page_title: Consumer unit
section_title: RCD protection types
hierarchical_section_title: Consumer unit / Examples / RCD protection types
caption_attribution_description: English: RCD Protection Consumer Dual Split-Load up to 17th edition Electrical Regulations standard BS7671.
context_page_description: A consumer unit is a type of distribution board.
context_section_description: Since the introduction of (BS 7671:2008 incorporating amendment no 1: 2011) 17th Edition IET Wiring Regulations, consumer units in the UK must provide RCD protection to all cables embedded in walls excepting high integrity circuits such as those for burglar alarms or smoke alarms.
  Consumer units have different methods of protecting circuits. For example, a dual split-load consumer unit can be arranged in a two-story dwelling as follows:
  RCD 1
  Upstairs Lights,
  Downstairs Ring Final,
  Garage Sockets,
  Cooker
  RCD 2
  Downstairs Lights,
  Upstairs Sockets,
  Shower,
  Heating
  By arranging the circuits like this, power will still be present on one of the floors if only one RCD trips out. Moreover, having sockets and lights on alternate RCD's means that if a faulty kettle downstairs trips that RCD for example, the kitchen lights will still be available, avoiding the hazard of investigating the fault in darkness.
  Another way to protect circuits under the 17th Edition IET Wiring Regulations is by fitting Residual Current Circuit Breaker With Overload (RCBOs) to every circuit, and although this is more costly than the RCD+MCB's option, it means any fault condition on a circuit trips only that circuit's RCBO, so the search for the fault is narrowed down from the start. When an electrician must be called out, this localised fault can be resolved faster (and therefore cheaper) in contrast with the RCD+MCB's arrangement, which only indicates a fault somewhere within that RCD's set of circuits. 
  Some older systems such as those that use MK or old MEM Consumer Units that had one fuse per spur, so for instance:
  Upstairs Lights Fuse 1
  Upstairs Sockets Fuse 2
  Downstairs Lights Fuse 3
  Downstairs Sockets Fuse 4
  etc..
caption: RCD Protection Consumer Dual Split-Load
exif: {"Image Make": "Apple", "Image Model": "iPhone 6", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "8.4.1", "Image DateTime": "2015:08:27 16:39:22", "Image ExifOffset": "168", "EXIF ExposureTime": "1/33", "EXIF FNumber": "11/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "100", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2015:08:27 16:39:22", "EXIF DateTimeDigitized": "2015:08:27 16:39:22", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "253/50", "EXIF ApertureValue": "7801/3429", "EXIF BrightnessValue": "5447/2035", "EXIF ExposureBiasValue": "0", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "83/20", "EXIF SubjectArea": "[1631, 1223, 1795, 1077]", "EXIF SubSecTimeOriginal": "030", "EXIF SubSecTimeDigitized": "030", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1721", "EXIF ExifImageLength": "1300", "EXIF SensingMethod": "One-chip color area", "EXIF SceneType": "Directly Photographed", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF FocalLengthIn35mmFilm": "29", "EXIF SceneCaptureType": "Standard", "EXIF LensSpecification": "[83/20, 83/20, 11/5, 11/5]", "EXIF LensMake": "Apple", "EXIF LensModel": "iPhone 6 back camera 4.15mm f/2.2"}