A look inside a British home electrical panel.

Note that in this video the panel is new and has no external circuits connected yet. When wired in and active there is a lot of exposed live metalwork that poses a shock risk. Changing a consumer unit is not a simple DIY task due to the presence of a high current supply that poses a shock and burn hazard if touched or bridged.

In the UK we have a really simple electrical system. Just a three phase system with 240V between each phase and neutral and 415V between any two phases. (230V/400V under European tolerance standards.)
A typical home will get a single phase and neutral with the three phases spread amongst homes in a street, while a factory or commercial premises will usually get all three phases.
The higher voltage means lower current and the single phase means that our consumer units (home electrical distribution boards) are very compact and simple inside.
Traditionally they contained an isolator with a busbar that went along a horizontal row of breakers, but these days the breakers are often grouped in sections, each protected by its own main RCD/GFI. This allows the RCD/GFI to protect all the wiring in the circuit and also ensures that if a leakage fault does cause an RCD/GFI to trip, it only turns off a small number of circuits in the house. In some instances every single circuit may have its own RCBO (Residual Current Breaker with Over-current) which protects each circuit against overcurrent and fault leakage.
The use of a DIN rail for mounting the breakers means that the panel can accommodate other modules if desired. Commonly things like time switches and power supplies. Alternatively a consumer unit can be used purely as a handy housing for a row of DIN modules with the added advantage of integral power busbars.
A typical British home gets a 60A utility fuse these days, although for larger homes or applications like vehicle charging that can be upgraded to a higher value if the incoming cable is suitably rated.
Typical circuits in a consumer unit are:-
Lighting. A radial circuit protected by a 6A circuit breaker. Usually wired with 1mm or 1.5mm CSA cable. The circuit usually bounces from room to room passing through a ceiling rose connector that makes it a very versatile system for lighting.
Radial power. Often a 16A breaker feeding a special application like a heating boiler control system or immersion heater. Usually wired in 2.5mm CSA cable.
Radial circuits are also used for high current loads like cookers and showers with suitable cables and breakers.
Ring power circuit. An unusual approach to running lots of high current sockets with a loop of cable that starts and finishes at a 32A breaker. Usually wired with 2.5mm CSA cable. People make entire careers out of inventing new and pointless ways to test ring circuits. Sometimes called a ring main as the first circuits were based on power distribution ring mains that are used in the electrical utility industry. Now called ring final circuits, a new name invented by the department of paperwork.

Other components to follow in future videos.

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[duke]

As an American electrician this panel not just being a box full of blatantly exposed death metal is mind blowing.

[illyaseagal]

It is a pleasure to look at a DIN rail based British panel. I cry every time I look inside a Canadian panel. Thank you for keeping the Queen safe from shock.

[frigzy]

I’ve been installing electrical panels in both Europe and USA. I really like how breakers just snap on without tools in American panels and bus bars are integrated. That makes an installation with 30-50 branches clean and easy. On other hand, I don’t remember having more than 10 breakers at once in an European panel. I think 220v system allows much more load per a branch. Also, European apartments are tiny - no need for many branches.

[Tom_Losh]

Compared to the usual panel in the USA, that one is elegant and straightforward.

[Lion_McLionhead]

Nice bubble level to keep the electrons from falling out.

[thadgiannetti]

I love this series, i'm just beginning to get my head around the likes of ring circuits and fused such a different electrical distribution design than in the US. you and Thomas Nagy are amperage ambassadors. keep teaching us.

[tubastuff]

I'd like to see a comparison with a modern German distribution panel (3 phase). Always seemed like a good idea instead of single-phase distribution. I'd also like to see a discussion of the UK "ring mains" system.

[ericjorgensen]

This is a very interesting video. Reading the comments, I've seen a some of them that say that since the UK uses 240 volts, they get more power for their 60 or 100 amp electrical service than the US (or Canada) does for an equivalent size service. That is simply not true for single phase service.  

So I thought a little information on how US/Canada split phase electric service works might be helpful for anyone who is interested.

US/Canadian electrical services are also 240 volts. But in the US the transformer has a center tap, which also provides 120 volts from the center tap (which is called the neutral and is grounded/earthed) to either of the 'hot' legs that are on each side of this center tap. This is called a split phase service. It is NOT a 2 phase service!

But a house with 3 phase service in the EU with a 60 or 100 amp service will get 173 percent of the power than a house with a similar size single phase service. So a house in the EU with 100 amp 3 phase service will have about 40, 000 watts available, almost the same amount of power that a US house with a 200 amp single phase service will have.

