flexible cord ampacities

[rcampbell]

not a big deal... im gonna give in and change the cord. but for future reference, i gotta know. 38.7 A appliance fed from a 50A, 208V, single phase ckt... used 6awg as i was out of 8's. fed it from recep and i made a cord/plug assemnly with 8/3 soow. inspector is questioning this since art. 400 rates 8awg soow at 40 A. he is saying that the cord is not rated to handle the 38.7 X 125%. the unit itself says to supply it with #8awg conductors. what am i missing? this inspector is tough, but reasonable, and i enjoy having these conversations with him, so any insight would be appreciated...

 

[xformer]

i would say that the cord doesn't have to be rated at 125%... only the branch circuit conductors have to be rated that. the branch circuit conductors end at the receptacle.

 

[iwire]

Why is 125% being brought into it?

What is the appliance, what does the nameplate say?

 

[Little Bill]

not a big deal... im gonna give in and change the cord. but for future reference, i gotta know. 38.7 A appliance fed from a 50A, 208V, single phase ckt... used 6awg as i was out of 8's. fed it from recep and i made a cord/plug assemnly with 8/3 soow. inspector is questioning this since art. 400 rates 8awg soow at 40 A. he is saying that the cord is not rated to handle the 38.7 X 125%. the unit itself says to supply it with #8awg conductors. what am i missing? this inspector is tough, but reasonable, and i enjoy having these conversations with him, so any insight would be appreciated...

I don't know if the 2008 Table 400.5(A) is different than the 2005 but the 2005 says for 8/3 SOOW is good for only 35A. I too wonder why the 125%?

 

[rcampbell]

little bill... the 35 A rating is from column A, which would be for 3 current carrying conductors in that cable. im working from column B since i only have 2 current carrying in the cable. xformer... thats what he brought up. he wondered if the cord is considered building wire. i wire... its a hot water machine, like an instant hot water dispensing type of thing. im thinking the 125% thing is coming up since it could be considered "continuously loaded" as per the appliance section of the nec. so my branch ckt is rated at 125% (50A), my branch wiring is good (6AWG), but my cord is only rated at 40A. the name plate says 208V, 38.7 A, 8050W, and it pretty plainly says to use 8AWG supply conductors. like i said, not a big deal to just swap the cord, but i thought this was interesting....

 

[Little Bill]

little bill... the 35 A rating is from column A, which would be for 3 current carrying conductors in that cable. im working from column B since i only have 2 current carrying in the cable. xformer... thats what he brought up. he wondered if the cord is considered building wire. i wire... its a hot water machine, like an instant hot water dispensing type of thing. im thinking the 125% thing is coming up since it could be considered "continuously loaded" as per the appliance section of the nec. so my branch ckt is rated at 125% (50A), my branch wiring is good (6AWG), but my cord is only rated at 40A. the name plate says 208V, 38.7 A, 8050W, and it pretty plainly says to use 8AWG supply conductors. like i said, not a big deal to just swap the cord, but i thought this was interesting....

I used column A because you said you used 8/3 which is 3 CCC w/gnd. You must have used 8/2 w/gnd.

 

[rcampbell]

little bill, 50% of the time i make the same mistake when ordering any hard service cord, but for some reason when youre talking mc cable or romex, the "/2" or "/3" only refers to all conductors other than the grounding conductor, but when youre talking flexible cable it refers to all of the conductors in the cable. so when i said "8-3 SOOW i meant a black, white, and green. now, every time i order a chunk of cable, i just tell them how many wires i need. not sure why they do that!

 

[Little Bill]

little bill, 50% of the time i make the same mistake when ordering any hard service cord, but for some reason when youre talking mc cable or romex, the "/2" or "/3" only refers to all conductors other than the grounding conductor, but when youre talking flexible cable it refers to all of the conductors in the cable. so when i said "8-3 SOOW i meant a black, white, and green. now, every time i order a chunk of cable, i just tell them how many wires i need. not sure why they do that!

 

[iwire]

i wire... its a hot water machine, like an instant hot water dispensing type of thing. im thinking the 125% thing is coming up since it could be considered "continuously loaded" as per the appliance section of the nec.

Insta hots are not continuous loads per the NEC.

 

[rcampbell]

yep, i wire... thats what the inpector and i came up with today and decided i was ok. a safer bet may have been to use the same installation on a 40 or 45A breaker, but a 50 was spec'd out by the customer and it is a legal install... thanks for the input!