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NEC 代码是什么？
美国国家电气规范 (NEC) 是美国安全电气设计、安装和检验的基准标准。它几乎是所有住宅、商业和工业领域电气法规的基础。无论您是为新住宅布线、安装工业电机，还是为太阳能电池阵列铺设导线管，NEC 都制定了相关规则，旨在保护人员和财产免受电气危害。
NEC 正式名称为 NFPA 70，由致力于降低火灾和电气风险的非营利组织美国国家消防协会 (NFPA) 发布。该规范于 1897 年首次发布，并随着电气系统的进步而不断发展，每次更新都变得更加全面。
为了确保 NEC 能够反映现代技术和安全实践，NEC 每三年由专家小组进行修订，专家小组成员包括电工、工程师、检查员、制造商、公用事业代表和安全倡导者。最新版本已被各州和地方司法管辖区采用，这使得 NEC 成为美国大多数地区具有法律效力的标准。
NEC 的范围广泛但定义明确。它涵盖：
- 电导体和设备的安装
- 布线方法，包括电线管和线槽
- 针对不同环境和占用情况的特殊考虑
简而言之，NEC 规定了如何安装电气系统以确保安全和合规。
专业提示： 想快速了解 PVC 导管的 NEC 规范要求？点击此处获取 专家对 PVC 导管 NEC 代码的见解。
NEC 代码的目的和含义
国家电气规范 (NEC) 的核心在于保障安全。其主要目标是保护人员和财产免受触电、火灾、电弧闪光和设备故障等电气危害。NEC 通过为各种场所（从家庭、学校到工厂和发电厂）的电气系统安全安装设定最低要求来实现这一目标。
NEC 的宗旨
NEC 并非旨在过度监管，而是旨在制定最低安全标准。它确保所有持证电工和检查员，无论所在地区或项目类型，都遵守相同的基本规则。通过遵守这些标准，电气专业人员可以降低灾难性事故的风险，并确保系统的长期可靠性。
虽然 NEC 乍一看似乎很复杂，但其结构是有条理的，其目的也很明确：
“切实保障人身和财产安全，避免因使用电力而产生的危害。”（NEC 第 90.1 条）
这份声明概括了 NEC 的使命。无论您是安装导管、设置配电盘，还是连接照明电路，NEC 都能提供清晰的框架，确保安全操作。
理解代码语言
NEC 使用具有法律和技术意义的特定措辞。理解这些措辞是正确应用该准则的关键：
“将” = 强制性的。必须遵守的要求。
“应该” = 推荐。不可强制执行，但被视为最佳实践。
“可能”或“允许” = 在限制范围内可选或允许。
例如，“导管应在每个出线盒 3 英尺范围内得到支撑”意味着该间距是要求，而不是建议。
NEC——一份动态文件
NEC 每三年更新一次，以反映新技术、改进材料、安全发现和行业最佳实践。每个版本都会根据实际反馈和创新进行调整，例如：
- 整合 太阳能光伏（PV）系统
- 规则 电动汽车充电站
- 标准 低压和智能系统
由于这种持续发展，NEC 已不再只是一本静态的规则手册。它是一份充满活力、不断发展的文件，能够适应现代需求，同时始终牢记其使命：保障人民安全。
重要的是要记住，NEC 设定 最低可接受标准在许多情况下，最佳实践或工程规范可能会超出这些要求，以增加安全性、寿命或性能，特别是在关键设施或恶劣环境中。
NEC 法规的关键部分
国家电气规范 (NEC) 分为若干条款，每一条都侧重于电气系统的特定方面。NEC 内容广泛，涵盖数百页内容和众多规则，但一些核心章节几乎涵盖所有项目或安装类型。了解这些关键条款，为遵守规范和安全的电气设计奠定坚实的基础。
第一章 - 电气装置的一般要求
《国家电气规范》（NEC）第1章构成了整个规范的结构和定义支柱。该章包含第100条和第110条，定义了关键术语并规定了所有电气系统的基本安装要求。这些一般规定适用于住宅、商业、工业和特殊用途的安装。
第110条规定了所有电气设备和安装条件的一般要求。该要求涵盖机械完整性、额定电压、环境适用性、可及性和间隙等关键领域。一些关键要点包括：
修改和可用故障电流
其中最重要的更新来自 第 110.24(B) 条，直接解决系统修改：
如果对电气装置进行的更改影响了服务中可用的故障电流，则需要执行以下操作：
- 必须验证或重新计算可用的故障电流。
- 服务设备必须具有适当的额定值，以处理其线路端子上更新的故障电流。
- 必须更新现场标记以反映新的可用故障电流（某些情况下不需要，请查看第 110.24 条）。
这是一项安全关键规则，旨在确保设备额定值与不断变化的负载和故障条件保持一致。如果系统短路电流增加，而配电盘未更新或重新贴标，则发生灾难性故障的风险会增加。
间隙和工作空间
该规范规定了配电盘和设备周围的最小工作空间尺寸：
- 面板前方至少需要 3 英尺的深度（取决于电压）。
- 工作空间必须整洁、方便、且光线充足。
- 任何管道或外来系统不得侵入该区域。
这些间隙确保人员的安全操作和维护。
标签和识别
断开装置必须有清晰的标记。
设备必须带有标明其电压、电流、瓦数或其他额定值的标记。
必要时，现场应用的危险标记必须耐用、可见且永久。
环境评级
设备必须适合其安装环境。例如：
室内设备不能安装在室外，除非它符合 NEMA 室外使用标准。
在潮湿的地方，必须使用防风雨外壳和导管配件。
根据位置不同，导管和配件应具有耐腐蚀、耐紫外线辐射和耐温度变化的能力。
第 2 章 - 接线和保护
美国国家电气规范 (NEC) 第 2 章是电气安全领域最重要的章节之一。它全面阐述了正确识别、布置和保护电导体和电路的要求。本章的主要目标是确保所有布线系统不仅能够正常使用，还能避免触电、过热、火灾和短路等危险。
关于分支电路
第210条 - 交流电不超过1000伏，直流电不超过1500伏的电路
电压和导体识别的一般规则： 对于 60 伏以上的直流分支电路，必须使用经批准的方式（例如红色或黑色外饰面或永久性标签）清楚地标记导体的极性。
GFCI保护要求： 许多易受潮或与水接触的场所的插座必须配备 GFCI（接地故障断路器）保护。这些场所包括厨房、浴室、屋顶、地下室、洗衣区和工业水生环境。此外，也列出了一些特殊情况的例外情况，例如工业实验室、融雪系统或医疗保健设施。
直流系统的分支电路： 导体必须在所有端接、连接和接头处进行标记，并特别考虑尺寸（4 AWG 以上或以下）和极性标记。
第235条 — 1000伏以上分支电路
第235条是对第210条的补充，适用于交流电超过1000伏或直流电超过1500伏的电路。与第210.3条类似，第235条包含一个表235.3，其中列出了适用附加保护要求的特定设备（例如，电机、母线槽、暖通空调系统）。
监督安装
在高压环境中，分支电路导体的尺寸可在工程专业人员的指导下确定。监督安装必须满足以下两项要求：
- 在工程监督下进行设计和安装。
- 维护和服务由经过培训并具有高压系统经验的人员执行。
这项规定有助于简化先进系统，同时确保只有合格的专业人员负责其设计和维护。
过流保护
过流保护对于防止过载、短路和接地故障造成的损坏至关重要。NEC 第 240 条概述了详细的规定，包括：
保护装置和可访问性
断路器和熔断器开关必须易于接近，手柄高度不得超过 2.0 米（6 英尺 7 英寸），除非有特殊例外情况（例如，母线槽、危险外壳或允许便携式接近的地方）。
多线分支电路
对于服务于单相、线对中性负载的多线电路，允许使用带有手柄的单独单极断路器来保护每个未接地的导体，确保同时断开。
抽头导体
无限长度的外部分接头 (240.21(B)(5))：NEC 允许无限长度的外部分接头导体，前提是它们满足严格的条件，包括防止物理损坏、终止于单个过流装置以及将断开装置放置在最靠近导体入口的易于接近的位置。
不可互换的保险丝
S 型保险丝的设计旨在防止与额定值较低的保险丝互换，通过确保仅安装额定值适当的保险丝来提高系统安全性。
变压器二次导体保护
变压器次级导体的过流保护取决于变压器的配置。某些配置，例如单相两线或三线三角形接线，可以通过一次侧过流保护器 (OCPD) 进行保护，前提是满足 450.3 中的条件和载流量限制。
翻新设备
特定的过流保护装置（例如低压电源断路器和机电继电器）可以进行翻新，但必须将其列为翻新装置并进行相应标记，以符合 110.21(A)(2) 的规定。
