Residential Wiring

[AC\DC]

lets end this so the CMP does not make it mandatory to have a circuit every 6' for "safety"

 

[AC\DC]

There is no Code maximum, but there is certainly best practice and experience.

I use very few 15 amp circuits, and when I do, it’s lighting only. I never put receptacles on 15A circuits.

I’ve done some places where each bedroom got its own 20A circuit, lights and receps combined, as space heaters were anticipated, but generally I like to keep them separate, so when the HO plugs in their space heater and electric blanket and a few toys all at once, and trips the breaker, they aren’t also in the dark, , but that’s not a Code requirement.

I try to use experience and common sense. I will put at least 2 circuits into garages, I never combine bathroom receptacles, each bathroom gets its own circuit, etc.

I ask what the budget is. if you're going to go cheap you get cheap. I hate waiting my time giving a Wonderfull designed home but they compare it to a cheap person and I waisted my time.
Hence why I gauge the client.

 

[LarryFine]

Both the town houses my mom has owned were wired the same way. Had to run downstairs every time she tripped the one upstairs.

That’s easy enough to fix by adding a new GFCI receptacle and re-wiring to lne side at the old one.

 

[TX+ MASTER#4544]

What are you trying to tell me with that post? As others have repeatedly said, there is no limit on the number of receptacles on a dwelling unit branch circuit.

His question was ...........how many receptacles can he put on a 15 amp circuit.
Multiple the square footage of the dwelling times 3 VA per square foot.
Divide that by 120 volts.
Then divide that by 15 amp circuit breakers that you will need.
Round up if you have a remainder (fraction thereof).

Then read 210-11 Branch Circuits Required (A) (B)
Knowing how many circuits you need will now allow you to evenly provide the approximate number of receptacles on the 15 amp circuit.
Do the same if you want to use 20 amp circuits.

Thanks for reading
TX+MASTER #4544

 

[AC\DC]

So if my home needs 6-15amp circuits- could I have 5- single dedicated receptacle and the the rest of the home’s receptacle and lighting on one??? Would not do that unless I hated the guy lol

I don’t have book on me but I don’t rember anything but how many you have to supply based on virtually the square footage

 

[retirede]

His question was ...........how many receptacles can he put on a 15 amp circuit.
Multiple the square footage of the dwelling times 3 VA per square foot.
Divide that by 120 volts.
Then divide that by 15 amp circuit breakers that you will need.
Round up if you have a remainder (fraction thereof).

Then read 210-11 Branch Circuits Required (A) (B)
Knowing how many circuits you need will now allow you to evenly provide the approximate number of receptacles on the 15 amp circuit.
Do the same if you want to use 20 amp circuits.

Thanks for reading
TX+MASTER #4544

That method describes how to evenly apportion the number of receptacles across the minimum possible number of circuits. If you do that, chances are you won’t have enough receptacles to satisfy the 6/12 rule unless it’s a completely open floor plan with few interior walls. I’d bet that no EC does this, ever.

The real answer is that here is nothing in the NEC that limits the number of receptacles on a general purpose circuit.

 

[Eddie702]

There is no limit to the # of receptacles or lighting outlets on a circuit weather 15 or 20 amp. The code is the MINIMUM standard. Limiting the # of outlets to 10 or so on a 15 amp circuit and following square footage requirement as @TX+ MASTER#4544 posted is the way I would go. If you have to add another circuit to meet the 6/12 requirement then so be it.

 

[garbo]

As an inspector I had plenty of homeowner complaints when they tripped breakers when using their exercise machines in bedrooms while someone was vacuuming (or such). Shame as these were often 500k+ homes with 15+ receptacles on a 15 amp circuit and multistory making new circuits practically impossible.
Low bid electricians, no GC requirements

Did some work on a custom house that today would cost at least $750K. Customer told me that her maid was unable to pull out the electric range to clean & mop under it. After the hack sparky installed the SEU cable to range he went down to the basement and pulled the cable tight. Used #14 NM cable where ever allowed. Worst was he placed the 3 bathroom & 2 outdoor receptacles on one 20 amp GFCI circuit breaker. Luckily the service panel was not far from the range so I replaced the cable and installed a 50 amp receptacle and cord set for range. Was able to run a new line to one bathroom and placed the two outdoor receptacles on a GFCI breaker.

 

[tortuga]

So here is a example (I think I have posted before);
Say we have an existing 15 Amp lighting and receptacle branch circuit that feeds 900 SQ FT of a house,
including the existing 300 SQFT kitchen, 400 SQ FT living room and a 1/2 the receptacles in a 400 SQFT master bedroom.
220.11 states in part:
Branch circuits for lighting and for appliances, including motor-operated appliances, shall
be provided to supply the loads calculated in accordance with 220.10.
220.12 & 220.14 (J) basically says we can use the 3VA/sqft from the table T220.12.

Step 1 calculate the dwelling space square footage supplied by this circuit
300 + 400 + (1/2 of 400 ) = 900 SQFT

Step 2 calculate the 'load' on our 15 amp branch circuit is 900 SQFT of dwelling space
900 SQFT X 3VA = 2700 VA

220.18 says the rating of a branch circuit is determined by the breaker, 15A breaker = 15A rating.

210.23 Permissible Loads states that Multiple-Outlet Branch Circuits that the load in no case can exceed the branch-circuit ampere rating.
Step 3 calculate the permissible load in square feet;
15 amps X 120 Volts = 1800 VA
1800 VA / 3VA-SQFT = 600 SQFT per 15A circuit.

