Technically, you can have as many outlets on a 15 amp circuit breaker as you want. However, a good rule of thumb is 1 outlet per 1.5 amps, up to 80% of the capacity of the circuit breaker. Therefore, we would suggest a maximum of 8 outlets for a 15 amp circuit. Show National Electrical Code & OutletsThe National Electrical Code (NEC) does not limit the number of outlets per circuit. The NEC only states that a circuit cannot supply more than 80% of the circuit breakers limits. This is so the circuit breaker does not constantly trip during regular use. So, if you have a 15 amp circuit with 20 outlets, you should be fine as long as you are not running more than 12 amps through the circuit at one time. While this would be an extreme case, read further to find out how many amps you may use on a circuit.  How Many Amps Will I Use?To find out how many amps you need or how many you will use, use this formula: 80%*(Amps) = Watts/Volts. Also, you should know modern-day U.S. outlets run on 120 volts (unless it is a special appliance connection like a dryer). So, if you are using a 15 amp circuit and you are using regular 120-volt outlets, then the max watts you can use is 1440 watts. This ensuring your circuit does not supply more than 80% of the total 15 amp circuit. All electrical appliances like TVs, chargers, and lightbulbs should state their wattage on the packaging so you can just add up the expected wattage from each appliance to get your total wattage for the circuit. How Many Outlets Are In Most BedroomsMost new construction bedrooms have an outlet every 6 feet, or on every wall. They would also have a junction box on the ceiling for a light and fan. For example, a master bedroom could have 7 outlets, and then a light fixture at the ceiling for a fan. All while, being on a 15 amp circuit. Final ThoughtsWhile there is no direct rule for how many outlets you can have on a 15 amp circuit, you should not have more than 1440 watts of power plugged into those outlets at one time. Again, a good rule of thumb is 1.5 amps per outlet, but stop at 80% of the total circuit breaker amperage so the breaker does not trip constantly. In the case of 15 amps, we recommend a maximum of 8 outlets. During our home inspections, while we do not count the specific number of outlets in any given room, we will ensure the amperage per room is appropriate. For example, a kitchen should have more than a 15amp breaker. If you have further questions, be sure to comment below! Learn about preventing power surges or how many outlets can you put on a 20 amp circuit.
2014 National Electrical Code By: Dennis Bordeaux | Sep 26, 2016 A multiple-outlet branch circuit is a branch circuit that supplies two or more outlets. With the exception of the required small appliance, laundry, and bathroom receptacle circuits in dwelling units, those outlets may be a combination of lighting outlets for luminaires, receptacle outlets for cord and plug connected utilization equipment not fastened in place (portable appliances) and or outlets supplying utilization equipment that is fastened in place. The load on the branch circuit is never permitted to exceed the ampere rating of the branch circuit, but simply adding up the nameplate rating of the utilization equipment does not guarantee code compliance. The rating of any one cord-and-plug connected utilization equipment which is not fastened in place cannot be more than 80% of the branch-circuit rating. For example, a cord and plug connected commercial coffee maker is connected to a receptacle on a multiple-outlet 20 amp branch circuit. Since the coffee maker is not fastened in place it can be rated up to 80% of the branch circuit, or 16 amps. The total rating of all utilization equipment that is fastened in place (other than luminaires) is not permitted to exceed 50% of the rating of a branch circuit that also supplies lighting and or receptacle outlets for other loads. In other words, the load for the utilization equipment that is fastened in place is limited to a maximum of 10 amps on a 20-amp rated branch circuit supplying a combination of lighting and or receptacle outlets for portable appliances. It is easy to exceed this limitation. For example, a 120-volt, 20-amp branch circuit in an employee breakroom supplies a wall mounted water cooler with a nameplate rating of 3 amps, a fastened in place ice machine rated at 8 amps, and a duplex receptacle for a portable microwave. The total rating of the equipment that is fastened in place is 11 amps (3A + 8A = 11A). This exceeds 50% of the rating of the branch circuit. At least one of the loads needs to be connected to a different branch circuit. In this example, a simple solution would be to connect the duplex receptacle for the portable microwave to a different branch circuit. The 50% limitation only applies if the branch circuit supplies a combination of utilization equipment fastened in place plus lighting outlets and/or receptacles for cord-and-plug equipment that are not fastened in place. Since both the water cooler and the ice machine are fastened in place, the connected load on the 20-amp branch-circuit is not limited to 10 amps if no other outlets are connected to the branch circuit. Learn more about permissible loads today! Log into your JADE Learning account or register a free account and begin taking online electrical classes to satisfy you continuing education hours.
