Ampacity 210.19(b) and 110.14(c)

[Max Headroom]

I have a 40 amp circuit supplying a 7005w load (2 oven broiler elements in a otherwise gas range) I have run two 8ga cu(ungrounded conductors) and two 10ga ( neutral and EGC) in 3/4 EMT across a rooftop 1 1/2 " above the deck. Location is Upland CA, ambient temp as near as I can figure is 88F. I want to add two 12ga cu for a range-hood circuit and would like to pull them in with my 8 and 10 ga., I'm using THHN/THWN. It never rains during the hot months and if it did the temperature would be much cooler if that matters. If I adjust for the extra 2 conductors (0.8) and correct from Table 310.15 (B)(1) starting from the 75C column to 87-95F (0.94) I get 50A X .8X.94=38.4A. The breaker is a 2P 40A federal Pacific stab-lok assuming 60 degree (it's an old panel) the nema 14-50 R is rated 75 degree. I think I'm fine but would greatly appreciate your input. I think 240.4 (b), 210.19 a1b and 110.14C1a2 confirm that? Thank you for any feedback

 

[wwhitney]

210.19(B) is for over 600V, so presumably you mean 210.19(A)(1)(b).

I'm using THHN/THWN.

Unless you are installed some very old new stock, it is surely rated THWN-2; please confirm the text on the conductors.

In which case with an ambient up to 95F, the temperature correction factor is 0.96, and the CCC adjustment factor is 0.8. That makes the conductor ampacity 42A for the #8 Cu, and 23A for the #12 Cu. So no problem protecting those at 40A and 20A, respectively.

Cheers, Wayne

 

[infinity]

Unless you are installed some very old new stock, it is surely rated THWN-2; please confirm the text on the conductors.

Not all manufacturer's rate their THHN/THWN conductors also as THWN-2. Southwire is one that doesn't in #10 AWG.

10-19 SD CU THHN-THWN-MTW-AWM UL/c(UL) BLUE 500 FT | Southwire

www.southwire.com

Application​

THHN copper conductors are primarily used in conduit and cable trays for services, feeders and branch circuits in commercial or industrial applications as specified in the National Electrical Code. Voltage for all applications is 600 volts.

• THWN- Wet locations not to exceed 75° C or dry locations not to exceed 90° C or locations not to exceed 75° C when exposed to oil

 

[LarryFine]

Right. The -2 suffix merely means that the wet rating is equal to the dry rating.

 

[Max Headroom]

210.19(B) is for over 600V, so presumably you mean 210.19(A)(1)(b).


Unless you are installed some very old new stock, it is surely rated THWN-2; please confirm the text on the conductors.

In which case with an ambient up to 95F, the temperature correction factor is 0.96, and the CCC adjustment factor is 0.8. That makes the conductor ampacity 42A for the #8 Cu, and 23A for the #12 Cu. So no problem protecting those at 40A and 20A, respectively.

Cheers, Wayne

Thank you Wayne, I will check that tomorrow and get back to the thread, that's very good information, thanks again.

 

[Max Headroom]

210.19(B) is for over 600V, so presumably you mean 210.19(A)(1)(b).


Unless you are installed some very old new stock, it is surely rated THWN-2; please confirm the text on the conductors.

In which case with an ambient up to 95F, the temperature correction factor is 0.96, and the CCC adjustment factor is 0.8. That makes the conductor ampacity 42A for the #8 Cu, and 23A for the #12 Cu. So no problem protecting those at 40A and 20A, respectively.

Cheers, Wayne

You are correct sir, 210.19 a1b thank you

 

[Max Headroom]

Right. The -2 suffix merely means that the wet rating is equal to the dry rating.

I will check for the -2 suffix tomorrow thank you.

Not all manufacturer's rate their THHN/THWN conductors also as THWN-2. Southwire is one that doesn't in #10 AWG.

10-19 SD CU THHN-THWN-MTW-AWM UL/c(UL) BLUE 500 FT | Southwire

www.southwire.com

If the THWN -2 text on the conductor is not present but only THWN then I would need to derate using the 75C column in table 310.15(b)(1) which would be 94%, 50A X .80 X .94 = 37.6A, The load is 29.19A according to the nameplate so wouldn't 210.19(A)(1)(b) apply making the installation compliant.

 

[Max Headroom]

You are correct sir, 210.19 a1b thank y

210.19(B) is for over 600V, so presumably you mean 210.19(A)(1)(b).


Unless you are installed some very old new stock, it is surely rated THWN-2; please confirm the text on the conductors.

In which case with an ambient up to 95F, the temperature correction factor is 0.96, and the CCC adjustment factor is 0.8. That makes the conductor ampacity 42A for the #8 Cu, and 23A for the #12 Cu. So no problem protecting those at 40A and 20A, respectively.

Cheers, Wayne

The text on the conductor is THWN-2, thanks all