So i'd say a branch circuit that is new or extended to supply more than 600 SQFT would be a violation.
But if I had a 600 SQFT room and every wall was entirely outlets
there would be no violation, provided the loads are the ones in 220.14 (J)

 

[tallgirl]

I'm British. For us we have have one lower floor lighting and another for the upper floor. This is typical for residences.

Y'all also run ring circuits, so not the same. Y'all also tend not to waste electricity on all the crap Americans do.

 

[don_resqcapt19]

There used to be a code section in Art. 90 that said a local jurisdiction would supersede the NEC if it were more stringent than the NEC section. That was in place at the time that I wired homes in the 80's. I've had several inspectors count openings on a circuit.

The only way that can happen is if the local jurisdiction would adopt a local amendment to the NEC, using the same process as they used to adopt the NEC itself. This has never been in Article 90 or any other part of the code.

 

[Besoeker3]

Y'all also run ring circuits, so not the same. Y'all also tend not to waste electricity on all the crap Americans do.

I agree with your points. Another difference with UK residential is that it is all 230V Hz, no 110V.

 

[tortuga]

I agree with your points. Another difference with UK residential is that it is all 230V Hz, no 110V.

Except for construction sites then you have 110V 50hz

 

[tallgirl]

Except for construction sites then you have 110V 50hz

The UK needs to attack us again so we can conquer them once and for all and fix their stupid electrical grid.

 

[tallgirl]

So here is a example (I think I have posted before);
Say we have an existing 15 Amp lighting and receptacle branch circuit that feeds 900 SQ FT of a house,
including the existing 300 SQFT kitchen, 400 SQ FT living room and a 1/2 the receptacles in a 400 SQFT master bedroom.
220.11 states in part:
Branch circuits for lighting and for appliances, including motor-operated appliances, shall
be provided to supply the loads calculated in accordance with 220.10.
220.12 & 220.14 (J) basically says we can use the 3VA/sqft from the table T220.12.

Step 1 calculate the dwelling space square footage supplied by this circuit
300 + 400 + (1/2 of 400 ) = 900 SQFT

Step 2 calculate the 'load' on our 15 amp branch circuit is 900 SQFT of dwelling space
900 SQFT X 3VA = 2700 VA

220.18 says the rating of a branch circuit is determined by the breaker, 15A breaker = 15A rating.

210.23 Permissible Loads states that Multiple-Outlet Branch Circuits that the load in no case can exceed the branch-circuit ampere rating.
Step 3 calculate the permissible load in square feet;
15 amps X 120 Volts = 1800 VA
1800 VA / 3VA-SQFT = 600 SQFT per 15A circuit.

So i'd say a branch circuit that is new or extended to supply more than 600 SQFT would be a violation.
But if I had a 600 SQFT room and every wall was entirely outlets
there would be no violation, provided the loads are the ones in 220.14 (J)
View attachment 2573742

This hurts my brain every time I see something like it.

Didn't someone calculate that if all of a 400A service was used inside a 3,000 sqft home, or something fairly large, that eventually it would catch fire and burn?

 

[Dennis Alwon]

Ask 20 electricians and you will get 10-15 different answers to your question. Personally, we used to wire all receptacles at 20 amps and all the lighting on 15 amp cir.
Back in my younger days I wired all lighting & receptacles with #12--I still can't believe I did that

 

[tallgirl]

Ask 20 electricians and you will get 10-15 different answers to your question. Personally, we used to wire all receptacles at 20 amps and all the lighting on 15 amp cir.
Back in my younger days I wired all lighting & receptacles with #12--I still can't believe I did that

All the people living in all those houses with kids who have giant gaming computers thank you. They can probably get by now that LED lighting and computer monitors exist, but I have to think there was a time in the 2000s when it would have been tight otherwise.

 

[Besoeker3]

Except for construction sites then you have 110V 50hz

That's why I said my point was residential.

 

[TX+ MASTER#4544]

That method describes how to evenly apportion the number of receptacles across the minimum possible number of circuits. If you do that, chances are you won’t have enough receptacles to satisfy the 6/12 rule unless it’s a completely open floor plan with few interior walls. I’d bet that no EC does this, ever.

The real answer is that here is nothing in the NEC that limits the number of receptacles on a general purpose circuit.

You're right but, that method describe above is according to NEC 2023 as I pointed out in my original response.

Again, if there's a lot of recess can lights at 150 watt lamp in each one then the licensed electrician will take that into consideration and possibly add additional circuits if necessary.
You can use 15 or 20 amp circuits for general lighting.

You will need some floor plugs when you have large open floor plans with few interior walls as you stated.
Remember, NEC is a minimum installation.

Only in commercial wiring there is a limit on the number of receptacles on a 15 or 20 amp circuit.

Thanks for reading
Comments accepted
TX+MASTER#4544

 

[tortuga]

This hurts my brain every time I see something like it.

Yeah I remember that one from when I was starting out and learning code, it was one of the first AHJ code appeals I remember, there was a inspector that enforced X number of receptacles on a circuit, and the electrician appealed it up the chain to some type of hearing, and the chief inspector for the state had to decide. As I recall the chief decided both were wrong, the local inspector could not enforce a max number of outlets but the electrician still failed because he had 900 SQFT on one circuit.