We are building a multi family dwelling. I am feeding the individual dwelling units with SE cable. I sized the SE cable per the table in 310.15(B)(6). The panelboards are fused at 100 amps, we pulled an SE cable with (3) #1 aluminum and (1) #4 aluminum which the table says I can use for 110 amps. The feeder, as definied in 310.15(6), is "the feeder between the main disconnect and the panelboard" located in the individual unit. The inspector is telling me that I cannot use this table for this application. He is saying that I have to comply with the rules stated in section 334.12 which limit type NM cable to the 60 degree column in 310.16. I also ran this by his supervisor who replied that this table was only "applicable for single phase feeders on a 3 phase 120/208 service." He lost me there...why would I put single phase feeders on a three phase service? When the inspector made this call we had already completed 4 out of 5 floors, getting cover inspections the whole way. Thoughts?
Table 310.15(B)(6)?
- Thread starter vanvan
- Start date
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So the service is 120/240V 1? 3W? If so, should be compliant.
Actually it is very common to have individual units of a multifamily dwelling powered 120/208V 1? 3W from a 208/120V 3? 4W service.
BTW its 310.15(B)(7) in the 2011 NEC.
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- Location
- Connecticut
- Occupation
- Engineer
It appears you have it right to me.
I don't know why the first inspector is quoting you Article 334 (NM) if you are use SE Cable (Article 338.)
His supervisor who said that Table 310.15(B)(6) only applies to single phase feeders on a 208/120V, 3ph service has it backwards. T310.15(B)(6) applies ONLY to 120/240V services, NOT to single phase feeders from a 208/120V, 3ph service.
In addition, SE is one of the conductor types specifically listed in Table 310.15(B)(16).
I don't know why the first inspector is quoting you Article 334 (NM) if you are use SE Cable (Article 338.)
His supervisor who said that Table 310.15(B)(6) only applies to single phase feeders on a 208/120V, 3ph service has it backwards. T310.15(B)(6) applies ONLY to 120/240V services, NOT to single phase feeders from a 208/120V, 3ph service.
In addition, SE is one of the conductor types specifically listed in Table 310.15(B)(16).
Umm... Table 310.15(B)(7) or (6) depending on code cycle???
It's been discussed here numerous times since the '05 Code changed the wording in 338.10 to include a reference to 334.80.
The wording was changed a bit in later Codes, but the controversy remains as to which Section trumps the other, the 334.80 60? rating or 310.16(B)(6).,
I think a majority of the folks agree with your assessment but a case can be made that the SE has a 85 amp rating.
After all the ranting and raving it is going to boil down as to how your AHJ decides.
I would make sure to discuss it with your highest ranking Code official, but you may find that is there ruling base on their interpretation of the NEC.
You profile indicates you are in WA and I believe their State Code addresses it. There are a number of WA folks who post here so hopefully you will see more replies specific to that State.
The wording was changed a bit in later Codes, but the controversy remains as to which Section trumps the other, the 334.80 60? rating or 310.16(B)(6).,
I think a majority of the folks agree with your assessment but a case can be made that the SE has a 85 amp rating.
After all the ranting and raving it is going to boil down as to how your AHJ decides.
I would make sure to discuss it with your highest ranking Code official, but you may find that is there ruling base on their interpretation of the NEC.
You profile indicates you are in WA and I believe their State Code addresses it. There are a number of WA folks who post here so hopefully you will see more replies specific to that State.
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
That is what I would look at before tearing anything out. If you can reduce needed feeder size by having lower load calculation it is possibly an easy way out.
Edit removed comment - I commented on something I misread in OP.
