Too many outlets

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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Not quite useless.

With receptacle outlets in a residence, the _real_ load is unknown, and therefore it is senseless to try to evenly proportion the real load.

However the _calculated_ load per square foot is known. So the minimum number of code required general purpose circuits is known. One can reasonably apportion the calculated load amongst the required circuits.

Exactly how to do this proportioning is IMHO not well clarified. Say you've calculated that you need 3 general purpose circuits. Do you proportion these circuits by number of outlets, or do you proportion these circuits by associated floor area? But with any reasonable installation you can come up with a reasonable division of the circuits and be just fine.

-Jon
 
infinity

infinity

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Location
New Jersey
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Journeyman Electrician
winnie said:
Exactly how to do this proportioning is IMHO not well clarified. Say you've calculated that you need 3 general purpose circuits. Do you proportion these circuits by number of outlets, or do you proportion these circuits by associated floor area? But with any reasonable installation you can come up with a reasonable division of the circuits and be just fine.
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Reasonable division is something that someone can claim to do but it is cannot be done without knowing the future loads. I think that we all try to divide the receptacle/lights up evenly but it doesn't really ensure that loads will be evenly distributed. I'll stick with my assessment in post #62. :)
 
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JohnE

JohnE

Senior Member
Location
Milford, MA
augie47 said:
Every so often, in inspecting, I would have a DIYer interpret the "six foot rule" as a receptacle every 6 ft. :)
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When countertop receptacle spacing changed (maybe 15-20 years ago, I don't remember) there was a very solid EC that misread the requirement and did a few houses with the receptacles no more than 2' apart. I was inspecting them and let him know....
 
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
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retired electrician
letgomywago said:
The receptacles in a dwelling for the most part are "lighting outlets" even the bathroom receptacle is in this portion although minimum size for it is 20a and is doesn't cover a large square footage
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How are they lighting outlets? The term lighting outlet is a defined term and does not include receptacles. The general use receptacles are included in the 3VA per square foot calculation which includes
  • (1)All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits specified in 210.11(C)(3) and (C)(4)
  • (2)The receptacle outlets specified in 210.52(E) and (G)
  • (3)The lighting outlets specified in 210.70
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
petersonra said:
No matter how many outlets you have, it always seems like you need more and end up with a bunch of power strips. While I am not a huge fan of power strips, I don't believe they are fires waiting to happen as a lot of electricians like to claim.
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I agree. I don't know any way in an existing home to set up an office with multiple computers, monitors, printer, and desk lighting, or a home recording studio with lots of very small loads, or a home entertainment system with multiple components without using power strips.
 
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letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
don_resqcapt19 said:
How are they lighting outlets? The term lighting outlet is a defined term and does not include receptacles. The general use receptacles are included in the 3VA per square foot calculation which includes
  • (1)All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits specified in 210.11(C)(3) and (C)(4)
  • (2)The receptacle outlets specified in 210.52(E) and (G)
  • (3)The lighting outlets specified in 210.70
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Bath lights can be on with the receptacle so long as it's dedicated for that bath. In a 60a service they were in the lighting section.
 
L

letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
don_resqcapt19 said:
How are they lighting outlets? The term lighting outlet is a defined term and does not include receptacles. The general use receptacles are included in the 3VA per square foot calculation which includes
  • (1)All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits specified in 210.11(C)(3) and (C)(4)
  • (2)The receptacle outlets specified in 210.52(E) and (G)
  • (3)The lighting outlets specified in 210.70
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Also pre 2020 nec the 3 va per ft was in table 220.12 that 3va included all that you listed. The general outlets are or were "lighting load" outlets
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Electriman said:
not happy with the number of receptacle and he does not want to approve the work.
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Ach well heaven forbid, tech HO how to install an outlet and tighten wire nuts and leave HO the outlets with pigtails and outlet plates.
 
