Grounds for 800a service

[Therealcrt]

I still don't understand. The drawing says, "4#500KCMIL, 1#3G". What is the 1#3G supposed to mean. I do read and produce One-line Drawings all day long, but there is no consistent style guide that I am aware of.

Thanks,

Mark

Might wanna think about switching careers then if that’s what you do all day long no offense but for 400 amp minimum size equipment grounding conductor it’s a number three copper with four number 500 KC Mills

 

[Therealcrt]

Is that a #3 EGC on an 800A Feeder with 500 MCM?

No sir allow me to help you understand the diagrams.. it says 400A lol the 800a is the service disconnect.. which doesn’t need an EGC. So yes the #3 with 4 #500 all copper would be correct for the 400a feeders

 

[infinity]

No sir allow me to help you understand the diagrams.. it says 400A lol the 800a is the service disconnect.. which doesn’t need an EGC. So yes the #3 with 4 #500 all copper would be correct for the 400a feeders

Yes that would be the correct size for a 400 amp feeder from T250.122 but what is shown on the drawing is not a feeder.

 

[suemarkp]

This 800A -> 400A connection appears to be a feeder tap. You can't "round up" the over current device on a feeder tap, so the conductors need to be rated for at least 400A. 500 KCMil is only rated at 380A. You need 600's. The EGC needs to be sized per the source over current device, not the terminating one. So for an 800A device, the EGC needs to be 1/0 copper.

Plan reviewer wasn't very thorough in this case or we are not seeing the whole picture.

 

[electrofelon]

This 800A -> 400A connection appears to be a feeder tap.

Unless i missed it, i think we need clarification on whether those are service conductors or feeder taps.

 

[infinity]

Unless i missed it, i think we need clarification on whether those are service conductors or feeder taps.

He said that the 800 amp disconnect is the service disconnect. The drawing shows double lugs for connection of the two sets of 400 amp conductors and an 800 amp OCPD. The 400 amp conductors are therefore taps.

 

[electrofelon]

He said that the 800 amp disconnect is the service disconnect. The drawing shows double lugs for connection of the two sets of 400 amp conductors and an 800 amp OCPD. The 400 amp conductors are therefore taps.

Ok I see it does say "2 sets of lugs" but they could be connected to the line side.

 

[infinity]

Ok I see it does say "2 sets of lugs" but they could be connected to the line side.

Good point, but given the way the drawing is designed you would need two sets on the load also.

 

[busman]

Might wanna think about switching careers then if that’s what you do all day long no offense but for 400 amp minimum size equipment grounding conductor it’s a number three copper with four number 500 KC Mills

The OCPD ahead of those feeders is 800A and therefore a 1/0 EGC is required. Hence my original question.

The heading of Table 250.122 says, "Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit, etc., Not Exceeding (Amperes)". It doesn't say to base it on the OCPD at the load end of the tap.

Mark

 

[busman]

He said that the 800 amp disconnect is the service disconnect. The drawing shows double lugs for connection of the two sets of 400 amp conductors and an 800 amp OCPD. The 400 amp conductors are therefore taps.

I took the assumption that the double lugs needed to be on the load side of the 800A disconnect since

No that is a tap according to what's mentioned in the OP. Also if the 400 amp disconnects have 400 amp fuses the 500 kcmil conductors are too small.

Agree on this one as well. The engineer made multiple errors in this OLD.

Mark