过压保护
过压保护对于保护电气系统免受瞬态电压浪涌（例如雷击、公用设施切换或内部系统故障引起的电压浪涌）的影响至关重要。NEC 第 2 章第 242 条对过压保护进行了规定，其中规定了浪涌保护装置 (SPD) 和浪涌保护器的一般要求和安装要求。
第 242 条涵盖低压和高压电涌保护：
- 第二部分规定了永久安装在不超过 1000 伏（标称）的场所布线系统中的 SPD。
- 第三部分讨论了安装在超过 1000 伏（标称）的场所系统上的浪涌保护器。
SPD 和浪涌保护器的要求
不允许修复（242.2）： 为确保可靠性和安全性，SPD 和浪涌保护器不允许进行翻新。必须始终按照原始制造和列出的标准使用。
接地要求（242.32）： SPD 接地连接必须符合第 250 条第 III 部分的规定，确保与接地电极系统正确连接。接地电极导体在金属外壳内运行时，必须符合 250.64(E) 中概述的具体条件，例如正确连接和防止物理损坏。
组件 SPD 的制造商安装 (242.18)： 4 类 SPD 和其他组件型浪涌保护器不适用于现场安装。它们必须由原始设备制造商安装，因为这些设备集成在设备中，而非独立的现场安装产品。
接地和接合
接地和连接是电气系统安全可靠运行的基础。NEC 第 2 章（特别是第 250 条）规定了性能和规范要求，以确保电气系统的接地和连接能够保护人员和财产免受触电、火灾和设备损坏。
目的和一般要求
接地和接合的总体目标是：
限制电压 因雷击、线路浪涌或意外接触高压线路而造成的电压波动。
稳定电压 正常运行期间接地。
建立低阻抗路径 以便于接地故障时过流保护装置的操作。
五大绩效要求
- 电气系统接地： 接地系统必须以限制电压浪涌并稳定电压的方式连接到地面。NEC 强调尽量缩短接地电极导体的长度，并避免不必要的弯曲或环路。
- 电气设备接地： 非载流导电部件（例如金属外壳）必须接地以限制这些材料上的电压。
- 电气设备粘合： 所有包含导体的导电部件必须连接在一起并连接到供电系统接地，以形成连续、有效的故障电流路径。
- 导电材料与其他设备的粘合： 可能带电的导电材料（例如管道、结构钢）必须与接地系统连接。
- 有效接地故障电流路径： 接地导体和连接导体必须形成连续的低阻抗电路，才能安全承载故障电流。需要注意的是，大地并非有效的接地故障电流路径。
交流电系统的接地要求
根据系统电压和配置，大多数交流电系统都需要接地：
低于50V的系统 如果出现以下情况，必须接地：
由一次系统对地电压超过 150V 的变压器供电。
系统未接地。
作为架空导线安装在室外。
50V至1000V之间的系统 如果出现以下情况，必须接地：
任何导体对地电压超过150V。
该系统为三相四线星形连接系统，使用中性线作为电路导体。
该系统为三相四线三角形连接，以中点作为电路导体。
不符合这些条件的系统可能被允许不接地运行，但仍必须符合相关的 NEC 安全和维护标准。
特殊接地注意事项
阻抗接地系统： 这些必须遵循 250.36 或 250.187 中的具体要求，使用电阻器或电抗器限制故障电流。
户外变压器： 当变压器位于室外时，变压器或另一个室外位置至少需要一个额外的接地电极连接 - 阻抗接地系统除外。
单独派生系统： 这些系统（例如变压器）需要自己的接地电极连接，并且必须遵循有关接地和导体尺寸的详细规则。
接地电极系统： 所有现有的接地电极必须粘合在一起以形成接地电极系统，包括棒、板、混凝土包裹电极和建筑钢材。
服务担保： 服务导体的金属外壳和线槽必须粘合在一起，以提供返回电源的连续路径。
第 3 章 - 接线方法和材料
NEC 第 3 章阐述了如何布线、支撑和保护电导体，以及在不同条件下允许使用哪些类型的电缆、线槽和外壳。该章根据电压等级、位置（室内或室外）、环境暴露、机械防护等因素，为布线系统设定了技术和安装标准。
第300条为NEC中的所有布线方法提供了基本规则，除非另有更具体的条款进行修改。该条款适用于线槽、电缆组件、外壳、接线盒和导线安装。本条款强调安全性、可达性、耐用性以及与其他系统的适当隔离。以下是本章的一些关键方面：
主要条款
- 机械保护： 必须保护导线和电缆免受物理损坏。例如，当导线和电缆穿过金属螺柱或框架时，必须使用套管或护环。
- 与其他系统的间距： 电气管道不能包含其他类型的系统（例如，水管、煤气管道）。
- 工作空间和通道： 插座和接线盒处必须有足够长度的导线（至少 6 英寸）用于连接或端接。
- 腐蚀性和潮湿环境： 必须列出在潮湿或腐蚀性场所使用的接线方法（例如，带有耐腐蚀配件的 PVC 导管）。
- 滚道填充和弯曲半径： 禁止过度填充线槽，并且导体必须具有足够的弯曲空间以避免绝缘损坏。
- 防火分隔： 穿过防火组件的管道或电缆周围的开口必须防火，以防止火势蔓延。
专业提示： 想知道两种常见的接线方法吗？在上一篇文章中，我们详细讲解了 隐蔽管道布线 和 地面导管布线您可以点击上面的文字来了解它们的优缺点，以及安装方法。
通用布线导体
第 310 条规定了住宅、商业和工业系统中大多数布线装置所用的电导体的类型、特性和额定值。
它涵盖：
- 导体类型： 允许使用实心或绞合铜、铝或铜包铝导体。
- 绝缘类型： 常见的绝缘类型包括：
THHN/THWN-2： 干燥和潮湿的地方，最高温度可达 90°C
XHHW/XHHW-2： 防潮、耐热
USE-2/RHH/RHW-2： 地下和服务入口使用
- 载流量： 导体载流量（载流量）的定义基于：
导体尺寸
绝缘温度等级
环境温度
管道内载流导体的数量
- 额定电压： 导体按其最大电压列出（例如，600V、1kV）。
- 平行导体： 对于大导体（1/0 AWG 或更大），允许并联多个导体以实现更高的载流量。
第 342 至 362 条 – 导管和管材类型
NEC 根据材料、结构和应用，为每种线槽系统提供了单独的条款。这些线槽用于物理保护导体、支持接地连续性，并允许导体布线符合第 300 条的规定。
NEC 代码中列出了 7 种类型的导管：
中间金属导管 (IMC)
IMC 是一种钢制导管，其管壁比硬质金属导管 (RMC) 更薄，但机械防护性能相当。它采用镀锌处理，具有耐腐蚀性能，并获准用于暴露、隐蔽和危险场所。对于需要强度但又兼顾重量和成本的户外或工业环境，IMC 是理想的选择。
刚性金属导管 (RMC)
RMC 是最重、最坚固的金属导管，由镀锌钢或不锈钢制成。它旨在提供最大程度的物理保护，可安装在所有环境中，包括露天和地下位置。RMC 通常用于高风险区域，例如关键基础设施、石化工厂或易受机械磨损或严重腐蚀的区域。
硬质聚氯乙烯导管（PVC）
硬质PVC导管 是一种由塑料制成的非金属管道，耐潮湿和腐蚀。它重量轻，易于切割，是地下安装、潮湿环境以及污水处理厂或沿海地区等腐蚀性环境的理想选择。PVC 导管在暴露于温度变化时必须与膨胀接头一起使用，并且通常使用溶剂型胶粘剂进行连接。
高密度聚乙烯导管（HDPE）
HDPE 导管是一种柔性非金属导管，具有优异的抗冲击性和柔韧性。它通常用于地下电力和通信系统，包括定向钻孔安装。HDPE 导管能够以较长的连续长度进行安装，且接头较少，因此非常适合大型公用事业和基础设施项目。
电气金属管（EMT）
EMT 导管通常被称为“薄壁”导管，由镀锌钢或铝制成，比 IMC 和 RMC 更轻。它广泛应用于商业建筑，尤其适用于中等防护即可满足需求的室内墙体和天花板。EMT 导管必须采用机械固定，并使用压缩或紧定螺钉接头连接。未经额外防护，EMT 导管不适用于直埋或腐蚀性环境。
柔性金属管（FMT）
FMT 由螺旋缠绕金属管组成，可为短而复杂的布线提供灵活性。它适用于因振动、移动或空间限制而无法使用刚性导管的情况。典型应用包括灯具线缆、电机连接和密封外壳。除非另有说明，否则不适用于潮湿或危险场所。
电气非金属管 (ENT)
耳鼻喉 ENT 是一种波纹柔性塑料管，适用于注重快速安装的室内应用。它重量轻，不含金属，可手动弯曲，非常适合用于住宅或商业建筑的墙壁、地板和天花板。ENT 通常与合适的配件和接线盒搭配使用，用于防火建筑，并简化了楼板或浇筑混凝土结构的安装。
导管安装的一般要求：
必须以特定的间隔牢固支撑和固定。
必须使用适当的套管或配件来保护导体。
