This video is perfect Bob, Thank you for sharing that. I’m pretty sure my ‘ah-hah’ moment grew me a new brain cell.
You brought it up.
Unlike in the U.S., South Korea does not use a 110V or 120V system but instead operates on a 220V 60Hz single-phase power system. In South Korea, neutral is mandatory for outlet (receptacle) circuits, and without it, normal operation is impossible. Additionally, this is a legal requirement under South Korea’s electrical installation standards.
However, in lighting circuits, it is common for the neutral wire not to be directly connected. Lights operate using only a switch and a line (hot) wire, while the breaker panel ensures circuit safety by managing the neutral connection. This means that lighting circuits can function without a direct neutral connection, but the overall electrical system still requires a neutral for proper power distribution and safety.
In conclusion, regardless of the country, neutral is essential for outlets, and even if a lighting circuit does not have a direct neutral connection, the breaker panel must ensure the protection of the electrical system—similar to how we frequently refer to GFCI (Ground Fault Circuit Interrupter) for electrical safety.
미국과 달리 한국에서는 110V 또는 120V 시스템이 아닌 220V 60Hz 단상 전력 시스템을 사용합니다. 한국에서 콘센트(아울렛)에는 반드시 중성선(Neutral)이 필요하며, 중성선이 없으면 정상적인 작동이 불가능합니다. 또한, 이는 전기설비기술기준에 따라 법적으로 필수적으로 요구됩니다.
다만, 조명(전등) 회로의 경우, 중성선이 직접 연결되지 않는 방식이 일반적입니다. 조명은 스위치와 전압 공급선(Line)만을 사용하여 동작하며, 분전반(배전반)에서 중성선을 관리함으로써 회로의 안전이 보장되도록 설계되어 있습니다. 즉, 조명 회로에서는 중성선 없이도 작동할 수 있지만, 전체 전기 시스템의 올바른 전력 분배 및 보호 기능을 위해 중성선이 반드시 필요합니다.
결론적으로, 어느 나라든지 콘센트(아울렛)에는 중성선이 필수적이며, 조명 회로에 중성선이 직접 연결되지 않더라도 분전반 차단기를 통해 전기 시스템의 보호가 보장되어야 합니다. 우리가 자주 이야기하는 GFCI(누전 차단기)의 개념과 유사하다고 볼 수 있습니다.
That is interesting, Jun. Thank you for telling us about the different system used in the Korean home.
What color is the neutral in Korea?
I’ve done a bunch of work in Germany and the neutral is often blue and often runs with the Earth ground and they seem to bond often as they can. We didn’t change any of it as the German safety law guys were, well, uhm Gestapo in strictness.
No, that is not correct. There are two legs (ends) of the secondary winding on the supply transformer. The Neutral (Grounded) conductor is a tap off the center of the secondary winding. The Voltage is determined by the ratio of the primary to secondary Windings . The standard ratio is 30:1 (7.2kV:240V). A center tap provides two legs, each with a 60:1 (7.2kV:120V) ratio.
The water analogy is the kindergarten analogy. It is accurate enough for DC, but not at all for AC. A tuning fork would be a better analogy for AC. A still better analogy is a Newton’s Cradle. When we set up the House of Horrors at InterNACHI House of Horrors in Boulder, I had a Newton’s Cradle to help students understand how current moves in an AC circuit.
I always use a Newton’s Cradle to explain AC, regardless of the audience.
Bob, you are right, as usual. The problem with AI as it is now, is that is is nothing more than a robust search engine. An expression as old as computers is “Garbage in, garbage out”. There’s a lot of garbage on the Internet for AI to cull from. The two legs of a single-phase system cannot be “Out of phase” with each other because there is only ONE phase. There is nothing to be out of phase with.
When you and I are both dead and gone I hope, for the sake of home inspectors, someone who understands electricity comes along to take our place.
That’s great info. Could you please explain how there is only one phase? I hear a lot about single phases and such…
Bobby Mascio
InterNACHI® Certified Professional Inspector (CPI)®
Illuminate Home Inspections
Woe, after all the posts and support, did you NOT watch the video that @rkenney shared with you?
WATCH IT! It should answer your question.
Edit: I’m curious what your background is? You keep mentioning “Pea Brain” but I feel that you’re just deflecting…a Home Inspector should not have a “Pea Brain”. LOL. I understand that this forum can be rough. With that said, we’re all here to learn and there are no dumb questions.
There is a single primary winding and a single secondary winding on the supply transformer and the windings are each turned in the same direction. There can be one or more taps off the secondary to derive different Voltages, or no taps. Large transformers usually have multiple taps near one end of the secondary winding so that the output Voltage came be adjusted to compensate for Voltage drop. Residential transformers have a tap in the center of the secondary winding. Instead of 240/120V, the tap could be moved to create, for example, 150/90V. Taps can be placed anywhere and in any number. It just happens to be the standard that there is one tap in the center for residenrial systems.
Sine wave graphs are drawn showing Voltage and current above and below a zero line. That can be confusing to someone who does not understand electricity. Such a graph can lead to the misunderstanding that the that the two legs are out of phase with one another, but they are not.
It doesn’t help that many electricians (who are mechanics, not engineers) often mistakenly refer to the two legs as being out of phase. As a trainer of both electricians and home/commercial inspectors, this is one of the deeply ingrained misconceptions that I routinely encounter and address.
That’s helpful! Thank you for taking the time to help my understanding of electrical matters.
Bobby Mascio
InterNACHI® Certified Professional Inspector (CPI)®
Illuminate Home Inspections
No. At any given moment, the Voltage would be between 0 and 169.7V (nominal). 120 is the RMS (effective) Voltage, not the actual Voltage.
Thank you, George
Bobby Mascio
InterNACHI® Certified Professional Inspector (CPI)®
Illuminate Home Inspections
In South Korea, green (or green-yellow) wires have long been used as grounding wires. While this is not a legal requirement, it has become a widely accepted industry practice among electricians.
In other words, electrical teams in South Korea have an unspoken agreement to use green wires for grounding, helping to reduce confusion in wiring installations and enhance safety.
한국에서는 오랫동안 초록색(녹색) 전선을 접지선(Ground)으로 사용해 왔습니다. 이는 법적으로 의무사항은 아니지만, 전기 업계에서는 초록색을 접지선으로 사용하는 것이 일반적인 관행으로 자리 잡고 있습니다.
As has already been explained, that is a false statement. The two legs are on the same phase. Therefore, they cannot be out of phase with each other.
Another important concept to understand is the relationship between Voltage and current. They CAN be out of phase with each other. The relationship is referred to as Power Factor.
ELI the ICE man is a mnemonic used to remember the relationship between voltage and current in a reactive (inductive and capacitive) circuit.
ELI:
In an inductor (L), the voltage (EMF) leads the current (I).
ICE:
In a capacitor (C), the current (I) leads the voltage (EMF).
When taken in aggregate, loads are almost always inductive. So, measured at the supply, Voltage is ahead of current. The more current and Voltage are out of phase, the less real power is delivered.
There are a lot of gimmick devices sold to improve electrical efficiency. I won’t go into a lot of detail about them because they have been discussed in this forum on other occasions. They are useless to residential consumers. On the other hand, PF correction is vitally important in large commercial and industrial electrical systems.
The important thing to remember is that while the two legs of a single phase cannot be out of phase, Voltage and current, not only can be, but they can be assumed to be out of phase by at least a few degrees, but never by 180°.