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Kevin, Licensed Electrician
Category: Electrical
Satisfied Customers: 2835
Experience:  29 years as a Licensed Electrical Contractor in Illinois, 5 year college Electrical Instructor, Former Electrical Inspector, Diploma in Digital Electronics, Former Illinois Licensed Home Inspector
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i obtained a older range that doesnt have the ampacity listed

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i obtained a older range that doesn't have the ampacity listed on it and it had a three prong plug....thinking i was good, i changed the plug out to a four prong (my outlet is) 50 amp. i have since found the kva rating and it is in two unequal legs. one is a 3 wire/120/240vac @ 12.5 kw. and the other is 120/208 @ 9.5 kw. the problem, i have a 40 amp breaker. am i going to have to change out the wiring in the panel and upgrade to a 60 amp breaker?
if so, should i go up to #4 since i'm guess about 15' of wire? name is XXXXX XXXXX I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!


1) Is this installation for a home or a commercial use?


2) Not sure what you mean by two unequal legs? The range should have a nameplate rating and the total wattage or KW should be provided. An electric range requires 120 and 240 volts using 4 wires (2 hots, 1 neutral and 1 ground) . If this will be installed in a home, there is no such voltage as 208 VAC in a house, as that is 3-phase. An electric range installed in a single family dwelling is single phase and 120/240 VAC.

Customer: replied 3 years ago.

well there is no label plate, just a sticker that had two lines that read what i wrote. this is for a home installation. i have a 40A breaker and the range appears to be 52A @ 12.5 kw/240vac

1) That's kinda what I figured but just wanted to make sure there was no total wattage on the nameplate. The 120/208 rating would be used if installed within a 3-phase commercial environment. Your rating is the 120/240 or 12.5KW.


2) If you apply Watt's Law where P = I x E, P = 12,500 watts and E =240 volts. Therefore, I = 12.5KW/240VAC = 52 amps. Therefore, the double pole breaker will need to be a 60 amp and the branch conductors will need to be 6 AWG stranded copper or 3 AWG stranded aluminum.


3) The voltage drop using 240 volts at 15 feet with a load of 60 amps results in a .4% voltage drop which is way less than the recommended maximum of a 3% voltage drop for branch circuits. Therefore, 6 AWG copper is OK for the 15 foot run. No need to go to 4 AWG.




Hope this helps.........If you have any additional questions, let me know and I'll be glad to answer them for you.


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1) Also, the receptacle will need to be a NEMA 14-60R and the plug will need to be a NEMA 14-60P (3 pole, 4 wire grounding type)


2) "X" & "Y" will be the 2 hot's, "W" will be the neutral and "G" will be the ground as labeled on the receptacle.

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