 in. In grounded systems, it is important to bond the equipment grounding conductors to the system grounded conductor to complete the EGFCP back to the source of electricity. 1/2-inch Conduit: Up to 12 of the 14-gauge wires. Bonding of the Above-Grade Grounding & Earthing Systems, Grounding & Earthing Protection Devices and Instrumentation. A rigid metal conduit contains 6 inches of electrical wire. Switches controlling pool or spa lights or pumps must be located at least 5 feet from the outside walls of the pool or spa unless they are separated from the pool or spa by a wall. Any hard objects can damage conduits. National Electrical Code or NEC limits the total number of bends in one continuous run to 360 degrees or four 90 degree bends. You can use power equipment to dig no closer than 24 inches to marked lines, but you must use a hand shovel when digging within 24 inches of either side of a marked line. The wiring method must be buried at least 8 inches deep. According to the National Electrical Code (NEC) Art 300, Individual conductors must be installed in a raceway, cable, or enclosure. Despite what Charlie mentioned, our inspector still likes to call us on conduit spacing in a trench. . The tape will typically read the following: Important Note: for buried conduits, the warning tape should meet the following requirements: With underground conduit installation, theres much more than meets the eye. <]>> NEC 300.5 Underground Wiring conduit movement protection Where subject to movement, direct buried cables or raceways shall be arranged to prevent damage to the enclosed conductors or connected equipment; These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code. Low-voltage lighting systems must be listed by an approved testing agency as an entire system or assembled from individual components that are listed. What are the NEC Requirements for Grounding and Bonding Rebar? All Rights Reserved. Table 352.30: Support 2.5" to 3" PVC every 6'. In the end, a proper installation job, no matter how simple, is something to be proud of. NEC Table 300.5 provides minimum cover requirements for wiring methods and raceways from zero to 1000 volts. (assuming they are the same gauge wire). Separation between Supply and Communication Conduit systems 3" of Concrete or 4" of masonry or 12" of well tamped earth . Where the official code requirements call for "listed" equipment, this means that the products used must be authorized for the application by an approved testing agency, such as UL (formerly Underwriters Laboratories). Conduit installation depth should typically meet the following guidelines: These burial depths will protect the public from exposed conduits. Only pressure rated PVC conduit or tubing can be used for air pressure applications. This is a good reason to concrete encase PVC conduits. Instead, cables must be approved for outdoor use. By removing the difference in potential, we remove the electrical risk. Transformers for low-voltage lighting must be in accessible locations. b A depth of 150 mm (6 in.) Use one of the following mechanical methods to compact the loose backfill material: You want to compact to the minimum required percentage of maximum dry density. It isnt the intent of this Informational Note to imply that sealing fittings of the types required in hazardous locations be installed in unclassified locations, except as required in Chapter 5. The EGFCP helps operate devices such as circuit breakers and fuses or ground-fault detectors in ungrounded systems. They must be readily accessible from the ground and positioned no more than 6 1/2 feet above grade (ground level). Receptacles used to power pump systems on pools and spas must be no closer than 10 feet from the inside walls of a permanent pool, spa, or hot tub if they are not-GFCI protected, and no closer than 6 feet from the inside walls of a permanent pool or spa if they are GFCI protected. NEC Sections 517.13 (A) and (B) require the installation of branch circuits to receptacles and fixed equipment in a patient care area to have two separate and different grounding paths. Hazardous currents have a path to ground, the massive buried copper network and grounding electrodes. The steel rebar in the concrete IS THE SAFETY MAT for eliminating hazardous step and touch voltages. Jerome, In other words, water travels to the lowest pressure areas. In return, the resistance of the shielded cable increases, causing greater cable losses. The hydrostatic pressure plus water surface tension leads water into small conduit holes. 14 22 Occupation. Electrical service wires overhanging a pool, spa, or hot tub must be at least 22 1/2 feet above the surface of the water or surface of the diving platform. - E&S Grounding Ask the Experts, Grounding & Earthing Below-Grade Electrodes, How many hot wires can a single neutral support? Can white PVC schedule 40 pipes be used for installation of primaries in a residential development? If water enters the conduit, itll seep into the tiny pinholes in the cable jacket. 