old construction in the US sometimes did this intentionally (so old, the house didn’t have grounds. Or to “pass” an inspection and sell a place) but if a licensed electrician sees this they have to fix it.
I’m dealing with a 75 year old house that’s set up this way, the primary issue this is causing is that a 50amp circuit for their HVACs are taking a shorter path to ground inside the house instead of in the panel.
As a result the 50 amp circuit has blown through several of the common 20amp grounds and neutrals and left them with dead light fixtures and outlets because they’re bridged all over the place.
If an HVAC or two does this, I’d advise against this for your 3200 watt AI rig.
EU, you don’t want to try to energize your ground. They use step down transformers or power supplies capable of taking 115-250 (their systems are 240-250V across the load and neutral lines. Not 120 across the load and neutral like ours.)
in the US. you’re talking about energizing your ground plane with 120v and I don’t want to call that safe… but it’s REALLY NOT SAFE to make yourself the shortest path to ground on say. a wet bathroom floor. with 220V-250v.
I can’t tell what practice you’re referring to. Are you perhaps referring to older wiring that connects large appliances to a neutral and two hots but no ground, e.g. NEMA 10-30R receptacles? Those indeed suck and are rather dangerous. Extra dangerous if the neutral wiring is failing or undersized anywhere.
But even NEMA 10-30R receptacles are still 120V RMS phase-to-ground. (And, bizarrely, there’s an entire generation of buildings where you might find proper 4-conductor wiring to the dryer outlet and a 10-30R installed — you can test the wiring and switch to 14-30R without any rewiring.)
The exception for residential wiring is when the neutral feed from the utility transformer fails, in which case you may have 240V phase-to-phase with the actual Earth floating somewhere in the middle (via the service’s ground connection), which can result in phase-to-neutral and phase-to-ground measured anywhere in the house varying from 0 to 240V RMS.
> wet bathroom floor
A GFCI receptacle adds a considerable degree of safety and can be installed with arbitrarily old wiring. It’s even permitted by code to install one with no ground connection as long as you label it appropriately — look it up in your local code.