discusion at work

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brian john

Senior Member
Location
Leesburg, VA
A 20a breaker can actually hold more than 20 amps. It will not magically trip at 20.0000001 amps, but the higher the amperage goes, the quicker it trips. 21 amps may never trip it, 22 amps may take 4 hours, 23 amps may take an hour, 24 amps may take 10 minutes.... It's called a trip rating curve or something like that.



I'll be there! Where is it?


Inverse time-current


In addition an old inspector once told me (I have posted this before). Put every outlet in the house on one 15 amp circuit (excluding the NEC mandated 20 SAC) and then install one dedicated 15 amp circuit and the home owner will overload the dedicated circuit.


See page 19

http://static.schneider-electric.us...rs/QO-QOB Circuit Breakers/0730CT9801R108.pdf
 
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newinspector1

Member
Location
NC
There is not a specific number but I was taught this formula.

(dwelling units in square feet x 3 volt amps per square feet)/ (15 amps x 120 volts per circuit) =number of circuits and round to the next highest number
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
What I actually do is to assign (i.e., on the Panel Schedule) a value of 180 VA to each duplex receptacle. Then I make sure that the total “assigned” load on any 20 amp receptacle circuit does not exceed 1920 VA. Thus, I never put more than 10 duplex receptacles on a 20 amp circuit. Most of the time, the number is smaller than that.

Please note, however, that we are now discussing design considerations. Nothing in the NEC would prevent me from designing a 20 amp branch circuit (residential or otherwise) that had 50 duplex receptacles.


Charlie I don't think that you could argue in your favor that you would be compliant with 210.11 (A) and (B). The only way I see is that branch circuit supplies some space that you only plug in incedental loads like a lot of those Wall worts that only consume a few watts. If that circuit was general use receptacles in commercial or a residence that tied in several entire bedrooms If i were the AHJ I would say is does not comply.
 

lefty

Member
Location
Oklahoma
I beg to differ 220.14 all occupancies, 220.16 additions to dwellings. I ask, can you tell me where in the code you can place as many as you want? My interpetation of the code tells me that there is a limit based on the va. I would add that a workman like manner would not install an endless number on a circuit, I hope you would agree.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I beg to differ 220.14 all occupancies, 220.16 additions to dwellings. I ask, can you tell me where in the code you can place as many as you want?
You know us. Tell us where it's prohibited.

My interpetation of the code tells me that there is a limit based on the va.
Code section?

I would add that a workman like manner would not install an endless number on a circuit, I hope you would agree.
On that, absolutely. Plus, I'm one of the guys here who prefer keeping lighting and receptacles separate in other than kitchens, too.

"Residential receptacle aren't just for lighting anymore."
 

lefty

Member
Location
Oklahoma
why would 220.14 and those following, not limit the number of receps and that is for dwelling and all occup. that is where i feel it is prohibited, the nec is not designed to be for untrained persons
 

tom baker

First Chief Moderator
Staff member
I don't do resd. 2 questions how many recp. can you put on 15 amp circuit i say doesn't matter. the guys say you can only go 80% of the breaker ampacity i laught at them hope i am wright

For residential, the receptacle loads are included in the 3 VA/SQ foot load calculation, and you can have as many as you care to install on a circuit.
The receptacles are spaced 12 ft apart in bedrooms and livingrooms, etc.

For commerical, you don't have to install any 15 or 20 amp receptacles at all.
But each one you install counts 180 VA per strap. Most will limit the number of receptacles to 12 on a 20 amp circuit.
And the 80% rule does not apply as receptacles are not a continuous load.

Sorry the posts got off topic but the above is your answer.
 

lefty

Member
Location
Oklahoma
the 3va/sqft is for calculating the load for your service. 220.14 determines the load in dwellings as well, i differ with you on the fact that you can have as many asyou can.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
why would 220.14 and those following, not limit the number of receps and that is for dwelling and all occup. that is where i feel it is prohibited, the nec is not designed to be for untrained persons
Please read all of the words in 220.14(I).
 

iwire

Moderator
Staff member
Location
Massachusetts
I beg to differ 220.14 all occupancies, 220.16 additions to dwellings. I ask, can you tell me where in the code you can place as many as you want? My interpetation of the code tells me that there is a limit based on the va. I would add that a workman like manner would not install an endless number on a circuit, I hope you would agree.

the 3va/sqft is for calculating the load for your service. 220.14 determines the load in dwellings as well, i differ with you on the fact that you can have as many as you can.

Lefty, lets think on this.

Lets say you decide to put a bedroom on it's own circuit and install the code minimum receptacles, lets say that is one on each of the walls for a total of four duplexs on the circuit.

I think can we both agree that circuit is not likely to be overloaded.

Now lets take the exact same bedroom and place 3 additional duplex receptacles per wall just because the customer wants that for convenience.

Now we have a total of 16 duplexs on that circuit.

Is it now overloaded?

Will the homeowners buy more electrical stuff to plug in just because there are more receptacles in the room?
 

lefty

Member
Location
Oklahoma
I stand down, i try to place a good useful system whever i work. i understand your point, and looking over my calcs i realized that, i said receps (duplex) that would mean 20 receps and 26 respectivly. But I still have question regarding 220.14, does that refer to dwellings, and why or why not. But respectfully I hope nobody loads up a circuit with as many as you want, I hope we are all using a workman like manner in placing the quantity of receps.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Lefty, lets think on this.

Lets say you decide to put a bedroom on it's own circuit and install the code minimum receptacles, lets say that is one on each of the walls for a total of four duplexs on the circuit.

I think can we both agree that circuit is not likely to be overloaded.

Now lets take the exact same bedroom and place 3 additional duplex receptacles per wall just because the customer wants that for convenience.

Now we have a total of 16 duplexs on that circuit.

Is it now overloaded?

Will the homeowners buy more electrical stuff to plug in just because there are more receptacles in the room?

Well if that same circuit supplied all 4 bedrooms of a house and there were no other bedroom circuits. NOT per 220 14 but I would say definatley yes for the possibility of of a over loaded circuit.
I will stick to 210.11 (A)
" In all installations, the number of circuits shall be sufficient to supply the load served" 2005 NEC.
This wording leaves rom for interpretation. As a E for 20 years I would say that putting the entire house convinece outlets on one circuit would not be sufficient.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
I hope we are all using a workman like manner in placing the quantity of receps.

Lefty, what would that be?

In my living room there is a TV, PC, two 60 watt lamps, a ceiling fan, and three unused duplex receptacles. If receptacles were placed every three inches along the wall it would be great for when my wife wants to change the room around but the circuit would never see an increase in load, so how would that equate to workman like or unworkman like?

I believe the NEC takes into consideration that it is far better to have a 20, 30, 40, or more receptacles on a single circuit than to have homeowners run cheap extension cords all over a house.

Roger
 
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