Ground wire for 400 amp meter base

[Diesel Dan]

finally had the POCO set the pole on the property. Have the trench dug to the H-frame where the 400A meter base is mounted with two 200A disconnects.

Currently getting the disconnects wired(2/0 CU) along with a 50A (6-3)RV outlet and another 20A (12-2)GFCI for use until the house if finish framed. I need the state inspector to check the disconnects before the POCO will pull the wire to the base.

What size solid ground wire do I need for this setup?
IIRC, a single 200A uses a #4 solid for the ground rods, is that what is called for on this setup?

Thanks in advance.

 

[wyliesdiesels]

Max req size GEC/wire to rods is #6 cu.

 

[Aceman]

How did you come up with 2/0 CU for a 200 amp disconnect?

 

[Diesel Dan]

How did you come up with 2/0 CU for a 200 amp disconnect?

Chart 310.15(b)(6) found via google.
I have to have disconnects since the meter base is mounted 15' away from the house foundation on a wooden H-frame. One disconnect to the 200A house panel and one for the shop. Meter base is center mounted on the H-frame with one disconnect on each side.

Table 250.66 shows #4 for 2/0 CU.
So I'd run #4 starting at one panel, thru meter base, thru second panel and then tie into ground rods?

I realize MY SE cables are only 2/0 at each panel but didn't know if the 400A meter base would require larger.

My son wasn't much help since he's playing with that conductor that weights 22lbs/ft.

 

[Norcal]

How did you come up with 2/0 CU for a 200 amp disconnect?

The Urban Legend Code.


I see no way to use 2/0 CU or 4/0 AL on a 400A service w/o load calc's. Or a 200A non dwelling feeder either. But there is the mindset that you use 2/0 or 4/0 at 200A for everything.

Chart 310.15(b)(6) found via google.
I have to have disconnects since the meter base is mounted 15' away from the house foundation on a wooden H-frame. One disconnect to the 200A house panel and one for the shop. Meter base is center mounted on the H-frame with one disconnect on each side.

Table 250.66 shows #4 for 2/0 CU.
So I'd run #4 starting at one panel, thru meter base, thru second panel and then tie into ground rods?

I realize MY SE cables are only 2/0 at each panel but didn't know if the 400A meter base would require larger.

My son wasn't much help since he's playing with that conductor that weights 22lbs/ft.

That table only applies when it serves the ENTIRE load of a dwelling, subfeeds do not count, 2/0 copper THWN is only 175A and that is a standard size circuit breaker rating so you can't use the next higher rating rule if the calculated load was under 200A, 4/0 aluminum THWN is rated 180A and if the load was calculated under 180A, then 200A would be OK.

 

[Diesel Dan]

But there is the mindset that you use 2/0 or 4/0 at 200A for everything.

So are you implying I under sized my SE feed then?

 

[Norcal]

So are you implying I under sized my SE feed then?

If strictly relying on that table, then you did, BTW that table was removed from the 2014 NEC, see my edited post above, there is criteria that had to be met to use the table to undersize dwelling SE conductors.

 

[Diesel Dan]

Max req size GEC/wire to rods is #6 cu.

Thank you,
Didn't want to buy 46' of the wrong stuff since this is the first single meter split feed system I've worked on.

How did you come up with 2/0 CU for a 200 amp disconnect?

But there is the mindset that you use 2/0 or 4/0 at 200A for everything.

FWIW, the last 200A service panel I installed was in the 2012/13 time frame with 2/0 copper and it passed inspection.

 

[Diesel Dan]

Talked to a state electrical inspector today. For my area the 2/0 copper is fine, if I lived in the city under their POCO it would have to be rated +1 in size or a 3/0 copper.

Had I known there 2/0 creates such a fuss I'd have just done the 3/0 and have since found Home Depot carries 3/0 for less than what the supply house charges for 2/0.

The #6 ground conductor is what is commonly used, as previously stated, for a standard 1-2 rod ground system. However I've gone beyond code and installed 5 rods on 10' spacing so going with a #4 conductor. Inspector was impressed with this upgrade and stated code is just the minimum.

Thoughts on how people would run the #4 to connect the 3 panels?
The first GR is under the LH disconnect next to the pole.
Edit: Also need a ground wire to the ground bushing for the 3.5" metal conduit.

