Three family home service

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daveselectric

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I ma replacing the panels in a three family home. There are three meters.
The 1st floor suite has 1134 sq ft, the 2nd floor has 1008 sq ft and the 3rd floor has 246 sq ft. Each suite is fed with 100 amps. We installed a triple overhead meter base. The permit states "special notes and comments, Per 2011 NEC. With attention to Table 310.15(B)(7) sized for 300 amps." We used 4/0 aluminum for the rise abofe the meter base. In Ohio we are still using NEC 2011.

Is Table 310.15(B)(7) designed to cover the rise above the meter?
 
I believe for a multifamily you can have the riser conductors sized to the calculated load of the 3 units but if you want to have full capacity then you need to use T. 310.15(B)(16) formerly T310.16
 
daveselectric said:
I ma replacing the panels in a three family home. There are three meters.
The 1st floor suite has 1134 sq ft, the 2nd floor has 1008 sq ft and the 3rd floor has 246 sq ft. Each suite is fed with 100 amps. We installed a triple overhead meter base. The permit states "special notes and comments, Per 2011 NEC. With attention to Table 310.15(B)(7) sized for 300 amps." We used 4/0 aluminum for the rise abofe the meter base. In Ohio we are still using NEC 2011.

Is Table 310.15(B)(7) designed to cover the rise above the meter?
Click to expand...


301.15(B)(7) is only for conductors supplying an individual dwelling (read first sentence of the section)- you can not use it for conductors supplying anything but a single dwelling unit.


However the conductors in question can be sized to the load calculations. Just because you have 3 - 100 amp feeders does not mean you have a 300 amp load calculation. If you only had load calculations of say 55, 63, and 72 for each dwelling unit then the sum of those is 190 and you could run a 3/0 copper or 250 aluminum service or feeder conductor to supply these dwellings and there is also a possibility of reducing even more if there are demand factors that can still be applied to the entire service - I just did the simple route here of adding each individual feeder together. Example a range in one dwelling gets a different demand factor for the individual dwelling load calculation then all three ranges get for the entire service calculation.
 
I provided my input on a previous post based upon my experience as a breaker applications engineeo determiner as well as a DTDT csales and applications engineer for a major electrical equipment manufacturer.
Because of my knowledge of both products my marketing manager for the DTDT product line requested that I do a study of our transformer products along with a seasoned transformer design engineer to determine where there may be nuisance tripping issues. Since there are no tests avaiowed b the NEC that woukd provide thhe highest instantaneous lable regarding inrush across the pr.oduct line we used so sample data from those where information was available to establish a trend for the rest of the product line.
As stated in my previous post the higher the kva the inrush decreases, 115 and 80 deg c rise will increase inrush as well as energy efficient and K factor transformers.
Basically, there is no established values across the product line except for a few which lead to only ball park values. The safest thing to do is to use the largest PRI OCPD as allowed by the NEC to provided the highest instantaneous breaker to reduce the chance of nuisance tripping.
But I must say that I am impressed with the theorys expressed in this string of posts.
 
Last edited:
templdl said:
I provided my input on a previous post based upon my experience as a breaker applications engineeo determiner as well as a DTDT csales and applications engineer for a major electrical equipment manufacturer.
Because of my knowledge of both products my marketing manager for the DTDT product line requested that I do a study of our transformer products along with a seasoned transformer design engineer to determine where there may be nuisance tripping issues. Since there are no tests avaiowed b the NEC that woukd provide thhe highest instantaneous lable regarding inrush across the pr.oduct line we used so sample data from those where information was available to establish a trend for the rest of the product line.
As stated in my previous post the higher the kva the inrush decreases, 115 and 80 deg c rise will increase inrush as well as energy efficient and K factor transformers.
Basically, there is no established values across the product line except for a few which lead to only ball park values. The safest thing to do is to use the largest PRI OCPD as allowed by the NEC to provided the highest instantaneous breaker to reduce the chance of nuisance tripping.
But I must say that I am impressed with the theorys expressed in this string of posts.
Click to expand...
I apologize as it certainly appears as my Nexus did me in again as this response is for another subject.
 
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