Garage wiring
- Thread starter FBP
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al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Garage wiring
First of all, welcome to the forum.
Take a look at Table 220.12. If your lampholders and receptacles are going into a Dwelling, pay attention to the superscript "a" and go to the reference at the bottom of the Table.
"a" will lead you to 220.14(J). This quote:
First of all, welcome to the forum.
Take a look at Table 220.12. If your lampholders and receptacles are going into a Dwelling, pay attention to the superscript "a" and go to the reference at the bottom of the Table.
"a" will lead you to 220.14(J). This quote:
takes a bit of rethinking, especially given a background in commercial, non dwelling, wiring.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Garage wiring
What is the maximum wattage of each bulb you would use? If it's, say, 100 watts each, you could connect (120 x 20 x 0.8 = 1920) 19 of them.
As for receptacles, I'd ask what you're likely to plug into each one, and what is the maximum current of everything likely to be in use at one time.
If you always work alone, you could plug every tool you own in on one circuit, but if you have a friend working, or a refrigerator, split them up.
What is the maximum wattage of each bulb you would use? If it's, say, 100 watts each, you could connect (120 x 20 x 0.8 = 1920) 19 of them.
As for receptacles, I'd ask what you're likely to plug into each one, and what is the maximum current of everything likely to be in use at one time.
If you always work alone, you could plug every tool you own in on one circuit, but if you have a friend working, or a refrigerator, split them up.
- Location
- Massachusetts
Re: Garage wiring
There is nothing that says you have to.
Load that 20 amp circuit to 2400 watts if you want.
Larry why are you assuming that dwelling unit garage lighting is a continuous load?
There is nothing that says you have to.
Load that 20 amp circuit to 2400 watts if you want.
- Location
- Windsor, CO NEC: 2023
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- Hospital Master Electrician
Re: Garage wiring
Nothing says it's a bad idea, either.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Garage wiring
Thanx, George.
I, I took "a garage" to mean a single space, with all lights on a single switch, easily "leave-on-able" for 3 hours or more.
[ November 07, 2005, 10:39 PM: Message edited by: LarryFine ]
Thanx, George.
I, I took "a garage" to mean a single space, with all lights on a single switch, easily "leave-on-able" for 3 hours or more.
[ November 07, 2005, 10:39 PM: Message edited by: LarryFine ]
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Garage wiring
2.4 kW (or even 1.92 kW) of incandescant light is a lot of lumens. . .unless this is an airplane garage, or some other big and wide garage.
Let's go back to the opening post.
The question is: How many lampholders? Not Watts of bulb.
Answer: If I install one Watt bulbs, I can install 2,400 lampholders.
220.14(J) says that the only calculation for dwellings for general lighting is 3 W/ft?, where the square footage is determined by the outside dimension of the habitable floor space as specified by 220.12.
Garage, while included in the dwelling, is not habitable floor, so, adding the lampholders, even though one is adding load, doesn't affect the calculation. The end result is that the circuit can easily be overloaded if I turn it all on, whatever "all" is, but the NEC is clear to say in 90.1(B) that the rules "results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use."
In my opinion, dwelling general lighting calcultions and the resultant installation following that minimum standard is as clear an embodiment of 90.1(B) as it gets.
Question: "How many 20A 120v Duplex receptacles can go on one circuit?" (in a dwelling garage.)
Answer: There is no limit to how many.
2.4 kW (or even 1.92 kW) of incandescant light is a lot of lumens. . .unless this is an airplane garage, or some other big and wide garage.
Let's go back to the opening post.
The question is: How many lampholders? Not Watts of bulb.
Answer: If I install one Watt bulbs, I can install 2,400 lampholders.
220.14(J) says that the only calculation for dwellings for general lighting is 3 W/ft?, where the square footage is determined by the outside dimension of the habitable floor space as specified by 220.12.
Garage, while included in the dwelling, is not habitable floor, so, adding the lampholders, even though one is adding load, doesn't affect the calculation. The end result is that the circuit can easily be overloaded if I turn it all on, whatever "all" is, but the NEC is clear to say in 90.1(B) that the rules "results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use."
