210.20 Overcurrent Protection (A) Continuous and Noncontinuous Loads. Where a branch
circuit supplies continuous loads or any combination of continuous
and noncontinuous loads, the rating of the overcurrent
device shall not be less than the noncontinuous load plus
125 percent of the continuous load.
230.42 Minimum Size and Rating.
(A) General. Service-entrance conductors shall have an
ampacity of not less than the maximum load to be served.
Conductors shall be sized to carry not less than the largest of
230.42(A)(1) or (A)(2). Loads shall be determined in accordance
with Part III, IV, or V of Article 220, as applicable. Ampacity
shall be determined from 310.15. The maximum allowable
current of busways shall be that value for which the busway has
been listed or labeled.
(1) Where the service-entrance conductors supply continuous
loads or any combination of noncontinuous and
continuous loads, the minimum service-entrance conductor
size shall have an allowable ampacity not less than the
sum of the noncontinuous loads plus 125 percent of
Exception No. 1: Grounded conductors that are not connected to an
overcurrent device shall be permitted to be sized at 100 percent of the
sum of the continuous and noncontinuous load.
Exception No. 2: The sum of the noncontinuous load and the continuous
load if the service-entrance conductors terminate in an overcurrent
device where both the overcurrent device and its assembly are listed for
operation at 100 percent of their rating shall be permitted.
(2) The minimum service-entrance conductor size shall have
an ampacity not less than the maximum load to be served
after the application of any adjustment or correction
That calculated load likely has demand factors included in calculations. Actual connected load may very well be over your 1200 amp service, but is likely you seldom or never see 1130 either, presuming those calculations were done correctly.I took over a new building from the construction company. We have a 1200 amp service with a calculated load of 1130. I opened one of the service disconnects today to confirm the fuse size, I have 10 service entrance panels surrounding this 240 unit student housing building feeding various meter rooms and house panels. The panel is question, A phase has started to burn up! Probably a loose connection on the lug, beveled washer, the workmanship here in Tampa is ridiculous! I don't think the inspector even got out of his car!!
Anyway I am trying to reinforce my work ethics of not loading more then 80% or sizing up 125% of the calculated load. These are individual dwelling units, one, two and four bedroom units with full appliances, HVAC, water heaters etc...
Not really unless you need to address continuous loads as mentioned above.I have always followed the rule of not loading a circuit or main breaker more then 80%.
Is there a code article to back this up?
I actually did read the thread and I would ask you to read it again because you've missed the point. The point being that the NEC load calculations are very generous with the actual load at any given point in time being nowhere near the calculated load. If your 1200 amp service has a calculated load of 1130 amps there is nothing to discuss unless you are planning for future expansion.Read the thread!
I actually did read the thread and I would ask you to read it again because you've missed the point. The point being that the NEC load calculations are very generous with the actual load at any given point in time being nowhere near the calculated load. If your 1200 amp service has a calculated load of 1130 amps there is nothing to discuss unless you are planning for future expansion.
You're welcome. Just realize that your 80/125% factors may be good design parameters they are not the required code minimum. It's hard to argue with the contractor who installed a code compliant 1200 amp service that he did something wrong.Thank you, the damage on the lug is most likely a loose connection. When I submitted this to the electrical contractor that did the job, he asked if there were any unintended loads on this service. I have always worked a 80% rule or sized 125% of the calculated load. This would have meant a 1600 amp service. This is why I questioned if there were concrete articles in NEC. Thank you again.