DIYbanter - View Single Post - Load capacity of 200-amp panel

Doug Miller

In article , Sam E wrote:
On Sat, 24 Oct 2009 18:17:14 GMT, (Doug Miller)
wrote:

In article
,
wrote:

Consider this simple circuit analogy which is exactly what you would
have with a balanced load on a 240V service. It's a 240V voltage
source powering two 120ohm resistors.

____________ 240V___________
I I
I I
I I
---------120ohm---------120ohm---------
a b c

There is only 1 amp of actual current flowing in the circuit. Across
each resistor there is 120Volts and 1 amp of current flowing. So,
yes you have 1 amp flowing in EACH load, it is supporting two 1 amp
loads, but it's the same physical current flowing through each load.
The "service" is only supplying 1 amp of actual current, not 2.

What voltage do you measure between a and b? Between c and b?
What current do you measure between a and b? Between c and b?

That's what I meant when I said a 200 amp service cannot supply 400
amps of current.

But it can. 200A at 120V on each leg is a total of 400A at 120V. The two legs
of a residential electrical service are, in effect, two parallel circuits.
200A flowing in each of two parallel circuits is 400A total, not 200A.

You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same. The two legs function as two parallel circuits
with respect to 120V loads. Obviously they are indeed in series WRT 240V
loads.