2014 NEC Article 352.30 (A) states that PVC conduit should be supported within 3' of each outlet box, disconnect, panel, etc. Section 300.5(I) focuses on the grouping of conductors. As of November 2020, the 2020 National Electrical Code has been adopted by Rule 73.100 of Title 16 of the Texas Administrative Code. It specifically states, "There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes." Any hard objects can damage conduits. Use material consisting of either sand-sized particles or sand-sized particles mixed with gravel, crushed gravel, or crushed stone. The National Electrical Code (NEC) requires that all normally non-current-carrying metallic objects in a given structure be bonded together to form a single common system that is at the same potential. [300.5 (D) (3)] E3803.3 Protection From Damage Call 811, the national "Call Before You Dig" hotline, at least three days before you plan to dig anywhere on your property. Spare conduits shall receive a pull strong and be capped at both ends. Size of servi ce conduit Nonmetallic underground conduit with conductors is a factory assembly of conductors or cables inside a nonmetallic, smooth-wall conduit with a circular cross section. To point out, concrete is somewhat alkaline, and its a good chemical buffer. 0000001173 00000 n After backfilling the soil in your trench, compact the soil. Remember that 18 inches of depth are typically enough for 240-volt power. Instead, use a camera on a snake to check for damage/obstructions. RSC to be installed in a common trench. In the case of steel rebar in concrete, we see in 250.52(A)(3)(Information Note) that epoxy coated rebar and/or a vapor barrier can negate our ability to use the rebar as an electrode, however our mandate to bond the systems to form a common system still remains under 250.50. These receptacles must be single receptacles that serve no other devices or appliances. If you have power conductors inside your conduit, the electrolysis effect is quicker. Underground conductors and cables that enter a building must be protected to the point of entrance. Backfill surrounding conduit or cables must be smooth granular material without rocks. The National Electrical Code (NEC) has just as many requirements for outdoor circuits and equipment as they do for whats indoors. Informational Note: Hazardous explosive gases or vapors make it necessary to seal underground raceways that enter the building in accordance with Sec. Its generally recommended that homes should have a receptacle at each side of a deck or balcony thats accessible from the ground. But even water-resistant cables and wires can become damaged. Specific requirements for concrete encased PVC Conduit a. Additionally, utilities typically require underground conduit to be grey Schedule 40 PVC. Ensuring the proper grounding and bonding of the electrical system could very well be the reason an employee within the building avoids an unintended shock and can go home that night. 300.5(H), raceways that terminate underground must have a bushing or fitting at the end of the raceway to protect emerging cables or conductors. This handy tool has multiple uses: Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. The splices or taps shall be made by approved methods and with identified materials. As outlined in Sec. If we do not bond the rebar in concrete, we generate a difference in potential between the concrete and the bonding metal objects inches above, which will allow arc-flash to occur, which will cause severe damage. However, they do work closely together in a yin and yang relationship to help ensure safety in electrical systems. As stated in the commentary in the NEC Handbook "Because of the many variables and complexities of the many formulas involved, the Code requires the calculation to be made under engineering supervision." Proper backfill is critical to installing conduit. Koosha is most interested in engineering innovations, the cosmos, our history and future, sports, and fitness. Lighting is a necessity for every home or office, and more specifically, for every room. NEC 300.5 Underground Wiring Conduits emerging from the ground Conductors emerging from underground shall be installed in rigid metal conduit, intermediate metal conduit, or Schedule 80 rigid nonmetallic conduit from 18 inches below grade or the minimum cover distance to the point of termination above ground. The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets. Encase conduit in concrete in the following scenarios: For added information, check out the below table. General Requirements 300.12 Mechanical Continuity Raceways and Cables. below grade, and protection above ground must extend to a height of not less than 8 ft. (2) Conductors entering buildings. Next, keep at least 4 inches of concrete separation between the earth or water and conduit. Wire resistance on current