Ranges, Clothes Wires, Bonding Jumpers and 3-Wire Cords

[jar546]

NEC 250.140 – 2020 vs. 2023

The 2023 NEC reorganized and clarified Section 250.140, which governs how the frames of electric ranges, ovens, cooking units, and clothes dryers must be grounded. In the 2020 NEC, this section included an exception allowing the use of the grounded (neutral) conductor for bonding the frame on existing branch circuits without an equipment grounding conductor (EGC). That structure was replaced in 2023 with two subsections: (A) for new installations and (B) for existing ones.

Section 250.140(A) requires that all new circuits supplying these appliances include an EGC. These appliances must be grounded using the methods in 250.134 or 250.138. As a result, 3-wire cords are no longer permitted for new installations. Instead, a 4-wire cord must be used—hot, hot, neutral, and ground. When switching from a 3-wire to a 4-wire cord, the factory-installed bonding jumper between the neutral terminal and the metal frame must be removed. Failure to do this creates a direct connection between the neutral and the appliance frame, which violates code and will cause nuisance tripping of GFCI breakers, now required on many of these circuits under 210.8.

Section 250.140(B) applies only to existing branch circuits that do not have an equipment grounding conductor. In those cases, the grounded (neutral) conductor may be used to bond the metal frame of the appliance, but only if all of the following conditions are met:

1. The circuit is 120/240V single-phase 3-wire, or 208Y/120V from a 3-phase, 4-wire wye system.
2. The grounded conductor is at least 10 AWG copper, 8 AWG aluminum, or copper-clad aluminum (added in 2023).
3. The grounding contacts of any receptacles furnished as part of the appliance are bonded to the frame.
4. The grounded conductor is insulated, or uninsulated only if it's part of Type SE cable that originates at the service equipment.
5. If the SE cable originates at equipment other than the service, the grounded conductor must be insulated or field-covered using listed insulating material, like sleeving or tape, inside the supply enclosure.

Items (4) and (5) are the only portions of this code section that refer specifically to Type SE cable. These changes clarify when and how an uninsulated grounded conductor can be used and under what conditions it must be insulated.

In short, new appliance installations must use a 4-wire setup with a dedicated EGC, and the neutral-to-frame bond must be removed to avoid code violations and electrical hazards. The use of a 3-wire cord and bonding jumper is permitted only on compliant, pre-existing branch circuits that meet all the strict conditions in 250.140(B).

 

[wwhitney]

As a result, 3-wire cords are no longer permitted for new installations.

There is no substantive change here in 250.140 in the 2023 NEC (except the new option in 250.140(B)(5)). A new appliance installation can still use a 3-wire cord, if the existing branch circuit complies with the requirements in 250.140(B). Only a new branch circuit installation requires a separate EGC and the resulting use of a 4-wire cord.

In short, new appliance installations must use a 4-wire setup with a dedicated EGC

Again, the requirement for an EGC is not triggered by a new appliance installation, it is triggered by a new branch circuit installation.

Cheers, Wayne

 

[wwhitney]

(except the new option in 250.140(B)(5)).

Under the 2020 NEC, say you had a service panel with a type SE cable (2 insulated conductors and an uninsulated conductor) supplying a NEMA 10-50 receptacle for a dryer. That was compliant with 250.140(B) exception. Now if you add a service disconnect in front of the existing service panel, for whatever reason, turning the service panel into a subpanel, that branch circuit became no longer compliant. So adding the service disconnect triggered a requirement for a new branch circuit (necessarily with EGC) for the dryer.

With the new option in 2023 NEC 250.140(B)(5), that is no longer the case. The existing branch circuit can continue to be used, as long as the grounded conductor is "field covered within the supply enclosure with listed insulating material, such as tape or sleeving to prevent contact of the uninsulated conductor with any normally non-current-carrying metal parts."

Cheers, Wayne

 

[jar546]

There is no substantive change here in 250.140 in the 2023 NEC. A new appliance installation can still use a 3-wire cord, if the existing branch circuit complies with the requirements. Only a new branch circuit installation requires a separate EGC and the resulting use of a 4-wire cord.

Yes, "...reorganized and clarified..." means that.

Again, the requirement for an EGC is not triggered by a new appliance installation, it is triggered by a new branch circuit installation.

Yes, it does. If the appliance never existed, it is new. Otherwise, it is a replacement covered under 250.140(B).

 

[jar546]

One of the bigger issues with this is where the inspector must draw the line with new installations (not replacements, which are not under permit), regarding the bonding jumper where the cord is attached to the range and dryer. Some manufacturers still ship the appliances with the jumper in place, which would be a violation for a new installation. Is it the inspector's job to verify that connection, too, since it is made on-site?

 

[wwhitney]

Yes, it does. If the appliance never existed, it is new. Otherwise, it is a replacement covered under 250.140(B).

An appliance may be new without the branch circuit being new. Simple example, a range is replaced with a separate cooktop and wall oven, whose factory supplied whips are terminated to the junction box to which the range was formerly connected.

Is it the inspector's job to verify that connection, too, since it is made on-site?

No opinion on that, but the simplest way to verify would be to unplug the appliance and check for continuity between the EGC and neutral pins of the plug. So as a practical matter, does an inspector carry a continuity tester? Or should the inspector require that during the inspection the inspectee performs that test?

Cheers, Wayne