New heater wiring 55amps

[NickNt]

New Air handler with heater. Minimum ampacity is 55amps, running amps is 40amps per the nameplate
Some are saying 6 gauge romex is good for 50 amps, the but tables i'm finding are saying it's good for 55amps
Can anyone give me some clarification? Just want to purchase right wire and pass inspection.

Thank you.

 

[augie47]

#6 NM is god for 55 amps.

 

[Mr. Serious]

If they would ever change the unit out to one with more than 55 MCA, then it would be in violation. Not your problem right now, unless the change happens before the final inspection. Some units have a MCA between 55 and 60 amps. There's more discussion on this other thread: 10kw heater wire gauge?

 

[infinity]

As stated in the 60° C column of the NEC ampacity table #6 is a 55 amp conductor. Since you're using NM cable you're stuck with the 60° C ampacity. Switch to MC (75° C) and your cable is rated for 65 amps.

 

[letgomywago]

As stated in the 60° C column of the NEC ampacity table #6 is a 55 amp conductor. Since you're using NM cable you're stuck with the 60° C ampacity. Switch to MC (75° C) and your cable is rated for 65 amps.

Or SEU which I like using in these situations. All the same install as romex

 

[Mr. Serious]

Or SEU which I like using in these situations. All the same install as romex

SEU and SER fall under article 338, right? The article says "Types SE and USE." For some reason I thought they were also subject to the same 60-degree limitation, but I'm looking at 338.10 (B) (4) (a) (1) in the 2020 NEC now. It specifically says they're NOT subject to the 334.80 temperature limitation.

 

[infinity]

SEU and SER fall under article 338, right? The article says "Types SE and USE." For some reason I thought they were also subject to the same 60-degree limitation, but I'm looking at 338.10 (B) (4) (a) (1) in the 2020 NEC now. It specifically says they're NOT subject to the 334.80 temperature limitation.

The NEC has changed the requirements for SE cables several times over the past 4 or 5 code cycles. The ampacity may be based on 60° C if you go back a few cycles.

 

[Mr. Serious]

Would you happen to know whether the 2017 code requires type SEU to be limited to the 60° ampacity rating? I'm about to do an installation that I think will be subject to 2017 code, but I only have 2014 and 2020 code books.
It probably doesn't matter, since I don't think the inspectors in the jurisdictions I work in ever enforce 334.80 anyway, but I like to do things to code.

 

[augie47]

2017 allows 75° for SE Cable

 

[Tulsa Electrician]

Would you happen to know whether the 2017 code requires type SEU to be limited to the 60° ampacity rating? I'm about to do an installation that I think will be subject to 2017 code, but I only have 2014 and 2020 code books.
It probably doesn't matter, since I don't think the inspectors in the jurisdictions I work in ever enforce 334.80 anyway, but I like to do things to code.

From 2017 NEC