In the US higher loads like electric stoves, ovens, air conditioning, electric heating, water heaters, clothes dryers, etc., usually run on 240 volt circuits.  But I have a newer Miele heat pump dryer that runs on 120 volts.

What IS true, is that lighting circuits and circuits for receptacles for things that "plug in" are usually 120 volts. These have only 1/2 the power for the same number of amps, therefore the 120 volt branch circuits require thicker copper wire for the same amount of power, and these circuits are usually either 15 amps 14 AWG (1.63 mm) and 20 amps 12 AWG (2.06 mm) size wire.

The key to understanding how split phase electrical service works requires one to understand that all the 120 volt loads on leg A are essentially in series with all the 120 volt circuits on leg B, and are therefore wired across the 240 volt output of the transformer and that only the difference current between the loads on leg A and leg B flows back to the transformer on the neutral. On a well balanced installation, very little current flows back on the neutral.

US houses usually have larger electrical services than in the UK because homes tend to be bigger in the US, as well most of the US is hotter than Europe, so air conditioning is used a lot more. Where I live in SE FL we run the air conditioning most of the year, only have a few weeks, usually in January, where we don't use it.  

The common household service for most houses in the US is usually 200 amps, with some smaller houses wired for 150 amps. Older houses that have not been upgraded can have 60 or 100 amp service.  

In the US the "consumer unit", called a breaker panel in the US, tend to have a lot more circuit breakers. A typical 2000 s.f. house in the US will have 240 volt breakers (which take two positions) for the range, water heater, air conditioner/heat pump, air handler/electric heat, clothes dryer, and possibly other things like a hot tub, pool pump, separate oven, etc. 120 volt breakers are required for circuits to the kitchen counters (2 20 amp circuits required for the counter(s)), dishwasher, microwave oven, refrigerator, garage, bathroom(s), and 10 or more circuits for lighting and receptacles around the house. Larger houses can have many more circuits. Therefore in the US breaker panels tend to have from 30 to 40 positions for an average size house.

200 amps at 240 volts is capable of delivering 48, 000 watts. Larger houses have 400 amp services, and I have seen 7, 500 s.f. houses with 600 and even larger houses with 800 amp services, almost always single phase.  Usually a service larger than 200 amps will be split into multiple 200 amp panels -- for example a house with a 600 amp service will have the service split into 3 200 amp breaker panels, often with sub-panels connected to them.

I have only seen a few mansions that have 3 phase service in the US.

Electricity is cheaper in the US than in the UK and EU. Where I live, the cost is about $0.14 to $0.15 (US$) per KWH including taxes and fees. Probably soon to go higher considering the current situation.

Another interesting thing about US electrical service: there are no power company provided fuses for the service to a house. The transformer contains a fuse, but that fuse is only there in case of catestrophic failure. Normally it does not protect the wiring to or in a house, even if the circuit is severely overloaded. But the transformer fuse will usually blow if there is a bolted fault. If it doesn't, the wire between the transformer and bolted failure will quickly melt.  

There is a main fuse or more often a main circuit breaker that is part of the electrical equipment that is installed by whoever wires the house. This can be contained in the breaker panel or be a breaker that is separate from the breaker panel. The latest US electrical code requires a main disconnect (which can also be the main over current protection device) to be located on the outside of a single family house to enable fire fighters to easily disconnect the electricity.

In the EU and UK, almost all distribution transformers provide ~400/230 volt 3 phase power, so each transformer can serve a much larger area. For the same load and size/type of wire, a three phase distribution circuit can be more than 5 times longer than in the US with the same percentage of voltage drop.  

For example, after only 300 feet, 48, 000 watts of power at 240 volt single phase, will have a 5% voltage drop with 4/0 AL wire. The same amount of power at 400 volts three phase can run for 1, 660 feet (5% voltage drop). These calculations assume a power factor of 100. In the US the size of the wire used in overhead low voltage distribution is based on voltage drop, not the National Electric Code. You may see a #2 AL overhead wire connected to a 4/0 CU wire where it connects to a home's lead in wire.

It is common in the US that a single phase distribution transformer serve from just a single house in a rural area to several houses in suburban areas to perhaps 10 or more single family houses in an urban area. Common sizes of distribution transformers used for single family house residential areas in the US range from 10 kva to 100 kva, with the most common sizes being 25, 37.5 and 50 kva.

