I recently inspected a main service panel in a house that was reportedly built in 2009, for which service grounding could not be confirmed, and in any case was strangely configured, with 4 solid wires that were evidently 8 gauge copper consistent in appearance with grounding wires observed running from the main panel, and one such wire as a jumper across the water meter, which was in a closet above the crawl space, which was inaccessible, its opening obstructed by the finished basement wall and ceiling (nice!).
No exterior grounding rod connection was observed, either from the main panel or the meter, and most of the foundation was the inaccessible crawl space, with about 1/4 of the foundation being an almost completely finished basement, so the wire runs were not visible, except perhaps as noted near the water meter.
The 4 solid 8 gauge wires were consistent with 2 connections of 2x8 gauge wiring. Would such doubled grounding wires be proper if an Ufer ground was used that was obstructed from view? It seems such wires would have sufficient current-carrying capacity, but it’s certainly unusual.
I suspect an amateur update by whoever finished the basement, during which the only access panel I observed to the crawl space was obstructed; and most likely a basement floor drain was tiled over.
Grounding would be installed when the service is installed. This should have been inspected before the power was supplied. This is not something I would think would have been updated when finishing the basement.
150A, 2/0. I would have expected the equipment to have been approved upon construction, but observed no city inspection tags. Work looked tidy and generally good, except for the quirky grounding and lack of antioxidant on the aluminum conductors.
The basement had been extensively finished later (2014), and much of the labeling on the panel was occupant-specific, so it could have been updated on the sly.
Possibly. As noted in the original post, the crawl space under much of the house was inaccessible.
I was really interested in finding out of using 2 lighter gauge wires would be effective. I would think if bare wires were twisted together it would be like a heavier stranded wire, but if they’re just separate with the same origin and connection I could see how the loop could create problems in the event the grounding electrode needs to draw current out of harm’s way in an emergency.
Interesting read so far. In Canada, the ground must be a minimum of #6 for 100 amp and #4 for 150 amp. Not sure if you could twist the two together or not.
Not required, but recommended, as I understand. I’ve rarely seen a recent professional installation without it on aluminum main conductors. May be a precaution against corrosion if leakage occurs due to a poor seal at the top of the meter, damage to the cable sheathing outside, etc.
You cannot run smaller parallel GEC’s to make one larger one. The NEC would allow #6 copper for a 150 amps service with #2/0 aluminum SEC’s. Eyeballing the photo’s the bare conductors could be #6.
Thanks, Robert, thought that was the case. I suppose it’s possible they were 6 gauge, though they definitely did not look that heavy to me. definitely just a slightly heavier than the 10 gauge wiring typically used for AC or clothes dryer circuits. I worded the report accordingly, and advised them to check the city records to see of the work was approved. Even so, I’ve seen issues get past city inspections, such as improper sub-panel grounding in very recent construction.
I’d expect antioxidant would help protect the terminal connections where the water would not run off so easily, and where I’ve often observed some of the most significant damage from leakage into a main cable.
Still interested in the *reasons *why running smaller parallel wires does not conform to code.
A few things, first in general the NEC prohibits parallel conductors which are smaller than #1/0. In section 250.66 and the accompanying Table 250.66 there is no provision to make the single required size GEC out of parallel smaller GEC’s. You can run parallel GEC’s if you want but they would need to be sized according to T260.66.