In my opinion, dwelling general lighting calcultions and the resultant installation following that minimum standard is as clear an embodiment of 90.1(B) as it gets.
Question: "How many 20A 120v Duplex receptacles can go on one circuit?" (in a dwelling garage.)
Answer: There is no limit to how many.
allenwayne
Senior Member
Re: Garage wiring
Al you are 100 % correct as far as the # of receps allowed but with that many lights it seems demand might be a factor in power tool usage etc.
Al you are 100 % correct as far as the # of receps allowed but with that many lights it seems demand might be a factor in power tool usage etc.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Garage wiring
Hi Allen,
FBP's questions are about two different situations: (1)Lampholders on a 20 A circuit. (2)Receptacles on a different 20 A circuit.
I guess the real point of my statement is that the lampholder by itself does not have a VoltAmp load attached to it to calculate a number of lampholders from. The number of lampholders is unlimited.
Not all the lampholders have to have bulbs that work installed in them.
Hi Allen,
FBP's questions are about two different situations: (1)Lampholders on a 20 A circuit. (2)Receptacles on a different 20 A circuit.
I guess the real point of my statement is that the lampholder by itself does not have a VoltAmp load attached to it to calculate a number of lampholders from. The number of lampholders is unlimited.
Not all the lampholders have to have bulbs that work installed in them.
james wuebker
Senior Member
- Location
- Iowa
Re: Garage wiring
FBP, don't forget if your installing receptacles in a garage, they should be on a GFCI circuit. I wouldn't put over 6 on a circuit. To many on a gfci circuit can cause nusiance tripping on the gfci but I've seen more on a circuit and everything was OK.
Jim
FBP, don't forget if your installing receptacles in a garage, they should be on a GFCI circuit. I wouldn't put over 6 on a circuit. To many on a gfci circuit can cause nusiance tripping on the gfci but I've seen more on a circuit and everything was OK.
Jim
jeff43222
Senior Member
- Location
- Minneapolis, Minnesota
Re: Garage wiring
I just want to know where Al is getting his one-watt bulbs. I'm looking to save on my electric bill.
I just want to know where Al is getting his one-watt bulbs. I'm looking to save on my electric bill.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Garage wiring
This one is really 1.3 Watts. I rounded down.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
john m. caloggero
Senior Member
Re: Garage wiring
It is my understanding that the garage is on the premises of a dwelling unit. Table 220.12 does not provide the minimum volt-ampere load for the garage in question. Therefore, section 220.14(D) is applicable. So the number of keyless lampholders permitted on a 20A circuit is based on the volt-ampere rating of the lampholders connected the branch circuit. The keyless lampholder I checked has a maximum rating of 600 watts. For a 20A circuit, 20A x 120V = 2400 watts. 2400W divided by 600W = 4 lampholders. Seems rather restrictive, how often do you install 400 to 600 watt lamps in the garage? Looks like we need a proposal to clarify and make this less restrictive.
It is my understanding that the garage is on the premises of a dwelling unit. Table 220.12 does not provide the minimum volt-ampere load for the garage in question. Therefore, section 220.14(D) is applicable. So the number of keyless lampholders permitted on a 20A circuit is based on the volt-ampere rating of the lampholders connected the branch circuit. The keyless lampholder I checked has a maximum rating of 600 watts. For a 20A circuit, 20A x 120V = 2400 watts. 2400W divided by 600W = 4 lampholders. Seems rather restrictive, how often do you install 400 to 600 watt lamps in the garage? Looks like we need a proposal to clarify and make this less restrictive.
Re: Garage wiring
In most cases, wouldn't 220.14(J)(3) override part (D) based on the wording at the beginning of 220.14? Section 210.14(J)(3) refers you to the lighting outlets required in 210.70A and B. Those lighting outlets specified include accessory spaces to dwellings such as attached/detached garages, storage spaces, etc.
In most cases, wouldn't 220.14(J)(3) override part (D) based on the wording at the beginning of 220.14? Section 210.14(J)(3) refers you to the lighting outlets required in 210.70A and B. Those lighting outlets specified include accessory spaces to dwellings such as attached/detached garages, storage spaces, etc.
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