Were the Dwelling Services Feeders Found Under Sized!

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stuartdmc

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Newport Beach, Irvine, CA
NEC states,
For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, single-phase service-entrance conductors and service lateral conductors.

I conducted a site survey of a large multifamily apartment complex that was built in 1997, and found what I feel is a violation to the code.
I surveyed over 300 Apt. units, and found that every unit was being feed with a 100 amp OCPD with a #2 aluminum SEC conductor to a 100amp bus MLO sub-Panel in each unit.

Each block of apartments have a main electrical room with a multi meter section with one meter and one main circuit breaker enclosure for each apartment (housing the 100amp unit main).

Violation;
Feeds from the 100amp main breaker enclosure to the apartments Sub-panels (30-150ft away) should be per table 310.16 and not Table 310.15(B)(7). Correct?

Question;
Isn't the apartment panel a "Sub-panel" and is not considered the "Main Panel" therefore section and table 310.15 can not be used? and in fact the feeders should be a size #1 Alum.?
So, if the above statement is correct, should I suggest in my feasibility report, that the conductors or the main breaker be changes out to the correct size(s)?

Thanks for all your feed back.
 
stuartdmc said:
NEC states,
For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, single-phase service-entrance conductors and service lateral conductors.

I conducted a site survey of a large multifamily apartment complex that was built in 1997, and found what I feel is a violation to the code.
I surveyed over 300 Apt. units, and found that every unit was being feed with a 100 amp OCPD with a #2 aluminum SEC conductor to a 100amp bus MLO sub-Panel in each unit.

Each block of apartments have a main electrical room with a multi meter section with one meter and one main circuit breaker enclosure for each apartment (housing the 100amp unit main).

Violation;
Feeds from the 100amp main breaker enclosure to the apartments Sub-panels (30-150ft away) should be per table 310.16 and not Table 310.15(B)(7). Correct?

Question;
Isn't the apartment panel a "Sub-panel" and is not considered the "Main Panel" therefore section and table 310.15 can not be used? and in fact the feeders should be a size #1 Alum.?
So, if the above statement is correct, should I suggest in my feasibility report, that the conductors or the main breaker be changes out to the correct size(s)?

Thanks for all your feed back.
Click to expand...

You can use the "residential" rule for the feeders to each apartment. Notice it says multifamily dwelling. Even if this was done under, say, the 1993 NEC it was allowed then too.
One thing to note though is if this building is supplied by a 208Y/120 service with 120/208 single phase feeders to each apartment you could not use this rule. Note also that in the 2017 edition you could do this with a 208Y/120 service.
Either way in my view it is harmless.
 
texie said:
You can use the "residential" rule for the feeders to each apartment. Notice it says multifamily dwelling. Even if this was done under, say, the 1993 NEC it was allowed then too.
One thing to note though is if this building is supplied by a 208Y/120 service with 120/208 single phase feeders to each apartment you could not use this rule. Note also that in the 2017 edition you could do this with a 208Y/120 service.
Either way in my view it is harmless.
Click to expand...

Each buildings service meter sections are being feed with 120/208 3 phase 4 wire, but all apartment unit panels are 120/208v 1phase 3 wire. What do you think, Does it change thing's"
 
stuartdmc said:
Each buildings service meter sections are being feed with 120/208 3 phase 4 wire, but all apartment unit panels are 120/208v 1phase 3 wire. What do you think, Does it change thing's"
Click to expand...

IMO there is no such thing as 120/208 single phase three wire. You can have 208Y/120 service delivering only two of the three ungrounded conductors to a panel.
And you can generally use a 120/240 single phase three wire panel for that kind of 120/208 supply.

Does anyone ever see only two of three phases supplied by POCO as a service, or is it only found at sub panels?
 
GoldDigger said:
IMO there is no such thing as 120/208 single phase three wire. You can have 208Y/120 service delivering only two of the three ungrounded conductors to a panel.
And you can generally use a 120/240 single phase three wire panel for that kind of 120/208 supply.

Does anyone ever see only two of three phases supplied by POCO as a service, or is it only found at sub panels?
Click to expand...

We do this all of the time (CA)!
SCE/LADWP feeds the main service of multifamily complexes with 120/208V 3 phase 4 wire, we turn around an alter phases A-B, B-C, C-A again and again, we serve the units with single phase 120/208Y 3 wire!

The real reason for the study, is that the complex is going through a revamping/remodeling phase, they're adding AC/heating, Washer and Dryers, Microwaves, electrical ranges, that the units did not have before. For this reason I am concerned about overloading the feeders along with the unit panels, so if I suggest the complex replace the feeders to the correct sizes then it would make seance, and to being correct what violation were found.
 
