[zaarn]

What I learned when doing electrical work in germany, the procedure for safe electrical working is as follows:

- Switch off (at circuit breaker)

- Prevent switching on (lock the breaker)

- Check voltage free (multimeter cleared for 230V/120V operation with long, isolated test leads)

- Ground and short (put a plug into the socket connecting earth, live and neutral, you can DIY that at home safely by cutting open an unused cord and soldering all three wires together)

- Cover nearby powered equipment

[amluto]

> Ground and short (put a plug into the socket connecting earth, live and neutral

Hmm. Given that breakers in the US don’t disconnect the neutral, grounding the neutral can introduce potentially unpleasant stray currents.

On the flip side, as far as I can tell, it’s entirely possible for a code-compliant installation to give you a moderate zap if you touch the neutral with the breaker off: if you have a long feeder to the panel, and someone turns on a big, single-phase load on a different breaker, the voltage drop on the feeder neutral could zap you. Imagine a 50A inrush current a across 1 ohm. That’s 50V for a few cycles.

[MertsA]

No it can't. Neutral is tied to ground at the breaker panel. So long as that breaker is turned off, and the neutral isn't accidentally being used as the neutral for another circuit, then there's zero current across the neutral wire back to the breaker panel. The only difference between neutral and ground on that circuit at that point is the color, check the resistance between neutral and ground and you'll find that they're basically a dead short.

Shorting the neutral to ground as well as hot has the benefit that under fault conditions the neutral wire can become electrically hot and if there's a miswired circuit that has current passing through it shorting it to ground would prevent a shock hazard from forming when you disconnect the neutral wire.

[zaarn]

Atleast in germany the standard breakers don't either but the GFCI does and 3-phase breakers need to interrupt all phases. The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point. Plus the breakers will trip at 50A inrush anyway.

(From experience, 50V AC won't kill you unless you are standing in a bathtub and covered yourself in conductive gel, you'll just get some minor pain in most cases)

[amluto]

> The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point.

Hmm. Are phase-to-neutral loads permitted? If so, does this mean that the building and ground are allowed to carry neutral currents? This seems like a bad idea.

I’m not an electrician, but I’ve seen enough problems caused by “objectionable current” (the US code name for currents through what is supposed to be ground even in the absence of a fault) that I think that neutral should be treated as a hot wire whose voltage to ground just happens to be quite low. This would involve all breakers switching the neutral as well as having a reliable mechanism to detect neutral-to-ground faults.

Newer US GFCI devices are supposed to detect neutral-to-ground faults, so that’s a start, but I don’t think any of them will actually disconnect the neutral if such a fault is detected. They do this by inductively coupling a low voltage 120 Hz common mode waveform on hot + neutral, or maybe just on neutral. It’s a cute trick.

[zaarn]

Any building since 2007 has a GFCI installed (TAB2007-6.1§10 in Germany). Not as is common in the US in the sockets but in the breaker box itself. GFCI sockets and plugs are very rare and only exists for legacy installation that cannot be upgraded (insurance is expensive without one).

We use the TN-C-S system, wherein before the GFCI you have 3-phase with a PEN that is shorted to ground when it enters the building, then it is split into PE and N wires. The GFCI is 3-phase with only 1 phase being put into the building (usually, though multiple phases aren't uncommon in larger housings). The PE wire is connected to the heating system and various other ground potential points (either to provide ground or obtain ground potential). The N wire is shorted to PE before entering the socket (or the socket itself shorts these two). Once it leaves a socket the entire thing becomes unpolarized, so to speak, so devices after the socket can't short PE and N without polarized plugs.

This avoids problems with the inrush since the inrush voltage against ground will be grounded away shortly after entering the socket (and trip your breakers). It also means that it's less likely that a single broken wire results in the entire GFCI becoming useless, though if neutral is broken it can become somewhat dangerous (but the device stops working).

[matt-attack]

Step three, don’t forget to unplug your short circuitter before flipping back on the breaker.

[zaarn]

Usually you just follow this list in reverse; from bottom up and undoing what you did.