Residential Wiring

[James L]

Even if every bedroom has its own 15a circuit, turning on the lights to vacuum is likely to trip a 15a breaker, but one 20a circuit can supply several bedrooms because you're only going to vacuum one room at a time.

I don't even consider things like that when I'm wiring a run-of-the-mill house. For all I care, they can use a bathroom receptacle if they want to vacuum the bedroom.

As much as I can, I wire the same way I did back in the late '90s. I'm not going to change everything I do just because 1 in 500 houses needs a little bit more

 

[LarryFine]

It's not just that. There's less light dimming when receptacle loads turn on, which to me represents both better customer-perceived and better actual system performance.

A single 20a receptacle circuit and a single 15a lighting circuit can serve the same three bedrooms and hallway that might require three or four 15a general-purpose circuits.

 

[ptonsparky]

Other than the original AFCIs, we haven't tripped a breaker in 14 years. None due to overload.

Granted, we don't have a young family.

 

[TX+ MASTER#4544]

That is not correct. The VA per outlet is in article 220 and is for calculation purposes.

2023 NEC
Yes, calculations as follows.

Section 220.14( I )Receptacle Outlets ........." calculated at not less than 180volt amperes for each single or each multiple on one yoke".. (strap).
For commercial wiring for receptacles use 180 volt amperes. Not for residential.

A 20 amp circuit breaker and 12 gauge conductor..... (formula to find volt amperes) .....V X A = 120 volt X 20 amps =2400 volt amperes for a 20 amp conductor circuit capacity.

2400 VA / 180 VA per receptacle = 13.3 receptacles, round down to 13 receptacles. Check point: 13 x 180 VA = 2340VA just under the limit of 2400 VA.
Try using a 15 amp circuit breaker 15 x 120V = 1800 VA / ________________.

Thanks for reading
Comments accepted
TX+MASTER#4544

 

[roger]

2023 NEC
Yes, calculations as follows.

Section 220.14( I )Receptacle Outlets ........." calculated at not less than 180volt amperes for each single or each multiple on one yoke".. (strap).
For commercial wiring for receptacles use 180 volt amperes. Not for residential.

A 20 amp circuit breaker and 12 gauge conductor..... (formula to find volt amperes) .....V X A = 120 volt X 20 amps =2400 volt amperes for a 20 amp conductor circuit capacity.

2400 VA / 180 VA per receptacle = 13.3 receptacles, round down to 13 receptacles. Check point: 13 x 180 VA = 2340VA just under the limit of 2400 VA.
Try using a 15 amp circuit breaker 15 x 120V = 1800 VA / ________________.

Thanks for reading
Comments accepted
TX+MASTER#4544

Did you read the title to this thread?

 

[tortuga]

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

That is not correct. The VA per outlet is in article 220 and is for calculation purposes.

What would not be correct about that?
210.11 sends you to 220.10 to calculate the branch circuit load and the loads on the outlets.
210.23 states that the load you just calculated in 220 for the branch circuit cannot exceed the branch circuit rating.

 

[readydave8]

turning on the lights to vacuum is likely to trip a 15a breaker,

Must be a lot of lights

 

[ptonsparky]

I'll try two vacuums on the same 15 when I get home, just to see how long it takes to trip.

 

[Tulsa Electrician]

Next time my wife runs the vacuum I'll time her.
That should make an interesting dinner conversation.
If I'm not cooking my own while she times me. Now where is those ear plugs.

I'll try two vacuums on the same 15 when I get home, just to see how long it takes to trip.

Dang you have two. Must be rich.

If it trips the 15 amps breaker. I would provide pre vacume instructions so the breaker may not trip.

Step 1, All cooking and cleaning ( washer,Dryer,etc.) equipment not be in operation.

Step 2, Turn off all unnecessary lighting and make sure all device plugged into that circuit are in the off position and or unplugged.

Step 3, Turn HVAC thermostat to an off position so HVAC unit will not start or run during vacume cycle.

Step 4, if utility transformer feeds other houses only proceed after 10:30 pm and before 5 am.
Step 5, if not happy with 1-4. Hire a competent licensed electrician.

Recommendations:
Do not use for more than 3 hours at one time. If issue arises see preventive step 1-5*.

FPN. "If wired per NEC" appears on the contract. That's not a guarantee the vacume will run. It will guarantee if the 15 trips. it's doing it's job.

*Note: if your vacume has a name plate over 15 amps. Get smaller unit or see, step 5.

Personal note.
I can not count the times I have answer calls where the home owner had said the electrician that wired our house has said it's per code and there nothing we can do under any warranty. Some have offered to add additional wiring at an extra cost.
The owners position in most cases was I paid X, it should work.

Once I told a husband go buy a Dyson cordless and gift it to her. Now be sure to wrap it up real nice and seal it with a kiss. Take the old vacume to the garage.
Or pay us to add wiring.
Amazing what a night out and a gift can do. Wonder if it can be deducted from taxes as maintenance or up keep ?

Happy wife, happy life
Avoid steps 1-4 go straight to step 5.

