Adding outlets, and 15a vs 20a

I have a shed.  Workshop.  Mancave.  What have you.

The electrician ran 12 gauge wire for the outlets, connected to a 20 amp breaker.  The lights have 14 (I think) gauge wire, on a 15 amp breaker.  50 amp service.

I want to add more outlets, including splicing into the 14 gauge wire used by the lights. In hindsight, I'm wishing the lights were 12 gauge with a 20 amp breaker, so I have more power available for whatever I plug in.

I guess my question is, why wasn't it done entirely with 12 gauge wire and 20 amp breakers?  Is it significantly less expensive to run 15 amps with the thinner wire?    That's all I can think of, it was cheaper.  Maybe the electrician concluded that 15 amps would be more than enough for the lights, 20 amps would be unnecessary overkill.

Is there a problem, having lights and outlets on the same breaker?  

I don't believe there will be an issue with breakers popping, it's just me, using one tool at a time.  I just want the convenience of having an outlet handy regardless of where I'm standing.

There are concerns with what you propose.

The biggest issue is, if you don’t wire switched outlets just right they will not be
Lit when the switch is off. It can be done, just with pigtails on the right terminals.

As far as the lights go; lights never see amperage so they typically are wired for 14 wire for that reason with the 15 amp breaker.

It sounds to me your electrician did things right, at least in terms of typical usage. He might have done it because of code, as buried depth depends on a lot of factors including amps used and if gfci and why type of conduit.

But I have run a crap load of outlets on 12 gauge with a 20 amp breaker and had very few problems, even heaters and woodworking saws. An occasional trip but not often.

You should be fine, just watch YouTube videos on how to tap into a switch to get the power continuously for your outlet. Those might trip more often but only if you hook something like a tabkesaw to them. In that case run a dedicated  12/20 run to it

Gary Numan wrote:
Is it significantly less expensive to run 15 amps with the thinner wire?    That's all I can think of, it was cheaper.  Maybe the electrician concluded that 15 amps would be more than enough for the lights, 20 amps would be unnecessary overkill.

Exactly.

Yes, cheaper and definitely easier. Pulling and working with 12 ga. wire is a pain.

Gary Numan wrote:Is there a problem, having lights and outlets on the same breaker?  

One small concern might be the length of the 14 ga. wire run before it gets to the plug. Some electricians will put a lot of wire on a single breaker, assuming a low draw. High draw power tools will run, but the voltage will drop more over that long wire and the tool motor may run a bit hotter as a result.

Use of LED lighting will help on that circuit.

This might also help you to understand a little bit more.... and confuse you at the same time! Aren't I talented!! Let me use a good example first. Let's say you're taking your kids out on a boat. Because you are all safety conscious and you love your kids you are going to put them in life vests. You are not going to put a tiny little kid in a huge extra large  vest because he could just slip right out of it. That is not helpful. You are going to put him/her in a vest that fits well and will save their life.

We do the same thing with electricity. Light fixtures use very little power. Back in the day most fixtures used 60 or 100 watt bulbs and I'm guessing that the new LED lights use much less. Haven't worked as an electrician since 2000 so I don't know for sure. Anyway, let's just say you have an average of 5 100 watt lights on most of the time. 5 x 100 = 500 watts which is not much.  

You want to protect those small, flimsy lights that use very little power with the smallest breaker possible. Smallest is 15 amps. Just like putting your kids in a small, snug life vest. If you put that circuit on a 100 amp breaker it will never see a problem and trip. A 14 gauge wire will simply melt and your shed will burn to the ground before a 100 amp  breaker will trip. This is why.