导管必须没有锋利的边缘，并在需要的地方密封，以防止湿气或气体进入。
在受温度变化影响的长距离室外运行中需要使用膨胀配件（例如 PVC 导管）。
每种导管类型均受 NEC 中特定安装规则的约束，以确保布线系统受到保护、安全且符合规范。选择正确的导管类型不仅可以保持电气系统的完整性，还可以确保在各种环境条件下的安全。
笔记： 想了解 PVC 导管安装的细节？您可以 单击此处获取有关 PVC 导管安装的专业提示。
第 392 条 - 电缆桥架
电缆托架是用于工业和商业环境中布线和支撑电缆的结构支撑系统。第392条涵盖了电缆托架系统的设计、安装和使用，这些系统包括梯式托架、通风槽式托架、实心底部托架和金属丝网托架。
电缆桥架的类型
梯子托盘： 开放式横档有利于空气流通，方便电缆进出。
通风槽： 部分封闭，提供中等支撑和气流。
实心底托盘： 完全封闭，用于机械保护至关重要的情况。
金属丝网/篮子托盘： 重量轻、安装快捷，适用于控制和数据电缆。
NEC对电缆桥架的要求
载流量调整： 安装在托盘中的电缆可能需要根据填充和通风情况降低载流量。
填充计算： 托盘填充限制取决于电缆类型和尺寸——过度填充会减少散热。
接地： 如果列出并正确粘合，金属托盘可用作设备接地导体 (EGC)。
支撑间距： 必须定期支撑托盘以防止下垂或损坏。
专业提示： 还在为选择 Conduit 还是 Trunking 而困惑吗？别担心，您可以阅读这篇文章，快速了解 了解导管和线槽之间的区别，以及它们的优缺点，以帮助您选择正确的。
第五章 特殊占用
美国国家电气规范 (NEC) 第 5 章重点关注特殊用途——由于其功能、内容或环境而面临特殊电气安装挑战的场所和结构。第 5 章对通用规则进行了修改，以满足危险、医疗、农业、移动和娱乐等用途的特殊需求。
危险（分类）场所
危险场所是指可能存在足够数量的易燃气体、蒸汽、粉尘或纤维，从而可能造成火灾或爆炸风险的区域。NEC 根据危险类型，使用等级、分区、组别系统或区域系统对这些区域进行分类。
- 常见的环境包括化工厂、燃料储存区、面粉厂和喷涂区。
- 认可的接线方法包括防爆外壳、密封以及使用带有特殊配件的特定导管系统，例如 RMC、IMC 和 PVC 型。
- 设备必须列出并贴上环境标签，安装技术必须限制危险物质进入布线系统。
医疗保健设施
医疗保健设施对电力可靠性和患者安全提出了至关重要的要求。第517条涵盖医院、疗养院、诊所及类似环境。
- 它介绍了基本电气系统，包括生命安全、关键和设备分支，每个分支都有特定的安装和分离要求。
- 布线必须降低电气故障、医疗设备干扰和火灾危险的风险。
- 精确定义接地、冗余、独立电源系统和导管类型的要求，以保持性能和合规性。
农业建筑
Article 547 governs electrical systems in agricultural and livestock environments, where high moisture, dust, and corrosive agents like ammonia can degrade typical wiring.
- Wiring must be protected from physical damage and corrosive exposure using corrosion-resistant conduit and fittings, such as PVC-coated or nonmetallic materials.
- Bonding and grounding systems must minimize voltage gradients, which can harm livestock.
- This article also addresses the installation of lighting, receptacles, and equipment control in animal confinement areas and crop production spaces.
Manufactured Buildings and Mobile Homes
These articles cover the electrical requirements for factory-built structures, such as manufactured homes, mobile homes, modular buildings, and mobile home parks.
Electrical systems must allow safe and standardized connection to utility services.
Requirements include overcurrent protection, proper grounding, and use of approved flexible connections.
Parks and lots must provide weather-resistant and easily accessible service equipment, ensuring safe occupancy transitions.
Recreational Vehicles and Parks
These sections provide guidelines for recreational vehicles (RVs) and the facilities that serve them.
Wiring in RVs must be compact, safe, and protected from vibration and movement.
RV parks must provide power distribution systems with listed power outlets, overcurrent protection, and grounding suitable for mobile connections.
All components must be weatherproof and tamper-resistant when installed in outdoor settings.
Chapter 5 plays a critical role in ensuring that electrical installations remain safe, code-compliant, and functional in non-standard environments, above are just part of them. It recognizes that certain occupancies present elevated risks, such as explosion, equipment failure, or life safety threats—that demand specialized materials, installation methods, and protective measures.
Chapter 6 - Special Equipment
Chapter 6 of the National Electrical Code (NEC) addresses Special Equipment — a vital section that sets the safety and installation standards for emerging technologies and specialized systems. With rapid growth in electric vehicles, renewable energy, and modular data centers, this chapter is more relevant than ever. Below is an introduction to four important articles within Chapter 6:
