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Home > Archive > Electrical Engineering > June 2006 > NEC on Low Voltage
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NEC on Low Voltage
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| drietow@hotmail.com 2006-06-09, 8:21 pm |
| Does anyone know that requirements for low voltage wiring. I have a
situation where an exposed conduit with low voltage wiring reaches the
top of grade surface at my pool vault. It runs the length of the
surface for approximately 2 ft. I'm told low voltage needs to be
buried 18 inches down. Is that for all forms of low voltage or only
low voltage wires not incased in conduit?
If replying can you point me to the code number or page number of the
NEC book?
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| electrician@electrician2.com 2006-06-09, 9:21 pm |
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drietow@hotmail.com wrote:
> Does anyone know that requirements for low voltage wiring. I have a
> situation where an exposed conduit with low voltage wiring reaches the
> top of grade surface at my pool vault. It runs the length of the
> surface for approximately 2 ft. I'm told low voltage needs to be
> buried 18 inches down. Is that for all forms of low voltage or only
> low voltage wires not incased in conduit?
>
> If replying can you point me to the code number or page number of the
> NEC book?
First of all, there is no definition of low voltage wiring in the NEC.
Circuits for low voltage are generally Class 1, 2, or 3 as defined in
Article 725 of the NEC. Additional safety requirements are imposed by
Article 504 for intrinsically safe circuits. You need to define the
circuits that you refer to before rules in the NEC can be applied.
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| gfretwell@aol.com 2006-06-11, 4:21 pm |
| On 9 Jun 2006 15:34:50 -0700, "drietow@hotmail.com"
<drietow@hotmail.com> wrote:
>Does anyone know that requirements for low voltage wiring. I have a
>situation where an exposed conduit with low voltage wiring reaches the
>top of grade surface at my pool vault. It runs the length of the
>surface for approximately 2 ft. I'm told low voltage needs to be
>buried 18 inches down. Is that for all forms of low voltage or only
>low voltage wires not incased in conduit?
>
>If replying can you point me to the code number or page number of the
>NEC book?
You are looking for table 300.5 (burial depth) 680.22 distance from
pool and 725 for general limited voltage/current circuits.
The short answer is low voltage (<30v) can be buriued 6" down but
must still be 5' from the water's edge.
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| electrician@electrician2.com 2006-06-13, 5:21 am |
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gfretwell@aol.com wrote:
> On 9 Jun 2006 15:34:50 -0700, "drietow@hotmail.com"
> <drietow@hotmail.com> wrote:
>
>
> You are looking for table 300.5 (burial depth) 680.22 distance from
> pool and 725 for general limited voltage/current circuits.
> The short answer is low voltage (<30v) can be buriued 6" down but
> must still be 5' from the water's edge.
I respectively disagree with your short answer. The six inch burial
depth given in Table 300.5 is for Circuits for Control of Irrigation
and Landscape Lighting Limited to Not More Than 30 Volts and Installed
with Type UF or in Other Identified Cable or Raceway as found in Table
300.5 Column 5. It appears that Column 2, 3 or 4 would apply
depending on the type of raceway and circuit. However, if the wiring
cannot be routed 5 feet or more from the pool vault Section 680.10
would apply.
Section 680.10 Underground Wiring Location states. "Underground wiring
shall not be permitted under the pool or within the area extending 1.5
m (5 ft) horizontally from the inside wall of the pool unless this
wiring is necessary to supply pool equipment permitted by this article.
Where space limitations prevent wiring from being routed a distance 1.5
m (5 ft) or more from the pool, such wiring shall be permitted where
installed in rigid metal conduit, intermediate metal conduit, or a
nonmetallic raceway system. All metal conduit shall be corrosion
resistant and suitable for the location. The minimum burial depth shall
be as given in Table 680.10."
This table lists burial depths of 6 inches to 18 inches depending on
the type of raceway.
In other words, there is no short answer and the gentleman would be
well advised to consult with the local authority having jurisdiction if
there is one.
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| gfretwell@aol.com 2006-06-13, 3:21 pm |
| On 13 Jun 2006 00:25:58 -0700, electrician@electrician2.com wrote:
>
>gfretwell@aol.com wrote:
>
>I respectively disagree with your short answer. The six inch burial
>depth given in Table 300.5 is for Circuits for Control of Irrigation
>and Landscape Lighting Limited to Not More Than 30 Volts and Installed
>with Type UF or in Other Identified Cable or Raceway as found in Table
>300.5 Column 5. It appears that Column 2, 3 or 4 would apply
>depending on the type of raceway and circuit. However, if the wiring
>cannot be routed 5 feet or more from the pool vault Section 680.10
>would apply.
>Section 680.10 Underground Wiring Location states. "Underground wiring
>shall not be permitted under the pool or within the area extending 1.5
>m (5 ft) horizontally from the inside wall of the pool unless this
>wiring is necessary to supply pool equipment permitted by this article.
>Where space limitations prevent wiring from being routed a distance 1.5
>m (5 ft) or more from the pool, such wiring shall be permitted where
>installed in rigid metal conduit, intermediate metal conduit, or a
>nonmetallic raceway system. All metal conduit shall be corrosion
>resistant and suitable for the location. The minimum burial depth shall
>be as given in Table 680.10."
>This table lists burial depths of 6 inches to 18 inches depending on
>the type of raceway.
>
>In other words, there is no short answer and the gentleman would be
>well advised to consult with the local authority having jurisdiction if
>there is one.
Most of the time we are lucky to get the 6".
Telcos, landscapers and cable companies barely get it under the sod.
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