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Post by charles67 on Apr 15, 2018 19:57:13 GMT -6
Thank you for your support and your videos on electrical ranges. However, you did not mention the last part of article 220.55. This was a question on the masters exam that I did not know how to calculate. It states where 2 or more single phase ranges are supplied by a three phase 4 wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases. Can you give an example of a question and how you would calculate using this part of article 220.55? I emphasize, this was on the Texas master electrical exam 2018. Also could you demonstrate an equation using article 220.54 under the same guidelines however, using electric dryers instead of electric ranges? Thank you for your quick response. I am scheduled to take the masters exam again soon.
Charles McGregor
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Post by Electrical Code Academy Staff on May 1, 2018 11:44:55 GMT -6
Greetings Charles,
Sadly in a video I am not able to cover all aspects that could possibly come up on an exam. However, the good news for your question is that an example of how this is done in found in Informative Annex D, example D(5)(a) which will answer your exact question. They key to understanding this is to visualize the maximum number of ranges potentially between any two phase conductors. For example, if I have 10 ranges then you divide the number of ranges (10) by 3 = 4 ( because of rounding) x 2 = 8 and under 220.55, Column C you would get 23KW, you then would divide that by 2 for the per phase demand.
Check out Informative Annex D(5)(a) and you will understand. If you have additional questions please add them to this thread and I will try to check back with you.
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