120V in the USA

[ppppenguin]

A reasonable explanation of US domestic electrics with some attempts at justifying their methods:
https://www.youtube.com/watch?v=jMmUoZh3Hq4

The late Gerry Wells used to speak of "low voltage accents".

To add confuision the US also uses 277V/480V for industrial loads. We, the rest of Europe and many other places seem to get along nicely with 230V/400V for just about everything.

[ppppenguin]

Apparently Canada also uses 347/600V 3 phase. Ouch!
https://ctlsys.com/support/electrical_se..._voltages/

I suppose that they can conveniently support bigger industrial loads at low(ish) voltage. 2.25x what we can do on 230/400.

[colly0410]

Love how he has a dig at our ring mains & switches on sockets, & even electric showers, lol.... When I was there last year the hairdryer had an RCD on the plug as it was in the bathroom...

My mate who lives in Arkansas has 4 British 13 amps sockets on his work bench wired for 240 volts, I'm not sure if this is legal, I suspect not. But he's originally from Nottingham so rules don't apply to him, lol...

[ppppenguin]

Apart from Robin Hood, I didn't realise that Nottingham was such a lawless place. Now if you'd said Durham and Barnard Castle......

A socket wired for 240V in the USA will be have both live and neutral at 120V wrt earth. OK until you're dealing with live chassis kit when an isolating transformer will be essential.

Which reminds me of a conundrum about UK installations. We usually use single pole MCBs and RCBOs that only interrupt the phase wire. But according to the regulations, both phase and neutral are to be treated as live wires. The neutral is normally pretty close to earth but it's often a few volts away and amps can sometimes flow if you connect them together. There are differences between TT, TNS and TNC-S (PME) but that's not the point. If you're working on a circuit then the usual procedure is to turn off the MCB, lock it off (or lock the consumer unit) and keep the key while you're working. But that leaves the neutral technically live.

PS: Wouldn't have been an RCD on that hairdryer, it's a GFI over there

[Nick]

Yes, if you use an just MCB or an RCBO only the live is interrupted, but many installations are fully protected by an RCD, or at least the CU is a split box with the choice of RCD or not.

If the RCD trips it will disconnect both live & neutral, so having an RCD or being in a split box with the choice is the way to go.

[ppppenguin]

RCDs that cover a number of circuits are usually double pole. When they trip you lose half your circuits. When you have turned off an MCB to work on a particular circuit and accidentally short neutral to earth there's a good chance the RCD will trip and disconect several unrelated circuits.

My own house has the deluxe option of separate RCBO for each circuit. An RCBO is a combined MCB and RCD. But they are only single pole. No nuisance trips from other circuits but the neutral of the circuit I'm working on can still have a voltage on it. Technically it's still live.

Strictly we should use the terms "phase" and "neutral", as both are regarded as "live" in the wiring regs. I've just checked and this usage is defined by the IEC, not just locally in the UK.

[Mike Watterson]

In the UK anyway it's important esp. where the neutral is only earthed at a substation. Here in Ireland we don't have ring mains (usually) and neutral is connected to Earth and gets at least one 1.2 m earth rod. Either at the meter or main fuses, I forget which.

Also I never assume the wiring, especially lights is done correctly. I also can't see how the B&Q bayonet to Euro Edison Screen light socket adaptor is legal as the outer has a 50% chance of being live. I think historically the BC is not just in UK & Ireland but Greece, France and Cyprus.

It's interesting that T&E cable is gone, the one with the bare earth between live and neutral. It's now three insulated cores with the middle live. So wider. I once rewired a basement in the 1970s that had real paper insulated wires IN USE, with the lead outer and sealing pitch at the ends.

[ppppenguin]

In the UK we have a mix of TT (you provide your own earth rod, mainly for those with overhead supplies), TNS (earth supplied via sheath of cable, connected to neutral at substation, common in older areas) and TNC-S, aka PME (neutral earthed in many places, earth conencted to neutral at main intake, usual for newer supplies) You are always free to ignore the supplied earth terminal and use TT.

Neutral is always earthed at the substation in most countries.

Ring mains (correctly ring final circuits) are unrelated to earthing method. They are now deprecated for new UK instals. 20A radial with 2.5mm or 32A radial with 4mm cable are now the preferred circuits for sockets.

Some premises, notably petrol stations and farm buildings, aren't allowed to use PME. The risk of a fault causing neutral to rise too far above true earth is too high.

I've had to remove VIR (rubber insulated) cables that have gone either gooey or crumbly. Also lead outer with rubber inner. This was the deluxe option before WW2. Some was perfect. In other cases the rubber fails as with VIR. Used with nice junction boxes where clamps over the lead gave earth continuity.

[colly0410]

PS: Wouldn't have been an RCD on that hairdryer, it's a GFI over there

I put a photo of an American socket on my facebook page when I was in Florida last year as I thought it looked like a surprised face. My mate from Arkansas told me off & said "they're called outlets here, when in Rome." That told me, lol...

[ppppenguin]

Or more formally "receptacles", I think. They don't say "mains" either on the other side of The Pond. When I'm posting on Videokarma, the US based TV forum, I'm scrupulous about using UK spelling, terminology and metric. Sometimes I explain for the poor benighted souls with low voltage accents

One of my pet hates is people in the UK saying "plugs" or "plug sockets" instead of "sockets"