Witch Size Wire Is Best for Wiring a House

Firm Wiring for Beginners gives an overview of a typical bones domestic 240V mains wiring organization as used in the UK, then discusses or links to the common options and extras.

Further information on options is available in the Rewiring Tips commodity.

Prophylactic

• This article cannot practically cover everything.
• The writing of this article may be incomplete when yous read information technology.
• Laws and regulations change over fourth dimension.
• Interpretation of regulations and constabulary may change over time
• The article may assume noesis that some readers might not possess
• Unexpected situations may modify the specific requirements for some circuits.

For these reasons and more, ane should not carry out safety critical work based solely on wiki content. Information and plans should exist independently checked and verified earlier activeness.

Anyone installing wiring should as well understand some basic safety issues non discussed hither. This article is an introductory overview rather than a complete A to Z on rewiring, and assumes some basic electrical knowledge.

Regulations

Some regulatory requirements are mentioned in this article. These use to new wiring, and in many cases are not requirements for existing wiring.

Word Meanings

The Electric Glossary may exist useful.

Overview

Typical business firm wiring diagram illustrates each type of circuit:

In a typical new town business firm wiring arrangement, we have:

• Live & Neutral tails from the electricity meter to the CU
• A carve up load CU
• Ring circuits from 32A MCBs in the CU supplying mains sockets. 2 such rings is typical for a 2 up 2 down, larger houses accept more.
• Radial lighting circuits from 6A CU MCBs. 2 or more circuits typical.
• Earth connection from incomer to CU.
• 10mm² Main equipotential bond to other incoming metal services (gas, water, oil)

Systems often take some of the following as well:

• Dedicated circuit MCB & cablevision supplying cooker
• Dedicated high current circuit MCB & cable supplying shower
• 2 way lighting switching for stairs, big rooms & walk through rooms
• Outdoor lighting supplied by a 6A MCB, oft via a PIR movement detector switch.
• 16A MCB and cable supplying hot water immersion heater.

• 

  AEI Storage heater switch with dissever supplies for (unfused) off-peak supply on dedicated radial circuit and (fused) boost/fan supply on the socket circuit.

  A loftier electric current MCB supplying storage heaters. Sometimes these are run from the main CU, but frequently from a timeswitch controlled dedicated CU (with either a carve up "off top" electricity meter, or a dual tariff meter).

The radial lighting circuit has three common wiring options, which may exist mixed at will:

• "Loop-in" (as per diagram above). The circuit is fed to each lamp plumbing equipment in turn, and a separate cable connects from the fitting to the switch. (this is the nigh mutual method)
• Switch loop through (the circuit connects to each switch in plow, and a dissever cablevision goes from the switch to each lamp)
• Junction box loop in, where the termination and feed connectedness are done at junction boxes, and cables run to switches and lamps from there.

The diagram is shown with 6A lighting fuse and 32A ring circuit MCB. Other options are as well possible:

• 20A radial socket circuits
• 10A lighting circuits are occasionally used

Consumer Unit of measurement (CU)

The Consumer Unit, previously chosen a fusebox, contains these things:

• A main isolating switch. This switches off everything.
• In most cases at least ane RCD
• A fuse or MCB for each excursion. This cuts the power to the excursion in the event of loftier fault current.
• An earth connexion block which connects earth to the earth wires of the various circuits
• 1 or 2 neutral connexion blocks which supply the neutral connection to the Neutral wires of the various circuits

Each fuse or MCB supplies one circuit only. Ane circuit may supply anything from 1 to a large number of loads.

Carve up Load CU

Split load CUs have get popular in contempo years, and ubiquitous since 2008 with the introduction of the 17th edition of the wiring regs. They usually offer meaning advantages over the traditional unsplit CU blazon. See 17th Edition Consumer Units for more details.

A split up load CU divides the MCBs into 2 or more split banks. Each banking concern usually having its own RCD. At that place should also be a principal switch that volition switch the whole CU.

