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 DIY Chatroom Home Improvement Forum Breaker AMP question/opinion?

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01-02-2010, 09:07 PM   #1
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## Breaker AMP question/opinion?

I just found out that all the receptacles in the Living Room, Foyer, Office and all the lights in the Hall Way, Office, Garage, Kitchen, Living Roon and Dining Room are under one 20A breaker. These means a total of 21 Ligths and 8 receptacles under one 20A breaker.

Isn't a 20 AMP kind of a overkill for that setup? Is there a max number of receptacles or light fixtures that are permitted to be connected to one 20A breaker?

I'm familiar that 20 AMP is equal to 2400 WATT . At 80% max capability
can support 1920 Volt or 25.6 Light Fixture using 75watt ligth bulbs, but I'm puzzled that the electrician added the 8 receptacles under same breaker.

Alone the 8 receptacles will draw 12 AMP. Thus limiting max wattage for light fixture.

01-02-2010, 09:21 PM   #2
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Quote:
 Originally Posted by avtck I just found out that all the receptacles in the Living Room, Foyer, Office and all the lights in the Hall Way, Office, Garage, Kitchen, Living Roon and Dining Room are under one 20A breaker. These means a total of 21 Ligths and 8 receptacles under one 20A breaker. Isn't a 20 AMP kind of a overkill for that setup? Is there a max number of receptacles or light fixtures that are permitted to be connected to one 20A breaker? I'm familiar that 20 AMP is equal to 2400 WATT . At 80% max capability can support 1920 Volt or 25.6 Light Fixture using 75watt ligth bulbs, but I'm puzzled that the electrician added the 8 receptacles under same breaker. Alone the 8 receptacles will draw 12 AMP. Thus limiting max wattage for light fixture.
Why would a 20a circuit be overkill ?
In the US you can connect as many outlets as you want
It's usually not practical to do so

What do you have on each receptacle that draws exactly 2a each ?
Circuits can be loaded to 100% of their capacity, 1920 volts? I think you mean watts
Most never hit the Max load

Where are you located ?

What kind of lights ?

 01-02-2010, 09:27 PM #3 Super Moderator     Join Date: Mar 2005 Location: Welland, Ontario Posts: 18,829 Rewards Points: 24,000 Blog Entries: 11 Is the cable all #12? Are you having issues with the breaker tripping? If you answered yes,no then don't be concerned unless you are planning to add some additional loads to the circuit. In Canada we are limited to 12 device per circuit and lighting MUST be a 15 amp circuit.

 01-02-2010, 10:00 PM #4 Member   Join Date: Sep 2008 Location: Oregon Posts: 1,497 Rewards Points: 500 Every 120 volt outlet in my house is on a 20 amp circuit. The thing is that pesky vacuum cleaner! Plug all your regular stuff in, then plug in that vacuum and pop goes a 15 amp breaker! Or try to use a space heater in addition to everything else. Or some other power hog. Again a 15 amp breaker will not handle the load and will trip. Anyway I like 20 amp circuits. I don't have breaker tripping problems. So far as how many outlets, take the case of a work bench in a garage. It might have one of those power strips with outlets every 4 inches along the entire 8 foot length of the workbench. But you might only be using one or two of those outlets at any one time. So OK. But in a kitchen it is different. Lots of power hogs in a kitchen. So you might want just one outlet on its own circuit for the microwave. And just one outlet on its own circuit for the refrigerator. And just a couple of outlets on a circuit for the counter top outlets. And several circuits for the counter top outlets. This is because you have power hogs like a deep fryer, hot plate, electric skillet, bread machine, etc. which use a lot of electricity. Just a couple of these on the same circuit and it will pop a breaker. Then a living room is different. Just TV, stereo, lamps, maybe a phone. Not much electric use, so all the outlets in the room can be on the same circuit.** **That is unless you have a "neighborhood blasting" stereo system and a football field sized big screen TV - in which case you may want a separate circuit for the entertainment center. Basically if you are having problems with the breaker tripping, split off some of the things you mentioned above into a separate 20 amp circuit. Or add one new circuit to a power hog - maybe TV?
01-02-2010, 10:26 PM   #5
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Quote:
 Originally Posted by Scuba_Dave In the US you can connect as many outlets as you want
The NEC give a rateing for a rec at 1.5 amperes. So one of the correct ways to see how many outlets you can put on a circuit is take your breaker rating and devide it by 1.5.

Example 15 divided by 1.5 = 10
or 20 divided by 1.5 = 13.3 or 13

The other way is to take the square footage x 3 divide by the voltage then devide by your circuit ampacity gives you the minumn circuits for your general lighting circuits which will be slightly higher than the above equation.

Example 2000 sq ft house x 3va = 6000 divide by 120v = 50va then divide by 15a = 3.3 circuits or 4 - 15a circuits

You will still find this for a 2000 sq ft house will be 13 to 15 outlets on a 15a circuit.