Sorry for delayed response - yes we have calculated loads for our units. 4 diff types, 85 for two smallest and then 95 & 97 for the two larger. No solution from inspector yet, but am I correct in stating that we are debating about the outer jacket of our cable? We ran MC on lower levels and switched to SE on upper wood framed units. Both cables have same wire in them- XHHW-2. So with MC I can use 75 degree column at 100 amps (alum) but with SE I am limited to 85? Seems odd since both have 90 degree rated insulation. This being regardless of using table 310.15 b 6 (we are still on '08 cycle here) which gave us the 110. Oh one last thing the inspector did say that we could not use this table because we are 120/208 vs the 120/240. He based that on us being 120 degrees out vs 180 and more load on neutral. We did state that the neutral is sized 100% with no reductions.
Again thanks for all your input! Sorry if this choppy, typing on my phone.
Again thanks for all your input! Sorry if this choppy, typing on my phone.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The first thing that disqualifies use of 310.15(B)(6) is the fact that it is not a 120/240 system. The neutral of a wye system only carrying current from two of the three phases carries about the same current as the two phase conductors when they are balanced, making the neutral a current carrying conductor for the purposes of determining heat produced within conductors in a raceway or cable. I can't say this is the reason it is not allowed to use the table for 120/208 systems, but certainly would not surprise me if it is a major contributing reason as to why, or is it wye?:lol:
FWIW, 2011 NEC 338.10 excluded 334.80 from the installation requirement, then added where installed in thermal insulation one must use 60?C column ampacity. Perhaps you can convince your AHJ for a deviation to 2011 Code, that is as long as your feeders aren't in thermal insulation. Would make a difference of 85A rated at 60?C to 100A rated at 75?C.
@kwired - do agree about the table exclusion, it is kind of a white elephant in room, where orig inspector didn't even mention it at all as being a problem, but now that we are escalating a bit it has come up.
@smart$ - we will def look into this argument as our best recourse. We always say we are not building for the future when sizing our systems etc, but now gonna make the argument that we built for future code (at least here in WA)- ha! We'll see how it goes. Bottom line I think is that we do have a safe installation that is code compliant (at least for '11). I can't imagine the impact removing this installation at this point would be.
@smart$ - we will def look into this argument as our best recourse. We always say we are not building for the future when sizing our systems etc, but now gonna make the argument that we built for future code (at least here in WA)- ha! We'll see how it goes. Bottom line I think is that we do have a safe installation that is code compliant (at least for '11). I can't imagine the impact removing this installation at this point would be.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Worst case, if load calculation is low enough, just put in lower ampere feeder breakers.
mark32
Senior Member
- Location
- Currently in NJ
Hold on, I don't see what the issue is. Smarter people than I have already made their comments which makes me think I'm wrong but hear me out. According to 310.15(b)(6) one can use aluminum #2 for a 100a install in this multi-family dwelling. The article even states type SE so what's this guy's problem with it being fused at 100amps? (I'm taking this from the '05 code)
Two items of concern:
310.15(B)(6) references 120/240 v services and feeders. His install is 208Y/120.
Secondly, as referenced in earlier posts, some jurisdictions consider 338.10 to limit SE to it's 60 deg rating over the table.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
But this rule only applies to 120/240 volt three wire feeds. OP has 120/208 volts. This means 310.16 applies. 2005 did not have any rules stating to use type SE cable at 60 deg ratings. 2008, required to treat it like NM cable for interior installations effectively making it a 60 degree cable, 2011, now only says you need to treat it as 60 degree cable where installed in thermal insulation.
Text from 2005 NEC:
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
That is the reason (per 2014 ROPs); there are three CCCs, not two. If this makes sense to you would you mind explaining this to the rest of us for which this makes no sense?
- Location
- Massachusetts
That is the reason (per 2014 ROPs); there are three CCCs, not two. If this makes sense to you would you mind explaining this to the rest of us for which this makes no sense?
When you use just two hots and one neutral from a wye system the neutral carries more than the imbalance due to the phases being 120 degrees apart.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Sounds like you need to decrease the load.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
No, what I mean is that three CCCs require 0% consideration for 99.9% of the code, but somehow 310.15(B)(7) will catch a building on fire with more than two.
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