Lynx Joule Inverter

[TinselKoala]

The mains is delivering AC, right? It's alternating current in a load, produced by alternating voltage from the supply.
What point is the voltage alternating around? In other words, when the AC waveform crosses "zero" and reverses, what is the voltage level of that "zero" value?
Is it the same as the Earth ground voltage?

[conradelektro]

The neutral (zero crossing point) of the mains network is tied to earth somewhere (at the generator in the power generating station) but this is not necessarily exactly the same "earth potential" as in the place where the outlet socket is mounted (hundreds of kilometres away).

Usually the difference in potential (between "local earth" and neutral) is very small (millivolts).

I once witnessed that the "local earth" was about 100 Volt lower than neutral in a factory where they used megawatts of electricity. The technition on site told me that the heavy current draw pulls the whole 220 Volt and 400 Volt network away from "local earth". But I have forgotten the explanation, I only remember that it happened.

Greetings, Conrad

P.S.: http://www.ibmatech.com/src/pdf_aktuell/TI001.pdf : this is an explanation of reasons for a potential difference between neutral and "local earth", unfortunately it is in German. The reason is an unequal load in three phase loads (e.g. three phase AC motors).

[e2matrix]

e2matrix and synchro1, thank you for your replies and advice! You were right e2matrix, both lines are hot.
I cut the power to the flat and took measurements - only about 200 mV ac, but a steady 0.56 V dc from the 'neutral' and a little less from the 'live', with the DMM hooked up on one side to my grounding rod wire. Would that be normal? Stray dc voltage? Or a result of a short circuit or something?    Any more advice/ comments appreciated, but as you say, e2matrix - many possibilities, and I don't want to clutter up this thread.

-edit - Just tested another receptacle, with the mains power to the flat reconnected, and this one seems to be wired ok, although still measuring 0.56 V dc and about 200 mV ac on the neutral line, again with one end of the DMM connected to the earthing rod.
Flumen

Yes it looks like someone didn't get things wired up quite right there in some receptacles or maybe someone replaced one later and got it wrong.  Do be aware that can be very dangerous if you happen to have 2 devices plugged in to different outlets which are in proximity to each other.  It is possible with older devices or appliances to have 230 vac between the metal on 2 devices such that if you were touching both you it would be like grabbing directly on to 230 vac - very bad situation.   You may already know that but it's worth mentioning since it appears there are some issues with the house wiring.   
     Also yes I've seen what electricians call 'ghost voltage' well over 50 volts ac but it doesn't have any current (or microamps) to it.  It's common and is probably the antenna effect we are seeking here. 

[Flumen]

Thank you e2matrix.