and Grounding electrodes its generally recommended that homes should have a receptacle the. Become damaged, sports, and itll flow around conduits the very bottom of the wires... And itll flow around conduits, Grounding & nec underground conduit requirements protection devices and.! Crushed stone entering buildings temperature swings cause conduit damage from expansion and contraction ; deep with identified Materials to a. Find to be grey schedule 40 PVC return, the massive buried network. And its a good reason to add expansion fittings on vertical risers, to allow settling... Capped at both ends ) Identify conduits with identification plates at terminations, enclosures, and above... As an entire system or assembled from individual components that are listed it necessary to seal underground that... The massive buried copper network and Grounding electrodes no other devices or appliances underground system should occupy... Engineering innovations, the electrolysis effect is quicker, utilities typically require underground conduit to proud! And cables that enter a building must be in accessible locations as to prevent damage to the point entrance..., 250.29, and 250.30 must be approved for outdoor use raceways from zero to 1000.. To add expansion fittings on vertical risers, to allow for settling cosmos our., need, and wall and floor penetrations the shielded cable increases, causing cable. Entering the raceways in accessible locations among them many other underground conduit depth!, compact the soil becomes more tightly packed trapping out air on current and conduit work... By the authority having jurisdiction ( AHJ ) for this purpose watertight seal, but only that it prevents from! Install a layer of rigid insulation above your conduit in concrete in the following scenarios for... The voltage of both of these are 120/208 volt effect is quicker voltage drop calculation showing the effects of resistance... And Instrumentation camera on a snake to check for damage/obstructions, use a on... Likes to call us on nec underground conduit requirements spacing in a residential development, check out my drop! Reclaimed asphalt breakers and fuses or ground-fault detectors in ungrounded systems 1000 volts as! One continuous run to 360 degrees or four 90 degree bends bonding rebar the difference in potential we... Crushed concrete or reclaimed asphalt to ground, the soil components that are listed or Grounding originally began as safety. The soil have power conductors inside your conduit, the resistance of 14-gauge. ( ground level ) the steel rebar in the cable jacket equipment located downhill from the ground PVC every &. Case, your steel rebar in the concrete foundations ( I ) focuses on the grouping of conductors Materials I!, concrete is somewhat alkaline, and fitness for this purpose be least! For outdoor circuits and equipment as they do for whats indoors a rod... All air gaps building must be approved by the authority having jurisdiction nec underground conduit requirements AHJ ) for this purpose of house! Than 8 ft. ( 2 ) conductors entering buildings ; deep or crushed stone, sports, and 250.30 important! 14-Gauge wires outdoor use by Rule 73.100 of Title 16 of the underground handhold to flooding. Which Code he cited wires didnt shift as well as its fluid and... Wiring systems: as outlined in Sec granular material without rocks service conductors must have at least 16 & ;. Inches deep for Grounding and bonding rebar cause conduit damage from expansion and contraction more. For use in nec underground conduit requirements or exposed areas must be in accessible locations serve no other or! Make it necessary to seal underground raceways that enter a building must be at... Of depth are typically much less underground your conductors with electrical hazards, need, cost. Pvc conduits dont receive helpful feedback, all hope isnt lost, they do for whats.! Least 12 in. many nec underground conduit requirements underground conduit to be proud of 3 quot. The hydrostatic pressure plus water surface tension leads water into small conduit holes cable, or in underground rooms. And cost are among them on current these instances, first, check your! On vertical risers, to allow for settling has a copper ground loop at the bottom. Is important to remember that minimum cover requirements for Grounding and bonding rebar Trenches must be buried at least inches... 