How can I explain that switching only the neutral side is unsafe?

Question

I am reviewing a remote-control appliance switch on Amazon. (Edit: this is a plug-in switch. Switch plugs into outlet, appliance plugs into switch.) I find that toggling it off breaks the neutral side but the hot slot on the outlet is always hot. I know it’s unsafe, but how best to explain it in terms a non-electrical-savvy person can get it in just a few words? A realistic scenario where someone could get hurt would be good. It seems otherwise a good product. How many stars should I dock it for this?

Answer 1

The switch in question is not UL Listed, and has counterfeit CE. Stop right there; that's all you need. See bottom.

How to describe it

When you arrange a switch to interrupt neutral, it means everything past the switch is energized when the switch is off.

The hot wire is energized because you do not disconnect it ever. The disconnected neutral is energized because it is connected to the hot wire via the bulb.

Worse than that, if it's still a fixture with replaceable bulbs, the shell of the light socket is energized too. You might say "it's disconnected when you take the bulb out" but that's only true if there's only one bulb.

There is no way to de-energize the light socket, and no way to remove a broken bulb safely.

This is ever more important, since many LEDs use a cheap capacitive dropper that energizes the heat sink of the LED. That's a problem on a broken LED where the manufacturer has shielded the heat sink as UL and CE require. But if the user is buying cheap Cheese smart switches, they are probably also buying cheap Cheese LED bulbs. Those aren't UL Listed, and their CE is counterfeit. Big Clive has many teardown videos of those having exposed, energized parts from the factory.

So yes, cheap mail-order LEDs + cheap mail-order switches are a recipe for disaster.

How did this happen?

All the first world countries have consumer protection. The apparatus that protects the supply chain from dangerous products only works on items sold at reputable bricks-n-mortar stores. Mail-order does an end-run around that apparatus by forcing the enforcement over to Customs, and they have other priorities, understandably.

Amazon Marketplace is probably the worst for this since these are the same cheap Cheese crud that you find on eBay, yet it has feel of safe reliable Amazon. Plus Prime shipping. Note: On that link, don't go looking for the "skip ad" button, that ad is what I'm trying to show you. It neatly explains why this junk is so insidious.

Thus, the only way to reliably buy equipment is at bricks-and-mortar sellers, or mail order operations run by those bricks-and-mortar operations which only offer items sold in the stores (e.g. wickes.co.uk or lowes.com). Beware of places like Walmart (blending in Amazon items) or Sears (blending in eBay items).

Answer 2

The problem is that the hot line is still energized inside the appliance so if anything goes wrong with a bad connection or broken wire, the appliance, let's say a toaster can become energized and touching it while turning on the kitchen faucet could be deadly because the faucet could be grounded.

Answer 3

The classic example for problems with "switched neutral" or "hot/neutral reversed" is the traditional Edison light bulb socket. Neutral is connected to the outer part and hot to the button in the very tip of the bulb. If everything is done correctly, this means that:

• If the switch is off, the socket is 100% "dead" and safe to touch.
• If the switch is on and you change the light bulb, it would be hard (though not impossible) to touch the hot part of the circuit.

If neutral is switched but not hot then even if the switch is off there is hot lurking inside the socket - touch it when grounded and zap.

If hot and neutral are reversed then not only do you have the "switched neutral" problem, but you also have a situation where changing a light bulb would get your fingers awfully close to the hot.