 

[andyman]

Funny how much electricians tend to struggle with residential wiring codes. It seems like things are more cut and dry in commercial electrical like having a 180VA calc for receptacles. My method for wiring resi is to make sure all circuits that have a specific purpose are on a dedicated circuit. Most of the time you don't have a choice on this and the code requires it. Bathrooms, kitchens small appliance, laundry, dining room, these all require dedicated branch circuits. All of your appliances and heating will require dedicated circuits. Aside from this your major load is going to be lighting and you should be cautious not to overload your typical 15A lighting circuits, even with LED lighting you can run into problems with inrush current so I am careful not to go crazy and I stick to around 20-30 fixtures per 15A circuit even though the actual load is much probably going to be much less. That being said for a 2500 squ ft house you probably have 7 or 8 kitchen circuit this would inculde the DW, Pantry, K1, k2, Hood, micro, disposal, fridge, insta hot, etc. then you have 2 or 3 bathroom circuits for lights and receptacles ( I always combine the lights onto the receptacles for bathroom circuits to make it easy to GFCI protect any fan or light in the tub shower area), on site septic pumping system is good for a couple circuits, floor heat, ERV, garage rcpt, washing machine, dryer, range, EV charger, hot tub, heat pump #1, Heat pump #2, Boiler, circulation pump, Media panel for communications equipment.
With this list you can see that there are already a lot of circuit in a dwelling and because of this it is totally fine to use 4, 20A general receptacle circuits to pick up the living areas, hallways, bedrooms, etc.. Doing this you may end up with 20-30 receptacles on a branch circuit but it's not going to be a problem because all of the areas of high load are dedicated. The hallways, living areas, bedrooms are mostly just people plugging in a lamp or cell phone. Biggest load someone will plug in will be a vacuume cleaner and a 20A recpt. circuit handles this fine. If you start giving every bedroom and or office space a dedicated recept. circuit you are going to run out of space in your load center and need a sub panel. 15A receptacle circuits are useless in my opinion.

 

[ptonsparky]

15 amp are entirely suitable in most residential applications.

 

[James L]

I have never been called back for overload issues on a 15 amp circuit.

 

[LarryFine]

15A receptacle circuits are useless in my opinion.

Except for specific instances, I agree with that. One 20a receptacle circuit can work where two or three 15a receptacle circuits might be needed.

I typically wire a "kids' floor" of three bedrooms w/ceiling lights/fans, closet lights, hallway, and bath light/fan with one 15a and one 20a circuit.

With all 15a circuits, you'd probably need four circuits, especially when vacuuming: one for each bedroom and the fourth for the hall and bath.

 

[LarryFine]

I have never been called back for overload issues on a 15 amp circuit.

I haven't with any of my own jobs, but I have been called for that problem several times, mostly when vacuuming, because they tend to turn on all of the lights.

One obvious solution is separating lighting loads, which are predictable, from receptacle loads, which aren't to a great degree. I usually run one or two new circuits.

One circuit can be divided into three. Separate it into thirds at two points, then run one 3-conductor cable to a receptacle between the second and third sections.

 

[James L]

With all 15a circuits, you'd probably need four circuits, especially when vacuuming: one for each bedroom and the fourth for the hall and bath.

So it takes 60 available amps to do what a lone 20 p circuit will do? 🫣

 

[James L]

I haven't with any of my own jobs, but I have been called for that problem several times, mostly when vacuuming, because they tend to turn on all of the lights.

One obvious solution is separating lighting loads, which are predictable, from receptacle loads, which aren't to a great degree. I usually run one or two new circuits.

One circuit can be divided into three. Separate it into thirds at two points, then run one 3-conductor cable to a receptacle between the second and third sections.

How many circuits do you add to mitigate dimming of lights when an air conditioner turns on?

I'm not just being facetious, there's an excellent point to be made here.

Vacuum dimming might happen once a day, and electricians are going out of their way to try to stop it

Air conditioning dimming will happen 30 times a day, and electricians are content to tell their customer that's just the way it is.

Motors make lights dim. It's just a reality. They can always get a battery powered unit if they don't like it

 

[LarryFine]

So it takes 60 available amps to do what a lone 20 p circuit will do? 🫣

To make my point, let me take it to the extreme:

Even ten 15a circuits can not supply certain loads that one 20a circuit can.

 

[ptonsparky]

The only time we've had two vacuums running on the same circuit was when the window wells flooded. I can't imagine 4.

 

[LarryFine]

How many circuits do you add to mitigate dimming of lights when an air conditioner turns on?

Presuming you mean a central system, that's a matter of the service sizing.

I'm not just being facetious, there's an excellent point to be made here.

Mine or yours? ()

Vacuum dimming might happen once a day, and electricians are going out of their way to try to stop it

No, I have no problem with vacuuming. I'm all for it. Even once a month, the circuit has to carry it.

Air conditioning dimming will happen 30 times a day, and electricians are content to tell their customer that's just the way it is.

True, but I'm talking about breakers tripping (circuit issue), not lights dimming (service/feeder issue).

I do believe there is a perceived-quality effect that is lessened with 20a circuits' lower voltage drop.

Motors make lights dim. It's just a reality. They can always get a battery powered unit if they don't like it

Absolutely, and I have told more than one customer they don't need a new service because of it.

Again, I'm referring to calls that the vacuum trips bedroom circuits when the lights are on.

 

[LarryFine]

The only time we've had two vacuums running on the same circuit was when the window wells flooded. I can't imagine 4.

Imagine moving one vacuum from room to room, and tripping the breaker if the lights are on.

Even with all 15a circuits, dividing the lights and receptacles onto separate circuits would help.