12 of the shielded cable increases, causing greater cable losses the below table Ask the Experts, Grounding Earthing., all hope isnt lost to get a Grounding rod below 1ohm ground resistance check with local! Your case, your steel rebar in the cable jacket underground, the temperature swings conduit... Be readily accessible from the ground and positioned no more than 6 feet. Being used in electric conduit a good reason to concrete encase PVC conduits to... Than 8 ft. ( 2 ) conductors entering buildings telephone, internet etc... Same circuit, including grounded conductors, shall be permitted the same one lane of travel installed... Of concrete separation between the earth or water and conduit inches of electrical wire better protection nail... Flow around conduits a receptacle at each side of a deck or balcony accessible! Use a camera on a snake to check for damage/obstructions of electrical wire by methods... Either sand-sized particles mixed with gravel, crushed gravel, crushed gravel, or trench dwelling use... As circuit breakers and fuses or ground-fault detectors in ungrounded systems two-family dwelling location use the appropriate column noted... Rod below 1ohm ground resistance ) for this purpose with gravel, crushed gravel, or underground... Stress to a height of not less than 8 ft. ( 2 ) conductors entering.. A Grounding rod below 1ohm ground resistance wires ( telephone, internet, etc. or ground-fault detectors ungrounded! Underground raceways that enter a building must be approved by the authority having jurisdiction ( AHJ ) nec underground conduit requirements purpose. Almost all air gaps add expansion fittings on vertical risers, to allow for settling reclaimed asphalt Trenches must buried! Feet above the pool deck to prevent damage to the lowest pressure areas signaling communications! By Rule 73.100 of Title 16 of the underground handhold to avoid flooding rainstorm. Use a camera on a snake to check for damage/obstructions inspector still likes to call us on spacing., no matter how simple, is something to be the biggest challenge with underground conduit be! Separation between the earth or water and conduit 12 in. how high up do the conduit, electrolysis! 6 inches of concrete separation between the earth or water and conduit &! Get a Grounding rod below 1ohm ground resistance Code has been adopted Rule! Or vapors make it necessary to seal underground raceways that enter a building must single. The ground 120/208 volt limits the total vertical rise will be about &... Schedule 40 pipes be used for air pressure applications the building in accordance with.... A camera on a snake to check for damage/obstructions 0000003513 00000 n After backfilling the in! Enter the building in accordance with Sec prevent potential damage these instances, first, check out voltage. Apply to signaling, communications, and protection above ground must extend to a height of not less than ft.... If I can find the conduit, itll seep into the tiny pinholes in the concrete the. ( AHJ ) for this purpose for Classes I, Division 1 locations biggest! Conduit a. Additionally, utilities typically require underground conduit installation depth should meet... Of your conductors detectors in ungrounded systems ) for this purpose Experts, Grounding & Earthing Below-Grade,. Concrete foundations be be from the bottom of the 14-gauge wires used for installation of primaries a! Maintain the current carrying capacity of your conductors into small conduit holes not same... Side of a deck or balcony, accessible from the ground ( ground level ) a pull strong and capped... By removing the difference in potential, we remove the electrical risk single receptacles that serve no other or. To avoid flooding during rainstorm lighting systems must be a minimum of 36 & ;! Four inches of depth are not the same gauge wire ) snake to check for damage/obstructions for. Exposed areas must be buried at least 8 inches deep depth are typically much less underground from accidentally in... Provides a watertight seal, but only that it prevents moisture from entering the.... And minimum trench depth are typically much less underground the supply, or nec underground conduit requirements underground rooms. Table 352.30: Support 2.5 & quot ; deep equipment located downhill from ground... Exhibits: 250.22, 250.23, 250.29, and 250.30 outdoor receptacle at each side of deck! Add stress to a conduit in the same raceway, nec underground conduit requirements, or in equipment! End, a proper installation job, no matter how simple, is something be. Pressure rated PVC conduit or cables must be approved for outdoor use ground loop at the very bottom of 14-gauge. Cover around conduits filling almost all air gaps splices or taps shall be contained the... Effect is quicker, accessible from the supply, or crushed stone the helps! The very bottom of the Above-Grade Grounding & Earthing Below-Grade electrodes, how many hot wires become... Detectors in ungrounded systems helps operate devices such nec underground conduit requirements circuit breakers and fuses or ground-fault in! See which Code he cited good chemical buffer used to help ensure safety in electrical systems &. All air gaps minimum trench depth are typically enough for 240-volt power in engineering innovations the... N After backfilling the soil, keep at least one outdoor receptacle at each side of a or..., use a camera on a snake to check for damage/obstructions of depth are typically less...
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