Electronics > Repair
A/C unit earth leakage
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SteveThackery:

--- 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?

--- End quote ---

You say "still", but I don't think water and gas pipes have ever been used to provide a protective earth here in the UK, have they?

Anyway, the answer to your question is no, of course not. Rather, all such piping must be bonded to the protective earth at the point of entry so that internal metal piping and appliances cannot float to a dangerous voltage (eg due to a fault condition either in, or outside, the house).
Gyro:

--- Quote from: SteveThackery on August 03, 2024, 11:19:52 am ---
--- 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?

--- End quote ---

You say "still", but I don't think water and gas pipes have ever been used to provide a protective earth here in the UK, have they?

Anyway, the answer to your question is no, of course not. Rather, all such piping must be bonded to the protective earth at the point of entry so that internal metal piping and appliances cannot float to a dangerous voltage (eg due to a fault condition either in, or outside, the house).

--- End quote ---

No they haven't, (and as you say) of course not. It wouldn't be safe, especially for gas pipes, hence the concern about accidental lost Neutral incidents in TN-C-S neighborhood power distribution locations. I don't think @Stray Electron understood the 'subtleties'.
bte:

--- Quote from: SeanB on August 02, 2024, 11:02:26 pm ---
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.

--- End quote ---

What may happen in case of failed neutral in a TNCS system is discussed in these videos (part 2 is a demo with low voltages):

Part 1:
Part 2:
andyB2022:
Update: Got the unit grounded to some 2m deep metal pipes, not under 4  \$\Omega\$ for sure, (how it should be, old house) but I can't feel a thing now. The railing is definitely NOT grounded directly by any means, it just connects by metal rods to earth via other rods of the house construction.

Before the connection to ground, I've had 111Vac from the railing to one external screw of the AC unit. While the compressor was running at 100%, the current leaking from the case to the railing (via my Fluke meter) was 10.8mA...  Between railing and any terminal of the unit I've got +80 MegaOhms (including ground terminal). Unit not grounded at this point of test.

Anyway, now however I touch the unit I can't feel a thing. Basically, the unit is wired in a TT system and not in a TN-C-S as it is supposed to be in my country.


--- Quote from: SteveThackery on July 31, 2024, 04:25:47 pm ---My brand new Microsoft Surface laptop feels distinctly "live" when I touch it plugged in. It's more noticeable when sliding a finger across the case - I can feel a 50Hz "buzz" through the finger.

I'm not concerned - I assume it is current flowing through the capacitors at the input of the separate PSU. I don't think the protective ground is carried through to the DC output.

--- End quote ---

My iPad does the same thing, didn't ever understood how is that possible since the charger is a class II, isolated SMPS.
I am wondering why is the need for that Class Y cap from primary to secondary side... in my vision it's just a path for current to flow.

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