 01-02-2010, 10:32 PM #6 Member   Join Date: Jan 2009 Location: South of Boston, MA Posts: 17,248 Rewards Points: 2,000 As I understand it that is for calculating load I've yet to see a specific code reference that indicates a Max number of outlets that can be connected in a residential setting
01-02-2010, 11:39 PM   #7

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Quote:
 Originally Posted by Scuba_Dave As I understand it that is for calculating load I've yet to see a specific code reference that indicates a Max number of outlets that can be connected in a residential setting
That's because there is no such code.

The set up the OP described is fine for an older home, but you may run into a few problems when running kitchen appliances like toaster ovens and microwaves on that same 20 amp circuit. This is likely an old house and I suspect the 20 amp breaker is under 14 gauge copper. You might want to check that.
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 01-03-2010, 12:48 AM #8 Newbie   Join Date: Jan 2010 Posts: 20 Rewards Points: 10 Let me clarify again. a) Why would a 20a circuit be overkill ? I meant only one 20a circuit might be insufficent to run 29 outlets (21 lights + 8 recep) all at once. b) What do you have on each receptacle that draws exactly 2a each ? Nothing is using that many AMP. As codeone mentioned the NEC give a rating for a receptacles at 1.5 amperes. c) although circuit can be loaded 100%, it is safer/best to use 80% of total capacity for when computing the max capability d) I'm Located in the USA e) The house is 4 years old f) The cable are either 12.2 or 12.3 g) Are you having issues with the breaker tripping? No . d) Are planning to add some additional loads to the circuit. Yes. h) Bath, kitchen, Garage , Bedrooms have their dedicated outlets My main concern was that the max number of outlets connected to a single 20a Circuit was insufficent when calculating load using 75Watt or 100Watt bulbs. If I were to use : 21 100Watt bulbs (2100 Watt) + 8 Receptacles (1440Watt) ====================== Total 29.5 AMP, therefore a 20a breaker will trip. I don't understand why the electrician would do that. If were me. I would had added an additional breaker and split the system 15AMP for lights and 20AMP for Receptacles. Anyways thank you for the responces..
01-03-2010, 05:07 AM   #9
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Quote:
 Originally Posted by codeone The NEC give a rateing for a rec at 1.5 amperes.
Wrong. That does not apply to residential. 220.14(I) and (J)
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 01-03-2010, 05:12 AM #10 Master Electrician     Join Date: Mar 2007 Location: Baltimore, MD Posts: 332 Rewards Points: 250 The circuits you mentioned are considered General Lighting. 3 VA/square ft. 20 amps x 120volts = 2400VA. 2400VA/3=800 square feet. Now, personally, I would have installed 2 or 3 circuits. (hard to say without seeing for myself) __________________ John from Baltimore One Day at a Time "Experience is what you get when you were expecting something else" "The bitterness of low quality lingers long after the sweetness of low cost is forgotten"
01-03-2010, 07:20 AM   #11
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Quote:
 Originally Posted by JohnJ0906 Wrong. That does not apply to residential. 220.14(I) and (J)
If you are trying to do a good installation that will not give problems for your customer what I was pointing out it was one way to keep them from having problems.

It would also have kept "avtck" from having the concern he has.

Last edited by codeone; 01-03-2010 at 07:25 AM.

01-03-2010, 07:24 AM   #12
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Quote:
 Originally Posted by codeone If you are trying to do a good installation that will not give problems for your customer what I was pointing out it was one way to keep them from having problems.
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01-03-2010, 07:33 AM   #13
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Quote:
 Originally Posted by JohnJ0906 The circuits you mentioned are considered General Lighting. 3 VA/square ft. 20 amps x 120volts = 2400VA. 2400VA/3=800 square feet. Now, personally, I would have installed 2 or 3 circuits. (hard to say without seeing for myself)
The example I used was with min code which is 15 A circuits.

Using 20 a circuits would require 3 circuits.

2000 square ft x 3 va = 6000 divide by 120volts = 50 va divide by 20a breaker size = 2.5 or a need of 3 circuits

01-03-2010, 07:43 AM   #14
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Quote:
 Originally Posted by codeone The example I used was with min code which is 15 A circuits. Using 20 a circuits would require 3 circuits. 2000 square ft x 3 va = 6000 divide by 120volts = 50 va divide by 20a breaker size = 2.5 or a need of 3 circuits
Since the OP didn't give a square footage, I went the opposite way - a 20 amp general purpose circuit can cover 800 sq ft. We simply don't know the size of the area that circuit covers.
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01-03-2010, 07:49 AM   #15
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Quote:
 Originally Posted by avtck My main concern was that the max number of outlets connected to a single 20a Circuit was insufficient when calculating load using 75Watt or 100Watt bulbs.
All light fixtures have a very important label on them. The max wattage allowed. If the max is (1) 60 watt bulb, that is what you use when calculating the circuit, not 75 or 100.

My real reason for pointing that out isn't really the load on the circuit, but the fact that I far too often see oversized light bulbs installed in light fixtures, and that is a fire hazard - seriously.
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