Sub Panel wiring Q

[Nick1911]

Was warned about that too.  Apparently they have some conductivity meter around here which can tell if the ground rods are full size.

Not sure I buy it, with everything being all connected when the inspector arrives.  Regardless, proper grounding is a good idea.   Ground rods are cheap and easy to install.  [With a clever water drill and a fitting size air hammer anvil, carefully TIG'd together from an old bit of air chisel and a 13mm socket from a garage sale.    ]

[cassandra and sara's daddy]

I use a hammer drill but we have rock layers in some areas it's hard


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[zxcvbob]

For a 100A subpanel, I recall running 2-2-2-4 aluminum SER.  That was for a short run though, you may need to upsise if your run is long enough to cause more then the allowed voltage drop at full ampacity.

2-2-2-4 AL SER is perfectly fine for... [ahem] "120/240-volt 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that supply the total load to a dwelling unit and installed in raceway or cable with or without an equipment grounding conductor.  The grounded conductor shall be permitted to be not more than 2 AWG sizes smaller than the ungrounded conductors..."

The point of contention is the "total load to a dwelling unit" part.  1-1-1-3 AL can handle 100A without any qualifiers.  He should be able to get away with 2-2-2-4, but that's at the discretion of the inspector.  

(I used 4-4-4 aluminum "Periwinkle" triplex cable, overhead to my detached garage for a 60A feeder, then transitioned to two #6 copper and one #8 from the weather-head to the subpanel.  That was code at the time but would be illegal today.)

If you really want to see something scary, look up the cost of 3-3-3-5 copper cable.  

[Nick1911]

2-2-2-4 AL SER is perfectly fine for... [ahem] "120/240-volt 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that supply the total load to a dwelling unit and installed in raceway or cable with or without an equipment grounding conductor.  The grounded conductor shall be permitted to be not more than 2 AWG sizes smaller than the ungrounded conductors..."

The point of contention is the "total load to a dwelling unit" part.  1-1-1-3 AL can handle 100A without any qualifiers.  He should be able to get away with 2-2-2-4, but that's at the discretion of the inspector. 

That's good to know.  I'll have to review that bit of the NEC.  Thank you for pointing it out to me.

I use a hammer drill but we have rock layers in some areas it's hard

Hammerdrill is a good idea.  I probably would have used my rotary hammer, if I had a convenient way to attach the rod to the SDS drive output of the tool.

It's weird.  Sometimes I do things "the hard way" because it's easier for me with my tools and skills then the suggested route.

[cassandra and sara's daddy]

They make a "bit" for driving rods it's a hardened cup that twists it a lil and hammers it.   It was 150 bucks.
  And be careful a guy locally drove a ground rod in and nicked a gas line . It filled the basement and killed him the next day when he ignited it with a sparking tool. The word was that the gas leaking so slow and filtering through the soil filtered out most of the added scent. The utility guy marked the line as coming off the other corner of the house. It's a shame the guy was working in the basement and coulda caught the marking error. The line was visible in basement. I think he just assumed the markings were correct. As a guy who hit an underground service with a digging bar I know longer assume that

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[zxcvbob]

Hammerdrill is a good idea.  I probably would have used my rotary hammer, if I had a convenient way to attach the rod to the SDS drive output of the tool.

It's weird.  Sometimes I do things "the hard way" because it's easier for me with my tools and skills then the suggested route.

a "T-post driver" works pretty well, as long as you don't hit a layer of solid rock.  Even if you do, it works as well as anything else.  When the rod get far enough in you can't use the driver, switch to a small sledge hammer.

[RocketMan]

Sadly in some areas they are barred from advising you. "Liability issues"


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Very true.  Here they will advise you on whether what you intend to do will meet code and pass inspection. That much is very helpful. 
They can give general, high level advice.  They are barred from telling you how to do the nitty-gritty of the actual work.  And rightly so, I think.

[Hawkmoon]

They test the ground rods here now too. We drive two full length anymore just for one service panel. Never used too but it's less hassle than a rejection

Yep. Most builders around here do the same. (Or did, when there was any building going on.)

[Hawkmoon]

And on that note, around here, they require that each ground rod be run with it's own copper wire to the main panel.  Size depends on ampacity.  I think when I did my 200 amp panel, the city required 2x ground rods, each with #4 AWG copper wire to the ground bus.

That's not what the NEC calls for. The two ground rods (where two are used) are required to be bonded. Using two "home runs" to the same bus accomplishes that, but it's no better than jumping directly from one to the other, and just wastes wire.

[Doggy Daddy]

http://www.homedepot.com/p/Southwire-1-1-1-3-Aluminum-SER-Wire-By-the-Foot-13103790/205001799

Gee, thanks for that link. [/sarc]

Now Facebook is trying to sell me spools of wire!