I recently installed lights and outlets in our detached garage. This home is an older home built in the 1950's and currently ungrounded. To test my newly installed lights/outlets in the garage, using an extension cord from an ungrounded source and hooking it on to the newly installed circuits, everything works fine. Using my outlet tester, it showed everything was wired correctly. I would think it should show an "open ground" but it doesn't. I double checked my wiring and it appears to be fine. I DID ground the lights/outlets to the metal boxes which they are attached to.
Wiring – Why does the outlet tester show that the new, ungrounded outlets are grounded
wiring
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Best Answer
Are your wires in metal conduit? If so, you have grounded circuits and the tester is correct.
In any case, on new installations everything should be grounded. Old stuff can get away without connecting a proper ground but not new. Ground for new circuits has to make its way all the way back to the panel.
In addition, receptacles in a garage normally need to be GFCI protected either at the receptacle or the breaker. It is possible to install GFCI without an actual ground, but (a) that is not ideal and (b) that is normally only to retrofit some protection to receptacles that have no ground available. But the ground wire and GFCI perform different functions so having both where required - that always means ground, but GFCI only in certain locations - is the gold standard.