Another one to mull over....
NT
The CU, Consumer Unit or Fusebox provides overcurrent 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.
==Split Load CU== A split load CU has 2 halves with separate power switches. 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.)
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.
==Upgrades== Its often assumed that, being newer, [[MCB]]s provide better safety than [[fuse]]s, but the level of protection both provide is very similar, and both have minor pros and cons.
The main ways in which CUs can be upgraded are:
- Fitting a split load unit
- Elimination of touchable live parts, as found
- Incorporation of leakage protection
- Increasing the number of circuits rather than extending existing ones
- Adding provision for a shower, cooker, or other high current load
- Providing a separate feed for an outbuilding
- Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
- Replacement of an inadequate, damaged or faulty CU
- Making an old installation look modern
===Upgrading CUs on TT installs=== 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.
==MCBs & Fuses==
===Ratings===
- Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
- Immersion heater: 15/16A
- Socket circuits, ring: 30A fuse, 32A MCB
- Socket circuits, radial: 20A
- Cooker, shower: Usually 45A or more
- Small loads: 2.5A, 5A, 6A.
For information on type B, C and D MCBs, see [[MCB]]
==Live parts== 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]].
===Working on the CU=== 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.
==Trips== Tripping or repeated fuse blowing are normally caused by a fault outside of the CU itself.
- 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.
There are of course other possible causes of trips and blown fuses, the above is just a pointer to the most likely.
==Brands== Ashley
Contactum
MK
Wickes
Wylex
- Cheap & basic Wylex fuseboxes are very common in existing installs
- Fuses expose live parts if pulled with power on
- Overheating occasionally happens on high current circuit fuses (greater than 30A)
==See Also==
- [[House Wiring for Beginners]]
- [[Rewiring Tips]]
- [[:Category:Electrical|Electrical articles]]
- [[Special:Allpages|Wiki Contents]]
- [[Special:Categories|Wiki Subject Categories]]
[[Category:Electrical]]