MOV fire risk

[CosteC]

well it seems that I read about more MOV and RIFA explosions from europe. I don't think the US power grid is that bad of an idea. Split phase reserved for crazy devices that belong in the garage.

You pay a bit extra in copper weight but in general the failures are less spectacular.

and I noticed way more brown outs / surges in europe then in the USA. They have less local transformer in europe and there is more line effects that damage devices.


and its nice to be able to service most domestic things with a much less hazardous voltage.

230 V is more deadly when touched - true. RCDs however reduce this risk significantly.
120 V causes significantly more fires, this is hard to solve "electronically" and easier kills entire family. Power distribution network also is significantly more tricky and 11 kV is omni-present in suburban areas. European 15-20 kV is less exposed.
I however does not know any comprehensive statistics. Planet opts for 230 V rather than 110 V however. Possibly only due to reason of 3 phase 230V being more efficient.

Getting back to MOV issue, today I think USA standardisation is ahead in this matter with more restricted demand to protect against MOV overheating and fire. Still problem remains in good testing of product. Cheap imports are cheap imports with questionable design quality.

[coppercone2]

where is this risk of fires increased with 120V ?? who made these stats.

[coppice]

where is this risk of fires increased with 120V ?? who made these stats.

Arc fault fires seem to be a much bigger issue in the US than in Europe. I don't know is that relates to the tradeoff between voltage and current, or if US fittings are generally worse than European ones.

[Gyro]

That's probably the wirenuts and other crappy wiring practices, weak socket contacts etc. Not to mention all the general stuff pulling twice the current.

[SiliconWizard]

Yes, twice the current is like not negligible.

[coppice]

Yes, twice the current is like not negligible.

Its questionable if they have twice the current. The weak load that's possible from a US socket means they don't have most of the high consumption appliances, like 3kW kettles and 2.5kW hair dryers that are normal in 220-240V mains countries.

[coppercone2]

how much faster do you need that water boiled god damn

[AVGresponding]

how much faster do you need that water boiled god damn

Hey, when I want a cup of tea, I want it in the next few minutes, not the next day!   

[CosteC]

where is this risk of fires increased with 120V ?? who made these stats.

https://www.usfa.fema.gov/downloads/pdf/statistics/v19i8.pdf
https://www.ishn.com/articles/95801-electrical-malfunctions-a-top-cause-of-home-fires-in-us

I suppose higher currents, toxic relationship with wirenuts, widespread of wood in housing construction might have something to do with it.
Also USA sockets are famously horrible and famously widespread. More famous is only tendency of manufacturers to use thinner mains cables or make the out of aluminium.

I believe in 230 V systems mains impedance is of lesser importance, so it is easier to rupture a fuse if MOV of anything else go sideways.

[jfiresto]

... The weak load that's possible from a US socket means they don't have most of the high consumption appliances, like 3kW kettles and 2.5kW hair dryers that are normal in 220-240V mains countries.

At least in these parts, I would say that 3kW is not unusual. A few years back, our local Aldi ended up with a big pile of returned Strix-designed, 3kW electric kettles which were too much for the 10A circuits in many of the flats built the first couple decades after the war. I have since not seen more than ca. 2kW from Aldi Nord.

[5U4GB]

MOVs get increasing leakage when getting old. So they may slowly run hotter and hotter and thus can overheat without blowing a normal mains fuse. The MOV is usually not flamable (after all it is metal oxide), but the hot PCB and neighboring parts may catch fire.

I've always wondered about that, ten-cent MOVs get added to cheap power strips so the sellers can double the price by touting the "surge protection" it offers (the random-trigger incendiary functionality gets thrown in for free), but a while back I scored some NOS Islatrol IE-series DIN-mount hardwired power filters for a fraction of their pretty hefty new price, and a major design element was a "MOV array" which I wouldn't have expected in something that's rated for continuous operation over (at a minimum) its ten-year warranty period.  However I'm not that familiar with the design requirements for these things so maybe they're using them in some way that doesn't cause, or isn't affected by, their degradation over time.

