URD to detched garage

Status
Not open for further replies.
M

moresi

Member
Have to run 100 amp service to a detached garage / second floor apartment. Have conduit run from existing home into concrete wall (garage built into hillside) where it will stub directly into backside of panel. Same situation at house where a large pullbox is mounted in basement and conduit stubs from foundation into back of it. Would like to use URD as the conductors as I can get a great deal on a 500' spool of #2 AL URD 4 conductor. I know prior to '08 uses not permitted for URD / USE was less restrictive (338.12) but what are thoughts on having it supply a panel on the backside of a foundation wall and it being used as the means to service this garage?
 
mdshunk said:
It's normally also dual-marked as something like XHHW or RHHW, if that's what you're concerned about.
Click to expand...

Yeah, most of it is dual rated, but some isn't. You have to be careful. I have seen the stuff that is only single rated as USE.
 
moresi said:
Have to run 100 amp service to a detached garage / second floor apartment. Have conduit run from existing home..........I can get a great deal on a 500' spool of #2 AL URD 4 conductor.
Click to expand...

Did you mean to say a 90 amp feeder?
 
I should clarify. The wire is rated XHHW-2 which allows me the 100 amps but I am concerned as to if I am violating 338.12 B with using it to supply a panel that is located on the interior of the foundation wall. Although it is dual rated we still refer to it as URD and I do not want to have a conflict with the inspector. Am I to assume that the dual rated nature of it will make it o.k. to use? Now I need to do a calc. to ensure the wire is suitable for the imposed load.
 
None of what they sell in this area is dual rated. If it is in fact dual rated, then you can use is as you plan. There was no real change in the rules between 2005 and 2008 as the 08 change was only made because many installers do not look at the rules in the White Book.
 
jwelectric said:
Sorry but #2 aluminim is still limited to 90 amps no matter which insulation is on it.
Click to expand...
I agree many people use table 310.15(B)(6) for feeders when installing residential jobs without reading section 310.15(B) (6). for the restrictions. Also some people try to apply this section for other than residential.
 
jwelectric said:
moresi said:
I should clarify. The wire is rated XHHW-2 which allows me the 100 amps.
Click to expand...
Sorry but #2 aluminim is still limited to 90 amps no matter which insulation is on it.
Click to expand...
Moresi is correct that XHHW-2 is rated for 100a - but only in the 90? column of Table 310.16.

Mike is correct that you can't use the 100a rating - unless you have all 90?-rated terminations.
 
LarryFine said:
Moresi is correct that XHHW-2 is rated for 100a - but only in the 90? column of Table 310.16.

Mike is correct that you can't use the 100a rating - unless you have all 90?-rated terminations.
Click to expand...

Where in the code book does it state that a wire rated for 90 degress is limited to 70 degree ampacity if connected to a termination rated at 70 degree. Do you just consider this common sense?
 
Twoskinsoneman said:
Where in the code book does it state that a wire rated for 90 degress is limited to 70 degree ampacity if connected to a termination rated at 70 degree. Do you just consider this common sense?
Click to expand...
Take a look at 110.14
 
don_resqcapt19 said:
Take a look at 110.14
Click to expand...

Thanks

110.14(C)

(C) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.
 
# 2 conductor

# 2 conductor

Don't have my code book handy but I think #2 AL is approved for 100 amp residential service. 100 amp SEU is 2-2-4 Al.
 
iam14sure said:
Don't have my code book handy but I think #2 AL is approved for 100 amp residential service. 100 amp SEU is 2-2-4 Al.
Click to expand...
It is for a dwelling if it carries the full load of the service. T 310.15(B)(6) does not come into play here. 90 amps.
 
iam14sure said:
Don't have my code book handy . . .
Click to expand...
Since you don't have your Code book:

310.15(B)(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

Table 310.15(B)(6) permits 2 AWG Al to be used for a 100 ampere service if it meets the above requirements. This installation does not meet the requirements. :)
 
Status
Not open for further replies.
Top