3-prong to 4-prong Power Cord Conversion.

By jsrock516
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posted on Jul 16, 2008

This advice is on how to correctly install an ELECTRIC DRYER or ELECTRIC RANGE 220-240VAC power cord (US Standards).

3-Prong or 4-Prong – The Difference:

3-prong color code:

BLACK (HOT – 110-120VAC) – May also be referred to as L1
RED (HOT – 110-120VAC) – May also be referred to as L2
WHITE (NEUTRAL – 0VAC) – Usually grounded to the equipment frame via a jumper wire or metal strap.

4-prong color code:

BLACK (HOT – 110-120VAC) – May also be referred to as L1
RED (HOT – 110-120VAC) – May also be referred to as L2
WHITE (NEUTRAL – 0VAC) – DO NOT ground to equipment frame.
GREEN (GROUND) – Attach to equipment frame.

Which One to Use: According to the National Electrical Code (NEC), Article 250, installations after the year 2000, require the use of a 4-prong plug which incorporates a separate ground and neutral wire. If you currently have a home that uses the 3-prong receptacle and cord, you can continue to use it. You will have to upgrade to a 4-prong configuration, however, if you plan on relocating your current receptacle, or if the internal wires of the receptacle become damaged in any way and require repair.

Converting from 3-prong to 4-prong: Make sure you UNPLUG the appliance prior to any repairs. CAUTION: Voltages dangerous to life are still present even with the appliance turned off and still plugged in. Notably in the area of the terminal block where the power cords are installed. You will need to remove the old cord by following these steps:

With the appliance UNPLUGGED, remove the access panel on the back of the unit where the power cord enters.
With the cover removed, you will see a terminal block where the power cord is attached. The terminal wires will be colored with the WHITE wire in the middle, and the BLACK and RED wires on either end. NOTE: There should be a green jumper wire or metal bonding strap attached to the NEUTRAL (white) terminal wire.
Remove the terminal lugs holding the old power cord wires in place. CAUTION: Use care not to drop any nuts or screws inside the appliance.
Remove the bonding strap or ground wire from the Neutral terminal lug. NOTE: If disconnecting a ground wire, make sure you re-attach it to the appliance frame.
Loosen the screws on the strain relief connector that holds the power cord in place and remove old power cord. NOTE: If your appliance does not have a strain relief that clamps down and hold the power cord in place, it is highly recommended that you install one. This prevents chaffing of the power cord against the appliance casing, and prevents the terminal wires from being pulled and broken loose. This could pose a potential shock hazard or cause damage to the appliance.
Install new power cord by threading it through the strain relief connector and tighten down the screws.
Connect the new power cord to the corresponding colors at the terminal block (Black goes to Black, Red goes to Red, White goes to White). The difference is going to be a Green (ground) wire that will connect to the appliance frame. There’s usually a green grounding screw for this. NOTE: If you disconnected a green grounding strap in Step 4., you can connect these two wires at the same point.
Re-install access cover. Turn off the service breaker to the appliance PRIOR to plugging it back in. With the breaker in the off position, plug the appliance in, and THEN turn the breaker on. In the event, something was wired incorrectly, it is far better to have your hands away from the receptacle and controlled from a distance. Safety first.

Comment by jsrock516, posted on Jul 16, 2008

These steps will work for nearly all appliances that require a 220-240VAC power cord conversion. The power cords are usually rated at 250VAC, 30 amps, and are carried by any hardware store or appliance parts retailer.

ADDITIONAL NOTES:

If you desire to convert an appliance from a 4-prong to a 3-prong, make sure you reconnect the bonding strap and/or ground wire to the Neutral (white) wire at the terminal block.
On some newer appliances, it is REQUIRED that you use a 4-prong plug in order for the timer or clock circuits to function properly due to the way they are configured. Refer to your owner’s manual for the correct recommendation. Even if you currently have a 3-prong receptacle, you still may be required to upgrade to a 4-prong if you encounter this situation.
In many circumstances, new appliances are NOT sold with the power cord due to the various power configurations in homes. Always refer to the contents description on the shipping container the appliance comes with to see what additional items or tools may be required for installation.

I hope this information is found to be helpful.

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