Article 625 - Electric Vehicle Power Transfer Systems
Article 625 covers the installation and safety requirements for electric vehicle (EV) charging systems, including conductive, inductive, and wireless power transfer methods. It addresses equipment such as electric vehicle supply equipment (EVSE), connectors, and associated wiring. Key provisions include:
Scope: Applies to electrical conductors and equipment connecting an EV to premises wiring for charging, power export, or bidirectional current flow.
Equipment Requirements: EVSE must be listed or labeled for the application.
过流保护： Charging equipment is considered a continuous load; overcurrent protection must be sized accordingly.
Personnel Protection: Requirements for personnel protection systems, such as ground-fault circuit-interrupter (GFCI) protection.
Installation Guidelines: Specifications for cord and cable assemblies, including length and construction.
Location Considerations: Installation guidelines for indoor and outdoor locations, considering factors like ventilation and accessibility.
笔记： Want to know more about EV Charging Systems Codes? We listed four international standards for EV Charging Stations in our previous post, and you can click on the text above to read.
Article 646 – Modular Data Centers
Article 646 provides requirements for modular data centers (MDCs), which are prefabricated units housing information technology equipment and support systems. These units are rated 600 volts or less and include components like electrical service distribution equipment and HVAC systems. Key considerations include:
Definition: MDCs are prefabricated units consisting of an outer enclosure housing multiple racks or cabinets of IT equipment and various support equipment.
Listing and Labeling: MDCs must be listed and labeled for their intended use.
Working Space: Compliance with working space requirements to ensure safety during maintenance and operation.
Wiring and Grounding: Adherence to wiring methods and grounding practices suitable for the modular nature of these facilities.
专业提示： Want to know more about the types of electrical conduits and their applications in data centers? We have explained in detail the importance of electrical conduits and their applications in data centers in our last post. You can click on the text above to read more.
Article 690 - Solar Photovoltaic (PV) Systems
Article 690 provides the installation requirements for solar photovoltaic (PV) systems, excluding large-scale utility PV systems (covered by Article 691). It governs the PV array circuits, inverters, controllers, disconnects, grounding, and interconnections—whether stand-alone, interactive with other power sources, or hybrid—producing either AC or DC power.
Key highlights include:
Scope and Applicability: Covers residential, commercial, and industrial PV systems except for utility-scale stations. Multiple PV systems are allowed on a single structure with appropriate labeling and directories.
Equipment Requirements: PV components (e.g., inverters, modules, combiner boxes, rapid shutdown systems) must be listed or evaluated for the specific PV application.
Circuit and Voltage Requirements: Limits DC voltage to 1000V (600V for one- and two-family dwellings); conductor ampacity and maximum circuit currents must be carefully calculated; special provisions apply to bipolar circuits and systems with multiple voltages.
