Mike Dolt Enterprises
Mike Dolt Enterprises
User: Jpflex, Location: Victorville
Asked on: Tuesday, February 25, 2025 at 12:50 pm EST
Answered on: Thursday, March 6, 2025 at 9:03 am EST
Question: From NEC 210.23 (B)We know that if a circuit supplies either or both lighting loads, cord and plug utilization equipment not fastened in addition to equipment fastened in place, then the fastend in place equipment cannot exceed 50% of the circuit rating (breaker size determines circuit rating)If a utilization equipment not fastened in place is hooked to a circuit it cannot exceed 80% of the branch circuit ratingHowever, if you have fixed in place utilization equipments and no other lighting or cord and plug non fixed in place loads supplied by a circuit, apparently either equipment can exceed 50% of the circuit rating with total load not to exceed 100% of the load.For example 2 fixed in place appliances on a 20 ampere circuit. One at 19 amperes and the other load at 1 ampere, for 20 ampere total load.I thaught circuits (breakers) in general were not to be loaded over 80% of their rating but my NEC hand book says:"The requirement does not apply to a branch citcuit that supplies only fastened in place utilizatiin equipment. For example, a 20 ampere branch circuit that supplies a waste disposer and a dishwasher, neither appliance is restricted to 50% (10 amperes) of the branch circuit rating. The combined load of the two appliances cannot exceed 20 amperes" page 119 nec handbook 2023i disagree and belueve the circuit should be limited to 20 i amperes x 80% = 16 i amperes
You're bringing up a common point of confusion regarding NEC 210.23(B) and the general 80% loading rule. Let's break it down
NEC 210.23(B) is specifically about the ALLOWABLE LOAD on a multi-outlet branch circuit.
The 50% rule
This applies when you have a mix of lighting loads, cord-and-plug equipment not fastened in place, and fastened-in-place utilization equipment on the same circuit. The total of the fastened-in-place equipment cannot exceed 50% of the branch circuit rating.
The 80% rule for Cord-and-Plug equipment
This says that cord-and-plug-connected utilization equipment not fastened in place (like a vacuum cleaner or iron) must not exceed 80% of the branch circuit rating.
The EXCEPTION (and where your question lies)
If a branch circuit only supplies fastened-in-place utilization equipment, the 50% limitation does not apply. The total load on the circuit still cannot exceed the rating of the breaker or overcurrent protective device.
The 80% continuous load rule
This rule comes from a different section of the NEC (often 210.19(A)(1) for branch circuits and 215.2(A)(1) for feeders). It states that the overcurrent device and conductors must be sized to carry not less than 125% of the continuous load, which is the same as saying the continuous load cannot exceed 80% of the overcurrent device's rating.
Continuous Load Definition
The crucial point is what constitutes a "continuous load." NEC defines it as "A load where the maximum current is expected to continue for three hours or more."
Here's how it applies to your example
You have a 20-amp circuit with two fastened-in-place appliances: one drawing 19 amps and one drawing 1 amp (total of 20 amps).
NEC 210.23(B) (the 50% rule) does NOT apply because the circuit only supplies fastened-in-place utilization equipment. The important question is: Are either of those appliances considered a "continuous load?" If neither is a continuous load (i.e., they don't run for 3 hours or more at their maximum current draw), then your scenario is perfectly acceptable according to the NEC. The combined load is 20 amps, which is 100% of the breaker rating. If either is a continuous load, then the circuit is overloaded. You would need to either: Reduce the total continuous load to 16 amps (20 amps x 80%) Increase the overcurrent device to 25 amps, and use appropriately sized conductors for the 25 amp overcurrent device. (This may not be possible depending on the wire size).
Why the Confusion?
The 80% continuous load rule is often mistakenly applied across the board to all circuits, regardless of the load type. NEC 210.23(B) is a separate set of rules that apply specifically to multi-outlet branch circuits* with certain types of loads. The 80% continuous load rule is for any continuous loads on any circuit.
In summary
Distinguish between the multi-outlet branch circuit load limitations in 210.23(B) and the continuous load requirements in 210.19(A)(1) and 215.2(A)(1). They address different aspects of circuit loading.2. Determine if the loads are "continuous loads" (run for 3 hours or more). This is key to applying the 80% rule.3. When in doubt, consult with a qualified electrician or your local electrical inspector. They can help you determine the correct application of the NEC for your specific situation. Flag for review