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REQ:Breaker Maximum...6AL...?

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REQ:Breaker Maximum...6AL...? Joey_Bitchn' 08-02-2005
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Posted by CL (dnoyeB) Gilbert on August 3, 2005, 3:19 pm


TURTLE wrote:
>
>>Turtle,
>>The length of the wire is about 30 feet on the conservative side. I
>>didn't get a chance to check the draw on the circuit though. I'll try
>>getting that tomorrow assuming I can figure out how to do it
>>correctly.
>>Thanks for the help
>>Joe
>
>
> This is Turtle.
>
> The Ugly Book says you have up to about 50 feet or a little more for the 50
amp
> ability and 50 amp breaker. Your well under with 30 feet.
>
> TURTLE
>
>

This is odd, could you explain that to me? I am an automotive systems
engineer and I design the wiring for automobiles. The length of wire
has nothing to do with the fuse rating. The device on the end of the
wire also has nothing to do with the fuse rating.

Well ok, some devices can terminate a few different sizes of wire, and
this is a physical thing, nothing to do with current amount but with
diameter, etc.

So why does wire length matter for breaker size in a home?

--
Respectfully,


CL Gilbert


Posted by Percival P. Cassidy on August 3, 2005, 3:48 pm


On 08/03/05 03:19 pm CL (dnoyeB) Gilbert tossed the following
ingredients into the ever-growing pot of cybersoup:

>> The Ugly Book says you have up to about 50 feet or a little more for
>> the 50 amp ability and 50 amp breaker. Your well under with 30 feet.

> This is odd, could you explain that to me? I am an automotive systems
> engineer and I design the wiring for automobiles. The length of wire
> has nothing to do with the fuse rating. The device on the end of the
> wire also has nothing to do with the fuse rating.
>
> Well ok, some devices can terminate a few different sizes of wire, and
> this is a physical thing, nothing to do with current amount but with
> diameter, etc.
>
> So why does wire length matter for breaker size in a home?

I assume that he means that a longer wire will result in a larger
voltage drop, so one would use a larger wire to reduce the resistance
and the voltage drop -- and a correspondingly higher-rated breaker to go
with the larger wire.

Perce



Posted by Nathan Pralle on August 3, 2005, 8:28 pm



> I assume that he means that a longer wire will result in a larger
> voltage drop, so one would use a larger wire to reduce the resistance
> and the voltage drop -- and a correspondingly higher-rated breaker to go
> with the larger wire.

This is my understanding as well, and I've seen it in practice. Running
a 16A compressor on a 30A circuit done in 10/2 wire for 60 feet saw too
much drop across it to power the compressor in the winter. Bringing the
compressor within 6 feet of the box solved that problem.

Nathan


Posted by TURTLE on August 3, 2005, 8:44 pm



> TURTLE wrote:
>>
>>>Turtle,
>>>The length of the wire is about 30 feet on the conservative side. I
>>>didn't get a chance to check the draw on the circuit though. I'll try
>>>getting that tomorrow assuming I can figure out how to do it
>>>correctly.
>>>Thanks for the help
>>>Joe
>>
>>
>> This is Turtle.
>>
>> The Ugly Book says you have up to about 50 feet or a little more for the 50
>> amp ability and 50 amp breaker. Your well under with 30 feet.
>>
>> TURTLE
>
> This is odd, could you explain that to me? I am an automotive systems
> engineer and I design the wiring for automobiles. The length of wire has
> nothing to do with the fuse rating. The device on the end of the wire also
> has nothing to do with the fuse rating.
>
> Well ok, some devices can terminate a few different sizes of wire, and this is
> a physical thing, nothing to do with current amount but with diameter, etc.
>
> So why does wire length matter for breaker size in a home?
>
> --
> Respectfully,
>
>
> CL Gilbert
>

This is Turtle.

In the World of Electricians we have a simi-rule book called a Ugly Book which
will tell use what size wire, load size, and breaker size that matches a load
and keeps the voltage drop to less than 2% of Voltage. If you have 120 volts
service. You don't want more than 2% or 2.4 volt drop caused by the wirte size
being too small for the ampcity. The fastest way to burn up a hvac system is to
run it on low voltage.

TURTLE




Posted by Joey_Bitchn' on August 3, 2005, 7:31 pm


Turtle

I installed the 50 AMP Breaker and so far so good.I've had the A/C on
all day. The wires aren't even warm. The A/C unit read 37.5 AMP
minimum so I guess that with the 40 AMP breaker the initial voltage
drop over a few on/off cycles was enough for the relay not to
re-engage.
Thanks for the tip. If you lived in Fallbrook, Calif. I'd buy you
lunch for saving me the call to an electrician :-)

Cheers!
Joe


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