Arc-Fault and Ground-Fault Protection: DC circuits over 80V must have arc-fault protection; ground-fault protection (GFDI) is required for systems over 30V or 8A unless exempted.
Rapid Shutdown: Required for PV circuits on or in buildings to ensure firefighter safety—exceptions apply to ground-mounted and non-enclosed structures like carports.
断开方式： PV systems must have clearly labeled and accessible means to disconnect from other electrical and storage systems.
Wiring Methods and Accessibility: PV conductors over 30V that are accessible must be enclosed (e.g., MC cable or raceways); power converters can be installed on rooftops if disconnecting means are accessible.
Floating PV Systems: Must be suitable for increased mechanical stress, corrosion, and humidity, and allow for expected movement on water.
接地和接合： Allows functionally grounded, ungrounded, and solidly grounded DC circuit configurations with detailed grounding requirements for safety.
专业提示： Wait, besides NEC, are there other electrical codes to comply with? In the last article, we explained in detail about the types and code compliance of solar conduits. You can click on the text above to read more.
Article 694 – Wind Electric Systems
Article 694 of the NEC establishes the requirements for wind electric systems, including one or more wind turbines and associated equipment such as generators, inverters, controllers, and energy storage. These systems may operate independently or interact with other power sources, and may produce AC or DC output.
Key provisions include:
Qualified Personnel: Installation, wiring, and maintenance must be performed by qualified individuals.
Equipment Listing: Wind turbines and related components must be listed, field-labeled, or under supervised evaluation.
Overvoltage and Overspeed Protection: Systems using diversion load controllers must include a reliable secondary method to prevent turbine overspeed. Surge protective devices are required.
Receptacles: Maintenance receptacles must include GFCI protection and overcurrent protection.
Circuit Requirements: Output circuits are treated as continuous loads, with voltage and access limitations in residential settings.
Shutdown and Disconnect: Systems must include means for turbine shutdown and disconnection.
Wiring and Grounding: All wiring methods and bonding must follow NEC requirements for safety and system stability.
Chapter 7 - Special Conditions
Chapter 7 of the National Electrical Code (NEC) addresses Special Conditions—those electrical systems that either support life safety, operate during abnormal situations, or involve emerging technologies. This chapter is crucial for systems that require continuous, backup, or alternative sources of power, as well as systems designed for monitoring or signaling.
From emergency systems and legally required standby power to energy storage and fire alarms, Chapter 7 provides clear installation requirements to ensure reliability, safety, and code compliance.
Article 700 - Emergency Systems
Emergency systems are legally required electrical systems that must continue operating in the event of a power outage to protect human life and safety. These include systems powering exit signs, emergency lighting, fire detection and alarms, public safety communications, and critical ventilation.
Key requirements include:
Transfer Time: Automatic transfer switches to ensure power is restored within 10 seconds of an outage.
Circuit Separation: Emergency wiring must be physically separated from all other wiring systems unless in separate compartments.
Use of listed and reliable sources like generators or battery systems.
遵守 with testing, maintenance, and identification standards to ensure availability during emergencies.
Article 701 - Legally Required Standby Systems
Legally required standby systems are mandated by local or national laws to maintain certain functions during power outages, but they are not as critical as emergency systems. These may support systems like elevators, HVAC, and sewage pumps in larger buildings.
Highlights:
Power restoration must occur within 60 seconds of a utility power loss.
These systems must be separately identified and installed.
Fuel supply, ventilation, and control systems must meet specific operating time and reliability standards.
Article 706 - Energy Storage Systems (ESS)
With the rise of renewable energy and grid resilience efforts, energy storage systems (ESS) such as battery banks, flywheels, and ultracapacitors have become a critical part of modern installations. Article 706 is a newer addition to the NEC and covers the installation, protection, and labeling of ESS.
Key points include:
Installation: ESS must be installed per manufacturer’s instructions and Chapter 706 provisions.
Battery Types: Requirements vary based on chemistry:
Lithium-ion: Must include thermal runaway prevention and fire-resistant enclosures.
Lead-acid: Requires ventilation and spill containment.
Location Limits: ESS must be installed in approved rooms or cabinets, with required clearances and ventilation.
Shutdown Protocols: Systems must have clearly labeled, accessible emergency shutdown mechanisms.
专业提示： Is your business in the Energy Storage Systems (ESS) industry? In the last post, we listed four international standards and 7 tips to comply with them. You can click on the text above to learn more.
Article 760 - Fire Alarm Systems
Fire alarm systems are required for life safety, alerting occupants and emergency personnel to smoke or fire events. Article 760 outlines the wiring and installation rules for both power-limited and non–power-limited fire alarm circuits.
Key highlights include:
Circuit Types: Divided into:
Power-limited fire alarm (PLFA): Lower voltage; uses specific cable types (e.g., FPL, FPLP, FPLR).
Non–power-limited fire alarm (NPLFA): Higher power requirements; must follow general wiring rules.
电缆保护： Fire alarm cables must be:
Listed for fire resistance and routed to avoid physical damage.
Separated from other systems unless barriers are used.
Power Supply: Must have primary and secondary (backup) power, usually batteries capable of 24 hours standby and 5 minutes alarm operation.
标记： Junction boxes and conduits must be marked “FIRE ALARM CIRCUIT”.
Article 770 - Optical Fiber Cables and Raceways
Though not a traditional power system, optical fiber cables are vital for modern communication and control systems. Article 770 details the installation requirements for nonconductive and conductive fiber optic cables.
Covers fire-rated cable types (OFNR, OFNP).
Includes rules for raceways, bends, support spacing, and mechanical protection.
Emphasizes maintaining signal integrity and minimizing damage risks in high-performance networks.
Additional Best Practices for Special Conditions
While each Article within Chapter 7 includes highly specific requirements, some general best practices include:
- Documentation and Labeling:
Clearly label all systems, especially those involved in life safety or standby operation.
Maintain installation records, drawings, and test results as required by NFPA 70 and local AHJs (Authorities Having Jurisdiction).
- 环境考虑：
Systems located in wet, corrosive, or explosive environments (like those in combination with Chapter 5) must use listed enclosures, corrosion-resistant materials, and NEMA-rated equipment.
- Coordination with Other Codes:
Fire alarm and emergency systems must comply not just with NEC but also with NFPA 72 (National Fire Alarm and Signaling Code) and NFPA 110 (Standard for Emergency and Standby Power Systems).
