Electronics > Repair
A/C unit earth leakage
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Gyro:

--- Quote from: Uup on August 01, 2024, 06:48:37 am ---...
I once had to investigate a peculiar issue on a site, where two multi-story buildings were next to each other. There was a piece of metal (from a mast) on one building that was flapping in the wind and was hitting a metal rail on the building next to it.

The ground connection on the buildings connect with neutral (PME/MEN) and one of the buildings had an issue with that junction. It caused a voltage difference of about 2V between the buildings ground connections. However, every time the flapping metal touched the other building's metal rail a significant amount of current was flowing causing a surprisingly large amount of spurious emissions. [/i]

--- End quote ---

Yes, PME / TN-C-S, is increasingly raising issues of when is ground actually ground, particularly where there is a large unbalanced Neutral current (3-phase). It has come more to the fore with EV charger protection and there have been several documented cases of lost Neutral (between the substation and houses) which have severely tested the current carrying capacity of gas meters and associated metal pipework.
themadhippy:

--- Quote --- PME / TN-C-S, is increasingly raising issues of when is ground actually ground, particularly where there is a large unbalanced Neutral current
--- End quote ---
which is why ,in the uk at least ,were not supposed to extend such supplies outside the ole equipotential zone,but then who goes to the bother of converting the circuit for the air handling unit hanging on the outside wall to TT
LatvianOnJuice:
Just make sure that is really is the A/C and nothing else, ground it properly, and you should be good.
Stray Electron:

--- Quote from: Gyro on August 01, 2024, 09:14:32 am ---
--- Quote from: Uup on August 01, 2024, 06:48:37 am ---...
I once had to investigate a peculiar issue on a site, where two multi-story buildings were next to each other. There was a piece of metal (from a mast) on one building that was flapping in the wind and was hitting a metal rail on the building next to it.

The ground connection on the buildings connect with neutral (PME/MEN) and one of the buildings had an issue with that junction. It caused a voltage difference of about 2V between the buildings ground connections. However, every time the flapping metal touched the other building's metal rail a significant amount of current was flowing causing a surprisingly large amount of spurious emissions. [/i]

--- End quote ---

Yes, PME / TN-C-S, is increasingly raising issues of when is ground actually ground, particularly where there is a large unbalanced Neutral current (3-phase). It has come more to the fore with EV charger protection and there have been several documented cases of lost Neutral (between the substation and houses) which have severely tested the current carrying capacity of gas meters and associated metal pipework.

--- End quote ---


   Geez, in the UK are they still using water and gas pipes to ground electrical systems?  All homes in the US are required to have a copper plated ground rod driven into the ground immediately next to the incoming power line and connected to electrical panel and the ground wires of the home wiring.  That's been required since sometime before 1963 when we built a house.
SeanB:

--- Quote from: Stray Electron on August 02, 2024, 10:24:57 pm ---   Geez, in the UK are they still using water and gas pipes to ground electrical systems?  All homes in the US are required to have a copper plated ground rod driven into the ground immediately next to the incoming power line and connected to electrical panel and the ground wires of the home wiring.  That's been required since sometime before 1963 when we built a house.

--- End quote ---

No, more a result of old metal water and gas lines, and the need to have equipotential bonding to them for protection. Does mean that a failed neutral in the supply to the street can result in the return current being passed thorugh those pipelines, as they join all the houses together, and thus act as a neutral when combined with the TNCS supply, or even with a separate ground conductor and a connection for safety to a ground rod at the transformer. TT systems are very rarely found in most countries, unless you are living on a massive basalt and granite rock, which is a poor conductor, so grounding is hard, or are in one of the few countries with it.
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