Thread: Number of outlets on a single circuit?

Inspected a home today that had 16 outlets "protected" by a single 20-amp GFI breaker. Is there a maximum number of outlets that can be tied to one breaker such as this?

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"Inspected a home today that had 16 outlets "protected" by a single 20-amp GFI breaker. Is there a maximum number of outlets that can be tied to one breaker such as this?"


Depends on location. But the short answer is no.

Originally Posted by Greg Subick

Inspected a home today that had 16 outlets "protected" by a single 20-amp GFI breaker. Is there a maximum number of outlets that can be tied to one breaker such as this?

No, but keep in mind that a "little bit" of inconsequential leakage at things plugged into each of those outlets will be additive and will trip the GFCI - and there may really be nothing wrong.

Remember, "code" is "minimum", code is not common sense, code does not mean things will work well.

With "code" ... that GFCI tripping would not be a problem as the GFCI would be doing it job.

Thanks for the replies guys. GFI is doing its job, just appears to be one outlet on exterior that is causing some problems.

No restrictions on residential by the NEC*, non-residential does have restrictions on the number allowed.

* Some areas may have local amendments though.

3 watts per square foot and the amperage of the circuit will give you the number of square feet to be protected on a single circuit of 15 or 20 amps. It's really very simple math to figure it out. This comes directly from the NEC. I wouldn't expect local amendments to modify this area of code.

Hi Greg about your question do some calculation based on NEC 220.14 (I) It sez minimum 180 VA per outlet,that mean is 180W/120V=1.5Ax16 OUTLETS= 24 A.That breaker is little bit overloaded.That is why many electricians use as a rule no more then 10 outlets on general purpose branch circuits.

Originally Posted by Bob Winchester

3 watts per square foot and the amperage of the circuit will give you the number of square feet to be protected on a single circuit of 15 or 20 amps. It's really very simple math to figure it out. This comes directly from the NEC. I wouldn't expect local amendments to modify this area of code.

Hey Bob,
The section of the NEC referenced in your comment (NFPA 70 2008 NEC 220.12) only covers loads for service calculations, the NEC does not cover quantity of receptacle openings on a residential single circuit, though this is often misinterpreted.
I would like to reiterate a previous comment on this thread, the code is a minimum for safety, it is not a design standard for an efficient or properly designed project, nor is it intended for the non-electrical professional. (Not intended as a disparaging remark toward Bob! Your participation is appreciated!)
Cordially,
Bill Nolte, C.S.H.O.
Master Electrician
Fort Worth, Texas

Originally Posted by Bob Winchester

3 watts per square foot and the amperage of the circuit will give you the number of square feet to be protected on a single circuit of 15 or 20 amps. It's really very simple math to figure it out. This comes directly from the NEC. I wouldn't expect local amendments to modify this area of code.

The 3 watt per sq. ft. figure is only for calculating the size of the electrical service. There is nothing that requires this calculation be applied to circuit layout for supplying outlets in a residence. There are a small number of building officials who try to apply the calculation figures to actual outlet placement but they are few and far between as there is no force of law without a local ammendment. Use is a much better predictor of load and reason for circuit layout.

The figures used for service calculations are designed as a best guess for the total load on the electric service. They include the possibility that some rooms are going to be heavily loaded and some little or none.

The possibility that 2 adjacent bedrooms may have a ceiling light, a small table light, and maybe an electric clock are just as realistic as 2 adjacent bedrooms that have ceiling lights and fans, a quartz floor lamp, electric blanket, TV, stereo, computer, etc. etc., and easily overload a 15 AMP circuit on their own - keeping in mind teens are likely to have all of this and more in use at the same time.

Additionally, there is no rule that an outside receptacle can't be on the same circuit as a bedroom receptacle - how do you figure the Sq. footage for that circuit?

Originally Posted by Alexei Chaviano

Hi Greg about your question do some calculation based on NEC 220.14 (I) It sez minimum 180 VA per outlet,that mean is 180W/120V=1.5Ax16 OUTLETS= 24 A.That breaker is little bit overloaded.That is why many electricians use as a rule no more then 10 outlets on general purpose branch circuits.

I know it's been a long time since I have worked and studied, but for residential circuits we always used seven (7) as the maximum outlets on a 20 Amp circuit. Sixteen is just nuts...