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stuartdmc said:
Each buildings service meter sections are being feed with 120/208 3 phase 4 wire, but all apartment unit panels are 120/208v 1phase 3 wire. What do you think, Does it change thing's"
Click to expand...

Then it is a problem. you cannot use the table in 310.15(B)(7 of any year. I think it always pertained to 120/240v service.
 
stuartdmc said:
We do this all of the time (CA)!
SCE/LADWP feeds the main service of multifamily complexes with 120/208V 3 phase 4 wire, we turn around an alter phases A-B, B-C, C-A again and again, we serve the units with single phase 120/208Y 3 wire!
Click to expand...
I was asking about the main service for a site, not the individual units.
 
GoldDigger said:
IMO there is no such thing as 120/208 single phase three wire. You can have 208Y/120 service delivering only two of the three ungrounded conductors to a panel.
And you can generally use a 120/240 single phase three wire panel for that kind of 120/208 supply.

Does anyone ever see only two of three phases supplied by POCO as a service, or is it only found at sub panels?
Click to expand...

We have "single phase 120/208 three wire" for residential services here in central ny. It's not common but I have seen it a few times, only in cities. One time I didn't even know, and got a call from the utility saying I needed to go back and put a fifth jaw in for the meter....
 
GoldDigger said:
Does anyone ever see only two of three phases supplied by POCO as a service, or is it only found at sub panels?
Click to expand...

Yes, in areas of Boston and areas of some of the cities around it. The POCO ran three phase circuits underground and tapped off them with single phase 208/120 services to homes and other small services. In those areas we must use a five jaw meter socket for proper measurement.
 
iwire said:
Yes, in areas of Boston and areas of some of the cities around it. The POCO ran three phase circuits underground and tapped off them with single phase 208/120 services to homes and other small services. In those areas we must use a five jaw meter socket for proper measurement.
Click to expand...
That answers both of my questions. I just have a hard time calling that single phase since you have two out of three!

Now two wires from a three phase delta would indeed give you a single phase. Just not two voltages.
 
iwire said:
Yes, in areas of Boston and areas of some of the cities around it. The POCO ran three phase circuits underground and tapped off them with single phase 208/120 services to homes and other small services. In those areas we must use a five jaw meter socket for proper measurement.
Click to expand...

One of the two I came across didn't appear to be "planned" by the POCO. It looks like they got lazy and stole two phases from a three phase bank feeding some commercial stuff to run down an alley to feed a dozen houses. That is the one I didnt know about before hand. Now that I think about it, I fed that (100 amp service) with #2 Al...oops, the place has probably burnt to the ground by now :(
 
GoldDigger said:
IMO there is no such thing as 120/208 single phase three wire. You can have 208Y/120 service delivering only two of the three ungrounded conductors to a panel.
And you can generally use a 120/240 single phase three wire panel for that kind of 120/208 supply.

Does anyone ever see only two of three phases supplied by POCO as a service, or is it only found at sub panels?
Click to expand...
Rarely seen it but when I have it was a case of more then one customer supplied by a three phase source.
 
stuartdmc said:
Very good point!
Even though it's a single or multifamily unit? the 120/240v over rules? Maybe maybe not?
Click to expand...
The rule applies to a service or feeder conductor supplying an individual dwelling unit. This can be feeders coming from a meter center to each unit, a service disconnect on exterior of building with a feeder to a main distribution panel in a single dwelling unit, or other situations where the circuit in question is supplying all of the load of an individual dwelling unit. One condition in the past was it needed to be 120/240 volts nominal single phase, but as someone else has mentioned this will be allowed on 120/208 circuits in 2017 - but still the supply for an individual dwelling unit. I'd have to look to know for certain but I think that it is also limited to 400 amps maximum. I do know there is an upper limit.

What to do with the existing installation - simply mention at the time of construction this wasn't allowed, but starting with 2017 NEC it will be allowed.

If you wait until 2017 is in effect it is sort of pointless to say the original install was not compliant, but the new replacement is the same thing because it is now allowed:huh:
 
In commercial work AHJs will often let you use a smaller wire size. Ask the AHJ - they are the boss-not the NEC. Also what does you remodeled load calc show?
 
mlnk said:
In commercial work AHJs will often let you use a smaller wire size. Ask the AHJ - they are the boss-not the NEC. Also what does you remodeled load calc show?
Click to expand...

The AHJ does not make code. The code is the code. However the AHJ can interpret the code. I would not see how the justification to allow a reduction in Commercial would be a legitimate interpretation. Commercial it is expected that everything is on when in operation and for long and continuous use. No so in Residential.
 
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