How Many Outlets Can You Put on a Single Circuit Breaker? – NEC & IEC
The most frequently asked and searched question from home owners and DIY dudes is what is the exact number of outlets, receptacles and sockets which can be installed on 15A or 20A circuit breakers. While electrical engineers and electricians know the answer based on calculations and experience, let’s share the same rocket science information with you. Don’t worry, the formula and calculation can easily be solved by a 4 grade student.
Before going in detail, keep in mind that NEC (National Electric Code) doesn’t mention the exact number of outlets per circuit breaker. It only suggests that only 80% of load can be connect on a rated circuit breaker i.e. the load should not exceed the limit of 80% e.g. a 15A circuit breaker can only be used for 12A load points (15A x 80% = 12 A)
This way, based on a rule of thumb, a total of 8-10 numbers of outlets (rated for 1.5A) can be installed on a single pole, single phase 15A, 120V circuit breaker.
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Now let’s see the solved examples for 15A or 20A for 120V and 240V outlets and circuit breakers. In this solved example, we will show how to determine the suitable number of socket outlets and receptacles per circuit.
Determining the Number of Outlets on a Circuit
Method 1 – Basic Approach
Example: 120V – NEC – US & Canada
How many outlets can I put on a 15A, 120V circuit breaker?
First of all, we have to find the total wattage that can be handled by a single pole,15A, 120V breaker using the following basic formula.
P = V x I
Power Wattage = Volts x Amperes
Putting the values
Power = 120V x 15A = 1800 Watts
Ideally, a 15A, 120V single pole breaker will handle electric load about 1800W. But the National Electric Code doesn’t recognize it. The NEC suggests that 80% (0.8 of the breaker rating) of load can be put on a circuit breaker. In this case, the safe maximum load capacity handled by a 15A breaker is:
Power = 1800W x 0.8 = 1440 Watts
Now, the total number of outlets can be determined by dividing the power wattage by supply voltage.
Number of Outlets = 1440 Watts / 120V
Max Number of Outlets = 12
It means, a total of 12 numbers of outlets can be installed on a single circuit breaker having the rating of 15A, 120V (single phase single pole) for non-continuous load points.
To be on a very safe side to avoid unnecessary tripping of the breaker, you may again multiply the calculated number of outlets with 0.8. e.g.
Safe Number of Outlets = 12 x 0.8 = 9.6
This number fulfills the basic rule of thumb for finding the number of receptacles which is 1.5 amperes per outlet. In short, the safest numbers of outlets are 8-10 per circuit breaker rated for 15A, 120V, 1-P.
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Example 2: 230V – IEC – UK & EU etc
The above calculations are based on NEC where single phase voltage levels are 120V and 240V. The voltage level in the UK, EU and other countries is 230V.
To find the number of outlets in areas where the supply single phase voltage is 230V. You will have to divide the calculated wattage rating of the breaker by 230V.
For example, what is the total number of outlets which can be installed on a 10A, 230V circuit breaker?
Power = Volts x Amperes
Power = 230V x 10A = 2300 Watts
Power rating with safety factor of 80%
2300 W x 80% = 1840 W
Now divide by the supply voltage of 230V to calculate the total number of outlets.
2392 W / 230V = 8
It means, you can install a total and max 8 numbers of outlets on a 10A, 230V single phase MCB circuit breaker.
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Method 2 – When the Amp Rating of Outlet is known
How many outlets each of 1.5A can I put on a 15A, 120V circuit breaker?
As we know the amperage rating of the outlet is 1.5A.
To know the max # of outlets, divide the amps rating of the breaker by amps rating of the outlet.
Max Number of Outlets = 15A / 1.5A = 10
As NEC allow only the 80% load on the breaker, this way, the safest number of outlets on a single breaker is:
Safe Number of Outlets = 12 x 0.8 = 8
It shows, a total 8 numbers of outlets having the rating of 1.5 ampacity can be put on a 15 amp, 120 volt circuit breaker.
The same example and calculation can be followed for 15A, 20A, 30A etc 120V or 240V circuit breakers especially for outlets and general lighting fixtures. Keep in mind that a load exceeding 1200 Watts can be connected on a separate and dedicated circuit breaker. In addition, these calculations do not apply on 2-poles continuous load points and outlets that need complex configurations.
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Method 3 – When the Wattage Rating of Outlet is Known
How many outlets each of 80W can I put on a 20A, 120V circuit breaker?
First of all, calculate the total wattage rating which can be handled by 20A, 120V breaker
Wattage = Volts x Amperes
Power Wattage = 120V x 20A = 2400 Watts
Apply the safe limit of a breaker which is 80%.
2400 Watts x 0.8 = 1920 W.
Now, divide the wattage rating of the breaker by the wattage rating of the outlet.
Max Number of Outlets = 1920 W / 80W = 24
It means, we can install a total and max of 24 numbers of outlets each of 80W on a 20A, 120V circuit breaker.
Safest Number of Outlets = 24 x 0.8 = 19.2
The safe number of outlets are 19 which can be used on a 20A, 120V circuit breaker.
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