SER Cable Ratings

[Dennis Alwon]

Thank you Pete and that basically says what I have been saying is that there ought to be a ruling against the use of SE in this situation but as it stands now the NFPA is walking around this issue as it appears they missed it.

 

[augie47]

Thank you Pete and that basically says what I have been saying is that there ought to be a ruling against the use of SE in this situation but as it stands now the NFPA is walking around this issue as it appears they missed it.

I',m proud that you know what it says. I've readit 4 times and I'm still not clear :smile:
Same guy must have written the original change

 

[cpal]

Thank you Pete and that basically says what I have been saying is that there ought to be a ruling against the use of SE in this situation but as it stands now the NFPA is walking around this issue as it appears they missed it.

Dennis neither CMP 6 nor 7 can solve the problem with out the input Paul mentioned in his response to Peter.

This thread has been pretty god in regard to raising opinions, but opinions are silent withot proposlas and comments.

 

[Dennis Alwon]

This thread has been pretty god in regard to raising opinions, but opinions are silent withot proposlas and comments.

I agree and I am one of those who wants to make proposals but never seems to follow thru.

Here is the thread I started on this issue back in March 08

 

[M. D.]

The only opinion that is silent is the one that does not get posted,.. A whole lotta people read this site,..I'd venture that there has been more than one addition\change as a result of the sharing of opinions ..

 

[scwirenut]

If it is installed in the interior of a building, one cannot use Table 310.15(B)(6) for ampacity values, one has to use Table 310.16, 60C column for the final value.

If Im reading this correct, then I must use 300al SER for my 200amp feeder? I dont believe they make SER over 250al so are we forced to use 4/0 copper? I am looking at table 310.16 at the 60 degree C column without regard to specified insulation types. I believe the same column we use for NM

 

[augie47]

FYI, ALCAN is one manufacturer that makes it. It is currently being required in some areas of TN for 200 amp interior feeders and is locally stocked. That said, I undestand the requirement is debatable.
View attachment 3524

 

[madpenguin]

I'm with Pierre and cpal (and the OP's inspector).... This seems to come up rather frequently and probably won't stop til 2011......

I don't see how you can void 338.10(B)(4)(A) and 334.80...... As my final justification, the very first sentence of 310.15(B) clearly differentiates between Tables 310.16-310.19 ", and" Tables 310.20-310.21 as modified by...... The comma and the and being the operative separation. Unless you fall under Tables 310.20 or 310.21 then I don't see how you can modify anything by (B)(1) thru (B)(6).

If that's not the case, then why doesn't 310.15(B) read:
....Table 310.16 through 310.21 as modified by (B)(1) through (B)(6).....???

Interior SE.... 60 Celsius.... 310.16...... Unless you meet 310.20 or 21 then fine. Use 310.15(B)(6)..... But then it wouldn't be interior SE anymore so the point is moot.

 

[scwirenut]

my local has decided that if we use a molded case main breaker outside we can use 4/0 because the feeder serves the entire load, however, if we install a combo, and feed the HVAC out of the combo, we must use 300mcm because the feeder dosnt serve the entire load. kinda stupid i think.

 

[augie47]

my local has decided that if we use a molded case main breaker outside we can use 4/0 because the feeder serves the entire load, however, if we install a combo, and feed the HVAC out of the combo, we must use 300mcm because the feeder dosnt serve the entire load. kinda stupid i think.

it's handled that way in some areas around here also. you reduce the load so you increase the wire size . The entire subject needs CMP work badly and so far the 2011 Draft doesn't show much improvement IMHO.

 

[hillbilly]

I see it the other way around...the specific rule is 310.15(B)(6) and it modifies other rules. I don't see a need for an exception to use SE or NM as the main power feeder using 310.15(B)(6). Note that 310.15(B)(6) does not change the ampacity of the cables, it only permits them to be used for specific sized services. This works just like 240.4(B) which does not change the ampacity of the conductor...it only permits an oversized OCPD.

As far as the substantiation, that was from the submitter, a representative of a cable manufacturer, not from the CMP. There was no technical substantiation for this change.

I agree with don.

steve

 

[Dennis Alwon]

Originally Posted by don_resqcapt19
I don't see a need for an exception to use SE or NM as the main power feeder using 310.15(B)(6). Note that 310.15(B)(6) does not change the ampacity of the cables, it only permits them to be used for specific sized services.

I almost agree with Don. :grin: The use of NM is not mentioned in T.310.15(B)(6) so it cannot be used as the main power feeder oe for service entrance with that Table.

 

[Smart $]

it's handled that way in some areas around here also. you reduce the load so you increase the wire size . The entire subject needs CMP work badly and so far the 2011 Draft doesn't show much improvement IMHO.

I am sure you are aware of it, but FWIW to others, there were four 2011 proposals that were accepted in principle and reflected in the 2011 Draft, that 338.10(B)(4)(a) add text to make it read...

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.

However, also appended to that text in the draft is...

Where installed in thermal insulation, the ampacity shall be
in accordance with the 60?C (140?F) conductor temperature
rating. The 90?C (194?F) rating shall be permitted to be
used for ampacity adjustment and correction purposes, provided
the final derated ampacity does not exceed that for a
60?C (140?F) rated conductor.

 

[Dennis Alwon]

I see this as a good move for the NEC but it still does not clatify the use of T. 310.15(B)(6) when the cable is run in insulation.

 

[Smart $]

I see this as a good move for the NEC but it still does not clatify the use of T. 310.15(B)(6) when the cable is run in insulation.

I believe it does because also changing(???) is 310.15(B)(6) to no longer use the phrase "main power feeder". As such, all feeders will be subject to the same conditions. Yes, a "main power feeder" larger than service conductors may be required when the feeder is interior wiring run through thermal insulation.

The question I have thereafter is if 310.15(A)(2) Exception can overide 338.10(B)(4)(a) if run through thermal insulation not more than the distance specified in the Exception...???