The divide load CU has the post-obit advantages:

• Some wiring work tin be carried out with just a section of a CU turned off, perhaps retaining access to light and power while working.
• Almost all faults tin can merely accept out the power to part of the organization
• The split load arrangement ways both RCDed and non RCDed loads can be supplied from the 1 CU.

Split up load CUs are recommended, and this article volition presume the use of a split load CU.

Earthing

Earthing is a fundamental safety organization used in electrical installations. It works in co-ordination with circuit breakers MCBs, Fuses, and RCDs to ensure that an electrical supply can be asunder rapidly in the event of a mistake. This greatly reduces shock risk.

Most houses have an globe connection supplied by the electricity supplier. Those that don't (generally country houses several miles from the nearest town), use a local world rod instead.

The supplier's earthing terminal or your ain earth rod is connected to the CU earth block. Each electrical circuit in the business firm takes its earth connection from the CU earthing block.

Residual Current Devices (RCD)

The 17th and subsequently editions of the wiring regulations impose more frequent requirements to install RCD (or RCBO) protection than the previous 16th Edition. In general, Whatever cablevision which is buried less than 50mm below a wall's surface AND is Not mechanically protected, or wired in one of a number of specialised cable types that contain an earthed screen must have 30mA trip RCD protection. Such circuit protection may be derived from either an RCD protecting several circuits, or private RCD/RCBOs on each circuit.

New installations will have two or more RCDs. Older ones may merely have ane or none. (currently half the backdrop in the UK have none according to inquiry)

RCDs reduce the risks of injury from electrical shock (they don't eliminate it completely), however they tin can too introduce reliability and issues of their own if not used in an appropriate way. Historically RCDs were ordinarily simply used on some circuits rather than all.

With a supplier provided earth connection, the well-nigh mutual historical arrangement was a carve up CU with a RCD on one side, and no RCD on the other. Generally the RCD side is used to supply sockets and shower, with nigh other items on the non-RCD side.

With a local earth rod, the situation is dissimilar in that all circuits must be RCD protected, since a local world rod is non usually a sufficiently good earth on its own to clear all globe faults. So RCDs are used on all circuits even in older installations. A common option is to have the supply fed through a 100mA time delayed RCD, the output of which goes to a divide CU with RCD on ane side. This is not an ideal organisation, every bit a large earth leakage fault on the non-RCD side will cause consummate power failure, and sometimes disability to reset the power.

RCBOs

An RCBO is a combined RCD and MCB in one module, and is fitted in place of an MCB. RCBOs let individual circuits to be protected past their own RCD without any take chances that a fault in an unrelated circuit could cause information technology to trip. However protecting all circuits like this is more expensive.

Where RCBOs are used, they are fitted in the not-RCD side of the CU, and supply circuits needing RCD protection. See 17th Edition Consumer Units for details.

Neutral Connections & RCDs

Neutrals for circuits protected by different RCDs (or those from an RCD and not RCD protected circuit) must not be mixed. If any neutral wire is connected to the incorrect side, the RCD will trip.

The same principle is true for RCBOs, each RCBOed circuit needs to have its neutral connected to the RCBO neutral and not elsewhere.

RCD or not-RCD side

Historically, installations using a supplier world connection will run some circuits straight off the non RCD side of a CU. These include:

• Lighting circuits
• Immersion heater circuits
• Circuits
• Circuits where disconnection is undesirable (i.due east. freezers, fire alarms, boilers, etc)

All socket circuits, should have RCD protection since Plug-in are the source of almost all electrocutions.

Modern installations will typically provide boosted RCDs so that vulnerable circuits (i.east. lighting) are unlikely to exist affected by a nuisance trip, and so that circuit types prone to high earth leakage (e.g. things with heater elements and water in shut proximity) are separately protected from others.

Sockets

Sockets may be wired on band circuits or radial circuits. Mostly rings are used, equally they use less copper for most circuit layouts, they have condom advantages over radial circuits (sometimes debated), can provide more than power, and cover more floor area per circuit.

Band

Sockets are on 32A ring circuits in most house installations. These use a ring of cable (ie a loop), so that at the CU 2 cables are connected to the MCB instead of 1. An unlimited number of sockets may be continued on each ring.