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T

TX+ MASTER#4544

Senior Member
Location
Texas
Occupation
electrical Code instructor and mentor
Jpflex said:
TOTAL VA load for dwelling is outside diameter sq ft x 3 VA

So calculating the number of 20 ampere circuits would still be:

Total square feet x 3 VA / 120 x 20 branch circuit

However, after looking at my book it says that determining the number of receptacles allowed on one circuit would be 120 x 20 / 180 VA for NON DWELLINGS so you are right

Which means besides the 6 -12 foot spacing requirements I guess I do not know how many receptacles can be placed on a 120 v x 20 i = 2400 VA branch circuit for dwellings?

Does anybody know?
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T

TX+ MASTER#4544

Senior Member
Location
Texas
Occupation
electrical Code instructor and mentor
How to determine the required number of circuits for 120 volt receptacles that are needed for a 2500 sq.ft one family dwelling.
Note that this only for general lighting and receptacles. Does not include 2 small appliance 20 amp circuits, laundry or bath room(s).
Section 210.11 (A) Branch Circuits Required, 2023 NEC. Use Ohms Law as follows:
2500 x 3 VA /sf ft =7,500 VA
7500 VA / 120 volts = 62.5 Amps
Round up to 63 amps
63 amps / 15 amp circuit breaker = 4.2 or 5 (round up) 120v 15 amp circuits. Or you may use 20 amp rated receptacles.
Now let's use a 20 amp circuit and same 63 amps / 20 amp circuit breaker = 3.15 round up to 4 20 amp branch circuits. Check point: 4 x 20amps = 80 amps adequate for the 63 amp circuit.
If you use 15 amp circuit breakers x 5 = 75amps, a little more than needed but adequate.
Had you not rounded up to 5 circuits, a check point will prove to be incorrect thus, 4 x 15A = 60 amps. Our load is 63 amps.
Now,210.11 (B) Load Evenly Proportioned Among Branch Circuits. So, a licensed electrician that knows this will plan the branch circuits with that in mind but remembering there is a little edge built in to the equation and he likely use a rule-of -thumb for placing a certain number of receptacles on each of the circuits. And, keeping in mind that the lighting load will be included in the number of circuits.
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
letgomywago said:
In WA you need to calculate the square footage that is covered by the lighting calc so 1 circuit per 600ft^2 or so.
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Agreed I dont think its super complicated or special, 220.11 says the branch circuits are calculated per 220.10.
210.19(A)(2) deals with minimum conductor size for that load.
There has been some rearranging in 220 in various code cycles but you end up with 3VA per square foot and work backwards from that.

So going by the info in post#1:
Electriman said:
single family home 3300 sq ft, 4 bedroom two story. The owner has about 160 outlets.
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I would judge the branch circuits by two factors

#1 do a 220 calc for the branch circuits as letgomywago suggested;
(120V X 15A) / 3VA per sqft
1800/3 = 600 SQFT, so no one circuit should cover more than 600 SQFT of house.
One could check for "utilization equipment fastened in place" and/or motors on the general purpose circuits and adjust the square footage allowance accordingly.
Say there is a "utilization equipment fastened in place" load of 7.5 Amps:
7.5X120V = 900VA
1800VA-900VA=900VA
900VA/ 3VA per sqft =300SQFT

#2 As others have mentioned the load should be evenly proportioned.
presuming a new house the actual loads are unknown and will be evenly divided.
If the loads are known, like very custom home, then the installer should be able to explain how they are evenly proportioned.
To accomplish this I'd a 220 calc for the minimum number of circuits for the entire house, then divide the total number of recepts by that.

per article 220:
3300 X 3VA per sqft = 9900 VA

For 15A 120V circuits;
the maximum VA is 15A X 120V = 1800VA

Therefore the minimum number of circuits is;
9900 VA / 1800VA = 5.5
round up to 6 circuits

Load evenly proportioned;
160 Receptacles / 6 circuits = 26.6

Round up to 27
If more than 27 are on a circuit then they should be able to explain how the load is evenly proportioned.


If any one 15A circuit covers more than 600 SQFT then there is a violation.
Other than motors in 430.53, I think that is all that's enforceable NEC wise
 
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