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I am trying to do a little work and have an electrician check it. I have a range that is a 3 prong 50amp 125/250 (looks like the 10-50R).

List of materials purchased:

  • 50 amp Siemens Circuit Breaker
  • 25 ft of 6/3 Aluminum wire
  • Staples
  • Cable Brackets
  • 50amp 125/250V receptacle

I am aware that the code changed in 1999 requiring 4 wire, albeit after I purchased this stuff. Would it be better for longevity to install 6/4 rather than the 6/3 and have the 3 prong range plug rewired? Not even sure if you can install the 3wire, though it is an old house.

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You must always follow the most recently adopted code when installing new wiring, no matter how old the house is. With that said, the cord of a cord-and-plug attached device is beyond the scope of the National Electrical Code (NEC).

Installing a new range

When you purchase a range, they will also sell you the attachment plug. If you opt to install the stove yourself, they will ask you if you need 3 or 4 wire. This is because if you already have a 3 wire receptacle that was installed before the code change then you are not required to update the house wiring when installing the range.

When you're ready to install the range in the house, you'll follow the manufacturers installation instruction for a 3 wire attachment plug. Once the cord is attached to the device, simply plug it in and you're done.

Installing or modifying a range circuit

If you are installing a new circuit for the range (which it sounds like you might be), or modifying the existing range circuit, you must follow all currently adopted codes. This will likely mean running 4 conductor wire, and installing a 4 wire receptacle. Remember, the code is applied during installation, not when the materials are purchased.

Side Note: Technically, code applies at the time of inspection. However, the inspector will usually use the date the permit was granted. So if there was a code change after the permit was pulled, but before the inspection, the inspector will usually use the old code.

If your range has a 3 wire attachment plug, you'll have to follow the manufacturers installation instructions to change to a 4 wire plug.

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The topic of connecting aluminum to copper wire should be mentioned. Most electrical connectors are designed to connect to copper and not aluminum. Special care must be taken to ensure that the socket (and circuit breaker) is approved for use with aluminum. Also, dielectric anti-corrosion paste might want to be used. – Pigrew Feb 7 '13 at 15:03
@Pigrew Most circuit breakers and 50A receptacles are designed to accept aluminium wire, so there should be no mixing of copper and aluminium in this situation. It should be a direct run; with no splices or taps, of aluminium wire between the breaker and the receptacle. – Tester101 Feb 7 '13 at 15:19

Do you want to wire the plug for an old existing range or a new one? If it is older 3 wire, then a three wire plug is fine technically, but if it is designed for four wire, you should upgrade. An electrician most likely will want you to install a 4 wire circuit and modify the range to use a 4 wire plug. Also, if this is a new circuit where a range has not been installed before, then a 4 wire circuit should be installed. you can use the same breaker and exchange the 3 wire plug for a 4 wire plug. You will have to get new wire however.

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