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| − | '''Work in progress'''
| + | [[image:Fusebox 195-4.jpg|250px|right]] |
| | + | [[image:Main_switchboard,_c._1888_(Forty_Years_of_Electrical_Progress).jpg|250px|right]] |
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| − | The main articles dealing with Consumer units, aka fuseboxes, are:
| + | This article is a starting point for the various articles that deal with Consumer Units (or Fuseboxes as they used to be known). |
| − | * [[Changing a consumer unit]]
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| − | * [[Consumer Units]]
| + | The pictures on the right show 100 years of progress, from 1888 to 1988. |
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| | + | Related Topics: |
| | * [[House Wiring for Beginners]] | | * [[House Wiring for Beginners]] |
| | * [[Rewiring Tips]] | | * [[Rewiring Tips]] |
| | + | * [[Electrical Installation]] |
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| − | | + | Consumer unit articles: |
| − | The '''CU''', '''Consumer Unit''' or '''Fusebox''' provides fault current protection for all a house's electical circuits. It usually contains a switch to control all the circuits, and many also feature leakage current protection with [[RCD]] or [[RCD|RCBO]]s.
| + | * [[Consumer Units]] |
| − | | + | * [[MCB]] |
| − | | + | * [[Fuse]] |
| − | ==Split Load CU==
| + | * [[RCD]] |
| − | A split load CU has 2 halves (sometimes more) with a separate power switch for each half. So some of your wiring can be turned off while the rest stays on. So whatever may happen with your electrical system, you don't need to turn it all off. This enables you to have power in the event of a fault, and to have power while working on the installation itself. (There are exceptions of course, such as lightning strike or a major fire.)
| + | * [[Changing a consumer unit]] |
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| − | Split load CUs are common today (especially with wiring compliant with the 17th edition of the wiring [[regs]]), and can be recommended in nearly all cases.
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| − | ==Upgrades==
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| − | Its often assumed that, being newer, [[MCB]]s provide better safety than [[fuse]]s, but the level of protection both provide is similar, and both have pros and cons.
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| − | The main ways in which CUs can be upgraded are:
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| − | * Fitting a split load unit | |
| − | * Elimination of touchable live parts, as found
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| − | ** on many CUs when fuses are pulled,
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| − | ** always live parts are common on pre-war fuseboxes, though these aren't often seen now
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| − | * Incorporation of leakage protection
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| − | ** with [[RCD]](s)
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| − | ** with circuit discrimination using RCBOs | |
| − | * Increasing the number of circuits rather than extending existing ones
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| − | * Adding provision for a shower, cooker, or other high current load
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| − | * Providing a separate feed for an outbuilding
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| − | * Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
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| − | * Replacement of an inadequate, damaged or faulty CU
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| − | * Making an old installation look modern
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| − | ===Upgrading CUs on TT installs===
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| − | A little care is required over earth leakage protection when replacing a CU on a [[Earthing Types|TT install]], as a CU setup not specifically suited to TT use is likely to leave the system dangerous.
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| − | * CUs on TT systems should be insulated (ie plastic), not metal.
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| − | * A CU without full RCD cover should never be used where there is no preceding whole house RCD or ELCB.
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| − | * Where RCD is housed in the CU, a single RCD covering the whole house is no longer compliant, and can cause loss of power. A split CU with 2x RCDs is usually a good solution.
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| − | ==MCBs & Fuses==
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| − | ===Ratings===
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| − | * Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
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| − | * Immersion heater: 15/16A
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| − | * Socket circuits, ring: 30A fuse, 32A MCB
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| − | * Socket circuits, radial: 20A | |
| − | * Cooker, shower: Usually 45A or more
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| − | * Small loads: 2.5A, 5A, 6A.
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| − | For information on type B, C and D MCBs, see [[MCB]]
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| − | | |
| − | ===Level of protection===
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| − | In an ideal world all circuits would have suitable overcurrent protection as well as fault current protection. In practice there are a percentage of existing installs that fail to meet this requirement.
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| − | ==Live parts==
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| − | A lot of fuseboxes/CUs are in use that expose the user to live parts if fuses are pulled with the power on. Always turn power off before pulling a [[fuse]].
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| − | ===Working on the CU===
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| − | The switch in the CU is the main power switch for most houses. Thus exposed wiring will be live when the CU cover is removed, even with the switch off. Removing the main supply fuse before the meter solves this, but is illlegal, but its common practice nonetheless. Power companies have so far not objected to the practice, for an assortment of legal, safety and financial reasons.
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| − | ==Trips==
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| − | Tripping or repeated fuse blowing are normally caused by a fault outside of the CU itself.
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| − | * RCD trips are usually caused by a faulty appliance or a less than ideal installation design. See [[RCD]] | |
| − | * [[MCB]] trips are most commonly caused by blowing filament bulbs. Faulty appliances often also cause this. | |
| − | * RCBO trips may be due to either of the causes above, since an RCBO combines the functions of both MCB and RCD.
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| − | There are of course other possible causes of trips and blown fuses, the above is just a pointer to the most likely.
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| | ==See Also== | | ==See Also== |
| − | * [[House Wiring for Beginners]]
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| − | * [[Rewiring Tips]]
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| | * [[:Category:Electrical|Electrical articles]] | | * [[:Category:Electrical|Electrical articles]] |
| | * [[Special:Allpages|Wiki Contents]] | | * [[Special:Allpages|Wiki Contents]] |
| | * [[Special:Categories|Wiki Subject Categories]] | | * [[Special:Categories|Wiki Subject Categories]] |
| | + | * [http://www.flameport.com/electric/old_equipment/wylex_standard_brown_wooden.cs4 Wylex CUs pictured above] |
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| | [[Category:Electrical]] | | [[Category:Electrical]] |
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