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Old 08-08-2010, 11:38 AM   #1
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trying to get educated about house wiring


Hi,

I don't know much about electrical work and so I'm trying to get educated. We had one guy on site to give an estimate who told me something that doesn't make sense and I thought you folks could set me straight.

Background info:
We are gradually renovating our 25' x 25' attached garage to make it usable all year around. We are doing some of the work ourselves and hiring out other jobs. The project is now at the stage where we need to upgrade the electrical so we can get on with the insulation & drywall.

At this time the garage has one receptacle (it's wiring is hidden behind drywall) and one interior, 2 exterior lights. The interior light is controlled by a switch next to the receptacle and the other lights have switches near them on the other side of the garage. Except for the interior light switch, all the other wiring is easy to access (all the studs & rafters are open).

We've spent time figuring out what breakers go with what circuits and so know that the garage's 1 receptacle and 3 lights (plus 1 closet light in the interior of the house) go to one 20 amp breaker. Since that circuit seems have a lot of unused capacity, our plan was to expand it by adding 4 more ceiling lights and 2 -3 receptacles. We are also planning to add another separate 20 amp circuit.

Question:
So I thought to expand the existing circuit, one could tap into one of the cables (NM 14/2 with ground) we see running from the house to the lights (in particular the cable that powers the lights at the far end of the garage, not the one that runs to the ceiling light). This guy told me that receptacles have to be on their own circuit and lights on another. And went on to say the only way to add receptacles to the existing garage circuit would be to cut into the drywall to get to that receptacle's wiring.

I didn't think this sounds right but the guy has built houses and I haven't so what do I know?

And so is it true what this guy said - that lights must be on their own circuit and receptacles on another? Why would it matter what's on a circuit as long as it's not overloaded? I asked for clarification several times about this and he said the lights all on one circuit/receptacles on another has to be done in order to follow code. Is he right?

PS - if you can tolerate another dumb question based on what the guy told me. I thought that each circuit goes to and is controlled by it's own breaker. If what he said is true, then in our house 2 circuits (the garage light circuit & receptacle circuit) go into & are controlled by one breaker. Is that really the way it's supposed to work?

Sorry if my questions are painfully dumb. I promise I won't mess any actual wiring (I'm planning to install boxes & drill holes) - I just want to better understand it. Well, more than that, I want to know if this guy knows what he's talking about and if we should consider hiring him to work in our house.

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Old 08-08-2010, 11:49 AM   #2
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trying to get educated about house wiring


If it is 14-2 then it needs to be on a 15a breaer
12-2 is required to have a 20a breaker
Where are you located ?

Garage used year round - as living space ?
Or as a garage workshop ?
I'd want (3) 20a circuits in a a garage
I also prefer lights & circuits seperate...but not required in US
But it is a very good idea

If all wiring goes to one breaker - that is one circuit
Even if it is one set of wires that goes to lights
...and another set that goes to outlets

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Old 08-08-2010, 12:04 PM   #3
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Yes if you see 14/2 wiring, you must downgrade that breaker to 15Amps or you risk overheating/fires.
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Old 08-08-2010, 12:25 PM   #4
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Quote:
Originally Posted by Scuba_Dave View Post
If it is 14-2 then it needs to be on a 15a breaer
12-2 is required to have a 20a breaker
Where are you located ?

Upstate NY


Garage used year round - as living space ?
Or as a garage workshop ?

The garage won't be a living space but instead a workshop, exercise space, etc.

I'd want (3) 20a circuits in a a garage

We have been thinking of doing 3 20 amp circuits even though we don't foresee needing that much power but one never knows what we'll need in the future.


I also prefer lights & circuits seperate...but not required in US
But it is a very good idea

Why is it a good idea?
I can understand separate circuits for certain appliances and situations like that but don't understand why for lights.

If all wiring goes to one breaker - that is one circuit
Even if it is one set of wires that goes to lights
...and another set that goes to outlets
Oh. So in this situation, one could disconnect the wires going to the lights from the breaker leaving the wires going to the receptacles and still have a circuit?
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Old 08-08-2010, 12:35 PM   #5
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Yes, you can disconnect the lights and still have a circuit.

There are a couple good reasons to separate lighting from receptacles.

1. Lighting is a known load (just add up all the wattages of the bulbs). OUtlets are not. Who knows what you may want to plug in someday? Maybe a miter saw and a vaccuum? A fridge? It leaves you less room for unknown loads down the road.

2. If you do trip a breaker with an outlet...now you're in the dark.

3. When doing electrical work in the room....if you need to work on the outlets...lights are still on. If you need to work on the lights...you can plug a lamp in.

4. Most lighting circuits can be handled by a 15A breaker. 15A breakers can use 14gauge wiring...cheaper than 12gauge.

Might be a good idea, if you have multiple outlet circuits, not to bunch up all outlets on the same circuit together. Might want to leapfrog them. What I would do is, at each spot where you want an outlet, put two of them (one from each circuit). You could even get different colored outlets for each circuit.

This way if you decide to put, for an example, a fridge and an air conditioner next to each other, you could have two circuits nearby so you can feed one off each.
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Last edited by secutanudu; 08-08-2010 at 12:38 PM.
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Old 08-08-2010, 12:58 PM   #6
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Quote:
Originally Posted by secutanudu View Post
4. Most lighting circuits can be handled by a 15A breaker. 15A breakers can use 14gauge wiring...cheaper than 12gauge.
not to mention 14 gauge is much easier to work with. It is usually a different color too (white vs. yellow), making it easier to determine what wire is what in a wall.
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Old 08-08-2010, 01:04 PM   #7
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Quote:
Originally Posted by forresth View Post
not to mention 14 gauge is much easier to work with. It is usually a different color too (white vs. yellow), making it easier to determine what wire is what in a wall.
Yeah, MUCH easier to work with...make that #5
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Old 08-08-2010, 02:23 PM   #8
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A treadmill usually takes a dedicated 20a circuit
Beer fridge may take 7a
Power saws etc can pull 7a or more
AC if you do summer work
Power needed adds up real quick

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