[Siwastaja]

Very rarely, it can be much worse: since the supply is a 240VCT transformer, if the neutral comes loose for some reason (say, improper, faulty, or damaged wiring), more load on one side than the other will shift the neutral voltage, browning out one side and overvolting the other.  UL 1449 for example covers this.

Neutral or PEN faults are, if not common, very not-non-existing in the countryside here, and a regular-ish issue on TN-C-S distribution systems. Most of the electronics, lightbulbs etc. blowing up is least of the problems; dying is worse, much more dangerous is that PE and N are connected together at the distribution box, so with phases present without the PEN conductor, now every "earthed" metal surface is at a possibly high potential, through the low impedance of the connected loads. Instructions how to handle this situation go along the lines, "when you see some of your lightbulbs glowing dim and others very brightly, you are experiencing a neutral fault. Take a long non-conductive object, for example a log of wood, to carefully turn off the main switch in your metal-case distribution box. Don't touch any device or any metal object, or you die. Alternatively, go sit in the middle of the room and sob."

[Siwastaja]

Yes, twice the current is like not negligible.

Its questionable if they have twice the current. The weak load that's possible from a US socket means they don't have most of the high consumption appliances, like 3kW kettles and 2.5kW hair dryers that are normal in 220-240V mains countries.

This. Current is not twice, because all large loads in the US use 240V sockets. The opposite point can be made; German Schuko is officially rated to 16A, but fires are reported with sub-par sockets and plugs over 8A. Here, this is all we have, and 3kW loads must use this. In the US, 3kW loads use the same voltage, but plugs and sockets rated to actually survive 16A, and much more.

We mitigate by avoiding loads >10A which can be plugged in by end user completely; we just call an electrician every time we want to install a trivial thing like electric stove, to make a permanent connection - or do it illegally ourselves.

[Siwastaja]

True, yet USA split phase or two phase system is even more peculiar.

Split phase is NOT two-phase, and it's not that peculiar. There is a reason why the term split phase has been coined as a separate thing from two-phase. Two-phase systems have usually 90 deg phase difference so they produce a rotating vector, while a 180deg phase shift produces nothing useful. Split-phase is just a dual voltage single-phase system. AFAIK, two-phase systems aren't used for distribution anywhere, at least not in large scale, because of the awkward dimensioning of neutral wire for double the phase current; 3-phase distribution avoids that. But we still see two-phase design in stepper motors, some small BLDC fans, and in capacitor-run "1-phase" induction motors.

[Marco]

Two phase is an ancient and irrelevant historical artefact, forcing a differentiation between two phase and dual/split-phase has long become knee jerk pedantry rather than needed for clarity.

[dietert1]

Here in Sao Paulo we have a two phase mains distribution, with two times 120 V at 180° phase. It's a huge system like that. I can use all 230 V appliances i brought from Germany and i can buy and use US products, too. In our house we have two sets of sockets: white for 120 V and red for 240 V. Many modern appliances are "bivolt".

Regards, Dieter

[tooki]

Of course Apple sees easy money there, they will just argue it was a mains surge...
Please buy a new expensive thing from us!

Apple’s chargers are famously spare-no-expense designs made entirely with premium components. If they aren’t using MOVs, there’s a good reason. (And historically, Apple chargers have proven to be very durable.)

There are plenty of reasonable things to criticize Apple about, but power supply quality most certainly is not among them.

[BrokenYugo]

Yes, twice the current is like not negligible.

Its questionable if they have twice the current. The weak load that's possible from a US socket means they don't have most of the high consumption appliances, like 3kW kettles and 2.5kW hair dryers that are normal in 220-240V mains countries.

I would assume the very common 1500 watt 12.5 amp space heaters are the real killer. They're typically the only continuous heavy 120V load in the house. Combine with a loose socket or crappy 16 gauge extension cord (or worse yet 2 on one with a 20A breaker just hanging on), or some illegal flying splice in the wall or attic done with less than reputable wire nuts and there's the fire.

Some power tools and appliances also pull 12+ amps, but aside from the 12 amp leaf blower I can't think of any I use that do so for hours on end like a space heater will.