- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
Say I have a six-plex apartment building. What is the minimum size feeder I am allowed to serve the individual dwelling units with?
Apt Minimum Size Feeder
- Thread starter George Stolz
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
This may be affected by the local code applicable to apartments or other rentals which may require a larger feed then the NEC.
Tapatalk!
Tapatalk!
pjholguin
Senior Member
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
You have not listed enough information to give a qualified answer.
PJholguin
What else do you need?
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
It should be clear I am asking strictly for an NEC answer.
pjholguin
Senior Member
You would need to do load calculations to find the minimum load for each unit. Then you can calculate needed service and feeders.
Having said that I don't believe the NEC defines the minimum service for each unit within a multi-dwelling unit greater than 2; single/duplex units are restricted to 100amp minimum. Most of the multi-dwellings I have done are 100 amps and greater depending on the load calculations.
PJHolguin
Having said that I don't believe the NEC defines the minimum service for each unit within a multi-dwelling unit greater than 2; single/duplex units are restricted to 100amp minimum. Most of the multi-dwellings I have done are 100 amps and greater depending on the load calculations.
PJHolguin
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
IMO 100 amps based on 225.39(C). I know others will say that that is only for the disconnect but I disagree
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
While I would agree with you I think we need to think about 225.39(D) "All Others. For all other installations, the feeder orbranch-circuit disconnecting means shall have a rating of not less than 60 amperes"
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
IMO, The minimum would be based on your 220 load calculations.
To meet the requirement for a dwelling unit it would have a bath and provisions for cooking so I would think 2 kitchen and 1 bath circuit. Depending on the square footage, you might even get by with a 30 amp 240/120 feeder.
To meet the requirement for a dwelling unit it would have a bath and provisions for cooking so I would think 2 kitchen and 1 bath circuit. Depending on the square footage, you might even get by with a 30 amp 240/120 feeder.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I have heard those arguments but how do we reconcile 225.39. I have asked this question many times and can never get an answer locally. The art. is about the disconnect size but what good is that if the feeder isn't sized accordingly. It seems that this section is largely ignored. The same wording is in art 230.79 for services however 230.42(B) seems to enforce the conductors also being sized accordingly- we don't have that in the feeder section
Dennis: I guess someone would have to go way back and see what the ancient ROP/ROCs had to say. The intent may well be a minimum 60 amp feeder, but we get very adamant with "the Code says..." 225.39 specifically addresses the "disconnect means"...
I feel the intent was a 60 amp feeder, but I am hard pressed to enforce that if challenged.
In Georges situation if I had six 500 sq ft dwelling units with all gas appliances and gas heat, I can't see where I can require the owner/contractor to install all 60 amp feeders. I may be wrong, and hope that I am, but thats my read.
I feel the intent was a 60 amp feeder, but I am hard pressed to enforce that if challenged.
In Georges situation if I had six 500 sq ft dwelling units with all gas appliances and gas heat, I can't see where I can require the owner/contractor to install all 60 amp feeders. I may be wrong, and hope that I am, but thats my read.
Last edited:
To qualify under Article 225, the entire feeder must be outside or originate in another building.
I assume George is talking about a feeder within the complex...
FWIW, Article 215 only mentions the word dwelling in 215.2(A)(4) which basically says a dwelling unit feeder is not required to be larger than service conductors.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
In my view a 6 unit apartment building would require a minimum of a 60 amp feeder based on 230.79 or larger if Art. 220 calcs showed otherwise.
Article 230 concerns services, not feeders.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
My only excuse is it's early here and the brain is not fully up to speed.
I was thinking of individual services. But then obviously it would then not be a multifamily dwelling, rather a one family dwelling and would need 100 amps anyway.
Better put my thinking cap on before I respond further.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
The NEC doesn't do "good." It only does "safe." So my answer is that we don't have to reconcile it. It requires a minimum disconnect size, but it would allow a smaller feeder size. I could install a 60 or 100 amp rated fused disconnect, then install 30 amp fuses and a feeder rated for only 30 amps, and not violate 225.39.
My take on the question comes in three parts:
- Article 215.2(A)(1) tells us the minimum ampacity of any feeder must be not less than the calculated load.
- I infer that there is no minimum feeder size for each apartment, as the smallest allowable size will depend on the calculated load.
- I further infer that George is toying with us. :happyyes: My guess is that he would agree with statement 2, and is looking for us to argue our way around it. :roll:
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
My only excuse is it's early here and the brain is not fully up to speed.
I was thinking of individual services. But then obviously it would then not be a multifamily dwelling, rather a one family dwelling and would need 100 amps anyway.
Better put my thinking cap on before I respond further.
Though that doesn't apply here, six service disconnecting means grouped at one location is still "one service", but the sum of all the overcurrent devices could be more than the ampacity of the service conductors that supply them as well.
I am in the group that thinks the feeder to each dwelling could be as little as load calculations permit. Two qualify as a dwelling unit it must have permanent provisions for living, sleeping, cooking, and sanitation. No matter what it will have two 1500 VA small appliance branch circuits plus 3VA per square foot of general lighting minimum. If it has no other required loads to throw in the calculation that could possibly leave you with only a 30 amp feeder being all that is required.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I don't think 225 applies here either.
Interesting that you mention 215.2(A)(4). While not relevant to this discussion, I just noticed it has a typo. It refers you to 310.15(B)(6), it should be (7). (6) was correct in the 2008 code.
Also, 215.2(A)(4) has been removed in the 2014 NEC.
I find it curious that 310.15(B)(7) refers to ALL dwelling units. That seems to imply that 100 amp would be the minimum, but I don't see anything else in the code that says there is any minimum size feeder for an individual dwelling unit in a multifamily building.
- Status