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Low voltage (12v) wire in the same conduit as a 120v

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Low voltage (12v) wire in the same conduit as a 120v gore 01-28-2008
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Posted by gore on January 28, 2008, 6:51 pm
A friend wants to run low voltage wiring for his landscaping, but also wants
to run some feeds for larger lights elsewhere in the yard. He only wants to
punch one hole in his basement wall and was wondering if he could run the
12v wires from the transformer in the same conduit he uses to run a 120v
feed for his other lights. I tried looking in the 2005 NEC, but it led me to
other questions. In 300.3(C)(1) it says that the cables can be run in the
same enclosure as long as the insulation of the lower voltage circuit was
rated for the voltage of the higher voltage circuit. Then it says unless
it's a class 2 or class 3 device see 725.55. What would the class rating of
the low voltage lighting be?

Thanks
Shane



Posted by RBM on January 28, 2008, 7:16 pm
No, however he could run 12 volts through 120 volt conductors in the same
conduit




>A friend wants to run low voltage wiring for his landscaping, but also
>wants to run some feeds for larger lights elsewhere in the yard. He only
>wants to punch one hole in his basement wall and was wondering if he could
>run the 12v wires from the transformer in the same conduit he uses to run a
>120v feed for his other lights. I tried looking in the 2005 NEC, but it led
>me to other questions. In 300.3(C)(1) it says that the cables can be run in
>the same enclosure as long as the insulation of the lower voltage circuit
>was rated for the voltage of the higher voltage circuit. Then it says
>unless it's a class 2 or class 3 device see 725.55. What would the class
>rating of the low voltage lighting be?
>
> Thanks
> Shane
>



Posted by on January 28, 2008, 9:16 pm
wrote:

>A friend wants to run low voltage wiring for his landscaping, but also wants
>to run some feeds for larger lights elsewhere in the yard. He only wants to
>punch one hole in his basement wall and was wondering if he could run the
>12v wires from the transformer in the same conduit he uses to run a 120v
>feed for his other lights. I tried looking in the 2005 NEC, but it led me to
>other questions. In 300.3(C)(1) it says that the cables can be run in the
>same enclosure as long as the insulation of the lower voltage circuit was
>rated for the voltage of the higher voltage circuit. Then it says unless
>it's a class 2 or class 3 device see 725.55. What would the class rating of
>the low voltage lighting be?
>
>Thanks
>Shane
>

You can't run them in the same pipe or box unless they are both cables
(not individual conductors). Then you have to split them out before
you crack into the 120v cable. UF is really the only 120v cable you
could use. If he has a direct burial low voltage cable he can sleeve
both through the wall in one pipe, then split them out in the same
trench. You just can't keep them together in a box where he is making
120v connections.

Posted by bud-- on January 29, 2008, 12:22 pm
gfretwell@aol.com wrote:
> wrote:
>
>> A friend wants to run low voltage wiring for his landscaping, but also wants
>> to run some feeds for larger lights elsewhere in the yard. He only wants to
>> punch one hole in his basement wall and was wondering if he could run the
>> 12v wires from the transformer in the same conduit he uses to run a 120v
>> feed for his other lights. I tried looking in the 2005 NEC, but it led me to
>> other questions. In 300.3(C)(1) it says that the cables can be run in the
>> same enclosure as long as the insulation of the lower voltage circuit was
>> rated for the voltage of the higher voltage circuit. Then it says unless
>> it's a class 2 or class 3 device see 725.55. What would the class rating of
>> the low voltage lighting be?
>>
>> Thanks
>> Shane
>>

(330.3(C)(1) is wires not cables. So it does not apply to gfretwell's
answer.)

>
> You can't run them in the same pipe or box unless they are both cables
> (not individual conductors). Then you have to split them out before
> you crack into the 120v cable. UF is really the only 120v cable you
> could use. If he has a direct burial low voltage cable he can sleeve
> both through the wall in one pipe, then split them out in the same
> trench. You just can't keep them together in a box where he is making
> 120v connections.

I agree.

Combining *wires* in the raceway turns the class 2 or 3 circuit into
normal wiring or class 1. You then can't use the easier wiring methods
applicable to class 2 or 3.

--
bud--


Posted by John Grabowski on January 29, 2008, 7:47 am

> A friend wants to run low voltage wiring for his landscaping, but also
wants
> to run some feeds for larger lights elsewhere in the yard. He only wants
to
> punch one hole in his basement wall and was wondering if he could run the
> 12v wires from the transformer in the same conduit he uses to run a 120v
> feed for his other lights. I tried looking in the 2005 NEC, but it led me
to
> other questions. In 300.3(C)(1) it says that the cables can be run in the
> same enclosure as long as the insulation of the lower voltage circuit was
> rated for the voltage of the higher voltage circuit. Then it says unless
> it's a class 2 or class 3 device see 725.55. What would the class rating
of
> the low voltage lighting be?


It is permissible under certain conditions, but it is not a good idea. You
don't want those wires getting crossed. I certainly wouldn't advise a
weekend electrician to do it that way. They make enough mistakes as it is.
Mixing voltages is asking for trouble with a DIYer. If he rents a rotary
hammer from Home Depot, making a hole in the basement wall won't be a
problem.


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