15 amp versus 20 amp

[Ramper]

I am planning to put a few extra outlets in my "shop". I have 100 amp service and right now there are only two circuits. I plan to add three more (2 for outlets and one 240 volt for a heater).

Should I wire 20 amp circuits or just 15 amp?? I have nothing that has a 20 amp plug, but I was wondering if the cost is comparable should I just do it now?

 

[Stuart in MN]

Assuming you're in the USA, regular 15 amp receptacles can be used on 20 amp circuits as long as you have more than one (and a standard duplex receptacle counts as two.) I'd go with 20 amp circuits.

 

[Ramper]

I too live in MN

 

[Kriilin]

Actually, what I did is went with split 15A circuits, you just use 14/3 instead of 14/2 (common neutral) and a 2-pole breaker, assuming MN code allows it. I don't know if you can so split 20A.

 

[Charles (in GA)]

Actually, what I did is went with split 15A circuits, you just use 14/3 instead of 14/2 (common neutral) and a 2-pole breaker, assuming MN code allows it. I don't know if you can so split 20A.

What you are describing is an "Edison" Multi-wire branch circuit as described in NEC 210.4

210.3 describes the allowable ampere rating for "other than individual branch circuits" as being 15, 20, 30, 40, or 50 amperes.

It is very easy to have issues with GFCI breakers and receptacles used on Multi-wire branch circuits, and usually it is not worth the effort to use MWBC in a shop environment.

Charles

 

[Gary S]

Why run any 15 amp circuits for receptacles when there are available appliances and tools that require a 20 amp?
The cost is almost the same to run 20 amp and you just set yourself up for tripped breakers with 15 amp.
I have a 120v welder that requires a 20 amp circuit. I want to be able to use it wherever I need it, so I'd never consider a 15 amp circuit anywhere.
Also, my emergency 120v portable heater needs a 20 amp, as well as my Shopsmith, and my thickness planer. My wife's roaster also wants a 20.
No question for me.

 

[Justin C]

Code here in South Dakota required me to use 20 amp tamper proof gfci protected for my outlets. The inspector said i could use a 15 amp outlet after a 20 amp gfci but no more than 8 on the circit. I played safe and only did 5 per circit. For the price differance i would use the 20s. Also remember to get the 21 cubic inch box and not the 18.

 

[Rosco]

Why run any 15 amp circuits for receptacles when there are available appliances and tools that require a 20 amp?
The cost is almost the same to run 20 amp and you just set yourself up for tripped breakers with 15 amp.
I have a 120v welder that requires a 20 amp circuit. I want to be able to use it wherever I need it, so I'd never consider a 15 amp circuit anywhere.
Also, my emergency 120v portable heater needs a 20 amp, as well as my Shopsmith, and my thickness planer. My wife's roaster also wants a 20.
No question for me.

^^^^^^^ this

 

[mrb]

Code here in South Dakota required me to use 20 amp tamper proof gfci protected for my outlets. The inspector said i could use a 15 amp outlet after a 20 amp gfci but no more than 8 on the circit. I played safe and only did 5 per circit. For the price differance i would use the 20s. Also remember to get the 21 cubic inch box and not the 18.

i think you got something wrong with what your inspector said. 15 amp GFCIs are speficically rated 20 amps pass through.

 

[StaggeringGoat]

15 amp circuits are for people (builders) who are too cheap to use 12 gauge wire!

 

[sdowney717]

I second the bigger boxes when working with 12 gauge you need that. Get the biggest ones they have.

 

[mtne]

Personally I don't see the savings of buying 14awg to be significant enough to use it. Leave that to the homebuilders and the bean counters. Use 12awg and be done with it. That way you can use 20A breakers. As for most recepticals, take one and break the plastic face plate off........ likely as not the guts are the same as a 20A with the ability to accept the "T" arranged prongs. When deciding how many recepticals to use on a given circuit, calculate them at 180VA (per yolk = duplex receptical). With a 20A circuit at 80% allows you to put 8 duplex recepticals. That becomes 6 with a 15A circuit which either leaves you with more circuits or less places to plug in.............

 

[v8garage]

15 amp circuits are for people (builders) who are too cheap to use 12 gauge wire!

Amen, I just buy a roll of 12/2 and run all the 110 circuits with it.
V/8

 

[Ramper]

I just looked out there and there are three circuit breakers in the box that are currently not being used. Two 20 amps that I will use for the outlets (each with 4 boxes with a duplex outlet in each (the first one being GFCI) and a 60 amp 220 that I will use to wire an electric heater.

One last question. If I wire the 220 volt what wire would I use and can I just wire it to a box connect it to the breaker and just not turn it on? I am getting a heater, but I am unsure if I need to hardwire it or use a plug.

 

[Ramper]

So with a 100 amp service: 15 amp light circuit, four 20 amp circuits and one 60 amp 220. Is that too many???

 

[Jim Johnstone]

Couldn't agree more. I'm planning on gutting my garage on the house my wife and I just bought and rewiring it completely. 20 amp outlets all around!

My circular saw and miter saw are both 15 amp full load draw. Imagine running one of those while someone else in your garage plugs in an angle grinder or something else on a 15 amp circuit.

 

[Improved700]

So with a 100 amp service: 15 amp light circuit, four 20 amp circuits and one 60 amp 220. Is that too many???

Nope. Your box is rated for 100 amp. Which means having the proper sized wire feeding the box will allow you to pull 100 amps. You can have as many breakers in your box as allowed, which if you add up the amps of each breaker will be way over the 100 amps. But your not pulling all 100 amps at one time.
Hope that makes sense.
Where in Southern MN? I used to live in Rochester.

Kev

 

[Ramper]

I work in Rochester (teacher/coach at JM), but live in Stewatville. We have 13 acres. A 30 x 40 "shop" besides our 3 garage garage.

 

[Improved700]

JM grad...1987