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What gauge for neutral and ground in quadruplex URD cable?

What gauge for neutral and ground in quadruplex URD cable?

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  #1  
Old 06-04-19, 03:09 PM
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What gauge for neutral and ground in quadruplex URD cable?

Here's my situation and what I've figured out with my own research.
I'm building a guest house with a 100amp circuit and have a 190ft run from the service turnoff (meter). This measurement accounts for the wire not just the physical distance.
i found out I need 4 cables. Two hot, 1 neutral, and 1 true ground. I'm going with a quadruplex URD cable that I will bury 24" deep.
I planned on going with 2
/0 aluminum wire. I chose this based on a voltage calculator telling me that it will give me about 4% voltage drop which is under the required 5% max.

MAIN DILEMMA:
I'm having a hard time finding quadruplex where all 4 are the same guage. Making me think that maybe the true ground could be a smaller gauge? I found one that is 2/0, 2/0, 2/0, 1. Where it says in the tech specs that the Neutral Gauge is 1AWG. I assumed the neutral needed to be able to carry the same amount as the hot wires but it seems I could be wrong.

Any help here would be greatly appreciated. Thanks!

-Elliot
​​
 
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  #2  
Old 06-04-19, 05:34 PM
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URD is to be used only outside and cannot enter the structure. If this wire is going to enter the structure you need to use Mobile Home Feeder (MHF) the sizes will be either 2/0-2/0-1-4 or 2/0-2/0-2/0-1 and come in the correct marked colors.
MHF - https://www.mysouthwire.com/medias/s...4083567646.pdf

URD quadruplex has 3 phase conductors and 1 neutral, 3 black and 1 yellow striped. In your type of use the #1 neutral becomes the ground and needs to be marked green and one of the #2's needs to be marked white at the terminations to be used as a ground and neutral.
 
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Old 06-04-19, 07:07 PM
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MHF cables identify the conductor sizes as H-H-N-G.
 

Last edited by pcboss; 06-07-19 at 03:17 AM.
  #4  
Old 06-04-19, 07:42 PM
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URD Quadruplex is H-H-H-N, there is no identified ground. MHF is identified as H-H-N-G.
 
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Old 06-05-19, 05:08 AM
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Making me think that maybe the true ground could be a smaller gauge? I found one that is 2/0, 2/0, 2/0, 1. Where it says in the tech specs that the Neutral Gauge is 1AWG. I assumed the neutral needed to be able to carry the same amount as the hot wires but it seems I could be wrong.
For a feeder the equipment ground is allowed to be much smaller than the hots, and in residential work the neutral can almost always be a size or two smaller than the hots. There are tables and calculations for both, but assuming this is a normal residential service you can just use a standard size from the factory like 00-00-1-4.
 
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Old 06-06-19, 05:59 PM
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URD Quadruplex is H-H-H-N, there is no identified ground. MHF is identified as H-H-N-G.

Correct! All three phase conductors are the same size and the 4th conductor is a reduced neutral generally black with a yellow stripe. None of the conductors has green markings for a ground. 4-wire URD is a utility grade product and typically is used between a pad mount transformer or utility pole and a 3-phase 4-wire meter socket. URD cannot be used inside any structure as it lacks the required fire ratings. pattenp is also correct that you should be using Mobile Home Feeder (MHF).
 
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