Hello All,
(Again, please excuse me if this is the wrong subforum. Still getting used to posting here, although I've been lurking for a while.)
A little background: my home is relatively new (finished January 2013) and was built with two 225A-max panels in the garage and an outdoor combination metering panel on the exterior. Each of the interior panels are fed from the outdoor combination metering panel with a 150A (75C) breaker, each. The exterior and interior panels are connected via 2/0 AL XHHW-2 90C degree wire.
While doing my research on installing the NEMA 14-50 receptacle and the HPWC, I started to become familiar with the NEC, especially in relation to wire gauges, ampacity, temperature, materials, etc. According to my understanding of the "NEC Table 310.15(B)(16)" (http://www.barr-thorp.com/wp-content/uploads/2011/04/Digest-176-NEC-Tables.pdf), my builder's electrician should have used the 75C rating of the wiring (not 90C), as the breaker and panels are only rated for 60/75 degree. This would put the 2/0 AL XHHW-2 wiring at a 135A rating, not 150A, which the breaker is rated at. So, the builder should have used 1/0 or larger CU wire or 3/0 AL wire, correct? Not 2/0 AL? Is this a code violation?
I appreciate any available insight.
Imgur album of the suspected issue: Potential Code Issue - Imgur
(Again, please excuse me if this is the wrong subforum. Still getting used to posting here, although I've been lurking for a while.)
A little background: my home is relatively new (finished January 2013) and was built with two 225A-max panels in the garage and an outdoor combination metering panel on the exterior. Each of the interior panels are fed from the outdoor combination metering panel with a 150A (75C) breaker, each. The exterior and interior panels are connected via 2/0 AL XHHW-2 90C degree wire.
While doing my research on installing the NEMA 14-50 receptacle and the HPWC, I started to become familiar with the NEC, especially in relation to wire gauges, ampacity, temperature, materials, etc. According to my understanding of the "NEC Table 310.15(B)(16)" (http://www.barr-thorp.com/wp-content/uploads/2011/04/Digest-176-NEC-Tables.pdf), my builder's electrician should have used the 75C rating of the wiring (not 90C), as the breaker and panels are only rated for 60/75 degree. This would put the 2/0 AL XHHW-2 wiring at a 135A rating, not 150A, which the breaker is rated at. So, the builder should have used 1/0 or larger CU wire or 3/0 AL wire, correct? Not 2/0 AL? Is this a code violation?
I appreciate any available insight.
Imgur album of the suspected issue: Potential Code Issue - Imgur
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