[TheForge] Light bulbs and shop power

[Bruce .]

Ed,

Thanks for your contribution.

I'd like to point out that from the standpoint of the physics involved
(i.e, behavior of electricity and conductors) it is NOT true that the
length of the run doesn't matter.  The longer the run, the more the
resistance and the greater the voltage drop.  Voltage drop = heat
dissipation AND extra load on the circuit (and as the wire heats, its
resistance increase further, compounding the problem).  Just because
you can run a light bulb using a 6-foot extension cord, does NOT mean
you can safely run it using a 500-ft extension cord of the same gauge.

I suspect what you were saying is that given the wire sizes you
mention, the length of the run is not an issue.  With sufficiently
large wire, the voltage drop is minimal in any event, so a multiplier
(longer length) does not necessarily increase the voltage drop enough
to worry about.

However, there are on-line calculators for determining   Play with
this one, for example:  http://www.csgnetwork.com/wiresizecalc.html
It told me that a 10' run of 20A requires 14ga wire, but a 100' run of
20A requires 8ga wire!

And thanks for the comment about circuit breakers "getting weaker".
But exactly what does that mean?  Will they fail safe (open the
circuit before there's a real overload) or fail dangerously (not open
the circuit when they should)?  Any idea what the typical lifetime of
your typical household circuit breaker might be?

On Fri, Aug 3, 2012 at 11:10 AM, Ed Eccleston <edeccleston at att.net> wrote:
<snip>
 Rule of thumb is:
> 15amp breaker requires minimum #14 ga. wire...20amp= #12
> ga....30amp=#10ga....40amp=#8ga....
>     The length of the run is not so critical as long as the wire size is
> sufficient.  It's when you have a combination of long run, small wire size
> and larger draw that you get into hot water.
<snip>
 Oh, and final
> note, generally the more that a breaker pops, it gets weaker.
>       Yes, it's not inexpensive to get set up properly,  but it's sure a lot
> safer.
>
> Thanks for letting me blather.
>
> Ed Eccleston
>

-- 
Bruce
NJ