From the US perspective, what's the deal about devices requiring ...

I’m new to HA; just ordered some gizmos for testing and have a configured Pi waiting.

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I’ve been viewing lots of videos and much of the information appears to be slanted from the European electrical perspective. I keep running across some issue about the ‘neutral’ wire, and don’t understand what they’re talking about.

I realize Europe has no split phase and is 50hz. I don’t know what nomenclature they use to distinguish hot, neutral and ground, but I’d like to understand what the foreigners are talking about. When I go looking for a product on

and it cautions about neutral required or not I want to understand what the issue is.

I’m an EE so I understand things from the US perspective but this European neutral business has me wondering how they do their trivial house wiring and why there’s a distinction.

Thank you all.

The European ‘live’ and ‘light’ equate to the US ‘hot’ and ‘neutral’. I assume ‘ground’ has a name also. Is that it?

The European ‘neutral’ is part of the interconnect between a mundane multi switch wiring setup?

I wish each device just listed a wiring schematic, before and after, single and multi switch. No words necessary.

It would be nice if there were an international standard for colors, etc.

This is a typical 3-way (U.S.) light wiring:

The wire from the circuit breaker to the switch box is typically a 14-2 Romex cable:

Hot, Neutral and Ground

The wire from the rightmost switch in the drawing above is also 14-2 Romex.

The wire between the switches is called the “traveler” and is typically a 14-3 Romex:

In the U.S., a neutral wire is required in all junction boxes which includes outlet boxes, switch boxes and light boxes. All neutral wires are connected together and you never switch a neutral wire. The neutral is connected to earth ground at the circuit breaker box, and no where else.

All ground wires are connected together in all junction boxes they go through. At the circuit breaker, the ground wires are connected to earth ground, and no where else. Switches, outlets light fixtures, etc, usually have a ground lug that is also connected to the ground wire. You will often find these green pigtail wires used for this purpose:

@stevemann did a wonderful job of getting the right images for the US explanation, the one I’m familiar with. It appears the issue is just terminology differences. I figured it had to be something like that since switch wiring is about as low as you can go; there’s nothing that can be removed to make it simpler.

BTW - Since you mentioned WW-II …
Here, on the island, an electrician told me to forget about the ground wire for the commercial site I was building because it’s not necessary and saves money. He was confounded when I insisted on ground wires, since I was supplying the wire. I wanted his crew’s labor, not his advice.

During the wiring, I happened to see his workers had shoved 11 wires into one piece of conduit when I noticed them struggling. They were trying to get the 12th wire into 1" flexible conduit. I told them to pull every wire out and there will only be 3 wires per conduit. I told them to not reuse the stretched wire (because it was stretched). They knew I was some crazy Gringo for sure then.

There aren’t any terminology differences. Neutral in the EU is exactly the same as neutral in the US. The difference is the wire color (US: white, EU: blue) and the neutral to phase voltage (120V vs 240V). This has nothing to do with split phase when talking about lighting fixtures. In both regions, lighting circuits (and most outlet circuits too) are done with single phase wiring: one neutral, one phase.

Additional reading:
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Historically, no neutral was available in a switch box (but it is always available in outlets), because it technically isn’t needed there for dumb lighting. This was true in both US and EU. More ‘recently’ neutral has started to become available at switch boxes, making things like smart switches or modern dimmers easier to install. Dumb three way switches do not need a neutral either. They use a traveler switching the phase only.

When looking at single phase circuits, there is no difference between EU and US functionally. The grounding system is slightly different due to the use of GFCI’s at the breaker panel in the EU, but that doesn’t affect the neutral in anything after the panel.

Things become very different when talking about multi-phase circuits though (split-phase in the US vs three-phase in the EU).

Yes, it is. In the U.S. it is a code requirement that wall-switches have a ground wire.

A ground wire to the switch is not required if the switch is being installed in a metal box and grounded through the plaster ears. Even then I ground the switch just to keep the inspector happy.

Switches that have plastic housings will have a ground wire. In fact the manufacturer cannot obtain an Underwriter’s Laboratories (U.L.) approval without a ground.

Power outlets in Europe differ from those in the US mainly due to historical development, variations in voltage standards, and safety regulations. 

European countries standardized their outlets to support 220-240V systems, while the US adopted a 110-120V standard, influencing power outlet design and functionality. 

These differences reflect the distinct technological advancements and safety protocols each region prioritized over time.

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Why Do the US and the UK Have Different Plugs?

The US and the UK have different plugs due to their independent development of electrical systems and safety standards. 

After World War II, the UK adopted the BS plug, which includes a grounding pin for safety and is designed to handle the UK’s higher voltage of 230V. 

In contrast, the US had already standardized its electrical system at 110-120V and adopted the NEMA 1 and 5 plugs, which are simpler and smaller. 

The variations in voltage and safety regulations led each country to create plugs and outlets best suited to their respective systems.

What Does a US Power Outlet Look Like?

A US power outlet typically has two vertical slots, often with a small round hole below them for the grounding pin. 

The two slots represent the live and neutral connections, while the hole at the bottom is for grounding. 

US outlets are designed for 110-120V electrical systems and usually support two-prong or three-prong plugs.

US Power Outlet: Types and Functions

Type A (NEMA 1-15)

• Function: This is an ungrounded plug with two flat parallel pins.
• Usage: It is commonly used for devices that don’t require grounding, like lamps or chargers.

Type B (NEMA 5-15)

• Function: This plug has two flat parallel pins and a grounding pin below them.
• Usage: It is used for appliances that require grounding, providing an extra layer of safety.

What Does a UK Power Outlet Look Like?

A UK power outlet, also known as a BS outlet, features three rectangular slots in a triangular configuration. 

The top slot is for the grounding pin, while the bottom two are for the live and neutral connections. 

The UK outlet is designed for a 230V system and is considered one of the safest due to its built-in fuse, which protects against overloading.

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Power Outlet EU: Types and Functions

Type C

• Function: This is a two-pin plug used primarily for devices with lower power requirements.
• Usage: It’s common in Europe for small electronics like chargers and kitchen appliances.

Type F

• Function: Similar to Type C but with grounding clips on the sides, offering added safety.
• Usage: It is used for larger appliances like refrigerators and washing machines.