Ampacity of URD

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mbrooke

mbrooke

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Hv&Lv said:
https://lmgtfy.com/?q=whats+the+amp+rating+of+URD

couldn't resist...:lol:
still not done with the Mho reverse zone...
Click to expand...

:roll::roll:














:p:p:)

The thing is Google takes me to table 310.16, but my understanding is that URD is not listed in the NEC. Using the table certainly won't hurt, but I feel the values are way to conservative for direct buried cable.

Appreciate that MHO is on the noggin.
 
G

GoldDigger

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Some URD is dual rated as a valid NEC type. If you look at the ampacity of that gauge of that cable type it should give you a starting point for the ampacity of unrated URD.
 
kwired

kwired

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I can't recall seeing any that doesn't at least have USE rating on individual conductors. can't tell you if there is types out there that are not AA8000 series alloy, seen some that are not marked at all, but those that are marked USE/RHW usually also have alloy marking on them.
 
H

Hv&Lv

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mbrooke said:
:roll::roll:














:p:p:)

The thing is Google takes me to table 310.16, but my understanding is that URD is not listed in the NEC. Using the table certainly won't hurt, but I feel the values are way to conservative for direct buried cable.

Appreciate that MHO is on the noggin.
Click to expand...

Not all Google. My link, the first one.
people ask you the ampacity of URD.
Answer: depends...
where is it going to be used?
NEC has requirements of termination temperatures, and load calculations.
It shouldn’t be used for an NEC application, generally, it isn’t listed for that purpose. If it is, it has to have an NEC designation like RHW or something like that.
Used in a POCO application, the numbers are totally different than you would see in the NEC.
Plus, there are other factors to be considered when POCO sizes wire.
Guys here may install a service with 350 copper going up a riser, only to see we will feed it with 1/0 AL.
for UG, you may install a 400 amp service, we will feed it with 4/0 AL URD wire, or in some instances, 2/0 AL.
 
mbrooke

mbrooke

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Hv&Lv said:
Not all Google. My link, the first one.
people ask you the ampacity of URD.
Answer: depends...
where is it going to be used?
NEC has requirements of termination temperatures, and load calculations.
It shouldn’t be used for an NEC application, generally, it isn’t listed for that purpose. If it is, it has to have an NEC designation like RHW or something like that.
Used in a POCO application, the numbers are totally different than you would see in the NEC.
Plus, there are other factors to be considered when POCO sizes wire.
Guys here may install a service with 350 copper going up a riser, only to see we will feed it with 1/0 AL.
for UG, you may install a 400 amp service, we will feed it with 4/0 AL URD wire, or in some instances, 2/0 AL.
Click to expand...

What are the numbers in POCO applications?

Unless URD is listed 8000 series AL, it can't be used on NEC terminations- at least thats what I've assumed.
 
mbrooke

mbrooke

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kwired said:
I can't recall seeing any that doesn't at least have USE rating on individual conductors. can't tell you if there is types out there that are not AA8000 series alloy, seen some that are not marked at all, but those that are marked USE/RHW usually also have alloy marking on them.
Click to expand...

The ones that aren't marked have my interest- I've always assumed that they can't be used under any NEC conditions.
 
PaulMmn

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romex jockey said:
Is the term 'URD' trade slang?
:dunce:
~RJ~
Click to expand...

Pretty much so: URD wire definition is “Underground Residential Distribution wire”

People who don't like typing on those itty-bitty phone 'keyboards' love to abbreviate things! When I find one of those unfathomable TLAs I usually do a quick Google search for >electrical WidgetName<

TLA-- Three Letter Acronym
 
Julius Right

Julius Right

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When I worked in an utility once, I did myself all the calculation according to Neher and McGrath. It was 30 years ago when Visual Basic 6 was a vogue. The problem was the prospective load calculation. You may take it as the transformer rating or more if you can expect an amplification.
 
mbrooke

mbrooke

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Julius Right said:
When I worked in an utility once, I did myself all the calculation according to Neher and McGrath. It was 30 years ago when Visual Basic 6 was a vogue. The problem was the prospective load calculation. You may take it as the transformer rating or more if you can expect an amplification.
Click to expand...

You mean a trafo can take an overload because it has thermal mass, but not a cable?
 
Julius Right

Julius Right

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Electrical Engineer Power Station Physical Design Retired
It seems a cable could overcome 31.8% overload in cable duct for 4 hrs.-for instance- but transformer only 5%.

See IEEE 5796/1993 Table 6 compare with IEEE 242/2001 9.5.2 Overload capacity[for cable].

I thought if one intends to replace the actual transformer with another larger and keep the secondary cable.
 
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