Parallel 200 amp panel questions

[ccarrington]

Hi fellow inspectors.

I just wanted to get some second opinions on this, as it is new construction and may turn into a litigation inspection… So I gotta be really careful to be factually correct. I am not very experienced with a two (parallel) main panel set up in regard to grounding and bonding.

Here are the stats:

A. The meter is a 320 Amp rating (I think) See photo

B. The meter has a solid core ground wire to earth, 6AWG (I can’t determine the AWG of the electrical drop wires, as it’s locked in the sealed meter panel, but would a 6 AWG ground at a 320+amp meter panel be correct?)

C. Two (2) SEC panels are side by side, both with 200 amp main breakers.

D. The feeder wires from the meter to both panels are THHN 2/0 Copper. (Is this correct to use on a circuit feeding a 200 Amp main breaker?)

E. The left panel has a GEC wire of #4 AWG connected from that panel’s neutral/ground buss, which went back to the meter base panel (A). The right panel does not have this connection back to the meter base. (However, there is confirmed electrical continuity between left and right panel. I assume there is continuity between the panels because of the neutrals are connected together in the meter panel)

F. I did not observe any other connection to common points of ground for either panel (earth, UFER, or cold water pipes. (If there are any, they are concealed and are less then 10 AWG) I feel that both panels should be bonded to two separate points, Earth and UFER or a cold water pipe, and that the bonding wires must be 4AWG copper or larger.

My understanding is that essentially the panels are totally parallel; it’s two separate 200 amp service entrance panels, not 400 amp, with probably a 320 amp total capacity between the two panels. But I feel both panels must meet the bonding and grounding requirement like they are individual panels… is that correct thinking.)

Additional observations about the panel and electrical system at first inspection:

G. There was a 240 volt pool pump in panel (2 each 110 VAC breakers) with no common trip. This is already fixed.

H: Thee left phase connection to right panel was never tightened. There was significant heat rise on this wire, See IR photos of panels.

I. There is no AFCI protection in this home.

J. There is missing GFCI protection at several required places.

I would greatly appreciate the opinion of highly experienced electrical inspectors/ electricians…

Thanks.

[Paul W. Abernathy]

OK.....Let me see if I can break this down for you since my PT this morning was cancelled.

1.) If the 6 AWG is going to a ground rod then it is perfectly fine, if no other GE's exist in this dwelling then the GEC to the man made electrode ( ground rod ) in 6 AWG would be fine.

Remember in the case of the GEC to a ground rod, lightning could careless if it is a 200A service or a 1000A service......makes no difference on that part.

2.) The 2/0CU to each panel is fine...would not fret on that.

3.) Now....the reason you are getting cont. between the both with only (1) going back to the meter is because the code demands the "Neutral" or "Grounded" conductor be together in that location based on the setup you are describing.

4.) Now.....bonding is a different issue than grounding, if there are metal water piping in the dwelling ( ie. copper piping ) then it is required to be bonded...but only from one of the enclosures...

The service itself is as you say probably 320 Cont. and 400 Non-Cont. as that is how most are that I run into.

Gotta run...if I left anything out just let me know.....

[William J. Decker]

We have had these setups around here for years. Ground is usually done at the meter. Two sets of SE conductors come in from the meter, which has a double lug setup (one for each panel). The thermal looks OK.

I see no problem. The connection to the water pipe is probably not for grounding, but for bonding.

But, I defer to Paul. He is much cuter (especially since he is now working out ).

[Marc Benz]

Cortland :

this is a very typical 400 amp service there and the 2/0 CU is very common just like single 200 amp service is [ that fine for resdental useage but commercal area that diffrent story ]

#6 bare or green wire for going to ground rod[s] that fine useally #6 or larger will serve this

speaking of AFCI you have to forgive me for a min i do not know what NEC code cycle you are on [ 99, 02 ,05 plus local code addments there ]

if your local or state code do not allow the AFCI it should be on the state code guideline

as what other speaking about the " 320/400 " service this is very common arrangement

Merci , Marc

[Marc D. Shunk]

I don't see any particular problems in these panels, and I don't really call a 20 degree rise significant. The lug may be loose, but given the variety of loads in a dwelling, this might have been the only phase in that one panel with a heavy load on it at the time. Certainly noteworthy, but may not be a legitimate problem upon investigation by an electrician. Here's a more typical presentation of loose connections, with a more typical temperature rise associated with a loose connection: