EW1 Posted July 9 Posted July 9 I added some devices to my daughter’s apartment in NY (keypads, switches, etc). However, I was surprised to find no ground wires. All the boxes are metal and the wire is in metal conduit. Are the boxes and conduit the ground? Should I be tapping into that? Nothing preexisting seems to be wired to the boxes or conduit.
Brian H Posted July 9 Posted July 9 (edited) They should be tied back to safety ground. Through the metal boxes, conduit. Back in the breaker box. Bet you will also find the ground pin in outlets grounded through the outlets mounting brackets and not a physical ground wire to the outlets ground screw. If you have any high voltage appliances. Are they 220VAC or 208VAC? 208VAC would be one phase in a there phase feed or 220VAC split single phase. Edited July 9 by Brian H
larryllix Posted July 9 Posted July 9 I suspect there was a time in history where the metal pipe and boxes were used as a grounding system and no copper conductor was required. Later this became outlawed and a separate grounding conductor was required. In @Brian H comment above we used to raise the 208v up to 216v in an attempt to make it more compatible with240v appliances (stove burners and baseboard heaters run too cool, etc..) but that made the 120v phases run at 125vac. Still within utility specs, but sure makes a lot of complaints about high voltage until people get better lightbulbs. Many bulbs didn't like the 125vac on 120vac rated bulbs and popped them after a few days to a few weeks. I am not sure how it affected the new LED bulbs. They came after my time.
ELA Posted July 10 Posted July 10 20 hours ago, larryllix said: I suspect there was a time in history where the metal pipe and boxes were used as a grounding system and no copper conductor was required. Later this became outlawed and a separate grounding conductor was required. You suspect? NEC 250.118(A)(13) says it is ok.
larryllix Posted July 11 Posted July 11 (edited) 7 hours ago, ELA said: You suspect? NEC 250.118(A)(13) says it is ok. Behind a paywall but That is not legal in Canadian Safety Code but I thought it was or still is in some American Electrical code(s). I remember there was a difference between EMT systems and full conduit pipe also. Edited July 11 by larryllix
jec6613 Posted July 11 Posted July 11 On 7/8/2024 at 11:28 PM, EW1 said: I added some devices to my daughter’s apartment in NY (keypads, switches, etc). However, I was surprised to find no ground wires. All the boxes are metal and the wire is in metal conduit. Are the boxes and conduit the ground? Should I be tapping into that? Nothing preexisting seems to be wired to the boxes or conduit. In most cases, there should be a screw hole in the back of the box, you can pick up a bag of green grounding screws to give a positive connection to the conduit system.
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