awesomesauce
Member
- Location
- Colorado
Forgive the stupid question: I'm merely an "electronics guy" in need of some perspective from the experts....
Our company hired a commercial electrician to install a 480V 200A (3 phase) feed to a new piece of equipment. Electrician connected the chassis ground of the equipment to the service disconnect enclosure via the green ground screw and nothing else. So there is a 3/0 green wire (from the equipment) going to this giant screw terminal, which is then connected to the service disconnect box (and nothing else) via a long, green-annodized, 6-32 screw (and that's all). We discovered this problem when we found out that the equipment wasn't grounded - turns out, the green screw wasn't even tight (so it wasn't making connection).
The feed to this service disconnect is 3-phase, 480V, 200A, done with 4/0 wire for the phases, and there is a 10AWG green wire that bonds the service disconnect box.
My understanding from 250.122 is that the ground should be at least 6AWG copper, since there is 200A available on the supply.
I assume the green screw is completely insufficient, but how big of deal is this? Thankfully, no one got hurt, but when the electrician comes to fix it (which I assume will involve pulling a new 10AWG ground), how loudly should I be yelling?
Our company hired a commercial electrician to install a 480V 200A (3 phase) feed to a new piece of equipment. Electrician connected the chassis ground of the equipment to the service disconnect enclosure via the green ground screw and nothing else. So there is a 3/0 green wire (from the equipment) going to this giant screw terminal, which is then connected to the service disconnect box (and nothing else) via a long, green-annodized, 6-32 screw (and that's all). We discovered this problem when we found out that the equipment wasn't grounded - turns out, the green screw wasn't even tight (so it wasn't making connection).
The feed to this service disconnect is 3-phase, 480V, 200A, done with 4/0 wire for the phases, and there is a 10AWG green wire that bonds the service disconnect box.
My understanding from 250.122 is that the ground should be at least 6AWG copper, since there is 200A available on the supply.
I assume the green screw is completely insufficient, but how big of deal is this? Thankfully, no one got hurt, but when the electrician comes to fix it (which I assume will involve pulling a new 10AWG ground), how loudly should I be yelling?