220.14 Other Loads—All Occupancies Knowing how to perform load calculations in accordance with the National Electrical Code (NEC) plays a significant role in an electrician’s professional career. Before installing branch circuits, feeders or services on a job, loads must be calculated. Branch-circuit load calculation requirements are in Part II of Article 220. After calculating branch-circuit loads, conductor sizes and ratings for overcurrent protection must be determined. Results from calculations in Part II of Article 220 are used in conjunction with specifications from 210.19 to size branch-circuit conductors. Sizing of branch-circuit overcurrent protective devices must be done in accordance with 210.20 and Part II of Article 220. To size feeder (and service) conductors and overcurrent protection, loads must first be calculated in accordance with Part III or Part IV of Article 220. Last month’s column concluded by covering fixed multioutlet assemblies in 220.14(H). This month, the discussion continues with more requirements for general-use receptacles and outlets not used for general illumination. Load calculations for receptacle outlets are covered in 220.14(I), (J), and (K). A receptacle, as defined in Article 100, is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke (see Figure 1). Sometimes there is confusion pertaining to a single duplex receptacle on a branch circuit with no other devices. Although a duplex receptacle is installed and mounted by one strap or yoke, it is considered two receptacles. A branch circuit supplying only a duplex receptacle and no other device is not an individual branch circuit. An individual branch circuit, as defined in Article 100, is a branch circuit that supplies only one utilization equipment. Except for dwelling occupancies and, under certain conditions, banks and office buildings, the calculated load for receptacle outlets is 180 volt-amperes for each single or for each multiple receptacle on one yoke. The load calculation for a single receptacle is 180 volt-amperes. The load calculation for a duplex receptacle is 180 volt-amperes. The load for three receptacles on one yoke or strap is also calculated at 180 volt-amperes (see Figure 2). To calculate receptacles in accordance with 220.14(I), multiply the number of receptacles by 180 volt-amperes. For example, what is the calculated load for 30 15-ampere duplex receptacles in a retail store? Multiply the number of receptacles by 180 (30 × 180 = 5,400). The minimum calculated load for 30 15-ampere duplex receptacles in a retail store is 5,400 volt-amperes. The calculated load for 20-ampere receptacle outlets is no different than the calculated load for 15-ampere receptacle outlets. For example, what is the calculated load for 30 20-ampere duplex receptacles in a retail store? Although 20-ampere receptacles have a higher rating than 15-ampere receptacles, the calculated load is exactly the same. The minimum calculated load for 30 20-ampere duplex receptacles in a retail store is 5,400 volt-amperes (30 × 180 = 5,400) (see Figure 3). The calculated load is used to determine the maximum number of receptacles permitted on a branch circuit in all but dwelling occupancies. The ampere rating of the overcurrent protective device is what determines the maximum number of receptacles on a branch circuit. For example, the maximum number of receptacles on a 15-ampere breaker (or fuse), supplied by a nominal source voltage of 120, is 10. The calculation can be performed either by converting the ampacity rating to volt-amperes or by converting volt-amperes to amperes. Use Ohm’s Law to find amperes when volt-amperes and voltage are known (I = W ÷ E). Divide 180 by 120. The calculated load for one receptacle supplied by 120 volts is 1.5 amperes (180 ÷ 120 = 1.5). To find the maximum number of receptacles permitted on a 15-ampere breaker, divide the rating of the breaker by 1.5 amperes (15 ÷ 1.5 = 10). The maximum number of receptacles permitted on a 15-ampere, 120-volt breaker is 10 (see Figure 4). Because of provisions in Table 210.21(B)(3) and Table 210.24, 20-ampere receptacles are not permitted on a branch circuit having a rating of 15-amperes. Because of the higher rating on a 20-ampere breaker, more receptacles are permitted than on 15-ampere overcurrent devices. The calculated load per receptacle is the same, 1.5 amperes. To find the maximum number of receptacles permitted on a 20-ampere breaker, divide the rating of the breaker by 1.5 amperes (20 ÷ 1.5 = 13.3 = 13). The maximum number of receptacles permitted on a 20-ampere, 120-volt breaker is 13 (see Figure 5). In accordance with Tables 210.21(B)(3) and 210.24, these receptacles can be 15-ampere, 20-ampere or any combination thereof. Although a single receptacle and duplex receptacle do not share the exact same definition, they are counted the same in a load calculation. Unless specifically stated in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke [220.14(I)]. For example, what is the branch-circuit load calculation for 30 15-ampere single receptacles in a retail store? The calculated load for 30 15-ampere single receptacles is the same as it would be for 30 15-ampere duplex receptacles, 5,400 volt-amperes (30 × 180 = 5,400) (see Figure 6). Some companies manufacture a single device containing four receptacles. Since there are four receptacles associated with this single piece of equipment, the load calculation is different. A single piece of equipment consisting of a multiple receptacle composed of four or more receptacles must be calculated at not less than 90 volt-amperes per receptacle [220.14(I)]. For example, what is the load calculation for a quad receptacle manufactured as a single device? Multiply the number of receptacles by 90 volt-amperes (4 × 90 = 360). Because there are four outlets in this single piece of equipment, the calculated load is 360 volt-amperes (see Figure 7). Two duplex receptacles in the same box and under one double-duplex receptacle cover plate, also has a calculated load of 360 volt-amperes. Not because it is one piece of equipment, but because the receptacle outlets are on two different yokes (2 × 180 = 360). Likewise, two single receptacles in the same box and under one cover must be calculated at 360 volt-amperes. The last sentence in 220.14(I) states that this load calculation provision does not apply to receptacles on small-appliance and laundry branch circuits in dwelling units. Receptacle outlets of 15- and 20-ampere ratings in dwellings are included in the general lighting-load calculations of 220.12. No additional load calculation is required for such outlets. Next month’s column continues the discussion of load calculations.
MILLER, owner of Lighthouse Educational Services, teaches custom-tailored classes and conducts seminars covering various aspects of the electrical industry. He is the author of Illustrated Guide to the National Electrical Code and NFPA’s Electrical Reference. For more information, visit his Web site at www.charlesRmiller.com. He can be reached by telephone at 615.333.3336, or via e-mail at . |
What is the maximum number of outlets that may be connected to a branch circuit when the connected load is not known?
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