15A plug on a 20A circuit?

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  #1  
Old 05-14-12, 07:03 PM
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15A plug on a 20A circuit?

I think I know what I need to do here, but if you all think otherwise, maybe I can save some money.

I have a power cord going to a 120v, 1500w water heater element that needs a new plug. The instructions say to use a 20A-rated plug, but nowadays these only come with the horizontal prong. Since my house doesn't have receptacles to accommodate this type of plug, I think I will need to swap the older receptacle with a 15/20 style. Or do I? Will putting a 15A heavy-duty plug on the end of the cord cause any safety problems?

Here are some more of the particulars:
  • the circuit is 20A with 12/3 wire
  • the element is being used for a portable submersible heater, and will potentially be under load for up to 30 minutes
  • the element does not list the amperage it draws
  • the only part of the entire circuit, including the 12 gauge cord on the element, that is not rated for 20 amps is the plug at the end of the cord.

Thanks for any thoughts you folks have,
Jeff
 
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  #2  
Old 05-14-12, 07:22 PM
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nowadays these only come with the horizontal prong
Hence the "T" slot for the neutral on a 20A receptacle.

  • the only part of the entire circuit, including the 12 gauge cord on the element, that is not rated for 20 amps is the plug at the end of the cord.
I would use the 20A plug.
 

Last edited by Nashkat1; 05-14-12 at 08:06 PM.
  #3  
Old 05-14-12, 07:35 PM
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The instructions say to use a 20A-rated plug
I am not sure what instructions you are looking at, but I suggest matching the old plug. 1500 watts 12 amps.
 
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Old 05-15-12, 03:50 AM
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Homemade heat stick

Thanks for the input. The project is for a DIY "heatstick", so The "instructions" are a compilation of various online how-to articles. Here's one example. There never was an original plug, so matching isn't an option.

My concern is that there will be a bottleneck of amperage at the plug, which may cause excessive heat when under continuous load. Am I off base in worrying about this?

Jeff
 
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Old 05-15-12, 05:06 AM
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As stated above, 1500 watts is 12 amps, well within the limits of a 15 amp device.
 
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Old 05-15-12, 08:36 AM
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My concern is that there will be a bottleneck of amperage at the plug, which may cause excessive heat when under continuous load. Am I off base in worrying about this?
Probably.

The total load is 1500W. The maximum allowable continuous load on a 15A circuit is 1440W, and the maximum allowable continuous load on a 20A circuit is 1920W. It seems unlikely that a heavy-duty 15A plug would hold up at 1440W but fail at 1500W. But you can go with the 20A plug for insurance if it makes you more comfortable.
 
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