Many properties (larger homes and any business premises and abive in the 
UK) are supplied with three phase electricity, which is 230v phase to 
neutral and 415v phase to phase. 120 Degree phase offset between the 
phases. Very potent (and useful!)

Our normal supply for residential is 230v phase to neutral, mostly as 
already mentioned  with N&PE joined at the cable entry to the property but 
some (e.g. pole fed) only have L and N provided and earth is via an earth 
rod (TT installation). RCD protection is mandatory in these circumstances 
(and essentially mandatory anyway now as increasingly regulations require 
more circuits to be protected). 30mA RCD protection for most circuits and 
100mA and / or time delay if upstream for discrimination.

The rest of Europe is 220v, so a little lower than the UK, but we 
harmonised by being +6% and -10% tolerance while the rest of the EU is +/- 
10%.

The US way with 220v centre tapped is quite noval, but 3 phase is great for 
workshops as it gives great torque in motors, though modern VFD controllers 
bridge the gap mostly.



On Friday, 21 March 2025 at 23:51:21 UTC David Pye wrote:

Not just the UK - the whole EU is like that!

David 

On Fri, 21 Mar 2025, 23:40 gregebert wrote:

Wow! I had no idea the full 220V was present in the UK; that's a very 
dangerous voltage to touch. In the US, neutral is connected to GND at the 
point-of-entry to the building and there is also a grounding rod though the 
electrical code only requires a maximum of 25 ohms to Earth (it varies due 
to soil condition), and definitely wont suffice as a redundant neutral.

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