- Maintenance & Testing:
Chapter 7 systems require ongoing inspection and testing, sometimes monthly, to meet compliance. System failures during emergencies often stem from lack of maintenance.
Chapter 8 - Communications Systems
NEC Chapter 8 provides the rules and requirements for communication circuits, including telephone systems, television and radio distribution, internet/data cabling, intercoms, and networked control systems. Unlike power circuits regulated in earlier chapters, Chapter 8 focuses specifically on low-voltage systems designed to transmit information, not power.
Article 800 - General Requirements for Communications Systems
This article outlines the general rules for installing communication cables and related hardware, including:
- Cable Types and Ratings:
Communications cabling includes types like CM, CMR, CMP, and CAT5e/CAT6/CAT6A for data.
Fire ratings matter: CMP cables (plenum rated) are required in ducts or plenum spaces due to fire safety concerns.
- Separation from Power Wiring:
Communication cables must be separated from power and lighting conductors to avoid electrical interference and induced voltages.
Dedicated raceways, barriers, or spacing are often required when running parallel to power circuits.
- 接地和接合：
All communications systems must be grounded at the service entrance or building entry point to limit voltage surges and ensure personal safety.
Bonding must be done using listed hardware, and must comply with Articles 800 and 250.
- Protection from Physical Damage:
Cables must be protected where they are subject to damage, such as in exposed locations or at penetration points through walls or floors.
笔记： Want to know the comms conduit differences between the US, Canada and Australia? In the last post, we listed the types and code compliance of US and AU communication conduits. You can click on the text above to learn more.
Article 820 - Community Antenna Television and Radio Distribution Systems (CATV)
Article 820 covers coaxial cable-based systems that provide TV, satellite, or RF signal distribution.
Key requirements include:
- 接地要求：
The coaxial cable’s shield must be grounded as close as practical to the cable entry point, typically with a grounding block.
- Surge Protection:
CATV systems must include surge protectors or listed antennas and splitters designed to mitigate lightning or transient voltages.
- Separation from Power:
As with other communication systems, CATV cables must maintain adequate separation from power wiring, especially when entering a building or sharing a raceway.
Common Applications
NEC Chapter 8 systems are commonly found in:
Commercial buildings – structured cabling, intercoms, CCTV
Residential homes – telephone lines, coaxial TV cable, internet wiring
Hospitals and schools – nurse call systems, paging, data networks
Smart buildings – integrated lighting and HVAC controls over data networks
Conduits Fit Into Communication System Installations
For physical protection, routing, and code compliance, communication cabling is often installed in non-metallic conduits, especially in underground or exposed areas. Some of the most commonly used conduit types for Chapter 8 applications include:
DB Conduit (Direct Burial Conduit)
DB-60 和 DB-120 PVC conduits are widely used for underground telecommunications lines.
These conduits are specially rated for burial without extra encasement and provide excellent resistance to soil corrosion, impact, and moisture.
DB conduit is ideal for running fiber optics and CATV lines from service pedestals to buildings, especially in campuses or housing developments.
HDPE Conduit (High-Density Polyethylene)
Flexible, corrosion-resistant, and suitable for long-distance underground communication cable pulls.
Often used in conjunction with fiber optic cables and microduct systems.
Common in data center backbones, utility corridors, and telecom provider networks.
波纹管
Lightweight, flexible, and easy to install in wall cavities or raised floors.
Frequently used for low-voltage drops, such as from a wall box to a data port or access control unit.
Available in halogen-free options for use in fire-sensitive areas.
Key Considerations
- Labeling and Identification:
Communication cables should be clearly labeled for identification, especially when multiple systems are installed together.
- Code Coordination:
While NEC governs safety, other standards like TIA/EIA-568, IEEE, and BICSI also guide performance and design. Compliance with both NEC safety codes and IT standards ensures optimal installation.
- Avoiding Signal Interference:
Maintain proper separation and shielding to avoid electromagnetic interference (EMI), especially in high-noise environments or where high-power equipment is nearby.
- Firestop Requirements:
When communication cables pass through fire-rated walls or floors, listed firestop systems must be used to maintain the fire-resistance rating of the barrier.
Navigating NEC Compliance - A Step-by-Step Guide
Achieving NEC compliance is about ensuring that every part of an electrical installation is safe, code-compliant, and fit for long-term performance in real-world conditions. Whether you’re working on a residential upgrade, a commercial building construction, or an industrial-scale system, a systematic approach rooted in the National Electrical Code (NEC) is essential.
Here are some factors you need to know to complaint with NEC:
Define the Application Type
Start by identifying the occupancy type and specific systems involved. The NEC structures many of its rules around the nature of the building or system:
Residential, commercial, or industrial
Hazardous locations (e.g., petrochemical plants)
Special occupancies like healthcare, agriculture, data centers, or EV infrastructure
Will it include systems like fire alarms, emergency power, or communication cabling.
Identify the Correct Code Edition and Local Amendments
Always verify the NEC edition adopted in your region. While the NEC is updated every three years, not all states or jurisdictions immediately adopt the latest version. Also, many municipalities add local amendments that override or supplement NEC rules.
To stay compliant:
Confirm the NEC edition adopted locally (e.g., 2020, 2023)
Review any state-specific electrical codes.
Coordinate with the Authority Having Jurisdiction (AHJ) early in the design phase.
Evaluate the Installation Environment
Electrical materials and methods must be selected with field conditions in mind. The NEC emphasizes suitability based on:
Ambient temperature: Conductors must be derated when installed in high-temperature areas (e.g., attics, rooftops). See NEC 310.15(B).
Moisture and corrosion: Use watertight and corrosion-resistant enclosures and raceways in wet locations (e.g., outdoor, underground).
Exposure to sunlight: Materials installed in direct sunlight must be UV-resistant.
Physical damage potential: In areas subject to impact or movement, raceways must be heavy-duty or mechanically protected.
Select NEC-Compliant Wiring Methods and Materials
Refer to Chapter 3 for acceptable wiring methods based on the project environment and NEC scope. Choices must consider:
Conductor type and insulation (e.g., THHN, XHHW-2, MTW)
Conduit system (e.g., EMT, RMC, PVC, ENT)
Cable assemblies (e.g., NM, MC, AC cables)
Boxes, fittings, connectors, and support
All materials must be listed and labeled by a recognized third-party testing agency (e.g., UL, CSA) and used in accordance with their listing.