One ring circuit per floor is a fairly common arrangement, but past no means the only option. Larger houses generally have more than rings. Its besides common to have a ring defended but for sockets in the kitchen since that is where you will discover many of the highest power consuming appliances in a modernistic house.

2.5mm² cable is usually used for band circuits. 4mm² is used when cable volition exist under insulation or bunched with other cables.

Spurs

Spurs are permitted, merely sockets should be included in the ring rather than spurred wherever practical. Spurring is best only used for later additions to circuits.

Rules use to the loading and number of sockets allowed on the end of a spur.

Spurring sockets prevents the easy later addition of more sockets in some positions, as a spur may non be spurred off a spur. Spurs also forbid the addition of more sockets at existing spurred positions, whereas a practically unlimited number of sockets can exist added where a socket is in the ring. Bear in mind the number of sockets wanted has risen greatly over the years, and can only be expected to rise further.

Radial

Radial socket circuits are used less oft. These use a single cable from CU to socket, then a single cable to the next socket along the line etc. Radials utilize more copper on nigh circuits, though less cable on physically long narrow shaped circuits. Connection faults have greater consequences than with band circuits. (Confusion over the relative condom of ring & radial circuits is widespread.)

• 20A radials use 2.5mm² or 4mm² cable.
• 32A radials use 4mm² cable

Number of Sockets

Minimum and desirable numbers of sockets recommended per room are given. Recommended numbers are inevitably a affair of opinion, and are simply recommended equally a starting point for consideration.

• Sleeping room
  • Minimum: i double socket at each of 2 locations
  • Recommended: 2x double sockets at each of iv locations (in or near corners) + a double socket at side of unmarried bed, or a double socket at each side of double bed. 2 way lighting switches controllable at door & bedside.
• Corridor
  • Minimum: none
  • Recommended: one double socket for a short corridor, 2 or maybe more in a long one. Put 1 where a hall table might become.
• Kitchen
  • Minimum:
  • Recommended: Under worktop: 4 or 5 double sockets. Over worktop: i double socket per 2 metres. All sockets on band circuit, no spurs. 2A or 5A sockets on lighting excursion: one higher up each ready of cupboards, one below each set of cupboards, ane away from cupboards & worktop.
• Lounge:
  • Minimum: 1 double socket at each of 2 locations
  • Recommended: 2x double sockets at each of 4 locations (in or nigh corners) + 1-iii double sockets where PC or AV equipment is to exist used. If the room has 2 or more than doors, 2 fashion lighting switches controllable at each door. iv-6x 2A or 5A sockets on lighting excursion.
• Utility room:
  • Minimum: i double socket
  • Recommended: 2 or 3 double sockets, all on ring circuit
• Bathroom:
  • Minimum: no sockets
  • Recommended: none. 1 socket somewhere out of easy reach in zone 3 if you wish to use an apparatus in the bathroom (eg washing machine or dehumidifier). A shaver socket at the sink is an option, but plugging items in exterior the room is probably better practice.
• Home Office:
  • Minimum: a double socket at 2 locations
  • Recommended: 2x double sockets at each of 4 locations (mostly well-nigh corners), plus anything from 2 to 6 double sockets where calculator or other business appliances volition become.
• Small shed:
  • Minimum: no electricity supply
  • Recommended: if far from the house, a double socket can exist useful. If you lot'll spend time in information technology, a light too.
• Large shed:
  • Minimum: no electricity supply
  • Recommended: enough of lighting & sockets according to size & proposed use. Given the trend for electricity use to rise over the years, an overrated feed cable may prove useful in time.
• Greenhouse:
  • Minimum: no electricity supply
  • Recommended: A splashproof double socket in a higher place caput height can exist handy. For a dedicated horticulturalist, fluorescent lighting, a couple of splashproof double sockets positioned at head height or to a higher place, and a 13A socket for discharge lighting can all come up in useful.

