| I am doing th electrical on my brothers new house.... here is the question?
| the main pannel is a 400 amp pannel and then a set of 200 amp breaker to the
| house from the 200 amp breakers 65 feet to a disconect and then 65 feet more
| to the 200 amp sub pannel .....
Your wording for this is not clear to be 100% certain I can visualize
exactly what the situation is.
Is the 400 amp panel in the same house as the sub panels?
Which of these is true:
1. There is only 1 200 amp subpanel and some branch circuits originate
in the 400 amp panel.
2. There are 2 (or more) 200 amp subpanels, but also some branch circuits
originate in the 400 amp panel.
3. There are 2 (or more) 200 amp subpanels, and NO branch circuits
originate in the 400 amp panel.
Are both 65 feet sections of feeder inside the house? Or is one or more
of them outside (maybe between buildings)?
A pictoral diagram would help. Another method to better describe things
is to sequentially list the components encountered in exactly the order
starting at the service feeder coming from the utility presumably going
to a meter first.
| the question is does he need to run a ground wire or ground the pannel with
| a ground rod and both a ground rod and a 4 gauge ground wire
| and is 4 X 4 ott and a 2 ott aluminum wire large enough to do this
The general description is this. There needs to be a bonding point that
bonds the neutral and the grounding wire (EGC) somewhere between the
meter for the service entrance and the first disconnect (which could be
the main in a main breaker panel if that is the first box the service
feed goes to after the meter). That bonding point is also connected to
the grounding electrodes (I recommend always at least 2 electrodes, even
if the quality of the electrodes meets the requirements that allow 1).
From the bonding point all feeds and branch circuits must carry a grounding
wire (EGC) that is separate from the neutral (some circuits may not have a
neutral, but would still have the grounding wire). Subpanels in a separate
building must have the grounding wire connected to grounding and MUST NOT
bond the neutral to the grounding wire (and therefore must have separate
bus bars for ground and neutral with the neutral bus bar insulated from the
matallic enclosure). I recommend even the main panel be wired with this
practice (separate bus bars, neutral insulated) even though it would not be
required if it contains the bonding point.
If you have a separate disconnect between the main panel and the meter,
then the bonding point must be in that disconnect and the main panel must
be wired like a subpanel.
Under certain circumstances that I don't know much about, you may ground
and bond two (maybe more, I don't know) parallel main panels together.
I believe they must be close to each other for this to be allowed. It's
done a lot so I presume it is allowed, but I don't know the details. But
it also seems you are not taking this approach, anyway (I wouldn't).
If the construction involves metallic conduit or metal armored/clad cable,
and specific branch circuits will be used for life support equipment,
computers, or sensitive media electronics, I recommend including in these
circuits an "isolated ground" wire, which is a separate grounding wire
not used to grounding the metallic points that the primary grounding wire
would be doing, and use "isolated ground" type receptacles, with these
branch circuits originating from the main panel even if that means a long
branch circuit run. That "isolated ground" wire will usually be a green
wire with a yellow stripe to identify it apart from the main grounding
wire. Such a circuit should also be available at the point where Cable TV
and telephone wiring enter the house (which should be very close to the
main electrical entrance for common grounding).
I also recommend any "3 wire" circuits (dual voltage), which are usually
found serving kitchen ranges and laundry clothes dryers, also be fed
directly from the main panel (regardless of the conduit/cable type).
I recommend not using any shared neutral circuits. But if you are already
committed with some, I recommend these originate from the main panel.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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