Here's the confusing part.... try to follow me... O.K.? First.... Watts divided by voltage equals amps. That 500 watt lighting circuit (all lights are on) divided by 120 volts equals just 4.1 amps. Very little. The smallest breaker you can put it on is 15 amps. Now for the fun part. No offense to anyone but I used to always think that guys just made this way more complicated then it had to be just to confuse people like me! Again, no offense.
1. A breaker is only designed to handle 80 percent load at any time. So a 15 amp breaker will only hold 12 amps for extended periods (using 14 gauge wire). Like I said, they made it far more confusing than it has to be.
2. A breaker does not trip because it gets hot. It trips when the load is over 80 percent. The bigger the load is, the faster it will trip. If the load is suddenly 16 amps it will trip in a couple of minutes and if it is 20 amps it should trip instantly.
3. Let's say one of your light fixtures shorts out and starts to burn. It burns off the wire's coating and the hot wire touches the ground or neutral. (Because they are all contained in one sheath close to each other for just this safety reason) When the hot wire touches the ground or neutral wires it starts to suck down all that power from the hot wire, far more than 12 amps and the 15 amp breaker will trip in just a few minutes and hopefully stop the fire from getting worse. It will never pull enough power to ever trip a 100 amp breaker. Your shed will burn down first.

Lots of appliances use 10 to 14 amps (check out you appliances.... remember.... watts divided by voltage equals amps. So most receptacles in kitchens, laundry rooms, sheds etc. use 12 gauge wire on  20 amp breaker which can hold a load of 16 amps. (80 percent) Most dryers use 24 amps and are put on 30 amp breakers.(80 percent) Etc.

Your electrician did the right thing under most circumstances. You can add receptacles to your lighting circuit (using 14 gauge wire) or lights to your receptacle circuit (using 12 gauge wire) now that you know how it works. Oh, and happy gardening everyone.  

Excellent recommendations all.  Appreciated!

Excellent analogy Debbie!

I am in the same situation as you are Gary but plan to upgrade my shop in a different way. I plan to put in a sub panel and tap off that instead.

It’s not a better or worse way to do it, just different. It is a bit more costly but puts a lot of potential power in my shop since I can tap into the main leads from the power company and not use valuable circuits in my main panel. This will give me 100 amps in the shop that can be broken down into (20) circuits ranging from 120 volt to 240 volt.

One point not mentioned too is; one reason lights tend to be wired on a separate circuit from outlets is, if you overload an outlet, and the breaker trips, you also lose the lights. In most situations it’s in incident, but in others downright dangerous.

In a shop setting for instance, you trip the breaker, the lights go out, but that sawblade on the table saw us still turning… fast… now in the dark.

Again, not so likely, but a reason lights are wired on their own circuit.

John C Daley wrote:Use of LED lighting will help on that circuit.

The US changed its light policy a few years ago and while you can get incandescent light bulbs, it’s getting harder and harder to even find them and for good reason. The first batch of led bulbs that came out were not so great, but the new versions are really nice. In the wiring of homes world, it changed everything!

I just made this light from a Hobby Lobby find and put in (2) 100 watt equivalent bulbs. Since an appliance only cares about actual draw and not light equivalent, those two 100 watt light equivalent bulbs only consume 24 watts. (100 watt equivalent equals 12 watts of current draw)

So when you see a lamp holder that says “max 60 watt bulb, with led bulbs you can put a 400 watt light equivalent bulb and still only draw 48 watts, well under the 60 watt.

Thank goodness. As I get older I find I need more light. I never buy anything less than 100 watt equivalent any more because I like the extra light and I don’t have to worry about burning down my home!

Again, this is the new light I made last week from a $34 Hobby Lobby find, using lamp holders I had kicking around. It took me about an hour to make but looks good I think, at least in our old house.

The job of the breaker is protect the WIRE that it feeds. You can do a thought experiment about what might happen if you stubbed from a 60a AC circuit with 14ga wire, which has an ampacity of 25a for the expensive THHN, and you ran say 40a through it (a welder, a window ac, and some cook tops).

You can physically attach a lower guage wire and this might be within codes in certain situations. You should never create a situation where it is possible to pull more amperage than the wire can safely handle.

If you want to plan out the improvements yourself please look at an ampacity chart. Most wire companies have them posted on their websites.