Lighting

Radial circuits are used for lighting. There is one lighting excursion on each lighting MCB. Lighting circuits are usually on a 6A MCB or 5A fuse, though 10A can be used (with some extra restrictions (now removed in the 17th edition of the wiring regs)) for large circuits. However if the area served is large, more 5A or 6A circuits would in most cases be preferable.

lighting circuits are typically wired in 1mm² or 1.5mm² T&E cable (1.5mm² allows a longer cablevision run, before suffering too much voltage drop).

Fuse or MCB

Filament lamp failures can trip MCBs, and then fuses accept an reward over MCBs for lighting circuits, every bit they rarely nuisance trip on bulb failure. (Less sensitive type C and D MCBs tin often be used to assist reduce this problem.)

Loop-in Wiring

The power feed cable may go to either the switch or the bulbholder. If it goes to the bulbholder, this is called loop-in wiring, and the ceiling rose (a junction box with a downwardly facing cable outlet) then uses 4 sets of connections instead of 3, the extra i being a switched alive.

With loop-in wiring, the cable from the ceiling rose to the switch has 3 conductors, namely earth, unswitched live and switched live. Regs conformance requires that brown sleeving exist fitted over the neutral coloured usher at each end of the switch cable since it is being used as a live.

A typical view inside a ceiling rose:

Which is a little easier to sympathise in schematic form:

All cable colours are as expected except for the switched live. Calorie-free switches are normally wired with standard T&E, which means the switched live wire will be black (existing installs) or blueish (new installs) - this should exist marked with live coloured tape or sleeving (though alas this is oftentimes missing).

And then beware, if you have down a rose without paying attention to which wire is which, and you re-connect all the blacks or blues together, your fuse or MCB volition trip.

Unmarried & Earth

A less commonly met system of wiring lighting circuits.

The permanent lives and switched lives of the circuit apply the unmarried cadre and earth cablevision (blazon 6241Y).

This run starts from the MCB and loops between the lightswitches to provide a permanent alive and earth to the lightswitches. Another length of 6241Y is then used from the lightswitch to the calorie-free fitting to provide a switched live and earth at the light plumbing equipment.

The neutral cable is a double sheathed cable (6181Y with a blue inner sheath) that runs from the CU neutral busbar and from lite plumbing equipment to light fitting (there volition only be one neutral at the finish of the circuit).

It makes information technology easier to put calorie-free fittings up as there are less cables to mess with at the plumbing fixtures.

Other Wiring Options

In addition to the common Loop In scheme shown above, other systems are also ofttimes used. These are Switch loop through which makes all the connections at a switch. There is also junction box wiring which is basically the aforementioned as the ceiling rose organization except there is no local connexion to a lamp - so its improve suited to remote lamps like wall lights. All combinations of these can be on the same excursion if necessary :

Two Manner Switching

Two way switching means having two or more than switches in dissimilar locations to control one lamp. They are wired then that operation of either switch volition control the light(s).

Calorie-free circuit earthing

In some older properties (typically wired in or before the mid 1960s), its not uncommon to find lighting circuits without an earth wire. Intendance should be taken if you take such a excursion to ensure that simply appropriate light fittings and switches are used. Most metal lite fittings and switches will require earthing, only those marked with the double insulated symbol do non need an globe connection. Most plastic switches and light fittings are also condom for use on circuits with no earth.

Note the earth wire in the T&E must be run to all switches, junction boxes & low-cal fittings, including those that are currently plastic. It is non permitted to borrow an globe from another circuit. Ideally the non-earthed circuit ought to be re-wired, or at least have a RCD installed to protect it.

For more information nigh unearthed lighting circuits see Lighting Circuits Without an Earth

Outdoor Lighting

Outdoor lighting is usually run on its own radial excursion off its own MCB in the CU. Usually this is a 6A MCB, just lighting is less likely to cause problems if run on a 5A fuse. Exterior cabling must be appropriate for utilize outside (many cablevision types degrade under prolonged exposure to sunlight for example).