For Special Occupancies and Equipment
If your project includes special occupancies or special equipment, apply specific rules beyond general wiring practices. Examples:
Healthcare: Requires isolated grounding, redundant circuits, and essential system separation.
危险场所： Mandates explosion-proof fittings and sealed conduit systems.
Agricultural Buildings: Require corrosion-resistant and dust-tight enclosures.
Fire Alarms: Must meet survivability and separation requirements.
NEC also defines clearances, circuit separation, and system labelling rules that are critical to safety and inspection.
Ensure Grounding and Bonding Integrity
Refer to NEC Article 250 for proper grounding and bonding, including:
Grounding electrode systems (e.g., ground rods, building steel)
Main and supplemental bonding jumpers
Equipment grounding conductors sized according to NEC Table 250.122
Improper grounding is one of the most common causes of NEC violations and electrical hazards.
Calculate Conduit Fill, Ampacity, and Voltage Drop
Proper wire sizing must consider:
Ampacity derating: Based on ambient temperature and number of conductors.
Conduit fill: Overfilling leads to overheating.
Voltage drop (recommended max 3% for branch circuits): Especially critical for long runs and energy-efficient designs.
Schedule Inspections
Coordinate with the AHJ for inspection stages, such as:
Rough-in inspections: Check wiring, supports, and boxes before finishes are applied.
Final inspections: Ensure proper device installation, labeling, grounding, and safety clearances.
Additionally, perform system tests like:
Continuity and insulation resistance
Polarity and GFCI/AFCI verification
Load balancing and voltage readings
For commercial and industrial systems, commissioning and third-party validation may be required.
The NEC provides a consistent framework for safe, functional electrical installations, but true compliance requires more than just code references. Professionals must consider installation environments, equipment ratings, material compatibility, and local rules every step of the way.
By following this structured guide and aligning each phase of your installation to NEC provisions, you can deliver systems that are safe, efficient, and future-proof.
10 Commons NEC Violations and How to Avoid Them
Even skilled electricians and experienced contractors can encounter National Electrical Code (NEC) violations, many of which are surprisingly avoidable. These missteps can delay project approvals, create safety hazards, or lead to costly rework. Understanding the most common pitfalls and how to prevent them is key to maintaining both compliance and safety.
Here are several frequently encountered NEC violations, along with practical advice on how to avoid them.
Inadequate Grounding and Bonding
One of the most frequent issues in electrical installations is poor or missing grounding and bonding. This can lead to equipment damage, shock hazards, or unreliable system performance.
How to avoid it:
Ensure all metal components and systems are properly bonded and connected to an effective ground. Use appropriate connectors and follow correct installation practices for grounding electrodes and conductors. Never rely on flexible metal conduits or enclosures as the sole path to ground.
Overfilled Junction or Outlet Boxes
Stuffing too many wires into a single electrical box without accounting for space requirements can lead to overheating or damaged insulation.
How to avoid it:
Always size electrical boxes according to the number and size of wires, devices, and clamps inside. Use larger boxes or box extensions when needed. Plan box fill before pulling conductors to avoid overfilling during installation.
Conduit Overfill and Poor Bending Practices
Running too many wires through a single conduit or using sharp, cramped bends can make maintenance difficult and lead to wire damage.
How to avoid it:
Limit the number of wires in each conduit to prevent excessive heat buildup. Maintain proper bending radii to ensure easy wire pulling and avoid stress on the insulation. Choose conduit sizes that allow for future wiring adjustments.
Missing GFCI or AFCI Protection
Omitting required safety protection, such as Ground-Fault Circuit Interrupters (GFCIs) or Arc-Fault Circuit Interrupters (AFCIs), is a common oversight—especially in kitchens, bathrooms, outdoor spaces, or bedrooms.
How to avoid it:
Know where these devices are required and include them in both design and installation phases. Use labeled GFCI/AFCI receptacles or breakers, and test them after installation.
Loose or Unsupported Cables and Conduits
Failing to secure cables or conduits can cause sagging, mechanical damage, or even failure under stress or vibration.
How to avoid it:
Support all wiring methods securely with proper fasteners at regular intervals. Avoid over-tightening straps, and use approved supports compatible with the conduit or cable type.
Using Incorrect Connectors or Fittings
Improvised or incompatible fittings can result in poor electrical continuity, mechanical weakness, or moisture intrusion.
How to avoid it:
Only use listed connectors and fittings that match the type and size of conduit or cable being used. Avoid mixing metal and plastic components unless specifically approved.
Ignoring Temperature Ratings or Ampacity Adjustments
Neglecting to consider high ambient temperatures, insulation type, or bundled conductors can lead to overheating and premature equipment failure.
How to avoid it:
Use wire types with insulation suitable for the environment, and adjust ampacity when cables are bundled or installed in hot areas like attics or near heating systems. Select conduit materials that perform well in those temperatures.
Poor Identification of Conductors
Using the wrong color or failing to label wires clearly can confuse maintenance personnel or lead to unsafe connections.
How to avoid it:
Follow consistent wire color conventions: black or red for hot wires, white or gray for neutrals, and green or bare copper for grounding. When color is unclear, label conductors clearly at both ends.
Insufficient Working Space Around Panels
Installing panels in cramped or obstructed areas makes safe operation and maintenance difficult—and can lead to code violations during inspection.
How to avoid it:
Ensure that electrical panels and service equipment have clear, unobstructed access with adequate working space in front and around them. Avoid placing panels in closets, bathrooms, or storage spaces.
Lack of Weatherproofing in Outdoor Installations
Failing to use weather-resistant materials outdoors or in wet locations can lead to corrosion, water damage, and dangerous short circuits.
How to avoid it:
Use weatherproof boxes, covers, fittings, and conduit suitable for wet or damp environments. Seal all connections carefully and install covers that protect outlets even while in use.
Staying Updated with the NEC - 3 Tips
The National Electrical Code (NEC) is not a static document—it is revised every three years to reflect changes in technology, safety practices, and the evolving needs of the electrical industry. Staying updated is not just recommended—it’s essential for compliance, performance, and safety.
Here are some points you can follow to ensure remain NEC-compliant and up to date.
Staying Compliant Through Education and Training
Continuing Education
Licensing authorities in many jurisdictions require electricians, engineers, and contractors to complete continuing education to renew their licenses. These courses typically cover updates in the latest NEC edition, with a focus on changes in definitions, requirements, and safety standards.
