wrote in message
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On Sun, 26 Jul 2009 09:14:15 -0400, "RBM" wrote:


wrote in message
...
On Jul 24, 7:18 pm, "RBM" wrote:
"Aaron Fude" wrote in message

...

RBM wrote:
"Aaron Fude" wrote in message
...
Hi,

I have a subpanel that is in a very convenient space and it is so
very
temping to put a lot of stuff on it (kitchen /includes 30amp stove
+
garage + central A/C + etc), but my electrician told me that it's
not
proper to draw more than half the amperage from the main panel. Is
that
so and what's the rational for it.

The sub-panel is 18ft away from the main panel and is fed by a
2-2-2-2
wire. I found this table

WG gaug Maxamps for chassis Maximum amps for power transmission
2 181 94

which I guess is saying that the max amps is 94, but I'm hoping
that
that's a rating for 100ft and I can go to about 125 over 18ft.

So I guess there are two questions in one:
1. Can I draw 125 amps on the basis that it's more that 1/2 the
total
service (200amps)?
2. Can I draw 125 amps on the basis that it's 2-gauge wire?

Thanks

Aaron

I would recommend running your heavy loads off of the main panel,
simply
to prevent lights dimming due to the smaller feeder (#2 vs. 4/0)

If this is an existing sub panel, it will have a main breaker in the
service panel, which will limit the current that can be pulled from
it,
which I can't determine, not knowing if it's feeder is aluminum or
copper
The subpanel is fed by 2-2-2-2 copper. Very strange that it would be
fed
by 4-#2 conductors. Typically, #2 copper is good for 100 amps, which
is
probably why the electrician recommends not exceeding half the
service
maximum on it


I don't know the code specific answer to how many amps you can draw
off a main panel, but I can tell you this. In a 4 year old house
here, I just finished helping a friend add a new line for a new
irrigation well. We hooked it to an 80A sub panel that was installed
for the pool eqpt and run off one of the two 150A main panels.
That sub panel had passed local inspection and is more that 50% of the
main.

Your friend has a 300 amp service split between two "main" panels. The
pool
sub panel fused at 80 amps is not greater than half the size of the main
panels. The OP has a 200 amp service, a 100 amp sub panel, and seems to be
asking if he can pull 125 amps on it


The real answer will come from a load calculation. Nothing else
matters. You can install a 200a sub panel on a 200a service if you
want, the code is silent on it.

What are the loads on that current service?

2ga cu is good for 115a so you can put a 125a breaker on it using the
round up rule.

240.4(B) Devices Rated 800 Amperes or Less. The next higher standard
overcurrent device rating (above the ampacity of the conductors being
protected) shall be permitted to be used, provided all of the
following conditions are met:
(1) The conductors being protected are not part of a multioutlet
branch circuit supplying receptacles for cord-and-plug-connected
portable loads.
(2) The ampacity of the conductors does not correspond with the
standard ampere rating of a fuse or a circuit breaker without overload
trip adjustments above its rating (but that shall be permitted to have
other trip or rating adjustments).
(3) The next higher standard rating selected does not exceed 800
amperes.



Unless it's 2/3 Romex. It's not at all clear to me, what he's run to the
sub. I know he said 2222 copper, but that doesn't make sense either.