Does NEC require new service calc include an allowance for growth?

grasfulls

Senior Member
I cannot find the requirement. I just had a city engineer mandate it with the words "It is in the NEC". I thought I read someplace it is a good idea, but that is not a requirement. I forget almost everything I read. I searched the NEC for "growth" - no words found, "allowance" several times but never relative, "service size" one time....then I thought, someone in here knows the answer.
 
Last edited:

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
This will get you close but it's not enforceable to require additional room for growth.

90.1 Purpose.
(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from
hazards arising from the use of electricity. This Code is not intended as a design specification or an instruction manual
for untrained persons.
(B) Adequacy. This Code contains provisions that are considered necessary for safety. Compliance therewith and
proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.
Informational Note: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for future increases in the use of
electricity.
 

grasfulls

Senior Member
400 amps to 600 amps

400 amps to 600 amps

This will get you close but it's not enforceable to require additional room for growth.
So, let's say the client wants to allow for growth but not make a jump from 400 to 600 amps. Is there a way to provide an electrical service rated at come value in-between? Like maybe a service drop to a CT enclosure for a meter then a gutter feeding one 100 amp panel with distribution and one 400 amp panel with two ea 200 amp disconnects = 500 amp service? Or do all service disconnect handles need to be together to comply with the 6-handle rule? oh yeah...i see that at 225.33, it should be ok!!
(A) General. The disconnecting means for each supply
permitted by 225.30 shall consist of not more than six
switches or six circuit breakers mounted in a single enclosure,
in a group of separate enclosures, or in or on a switchboard
or switchgear. There shall be no more than six disconnects
per supply grouped in any one location.
 

grasfulls

Senior Member
225.30

225.30

So, let's say the client wants to allow for growth but not make a jump from 400 to 600 amps. Is there a way to provide an electrical service rated at come value in-between? Like maybe a service drop to a CT enclosure for a meter then a gutter feeding one 100 amp panel with distribution and one 400 amp panel with two ea 200 amp disconnects = 500 amp service? Or do all service disconnect handles need to be together to comply with the 6-handle rule? oh yeah...i see that at 225.33, it should be ok!!
NO, that does not work, those are off of the load side of a service disconnect. Is there not a rule on one set of service entrance conductors feeding multiple disconnects (not to exceed 6) on a single family dwelling?
 

grasfulls

Senior Member
230.71

230.71

NO, that does not work, those are off of the load side of a service disconnect. Is there not a rule on one set of service entrance conductors feeding multiple disconnects (not to exceed 6) on a single family dwelling?
This one may do it:
230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each
service permitted by 230.2, or for each set of serviceentrance
conductors permitted by 230.40, Exception No. 1,
3, 4, or 5, shall consist of not more than six switches or sets
of circuit breakers, or a combination of not more than six
switches and sets of circuit breakers, mounted in a single
enclosure, in a group of separate enclosures, or in or on a
switchboard or in switchgear. There shall be not more than
six sets of disconnects per service grouped in any one location.
 

Carultch

Senior Member
Location
Massachusetts
I cannot find the requirement. I just had a city engineer mandate it with the words "It is in the NEC". I thought I read someplace it is a good idea, but that is not a requirement. I forget almost everything I read. I searched the NEC for "growth" - no words found, "allowance" several times but never relative, "service size" one time....then I thought, someone in here knows the answer.
The NEC does not require future proofing your design for growth. It can only establish whether the installation today is compliant or not. Because there is no objective way to know just how much growth to expect.
 

Carultch

Senior Member
Location
Massachusetts
Yes it is 220.87. ;) a load Calc will give you about 2.5 times your actual usage in many cases, so then a year later you use 220.87 with the utility data and you magically have a ton of extra capacity :)
So in that case, build a customer-owned interval recording meter in to the infrastructure, so that you have your own access to this data, and don't have to ask the utility for it (in the event that they don't have it or don't release it).
 
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