 

[dw1]

Looks good, but Move the white tape to the neutral conductor, you cant have a current carrying conductor identified as white, it can just be the black wire.

I cant tell, but is that an EMT connector coming into the bottom of the MB, it will need a ground bushing on it, as far as the ground wire, different utilities/jurisdictions have different requirements, you might want to ask, around here, we cannot bring the ground wire into the MB, it has to terminate in the panel.
They also require ICBT block, it is enforced around here, you might want to ask about that also. https://www.erico.com/catalog/literature/E828B-NAEN.pdf

 

[wyliesdiesels]

Yeah the white tape on the unground conductor is wrong as said above. Move to the neutral conductor/grounded conductor.

 

[Diesel Dan]

Moved the white tape.
The ICBT block is something the inspector mentioned (aka media block) and I just picked one up. They are cheap <$11.

Ground bushing wasn't in pic because they gave me a 3" instead of a 3.5" so had to exchange it. Just a #6 solid to a ground bar in one of the disconnects?

Interesting on no ground wire in MB, not how it was done in Ohio.

 

[dw1]

Moved the white tape.
The ICBT block is something the inspector mentioned (aka media block) and I just picked one up. They are cheap <$11.

Ground bushing wasn't in pic because they gave me a 3" instead of a 3.5" so had to exchange it. Just a #6 solid to a ground bar in one of the disconnects?

Interesting on no ground wire in MB, not how it was done in Ohio.

Yeah, different jurisdictions, different requirements, I agree, kind of silly. We can jump off the lug on the ground bushing to the grounded terminal inside the MB. See if your power company has an online handbook, most of them do and states exactly what they require/want. Your # 6 can be solid or stranded, if not green or bare, it needs to be identified with a piece of green tape.

 

[walrus]

Is that a new foundation? No concrete electrode?, ground wire to 20ft piece of rebar?

 

[wyliesdiesels]

Is that a new foundation? No concrete electrode?, ground wire to 20ft piece of rebar?

Need to have slab directly in contact with earth

 

[walrus]

Need to have slab directly in contact with earth

Really need a buried footer but maybe its just a slab on grade with foam under it? Doesn't seem likely with the blocks I see on it????

 

[Diesel Dan]

Grounding the slab will not work since it's on compacted gravel fill regardless of vapor barrier or foam. With the additional ground electrodes it does not have to tie into the footer.

Yes, new construction.
I have a thread going in the garage gallery if interested.

 

[walrus]

Grounding the slab will not work since it's on compacted gravel fill regardless of vapor barrier or foam. With the additional ground electrodes it does not have to tie into the footer.

Yes, new construction.
I have a thread going in the garage gallery if interested.

So you do have a footer? If so what code cycle are you on? There is no exception that I know of. Doesn't matter as long as your code enforcement guy is happy. Some places you'd be digging it up, you must have the concrete encased electrode.

 

[Diesel Dan]

Yes on a footer.
Code cycle? Please elaborate.

I'll check my pictures of the footer but I don't think t h ey left me a stub sticking out.

 

[wyliesdiesels]

He means what NEC code cycle is your AHJ(authority having jurisdiction) aka building department on?

2008, 2011, 2014?

 

[Diesel Dan]

That I don't know.
What I do remember is they are not adopting the fire sprinkler systems for residential buildings.

 

[dw1]

Online it says to check with Columbia Power and Water for NEC code cycle

 

[Diesel Dan]

I'm with Duck River co-op.
Have terrible Internet service at this camp ground and will have none at the property. Limited data on phone too.
PITA.

 

[Diesel Dan]

On the code, the co-op does not deal with the MB or disconnects. Have to call a state inspector.

 

[Diesel Dan]

Here is how I ran the ground conductors.
#4 from the GR to the left panel, left ground bar and all others to the RH ground bar of same panel. Used a smaller #6 to the ground bushing.
Waiting on a "trench" inspection from the POCO right now.

Thinking about adding a type 1 surge protector as well. Need to see how much the POCO wants for the one they carry.

 

[westom]

Here is how I ran the ground conductors.
#4 from the GR to the left panel, left ground bar and all others to the RH ground bar of same panel. Used a smaller #6 to the ground bushing.
Waiting on a "trench" inspection from the POCO right now.