Some believe the US system is safer because the highest potential to ground from any residential circuit is 120 volts.

If you have any questions this video explains split phase electrical service perfectly:

[JohnJoss]

Absolutely spot-on about accidently putting the bus-bar tag up behind the screw-clamp. I find that you have to hold the bus-bar up then tighten, say the right-most rcd screw. Then see if it is likely to fall down, but don’t actually let it fall. Then loosen the screw and move to the next screw, to the left, mcb screw, and tighten that, and see if the bus-bar is likely to fall. Then loosen that screw and move to the next mcb screw. Etc. Then, when you’re satisfied that all the tags on the bus-bar are in fact forward in the mcb and rcd clamps, actually tighten them all up. Bit of a pain doing this but, as you say, better safe than sorry. Couldn’t they be designed in such a way as to ensure that it isn’t possible to put the bus-bar tags in behind the clamp, do you think?
Nice videos, very helpful.

[denislostinlondon]

Reading the comments takes longer than watching the video. You have a global and knowledgeable audience.

[EdmundAycock]

I been retired for several years now. I forgot how much I loved my careers. This is ELECTRICIAN Pr0n. Thanks so damn much.

[Slugbunny]

These videos have been quite helpful for a fellow in the translation industry who has precious few contacts in the UK electrical field. Thank you, Clive!

[zh]

In re fireproof enclosures: when this house was rewired in the 1960s they installed a 3-phase system to drive the storage heaters and water heater via a timer using off-peak electricity. A few years ago this failed, and when the electricians opened the switch box they found that the switch gear had caught fire - but it was so well contained in the metal box that nobody knew about it while it was closed.

[Darknightful]

In Spain we still use plastic boxes. Normally it is used 40A General braker, 10A lighting, 16A for sockets, 32A for the oven and 20A if there are higher loads like washing machines, water heaters and drying machines. The norm is a bit old because in the past we used fuses in every outlet and light switch so maybe the 20A circuit could make sense to have more power in one circuit, but nowadays sockets with fuses are not available since everything is Schuko and common Schukos allow 16A maximum so the 20A braker is not suitable to protect a circuit with schukos.

[milksheihk]

Strangely in Australia, although we are generally more nanny state regulated than even the UK we don't have a standardised home electric panel, there are stendard breakers that have to be there but there's no standard configuration & no off the shelf modular system, it's just a steel (sometimes even wooden) fabricated box with a false panel on the inside with the meter & the required standard breakers & then behind that is any number of fuses. My house has two electrical boxes for some reason, both quite large, only one has the meter & beakers in it.

[jbek]

A wonderful description in the tone of reading a Haynes manual for a consumer unit. The BS7671 wizards are not gonna like you calling it 'Live' instead of 'Line' but hey..your soothing voice will trick them.

[timothybarney]

Capacity is pretty much in line with US consumer panels, in that common electrical services are 240V (line to line)/120V (line to neutral) at either 100A (smaller houses) or more typically 200A. Most panels (except for empty breaker positions) are designed with the two line bus bars behind occupied breaker positions so they're not completely exposed in the open. Neutral and ground bars are both connected to the metal housing via the tabs that hold the bars in the panel and the ground bar being positively connected to the housing via a bolt or lug. Biggest differences are that most US panels have space for typically 30-40 circuits and are sized so that they can be mounted cover flush with the wall in an available framing cavity or mounted on the surface and that the main breaker is only used when used as a main panel, with sub panels being protected by the sub-feed breaker at the main panel.

[JasperJanssen]

It’s a really strange system to us — here in NL we do everything with double poles, because it is required to isolate both sides of the circuit when you turn it off. So the RCDs are basically the same, but you get double busbars coming out of them (L+N) going through breakers with two inputs and to two outputs. Often these days, you get like plastic thingies that include both busbars in a single unit, or you get a busbar unit that’s integrated in the din rail, and the breakers have plugs on them that just plug into the proprietary rail (the rail then has wires coming out that you can wire into the output of the RCD).

[dnel]

I had an electrician quoting me for a new 18th edition unit to replace my self wiring fuse board very recently. This helped explain a few details he talked about so I'm glad I know he wasn't just baffling me with bs, it makes more sense now.

[JoshStLouis]

Being in the US, I had to mentally double most of the amperages. My furnace and water heater are each on a 50A breaker. The main one is 200A.