4-Prong Dryer Cord Wiring Diagram (NEMA 14-30)
This is a free printable 4 prong dryer cord diagram: download the diagram as SVG or open it and print to paper or PDF.
Wire a 4-prong dryer cord correctly to a NEMA 14-30 outlet — covering terminal identification, bonding strap removal, and code compliance.
A 4-prong dryer cord uses the NEMA 14-30 connector standard, which supplies 240 V AC via two ungrounded hot conductors (L1 and L2), one neutral conductor, and one separate equipment grounding conductor. This four-wire arrangement replaced the older three-wire NEMA 10-30 configuration because it separates the neutral and ground, eliminating the shock hazard that arose when the neutral-ground bond carried fault current through the appliance chassis.
The four conductors are colour-coded in North American practice: black for L1 (hot), red for L2 (hot), white or grey for neutral, and green or bare copper for ground. The terminal block inside the dryer has four positions labelled accordingly. Before connecting the new cord, you must remove or disconnect the bonding strap — a metal link that joins the neutral terminal to the chassis — because that bond is only appropriate for a 3-wire installation. Leaving the strap in place with a 4-wire cord creates a parallel ground path that violates NEC 250.140 and can energise the chassis under certain fault conditions.
The NEMA 14-30 receptacle is rated at 30 A, 125/250 V. The circuit is typically protected by a double-pole 30 A breaker and wired with 10 AWG copper conductors (or 8 AWG aluminium where permitted). The cord itself is usually 4 ft to 6 ft long with a minimum rating of 10 AWG, 4-conductor, 30 A.
This diagram is provided for illustrative and educational purposes only. Electrical work on appliances and fixed wiring must comply with the applicable national electrical code in your jurisdiction — NEC/NFPA 70 (USA), BS 7671 (UK), AS/NZS 3000 (Australia/New Zealand), or IEC 60364 (international). Always engage a licensed electrician where required by law, and verify all conductors are de-energised before beginning work.
How to wire 4 prong dryer cord diagram
- Isolate power at the panel Switch off the double-pole 30 A breaker supplying the dryer circuit. Place a lockout tag on the breaker. Verify the outlet is de-energised using a non-contact voltage tester on all slots before proceeding.
- Open the dryer terminal cover Remove the access panel at the rear of the dryer, usually secured by one or two Phillips-head screws, to expose the terminal block and the existing cord or knockout.
- Locate and remove the bonding strap Identify the metal bonding strap connecting the neutral (centre) terminal to the dryer chassis or ground bracket. Remove the screw securing it, slide the strap off, and keep it in a safe location in case the appliance is later reconnected to a 3-wire outlet.
- Thread and strain-relief the new cord Feed the 4-prong cord through the strain relief fitting in the appliance knockout. Tighten the strain relief so the cable jacket is clamped, not the individual conductors. Leave adequate conductor length to reach each terminal comfortably.
- Connect conductors to terminals Connect green or bare copper to the ground terminal (chassis screw or green-marked terminal). Connect white or grey to the centre neutral terminal. Connect black to the L1 terminal and red to the L2 terminal. Tighten each screw firmly — loose connections cause arcing and heat.
- Inspect, reassemble, and restore power Verify no conductors are pinched under the cover or near moving parts. Replace the terminal cover panel. Restore power at the breaker and test the dryer on a timed cycle to confirm correct operation of both heating elements.
Specifications
| Connector standard | NEMA 14-30 (North America) |
|---|---|
| Voltage rating | 125/250 V AC |
| Current rating | 30 A |
| Circuit breaker | Double-pole 30 A |
| Minimum conductor size (copper) | 10 AWG (5.26 mm²) |
| Number of conductors | 4 (L1, L2, neutral, ground) |
| Frequency | 60 Hz (North America) |
| Applicable standard | NEC/NFPA 70, ANSI/UL 817 |
Safety warnings
- Always isolate the circuit at the main panel and verify dead with a calibrated non-contact voltage tester before touching any conductor. 240 V AC is lethal.
- Remove the neutral bonding strap before connecting a 4-wire cord. Failure to do so creates a parallel ground path, may energise the appliance chassis, and is a violation of NEC 250.140.
