A 200 amp service has a meter and, per local code, a 200 amp disconnect on the outside of the building that is the service disconnect and a 200 amp overcurrent device. The interior panel is fed from the 200 amp disconnect with SER cable, which by definition, is a main power feeder. If the SER cable is encased in insulation, does the requirements of 338.10(D) apply to main power feeders?
De-rating SER cable
- Thread starter wyboy
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
IMO, yes the ser is permitted per art. 310.(15)(B)(6) but Gus and others may not agree. What code cycle are you under?
resistance
Senior Member
- Location
- WA
If the service is attached to the same structure, I agree with Dennis.
Been a long discussed situation on the Forum (and throughout our State). I think you can classify it as unresolved 
Some folks think 338.10 reducing the ampacity to the 60? rating trumps 310.15 and 215.2, others think not.
There are persuasive arguments either way so, in the end, you are at the mercy of the AHJ.
(In my area it is enforced differently by various inspectors in a 100 mile radius)
Edited:
Your profile says you are an inpsector. If, like us, have no guidance from a higher authority, I can only suggest you "search" the Forum and see the various disussions to decide what is "corret"
Some folks think 338.10 reducing the ampacity to the 60? rating trumps 310.15 and 215.2, others think not.There are persuasive arguments either way so, in the end, you are at the mercy of the AHJ.
(In my area it is enforced differently by various inspectors in a 100 mile radius)
Edited:
Your profile says you are an inpsector. If, like us, have no guidance from a higher authority, I can only suggest you "search" the Forum and see the various disussions to decide what is "corret"
Last edited:
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
When all else fails, ask your AHJ or size it to worst case scenario.
not to rehash a well discussed situation, but, for the sake of argument...and to point out the ridiculous.. assume you derate a branch circuit/feeder but not a "main power feeder"..
House 1 has a 200 amp outside disconnect (feed thru panel) with the HVAC unit fed from
the outside panel.
House 2, identical load, elected to feed the HVAC from the interior panel.
The feeder to the interior panel on House 1 carries less load that House 2 but since it's not "whole house" you must upsize it....
The entire situation is ridiculous and there are so many opinions since many read the Code differently.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Art. 338.10(B)(4) states 60C when used as a feeder. This may be true but T.310.15(B)(6) makes no mention of temp and specifically allows se cable. If you look at the table all those conductors and wire types are 75C or better but again the Table makes no mention of temp. We might infer that but IMO it is not written and there is no reason 338.10 should override this table.
resistance
Senior Member
- Location
- WA
Service Entrance Rated
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Check the abbreviations- it is there-- service entrance round. It is a 4 wire service cable used for often for sub panels.
ramsy
Roger Ruhle dba NoFixNoPay
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
Southwire makes a 90?c SER, so the 2011 NEC 338.10(B)(4) now limits SE ampacity in accordance with 60?c ratings, when in contact with thermal (building) insulation, in addition to cable bundling, 334 section II.
I agree with Augie that many contractors & AHJ's relying on NFPA tables may have overheated cable, devices, enclosures, PVC & liquidtight raceway for years this way.
338.10(B)(4)(Note 1) refers to other codes for wire-insulation temperature, engineered or table-derating methods, and 110.14(C). The NFPA handbook's commentary on 110.14(C), describes how this issue results in overheated equipment.Augie47 said:
If UL tells us, "no other table overrides 310.16 where conductor-termination temp. is concerned," then equipment must be listed for 310.16-adjusted temperatures, regardless of other tables. Designers, installers, & inspectors that miss this rule are most likely to overheat equipment.NFPA70 handbook Tenth Edition p.68 said:
Failures and liabilities from new electrical installations remain prolific enough to sustain cottage industries for thermal-camera imaging, expert-fire investigators, and litigators for bad-faith insurers denying claims.
The industry practice of avoiding engineering supervision, internationally-recognized formulas (IEEE), and standards (ICC), has relied instead on NFPA ? ampacity tables, factoring multiple adjustments, without temperature hierarchy, and derating schemes that treat inductive & resistive loads equally.
When equipment is overheated this way, NFPA ? ampacity tables for idiots makes everyone equal, since its difficult to distinguish licensed operator from their unskilled employee, or exploited laborer from unlicensed handyperson, side worker, or trunk slammer. Inspectors should approach everyone indoctrinated by the NEC with equal caution & skepticism.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I am fully aware of ser being rated 90C however when used as a feeder in insulation -- again depending on which code- it can only be used at 60C. My point was that T. 310.15(B)(6) does not use temp as a requirement but we may infer that from the table.
I agree there is no right or wrong answer here and it will be an ahj call. The Table needs a note to art 338.10 IMO if that is it's intent.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
This has been posted before but I hope this helps :
Aluminum SER cable specs
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet273
They also make it in copper but that's only for the wealthy contractors:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM8
There's a note at the bottom of the spec sheet that states : Dwelling - For units, conductors shall be permitted at listed ampacities as 120/240-volt, 3-wire, single-phase services and feeders per NEC Article 310.15.
This was based on the 2008 NEC.
Aluminum SER cable specs
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet273
They also make it in copper but that's only for the wealthy contractors
:http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM8
There's a note at the bottom of the spec sheet that states : Dwelling - For units, conductors shall be permitted at listed ampacities as 120/240-volt, 3-wire, single-phase services and feeders per NEC Article 310.15.
This was based on the 2008 NEC.
OK. Ignorant Brit here again.
What's the significance of a cable being service entrance rated?
Our BS7671 gives current ratings for various configurations of conductor, cable type, cores, class of insulation, method of insulation etc.
The current carrying capacity does not change with the application.
What am I missing?
What's the significance of a cable being service entrance rated?
Our BS7671 gives current ratings for various configurations of conductor, cable type, cores, class of insulation, method of insulation etc.
The current carrying capacity does not change with the application.
What am I missing?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I am not sure but I think what makes the cable service rated is the full size ground (neutral) with 3 wires and the sunlight resistance. There may be more to it then that but I am not sure.
I don't see anywhere that requires a wire to be service rated however I see art. such as 340 which states that UF cannot be a service entrance cable. Not sure why other than the 60C rating of the cable. You notice that none of the conductors in T.310.15(B)(6) for residences are 60C rated. The cables and wires are all 75C and 90C.
I don't see anywhere that requires a wire to be service rated however I see art. such as 340 which states that UF cannot be a service entrance cable. Not sure why other than the 60C rating of the cable. You notice that none of the conductors in T.310.15(B)(6) for residences are 60C rated. The cables and wires are all 75C and 90C.
elohr46
Senior Member
- Location
- square one
the neutral(grounded conductor) can be uninsulated and serves a dual purpose, carries normal current and fault current back to the source.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
On a service conductor there is only a neutral which is grounded to the can. Once we leave the service disconnect then neutrals and ground are separated-- hence the SER-- 4 wire- 2 hots, neutral and a ground. They make ser with a full size ground so it can be used as a 3 phase with neutral service cable.
- Location
- Massachusetts
It is not service rated
It is Service entrance cable it is abbreviated as SE
There is SE-U which is SE cable in a flat construction
There is SE-R which is SE cable in a round construction
Even though it is called service entrance cable is used for many other purposes
There is also USE which is underground SE cable
It is Service entrance cable it is abbreviated as SE
There is SE-U which is SE cable in a flat construction
There is SE-R which is SE cable in a round construction
Even though it is called service entrance cable is used for many other purposes
There is also USE which is underground SE cable
- Status