I’ve recently read that to prevent a potential difference forming, one should NOT connect one of the rack cabinet ground lugs to any earth (plug point).
Rather, the recommendation is to connect the cabinet to the “source” earthing point in the buildings distribution.
Having moved to an apartment (45+ floors), I do not have access to the “source” point. Therefore is it safe to assume the grounded UPS - which is mounted to the rack, would essentially tie the rack to ground by means of metal touching metal?
I’m basically aiming to prevent the rack case from being a shock hazard to anyone touching it.
I’ve got a decent fluke, although not a top end model. What would I be testing for?
I.e comparing case voltage with respect to earth from the wall? I’m assuming that case voltage vs wall (mains supply) and vs the protected UPS output is the same…
Start with checking potential between each of the legs to see if things make sense. Never assume the ground is actually grounded. If it is good, then check with the landlord about installing a GFCI outlet (or breaker) in its place.
The rack itself should be grounded already by way of having a machine in it and plugged in. The power supplies use their case as ground ref and so then the server case also becomes grounded and then also what the case is mounted to so long as its metal on metal.