- All fixed branch circuit wiring (panel to outlet) must be performed by a licensed electrician and inspected by the authority having jurisdiction. Codes vary — consult NEC/NFPA 70, BS 7671, AS/NZS 3000, or IEC 60364 as applicable.
- Use only cord rated at 30 A or greater with conductors no smaller than 10 AWG copper. Undersized cord creates a fire hazard.
- Do not use this diagram as a substitute for professional guidance. Electrical installations that do not comply with local codes may void appliance warranties and home insurance.
Tools needed
- Non-contact voltage tester
- Flathead and Phillips-head screwdrivers
- Wire strippers (suitable for 10 AWG)
- Adjustable spanner or nut driver for strain relief
- Lockout/tagout tag for breaker
- Multimeter (for verification)
Common mistakes
- Leaving the bonding strap in place when switching from a 3-prong to a 4-prong cord — this violates NEC 250.140 and creates a shock hazard.
- Reversing the L1 and L2 terminals — the dryer will still operate, but if the polarity convention matters for a dual-element heater timer, asymmetric faults can occur.
- Under-tightening terminal screws — loose connections arc under load, causing heat damage and potential fire.
- Clamping the strain relief on individual conductors rather than the outer jacket — the jacket provides the mechanical retention; gripping conductors alone can cut insulation.
- Failing to verify the circuit is de-energised before working — simply switching off the dryer is not sufficient; isolate at the panel.
- Using a 3-wire cord with a 4-wire outlet by jumping neutral to ground at the outlet — this is a code violation and a safety hazard.
Troubleshooting
- Dryer runs but does not heat
- Cause: One hot leg (L1 or L2) is not making contact — loose terminal, open breaker pole, or failed breaker Fix: Isolate power. Check that both the L1 (black) and L2 (red) terminals are tight. Use a multimeter to verify 240 V across L1 and L2 at the outlet. If only 120 V is present between hots, suspect a tripped or faulty breaker pole.
- Breaker trips immediately when dryer starts
- Cause: Short circuit in the cord, terminal block, or appliance motor/heating element Fix: Disconnect the cord from the appliance and reset the breaker. If the breaker holds, the fault is within the appliance. If it trips again, the fault is in the cord or outlet wiring — inspect for pinched or shorted conductors.
- Appliance chassis gives a mild shock or tingle
- Cause: Bonding strap not removed, or ground conductor not connected — neutral current flowing through chassis Fix: Isolate immediately. Verify the bonding strap is absent and that the green or bare ground conductor is securely connected to the chassis ground terminal. Check ground continuity from appliance chassis to panel earth.
Frequently asked questions
What is the difference between a NEMA 10-30 and NEMA 14-30 dryer outlet?
A NEMA 10-30 is a 3-wire outlet with two hots and a combined neutral/ground. A NEMA 14-30 is a 4-wire outlet that separates the neutral and ground conductors, improving safety by eliminating chassis energisation from neutral faults. Modern NEC editions require the 4-wire outlet for new installations.
Do I need to remove the bonding strap when fitting a 4-prong cord?
Yes. The bonding strap bridges the neutral terminal to the dryer chassis and is only valid for 3-wire installations. With a 4-prong cord the ground conductor provides chassis bonding independently, so the strap must be removed or repositioned to an insulating standoff to comply with NEC 250.140.
Can I convert a 4-wire dryer outlet back to 3-wire?
NEC 250.140 permits 3-wire connections only for existing branch circuits that have not been modified. New construction and rewired circuits must use 4-wire. Converting back may be a code violation; consult a licensed electrician and your local authority having jurisdiction.
What wire gauge is required for a 30 A dryer circuit?
A 30 A circuit requires a minimum of 10 AWG copper conductors (approximately 5.26 mm²). If aluminium conductors are used, 8 AWG is the minimum. All conductors must be rated for the installation method and ambient temperature per NEC Table 310.15 or equivalent.
Is it safe to wire a dryer cord myself?
The cord-to-terminal connection is a permitted DIY task in many jurisdictions, but the branch circuit wiring and outlet installation must be performed by a licensed electrician in most regions. Always isolate power at the panel, verify dead with a non-contact voltage tester, and follow your local electrical code.
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