Bryan Posted August 6, 2009 Report Share Posted August 6, 2009 I need help confirming my findings regarding the service entrance cable on today's inspection. The breaker is 100 amps being fed by number 4 TWH copper. My understanding, per code check, a number 4 service conductor wire size should be protected a 100 AMPS, and therefore, this set up should be adequate. Is my thinking along the correct path. Thanks in advance Bryan Quote Link to comment Share on other sites More sharing options...
hspinnler Posted August 7, 2009 Report Share Posted August 7, 2009 Hi Bryan, From Table 10 in 5th Edition of electrical code check, #4 Cu THW (not TWH) is rated for 100 Amps. The other Tables, 11-14, take into account allowable ampacities, ambient temperature correction, adjustments for conduit exposed to sunlight, and derating for condutor proximity. Quote Link to comment Share on other sites More sharing options...
Richard Moore Posted August 7, 2009 Report Share Posted August 7, 2009 What Hank said. 4-AWG copper is allowed for 100-amp SECs. Your set-up is OK. Quote Link to comment Share on other sites More sharing options...
Bryan Posted August 7, 2009 Author Report Share Posted August 7, 2009 Thank you for the quick responses. Bryan Quote Link to comment Share on other sites More sharing options...
Jerry Simon Posted August 7, 2009 Report Share Posted August 7, 2009 Thank you for the quick responses. Bryan Hi Bryan, Just food for thought...per your post, how does the 100-amp breaker protect those #4 service entrance cables? Quote Link to comment Share on other sites More sharing options...
Kyle Kubs Posted August 7, 2009 Report Share Posted August 7, 2009 Thank you for the quick responses. Bryan Hi Bryan, Just food for thought...per your post, how does the 100-amp breaker protect those #4 service entrance cables? Jerry, The breaker limits the amount of current that can be drawn through the service cables by the system, no matter which side it is on. It won't do anything for a short on those cables before the breaker, no matter how improbable but at that point the transformers limit protection should take over. Quote Link to comment Share on other sites More sharing options...
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