Xhhw

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winters1

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I just came across an entire condo complex that was built in the 70's. The main breakers are 150 amps. The 1/0 aluminum SER XHHW wire passes through the crawl space and up to the sub panel.

How did this pass inspection in the 70's?

Were the amp ratings in the tables reduced since then?

If so, is it still "legal"?


Tim
 
Welcome to the forum.:)

The oldest code book that I have avaliable is the 1978 code. In the Notes to Table 310-16 Note #3 has the what is now Table 310.15(B)(6). The Table is basically the same as the one today but it stopped at a 200 amp service. There is a bar by this section so I don't know what change from the prior code.

Sorry I couldn't be more help, I am sure another forum member will have access to older code books.

Chris
 
winters1 said:
. . . How did this pass inspection in the 70's? . . If so, is it still "legal"? . .
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I was in the trade in the late 70s and it was not code compliant then (assuming my memory has not failed me). It would have been fine if the overcurrent device were 125 amperes. The inspector missed it and since it was not compliant then, it is not compliant now. :)
 
Those mains could have been changed from 125 to 150 since the building was originally constructed.

But, if those are original breakers, then it would have been a violation even in the early 1970's.
 
raider1 said:
Welcome to the forum.:)

The oldest code book that I have avaliable is the 1978 code. In the Notes to Table 310-16 Note #3 has the what is now Table 310.15(B)(6). The Table is basically the same as the one today but it stopped at a 200 amp service. There is a bar by this section so I don't know what change from the prior code.

Sorry I couldn't be more help, I am sure another forum member will have access to older code books.

Chris
Click to expand...

The numbers you have in your 78 was the first time it appears in chart form the code. That's the reason for the bar. Prior to that, the sizes and amperages were listed in a sentence. "Types RH, RHH, RH, THW, and XHHW aluminum and copper-clad aluminum conductors shall be for sizes No. 2-100 Amp., No. 1-110 Amp., No. 1/0-125 Amp., Nol 2/0-150 Amp., No. 3/0-175 Amp. and No. 4/0-200 Amp."

In the 1971, the same figures are given at the bottom of Table 310.14, "Allowable Ampacities of Insualted Aluminum and Copper-Clad Aluminum Conductors".

In 1968, 3/0 was listed as good for only 170 amps. I trace those numbers back to the 1956, Chapter 10, Table 1a.
 
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