From pictures, that grounding looks good for code (human safety). But will compromise a protector (transistor safety. That ground wire goes between boxes before it goes to a ground rod. Best earthing (for transistor safety) needs that ground wire from the central box to go straight down to earth. No sharp bends. Not inside metallic conduit. One solid direct connection without any splices.

See those sharp bends in the left box? Those increase impedance. A surge from a Poco's protector (center box) must go straight down to earth - as short as possible, no sharp bends, and only one continuous wire.

Since it is inside metallic conduit, then the less effective solution connects a surge current to the metallic pipe. At the other end must also be a bond wire from that pipe to the many ground rods.

Also critical is to locate all other utilities short (ie less than 10 feet) to that same ground. That means phone, TV cable, satellite dish or OTA antenna. Or does a less than ideal setup as demonstrated by this utility:
http://www.duke-energy.com/indiana-business/products/power-quality/tech-tip-08.asp

With a still open trench, that is possible with a 2 AWG bare copper ground wire in that trench.

BTW best surge protection could have been installed when footing were poured. Too late now. But protectors do not define protection. That Ufer ground does. Your five rods means protection would be better (depending on what geology is down there).

 

[Diesel Dan]

I knew it would not be perfect and one thing I tried to do was only one conductor per clamp/screw.

So should the MB #4 go straight to the GRs and then #4 or 6 jumpers from the disconnects back to MB? That would put 3 conductors at that junction.

There is no ground conductor inside metal conduit and a media grounding bar is mounted on the post. Trench is still open and that is where I was to place the rods and conductor.

Thanks for the feedback, even if I does make more work for me.

 

[Diesel Dan]

Waiting on a inspection, fun process in itself.
A while back the POCO gave me the # for state inspector. After calling him and finding we have a different inspector now I called POCO again for new #. After a week of trying to get through the inspector asks why I'm calling him, to get an inspection I reply. We'll you don't call me go through the Poco.
Huh, well where do ya think I got his number?

Anyway I did find out he is using the 2008 NEC schedule.
Hopefully inspection will happen Thursday.

 

[Diesel Dan]

Inspection failed due to the 2/0 but still confusing.

Since I was doing a meter pedestal it is "required" to be 3/0 BUT if it was a rough-in inspection for the house/shop it would have been fine with 2/0. Inspector said since he doesn't know what I'm hooking to it then it has to be 3/0. Never mind 12' away is a 3,000 sq/ft residential structure! Plus I can't call for a rough in without any interior walls.

So when I do get the interior framing up and panels mounted I can run 2/0 for 20-25' but couldn't run it 2' inside the panels.

Oh, and the neutral with the white tape on the ends....not passable either. It needs the white tape to "candy cane" along the entire length, per the inspector. Yet another thing I didn't have to deal with on my last panel in 2012.

The ground wires were OK but I cleaned them up and re-routed.

 

[Aceman]

This is the reason why you don't allow inspections to be your guideline for how to wire something properly. That's what the code book is for. The last inspection you had back in '12, the inspector could of been having an off day and missed some things. And since everything passed, folks make the assumption they did it right. Not always true.

I've seen a lot of installs on here that passed that would be shot down in a second in our jurisdiction over here where the inspectors are well informed of the latest code rules.

 

[Diesel Dan]

This is the reason why you don't allow inspections to be your guideline for how to wire something properly. That's what the code book is for. The last inspection you had back in '12, the inspector could of been having an off day and missed some things. And since everything passed, folks make the assumption they did it right. Not always true.

I've seen a lot of installs on here that passed that would be shot down in a second in our jurisdiction over here where the inspectors are well informed of the latest code rules.

Many true points in this response.
However, I'm not in a position to argue with the inspector if he varies from the code book. As many people have found out over the years it's more about what the inspector (plumbing, electric, framing etc) wants to see.

The whole 2/0 vs 3/0 was the main thing and as I stated the 2/0 would have been allowed if I had conduit run to the residential structure. The former, more flexible, inspector would have let the 2/0 stand since it was apparent this meter base was to feed said structure.

Now, is there a line in the code book for having to "candy cane" the neutral leg or is white tape at the ends ok?