Table 300.5 Column 5

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Bjenks

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Everytime I read an low voltage residential landscape installation guide on the internet or from a manufacture, they say you can bury the LV cable about 2 inches under the ground. I can't find any code that allows that.
I looked at NEC 411 for something and it only says NEC 300 methods. When I look at T300.5 Col 5 it talks about control wires being 6" for all locations not specified. However, for all dwelling driveways, parking areas and used only for dwelling related purposes, it shows 18".

Based on what I see, for direct burial cables or conductors it looks like you have to go 18" even it if it lanscape lighting cables. Let me know if there is another code that would change that.
 
I think it is an absurd rule. I can install UF 12" in a resi job for lighting if it is on gfci but 18" for low voltage. :-?
 
jumper said:
Use a class 2 or 3 cable and transformer, and T300.5 does not apply. It only applies to chapter 3 wiring methods.

No minimum burial depth required for class 2 or 3 cables in 725 that I know of.
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Agreed, 411.5(D)(1) permits the use of Class 2 power supplies and Class 2 cables installed in accordance with Part I and Part III of Article 725. There is nothing in Part III that would require you to follow the burial depths in 300.5.

Chris
 
I always have buried the low voltage outdoor wiring under the mulch but when I saw col. 5 I thought had done it wrong. Glad to see I am wrong.
 
Here is the conundrum, get an underground inspection and all your empty conduits need to meet the requirements of 300.5. Now pull a class 2 or 3 wiring method into one of those conduits and 300.5 no longer applies. Go figure.
 
A Class 2 power supply for landscaping lighting is almost useless. The maximum rating of a Class 2 power supply is 5 amps (60 watt @12 volts). That would only drive one 50 watt MR16 lamp.
 
raider1 said:
Agreed, 411.5(D)(1) permits the use of Class 2 power supplies and Class 2 cables installed in accordance with Part I and Part III of Article 725. There is nothing in Part III that would require you to follow the burial depths in 300.5.

Chris
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Most landscape transformers are rated in incriments of 300W. Most run UF or THWN. I see the Class 2 & 3 if you are talking about indoor circuits through walls, floors, or ceilings. column 5 is for controlling landscape lights. Again, I don't see any code giving permission to bury in the mulch these cables unless there is a UL listing giving them permission.
 
Bjenks said:
Most landscape transformers are rated in incriments of 300W. Most run UF or THWN. I see the Class 2 & 3 if you are talking about indoor circuits through walls, floors, or ceilings. column 5 is for controlling landscape lights. Again, I don't see any code giving permission to bury in the mulch these cables unless there is a UL listing giving them permission.
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If you use a chapter 3 wiring method-UF-, you have to use 300.5.

If you use a 725, class 2 or 3 cable, you do not have to.
 
I wasn't expecting this discussion, but you can't define the wiring methods based on the fact you are using class 2 or class 3 wires. You are allowed to use the class 2/3 wiring based on the power-limited circuit and on the fact that the power limiting device is actually a UL listed class 2/3 device.

For Class 2 Circuits:
Power Supply generally limited to 100 Volt-amperes and maximum voltage of 30 volts.

For Class 3 Circuits:
Power Supply generally limited to 100 Volt-Amperes and maximum voltage of 100 Volts.

Look up UL1838 which is for Landscape transformers and there is one option for class 2, that says "The output of power units that are limited to Class 2 levels are permitted to be marked "Class 2." Luminaires intended for use only with a Class 2 power unit are marked "Class 2 only.""

So you would also need the luminaires, transformer and the lamps to be Class 2 rated in order to say you are going to follow NEC 725 wiring methods. Except for some cheap units, most Toroidal landscape transformers are 300W because of NEC 411 25A current limit per circuit at 12V.

Column 5 of 300.5 mentions UF or in Other identified Cable or Raceway at not more than 30V. That seems to cover a lot of territory.

Here is a great web link to read: http://www.iaei.org/magazine/?p=2290almost at the end It specifically says a major violation is the depth rule of 6? minimum for most locations.

Then you look at this link and they seem to say 0-6? is OK for LV cables? http://q-tran.squarespace.com/storage/Article%20411%20chart.pdf
 
jumper said:
Use a class 2 or 3 cable and transformer, and T300.5 does not apply. It only applies to chapter 3 wiring methods.

No minimum burial depth required for class 2 or 3 cables in 725 that I know of.
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I can't find a code that says class 2 or 3 cables don't have a minimum burial depth. I's not saying there isn't one, but I can't find it.
 
So you are saying that if you can get the circuit to fall under 725 and since there is no mention of burial depth in 725 you don't have to worry about it?

I don't see that conclusion. My understanding is you follow 300 methods unless you get a special situation in the 725. Then if 725 says you can do it differently then you can. If it doesnt say you can do it differently such as in burial depth then you stick with the general 300 depths. Otherwise if we can classified under 50v we would use the shortest chapters and not have to follow any rules since they didn't mention it in that chapter.

At least I am getting an understanding on why people are saying this now.
 
Bjenks said:
My understanding is you follow 300 methods unless you get a special situation in the 725. Then if 725 says you can do it differently then you can. If it doesnt say you can do it differently such as in burial depth then you stick with the general 300 depths. Otherwise if we can classified under 50v we would use the shortest chapters and not have to follow any rules since they didn't mention it in that chapter.
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Did you read 725.3?
725.3 Other Articles.
Circuits and equipment shall comply with the articles or sections listed in 725.3(A) through (G). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.
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300.5 is not referenced in Article 725, so it does not apply to Article 725 installations.
The fact that the voltage is under 50 volts does not automatically make it an Article 725 installation.

All of the rules in Chapters 1 through 4 apply to Chapter 7 installations unless the Chapter 7 Article says that they don't. In this case the Chapter 7 article says that only some of Article 300 applies and 300.5 is not one of the parts that apply.

Now when you get to Chapter 8, none of the rules in Chapters 1 through 7 apply unless the Chapter 8 article says that the other rules apply.
 
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Bjenks said:
. . . My understanding is you follow 300 methods unless you get a special situation in the 725. Then if 725 says you can do it differently then you can. If it doesnt say you can do it differently such as in burial depth then you stick with the general 300 depths . . .
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In recent years, I've learned that "Code silence" doesn't result in a fall back to a default use of other parts of the Code, rather, when the Code language leads one to a body of verbiage that tells one that it doesn't say anything at all about the question being asked, then, simply, there is no Code to guide the choice of answer.

Burial depth of Class 1, 2 & 3 cable in landscaping installs, and 725.3, are classic examples of the principal.
 
jumper said:
I think Class 1 cables gotta follow 300.5.

725.46 Class 1 Circuit Wiring Methods. Class 1 circuits
shall be installed in accordance with Part I of Article 300
and with the wiring methods from the appropriate articles
in Chapter 3.
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Yes.

My point is about the "Code silence".

725.46 leads to Art. 300. Following 725.3 one reads the reference to Article 300. That's not a silence.

The absence of language in 725, leading to 300, is an indeterminacy. That is, the Code says nothing, one way or the other. There may be regulation or enforcable language elsewhere, but it's not in the Code.
 
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