A common mistake I see is guys using 200 amp service entrance cable for commercial buildings.
Why couldn't someone use 4/0 aluminum SE with a 200 amp OCPD if the calculated load were 180 amps or less?
Pete
220.61 Feeder or Service Neutral Load.
(B) Permitted Reductions.
(2)That portion of the unbalanced load in excess of 200 amps
Very few electricians (actually none around here) calculate the load when upgrading a service to 200 amps. With residential you usually get the reduction because of the range and dryer loads but most commercial services do not involve those loads.
And how often do you come up with a neutral load that needs to have same size conductor as ungrounded conductors on a multiwire feeder or service? You can subtract any straight 208 or 240 loads from the total load on ungrounded conductors as they have no effect on neutral current.
With residential you usually get the reduction because of the range and dryer loads but most commercial services do not involve those loads.
Commercial services will often have a much higher percentage of line to line loads.
I?m not sure what you are asking but look at table 310.15(B) (6)
A common mistake I see is guys using 200 amp service entrance cable for commercial buildings.
Why couldn't someone use 4/0 aluminum SE with a 200 amp OCPD if the calculated load were 180 amps or less?
Pete
So do you know for certain they are using SE with reduced neutral... and not SE with full size neutral?220.61 Feeder or Service Neutral Load.
(B) Permitted Reductions.
(2)That portion of the unbalanced load in excess of 200 amps
So do you know for certain they are using SE with reduced neutral... and not SE with full size neutral?
I know they make SEU with a full neutral but since it is seldom used I have never seen it. The Neutral on a 4/0 seu is 2/0 and I would almost bet than many commercial jobs, barring those with high harmonics could have a reduced neutral. Also I have never seen SE cable on a large project but I suppose it may exist somewhere just not here.So do you know for certain they are using SE with reduced neutral... and not SE with full size neutral?
I don?t know like I said around here the calculations are never done on 200 amp upgrades So unless you do he calculations how can you reduce the neutral size.