Bathroom Electrics

Bathrooms (or rooms with showers) are "special locations" in the linguistic communication of the wiring regulations. This is because they are places where people are particularly vulnerable to serious injury from electric shock (due to being moisture and barefoot). In mod designs all bathroom electrics are supplied by RCD protected circuits.

Zones

Bathrooms are divided into iii zones, with different rules for each zone.

• Electrical fittings in the bathroom in zone 0 must arrange to IPX7 or better, and must be of an actress low voltage type.
• Electrical fittings in the bathroom in zones 1 & two must conform to IPX4 or better.
• Electrical fittings in the bathroom outside of the zones do not need to confirm to any specific IP rating, but must exist appropriate for the circumstance in which they are used.

There are too limitations to the blazon of electrical equipment permitted in each zone. Meet the Bathroom electrics commodity for more details.

Equipotential Bonding

All metal items that enter a bathroom from outside of the room (eastward.grand. copper pipes, electric excursion cables) are connected together using 4mm² dark-green/yellowish insulated wire. Connection is also made to each of the protective earth wires in each circuit that feeds an appliance in the bath (e.g. lamps, heaters, towel rail etc). This is called equipotential bonding and is designed to minimise exposure to dangerous voltages that may exist present during electrical mistake conditions. The wire is continued to metal pipes using BS 951 globe clamps. The wire is connected to radiators using connectors. It is permitted to place equipotential bonding connections immediately outside the bathroom if necessary. Note equipotential bonding can be omitted if all the circuits that enter the bathroom are protected by RCD(s) with trip thresholds of 30mA or less.

Sockets

Until the introduction of the 17th edition of the wiring regulation, sockets were not permitted in a bathroom at all, unless they were either a transformer isolated shaver socket, or sockets to power extra low voltage devices, both of which are permitted in Zone 2 or outside. For more than information on bathroom electrics, see Bath electrics.

Showers

An electrical shower will be fed on its ain high current cable, fed from its own MCB on the RCD protected side of the CU. For more than information on electrical showers, see Installing an electric shower

Kitchens

Modern kitchens often have a loftier concentration of electrical appliances, many of them loftier ability consumption devices. Hence they are worthy of special mention.

Cookers

All in one electric cookers (oven, hob & grill in one unit) are fed past a loftier electric current cable from the CU, typically on a 32A MCB. Unmarried cavity ovens with no hob are more oft put on a 13A plug. Almost hobs require their ain high current feed, but some are available that incorporate load limiting switching, and are designed to exist run on a 13A plug. Combi cookers (microwave & fan oven, with or without grill) are always on a 13A plug.

Equipotential Bonding

Opposite to popular belief kitchens do not need equipotential bonding.

Number of Rings

About kitchens are supplied past 1 ring circuit. However this may exist insufficient for large or all-electrical kitchens.

Misc Information

Role P

Complete rewires and a number of other electrical jobs are now covered past Part P of the edifice regulations. For more information on Part P, run into Part P

Cable Colour changes

Although the UK has used the European standard of Blue / Brown colouring for flexes for a long time, the same colour standard has also at present been adopted for stock-still wiring too. Hence yous need to be aware of the changes:

Old colours:

• Scarlet = Live
• Blackness = Neutral
• Bare or green/yellowish = Earth

New Colours:

• Brownish = Live
• Blue = Neutral
• Bare or green/yellowish = Earth

For more information on cablevision colours, see Wiring colour codes

Run into Also

For more info on firm wiring see

• Rewiring Tips
• Electrical Glossary
• Bathroom electrics
• Taking electricity outside
• and Category:Electrical

For more data on lighting see

• Category:Lighting
• Dimmers & Switchbanks

For more data on outdoor lighting, see

• Category:Lighting
• Rewiring Tips#Outdoor Security Lighting
• Dimmed PIR Lights
• Taking electricity outside

For more information on RCDs & RCBOs, come across

• RCD
• Rewiring Tips

• To suggest article improvements, click the 'discussion' tab at peak of folio
• Wiki Contents
• Wiki Subject Categories

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Source: http://wiki.diyfaq.org.uk/index.php/House_Wiring_for_Beginners

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