# Ampacity of SE and USE

#### tom baker

##### First Chief Moderator
Staff member
I know the answer but want to know why.
Table 310.104(A) lists USE as 75 deg C wet. There is no listing for SE cable
But for more than one conductor you go to Art 338.
338.10(B)(4) refers to 334 except for 334.80
SE used at the 75 deg C rating?

#### Dennis Alwon

##### Moderator
Staff member
SER is rated as se cable. There are 2 types ser and seu -- 4 wire or 3 wire...Se cable can be 75C but often is 60C. USE is a different animal altogether. Not sure what the "WHY" is you are looking for. Why is USE rated 75c Wet??? IDK

#### tom baker

##### First Chief Moderator
Staff member
OK then I need to ask where does the code say the temp of SE cable is based on 75 deg C insulation? didn't it used to be based on 60 deg?
We in Washington can't use USE or SE, but can use SER.

#### Dennis Alwon

##### Moderator
Staff member
OK then I need to ask where does the code say the temp of SE cable is based on 75 deg C insulation? didn't it used to be based on 60 deg?
We in Washington can't use USE or SE, but can use SER.

Since the ampacity of the conductors are 90C we can use the 75 C unless it is in thermal insulation. This rule has changed many times over the years.

I see your point as the code does a back door entrance on this. In 338 it states to exclude 334.80 which limits nm to 60C. That being the case we must assume that se is rated 75 especially with 90C wire. Art. 338 says to use art 334 so 334.112 states 90C

#### OTT2

##### Senior Member
The UL White Book (TYLZ) states the type of conductor insulation may be marked on the jacket. If not the temp is 75C.

"...PRODUCT MARKINGS
The Type designation of the conductors may be marked on the surface of
the cable. When used, this marking indicates that the temperature rating for
the cable corresponds to the temperature rating of the conductors. When
this marking does not appear, the temperature rating of the cable is 75?C.
Cable acceptable for installation in cable trays is so marked.
Cable may employ copper, aluminum, or copper-clad aluminum conductors.
Cable with copper-clad aluminum conductors is surface printed ??AL
printed ??AL.??..."

#### Gaffen99

##### Senior Member
Art. 338.10(4) of 2011 states that SE installed on the interior is to be rated at 60 degrees.

#### electrofelon

##### Senior Member
We in Washington can't use USE or SE, but can use SER.
Can I ask for a RCW or WAC code reference on that? Yes per WAC 296 46B 230 SE cannot be used as service entrance conductors "within a building or structure" but other than that I dont see any restrictions on USE, or SEU as a branch circuit or feeder wiring method.

#### Dennis Alwon

##### Moderator
Staff member
Can I ask for a RCW or WAC code reference on that? Yes per WAC 296 46B 230 SE cannot be used as service entrance conductors "within a building or structure" but other than that I dont see any restrictions on USE, or SEU as a branch circuit or feeder wiring method.

Se cable may be used as service conductors within a building.

#### electrofelon

##### Senior Member
Se cable may be used as service conductors within a building.
Yes per NEC. I was responding to Tom Baker's comment about use and se not allowed in Washington. (RCW = revised code of washington, WAC = washington administrative code)

#### HackElectric

##### Senior Member
Art. 338.10(4) of 2011 states that SE installed on the interior is to be rated at 60 degrees.
My code book must be broken.

#### GoldDigger

##### Moderator
Staff member
Art. 338.10(4) of 2011 states that SE installed on the interior is to be rated at 60 degrees.
In [2011] the actual wording in 338.10(B)(4)(a) (emphasis mine) is:

(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334, excluding 334.80.
Where installed in thermal insulation, the ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor.
Note also that the SE designation does not by itself specify a temperature rating, instead the temperature rating of the insulation of the conductors inside it must be used.
Informational Note No. 1: See 310.15(A)(3) for temperature limitation of conductors.

Last edited:

#### crtemp

##### Senior Member
Can I ask for a RCW or WAC code reference on that? Yes per WAC 296 46B 230 SE cannot be used as service entrance conductors "within a building or structure" but other than that I dont see any restrictions on USE, or SEU as a branch circuit or feeder wiring method.
I use SEU all the time for electric furnaces. Doesn't seem to be an issue and I'm in Washington

#### tom baker

##### First Chief Moderator
Staff member
Can I ask for a RCW or WAC code reference on that? Yes per WAC 296 46B 230 SE cannot be used as service entrance conductors "within a building or structure" but other than that I dont see any restrictions on USE, or SEU as a branch circuit or feeder wiring method.
Yes you are correct, we can't use SE for SE uses. But it can be used for non SE use