Originally Posted by Alexei Chaviano

Hi Greg about your question do some calculation based on NEC 220.14 (I) It sez minimum 180 VA per outlet,that mean is 180W/120V=1.5Ax16 OUTLETS= 24 A.That breaker is little bit overloaded.That is why many electricians use as a rule no more then 10 outlets on general purpose branch circuits.

Alexei,

Article 220 deals with services, not how to size a branch circuit.

Just because there are 16 places to plug utilization equipment in does not place any load on the circuit. The loading in a residence is too transient to make a statement like you did. I could also potentially overload a circuit that only had one duplex.

I think there is some code that would come into play on a circuit with lots of receptacle outlets. Electricians typically know this and limit the number which equates to excess wire length in most cases as a general practice in order to prevent a home inspector or code inspector with a voltage drop meter from finding a costly correction.

A footnote (NEC 210-19 FPN No. 4) in the National Electrical Code states that a voltage drop of 5% at the furthest receptacle in a branch wiring circuit is acceptable for normal efficiency. In a 120 volt 15 ampere circuit, this means that there should be no more than a 6 volt drop (114 volts) at the furthest outlet when the circuit is fully loaded. It also means that the circuit has a resistance that does not exceed 0.4 ohms.

Info from:
FAQ - Voltage Drop

Originally Posted by Bruce King

I think there is some code that would come into play on a circuit with lots of receptacle outlets. Electricians typically know this and limit the number which equates to excess wire length in most cases as a general practice in order to prevent a home inspector or code inspector with a voltage drop meter from finding a costly correction.

Info from:
FAQ - Voltage Drop

NO code inspector or Home Inspector can enforce any voltage drop issue UNLESS it is written into and adopted, by the local jurisdiction.
Voltage drop is not in the nec except as a fine print note, and fine print notes are not enforceable as code.
Article 90.5 (C) -Explanatory Material
Explanatory material ,such as references to othewr standards, references to related sections of This code, or information related to a code rule,is included in this code in the form of fine print notes ( FPNs). Fine Print notes are informational only and not enforceable as requirements of this code.

Originally Posted by Alexei Chaviano

Hi Greg about your question do some calculation based on NEC 220.14 (I) It sez minimum 180 VA per outlet,that mean is 180W/120V=1.5Ax16 OUTLETS= 24 A.That breaker is little bit overloaded.That is why many electricians use as a rule no more then 10 outlets on general purpose branch circuits.

That does not apply to dwelling unit receptacles.

For dwelling units, here is an example:
Q. How many receptacles are allowed on a 15 amp circuit?
A. How many do you want?

That is absolutely the answer for residential dwelling units.

For Canadian HI's, I gotta say this. In Canada, the maximum number of outlets on a 15 amp residential circuit is 12. Simple.

AFCI protection is only required on bedroom wall receptacles. That is why two adjacent bedrooms will have the wall outlets up to 12 all on one AFCI breaker and the bedroom lights on some other non-AFCI circuit. The third bedroom might have wall outlets and lights on the second AFCI. Not so simple. But only in Canada, and I can't speak for out east or Newfoundland.

If by "outlets" you mean receptacles, there is no general limit in the unammended NEC for residential general occasional use receptacles supplied by a single circuit. In other than residential there are limits which use for receptacles a VA rating per device (receptacle) of 90 va, or 180 for a standard "duplex".However, not all "outlets" are receptacles. Outlets are where electricity is "worked". There are limitations regarding fixed in place appliances with combination or motor loads, which are supplied by cord and plug connections sharing circuits with other "outlets" not exceeding 80%/50% of the rating of the circuit. Those other than pure resistive light loads (power supplies) work electricity differently.There are limitations as to the loading of "luminaires" on circuits too, other devices can "work" electricity.Just a few examples, point being...."outlets" include more than occasional use "receptacles". There are also a number of areas which require specific purpose circuits and receptacles and limit the areas or shared use by their application, with other "outlets" covered in certain circumstances which may apply to a particular residential system. For example a separate laundry occasional use receptacle circuit which is not shared by the laundry machiines, or receptacles in another area, but may serve an unlimited number of occasional use receptacles within the laundry area. As mentioned by R.M., local ammendment may apply as well.