Manufacturer and Industry Training
Many conduit, wiring, and equipment manufacturers offer product-specific training aligned with NEC updates. These sessions help professionals apply code requirements to real-world products and systems, especially in emerging fields like EV charging infrastructure and solar energy.
On-the-Job Experience and Mentoring
For apprentices and journeymen, learning on-site under the guidance of a master electrician is one of the most practical ways to build NEC knowledge. Experienced professionals often share field-proven practices that align with code requirements while improving installation efficiency and quality.
The Role of Inspections and Permits
Electrical Permits Ensure Compliance Before Work Begins
Before most electrical work can begin, contractors must apply for a permit. This process ensures that the design and scope of work meet NEC standards and local amendments.
Inspections Catch Mistakes and Improve Safety
Inspections are conducted at critical phases of a project—often before walls are closed and again after completion. Inspectors act as an essential line of defense, verifying installations are safe, code-compliant, and professionally executed.
Working With Inspectors, Not Against Them
Professionals who view inspectors as allies—not obstacles—tend to deliver better projects. A good relationship with local authorities can streamline approvals and improve understanding of evolving code interpretations.
Essential Resources for NEC Compliance
NFPA 70: National Electrical Code Handbook
The NEC Handbook, published by the National Fire Protection Association (NFPA), provides the full text of the Code with expert commentary, illustrations, and real-world application notes. It’s an indispensable tool for in-depth learning and design reference.
NEC Mobile App and Digital Access
NFPA also offers the NEC in a mobile app, making it easy to search, bookmark, and reference sections in the field. Many professionals use the app as a fast and reliable way to find answers on-site.
Local Code Amendments
Each city or state may adopt the NEC with additions or modifications. Always check with your local Authority Having Jurisdiction (AHJ) to confirm which edition is in force and whether any unique rules apply to your project.
Trade Associations and Online Communities
Organizations like IAEI (International Association of Electrical Inspectors), NECA (National Electrical Contractors Association), and IEC (Independent Electrical Contractors) provide access to training, publications, and forums where professionals can discuss code questions and stay updated on industry trends.
结论
The National Electrical Code (NEC) is more than just a rulebook—it’s the foundation of electrical safety across the United States and beyond. It represents decades of industry experience, real-world lessons, and engineering standards that aim to protect people, property, and electrical systems.
One of the most critical aspects of NEC compliance is choosing the right electrical conduit. Whether it’s PVC for underground runs, EMT for commercial interiors, or specialized low-smoke halogen-free solutions for sensitive environments, conduit selection directly affects safety, performance, and code adherence. Using properly rated conduits not only ensures regulatory compliance but also contributes to long-term system durability and resilience.
Ultimately, following the NEC leads to safer electrical installations, reduced fire and shock hazards, and fewer costly reworks or legal issues. For electrical professionals, contractors, inspectors, and engineers, understanding and applying the NEC is not just a requirement—it’s a commitment to quality and safety in every project.
常见问题解答
什么是国家电气规范 (NEC)？
美国国家电气规范 (NEC) 是由美国国家消防协会 (NFPA) 为美国电线和设备安全安装而制定的一套标准化指南。NEC 每三年更新一次，旨在保护人员和财产免受触电、火灾和电弧闪光等电气危害。它涵盖了从布线方法和导管类型到接地、特殊用途和可再生能源系统的方方面面。
国家电气规范是法律吗？
从技术上讲，NEC 本身并非法律，但一旦被州或地方司法管辖区采纳为建筑规范的一部分，便具有法律效力。美国大多数州和地区都采用 NEC（通常会进行修订），使其成为这些地区事实上的法律要求。合规性通常由当地电气检查员强制执行。
所有国家都有国家电气规范吗？
No, not all countries have a version of the NEC. The NEC is primarily used in the United States, although some other countries, especially in Latin America and the Caribbean, may use it or base their standards on it. Other countries typically have their own national electrical standards, such as:
IEC 标准 (International Electrotechnical Commission) used in Europe and many parts of Asia and Africa
加拿大电气规范 (CEC) in Canada
AS/NZS 3000 (Wiring Rules) in Australia and New Zealand
使用 PVC 管作为电线导管不好吗？
Yes. Only specific types of PVC conduit are approved for electrical use—you cannot use regular plumbing PVC (typically white Schedule 40 or 80) as an electrical conduit.
For electrical installations, you must use electrical-grade PVC conduit such as:•
- Rigid Polyvinyl Chloride Conduit (PVC Schedule 40 or 80) — marked and listed for electrical use
- 电气非金属管 (ENT) — also made of PVC, flexible, and used in certain wall or ceiling applications
These conduits:
- Are listed and labeled for electrical safety
- Provide protection against corrosion and moisture
- Must be installed following NEC requirements regarding bends, supports, burial depth, and temperature ratings
Using plumbing-grade PVC for electrical wiring is unsafe and non-compliant, as it may not have flame resistance, UV protection, or dimensional consistency required for pulling conductors.
我可以沿着导管外面铺设接地线吗？
No, running a ground wire along the outside of a conduit is not compliant with the NEC. Grounding conductors must be:
- Inside the raceway or cable assembly
- Protected from physical damage
- Installed in a way that ensures electrical continuity and conductivity
Exposed grounding conductors are susceptible to mechanical damage and corrosion, which can compromise safety.
根据 NEC，电源插座是什么？
根据国家电气规范 (NEC) 的定义，电源插座是指布线系统上用于将电流输送给用电设备的点。实际上，它通常指用于连接电器或设备的插座。然而，根据具体情况，该术语也可能适用于其他插座，例如照明插座、电机插座或设备插座。
国家电气规范 (NEC) 的最新版本是什么？
最新版本是2023 NEC，由美国国家消防协会（NFPA）发布。该版本每三年更新一次。
哪些法规涵盖电气装置？
美国的电气安装主要受 NEC (NFPA 70) 管辖。地方司法管辖区可能会采用 NEC 进行修订或不修订，并且可能制定自己的建筑或能源规范。加拿大主要受 CEC（加拿大电气规范）管辖，不同地区可能各自有自己的地方规范。
在美国自己做电气工作合法吗？
是的，但这取决于州和地方的管辖范围。在许多地区，如果房主获得适当的许可并通过检查，他们可以在自己的房屋上进行某些电气工作。但是，商业工作或高压系统通常需要持证电工。
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