Breakers and breaker box question

[kcult]

I have the trench dug and the wire ran under and into the house. I have the wire laid in the trench up to the shop. It'll sit like that until I decide where to mount the breaker box and punch a hole in the wall for the wire.

I was advised to use a 50A breaker in the house, a 40A main breaker in the box in the shop, and as many 20A breakers as I want circuits. Sounds reasonable. I also had help picking out the components this morning. The problem I have right now, is I was advised to get a box with a main breaker, or that would accept one, and the one picked out has a 100A main. When I unboxed the breaker panel, I noticed the 100A breaker looked different and mounted differently. I asked about this (through text) and was told swap the 100 out with the 40. But, it can't be done. The 100 bolts on and is shaped differently than the 40. It's not a clean swap.

My question is, is there any danger in using the box with the 100A main if the conductors are coming from a 50A breaker in the house? If that is a problem, what options do I have? I haven't run across a box, yet, that has a spot to use a regular 40A breaker as the main.

 

[heavydoc]

If you overload the circuit the breaker in the house will trip. So you will have to walk back to the house to reset it. I do alot of work in mine at night and it is a very dark walk back to the house to trip a breaker.

 

[kcult]

Don’t do it “wrong”. Do it as if it were being inspected by a qualified and trusted Master Electrician you are trying to impress.


What you describe might work, but would you be proud to show it to a qualified inspector?

I'm really not wanting to do it wrong, that's why I asked about options.

When I bought the house, there was a 12x16 outbuilding in that spot. I tore it down last summer and we had a 24x24 built. The old structure had a length of 12-2 wire running to it from a 20A breaker in the house. I've dug it up since then and am using that trench for my wires.

My problem now, though, is obviously getting the wrong breaker box.

 

[kcult]

Can’t you return the breaker box?

I can. That's not a problem.

 

[Burt Gummer]

@gunbelt

 

[LeeMajors]

I used this box and fed a double 60 amp breaker in the top left slot. Labeled it main. The way a feeds both legs works fine

 

[poller]

Like everything else in life, the electrical system is only as good as its weakest link.

You can't just consider the breaker box. You have to consider the entire electrical system.

What gage wires did you run from the house to the shop? That wire gage will determine the maximum current you can feed your shop. The "master breaker" in the shop panel must be rated for at most the current that the wire can support. For example, if you used 6awg multi-strand copper, you can draw up to 52 Amps.

You want the SAME size protection for the entire run. I.e., If you're planning on a 50A circuit, you want a 50A at the house feed and a 50A for the main breaker in the shop.

The main breaker in your panel is a different from the regular circuit breakers in physical size and type because its a) protecting two circuits, not one; and b) it acts as a main shutoff.

Your panel is fed by three wires: one neutral and two hot wires.

The voltages between wires are:
- hot1 and neutral: 120v
- hot2 and neutral: 120v
- hot1 and hot2: 240v

hot1 and hot2 run down the center in an alternating pattern, so that each position in the panel connects to either hot1 or hot2.

Spanning 2 vertical spaces connects to both hot1 and hot2 and gets you a 240v circuit (you'll want 240v for your water heater, welder, automotive lift, etc.).



If you run 20A circuits around the shop, please use 20A outlets.


The circuit breaker protects the circuit from drawing too much current, which generates heat and is therefore a fire hazard.

In a shop (or kitchen or bathroom), there is a high probability of a cord or appliance getting wet. Or, a cord getting cut (wrapped up in a drill, accidentally chopped by the circular saw, etc.). This can cause a short and people can (and do) die. A ground fault circuit interrupter (GFCI) will shutoff the circuit when this happens. A GFCI outlet will protect from the outlet to the end of the circuit, while a GFCI breaker will protect the entire circuit.

Thus, you should consider using a GFCI outlet at the beginning of a run, or a GFCI outlet.

Hope this helps....

 

[kcult]

@gunbelt

No.

 

[kcult]

Hope this helps....

Honestly, not a lot. But that's because of the content, not the delivery.

I'm a machinist, but I can do a few other things, as long as they are relatively simple (electrical, mechanic, carpentry, fabrication). This project is the biggest electrical to date and although my helper talks like it ain't nothing, he's not here and I'm trying to work on it while I have the time. Nothing is mounted or connected to anything at this time. I'm sorta in limbo.

As for the wire running from the house to the shop, it's this:

2-2-4 Stephens Aluminum Triplex URD Direct Burial Cable

600V Underground Distribution Cable. Sold by the foot.

www.wireandcableyourway.com

And I have a spool of 12-2 for inside the shop.

I'm not sure what to do or what to purchase now.

 

[two fingers]

Honestly, not a lot. But that's because of the content, not the delivery.

I'm a machinist, but I can do a few other things, as long as they are relatively simple (electrical, mechanic, carpentry, fabrication). This project is the biggest electrical to date and although my helper talks like it ain't nothing, he's not here and I'm trying to work on it while I have the time. Nothing is mounted or connected to anything at this time. I'm sorta in limbo.

As for the wire running from the house to the shop, it's this:

2-2-4 Stephens Aluminum Triplex URD Direct Burial Cable

600V Underground Distribution Cable. Sold by the foot.

www.wireandcableyourway.com

And I have a spool of 12-2 for inside the shop.

I'm not sure what to do or what to purchase now.

Why were you told to get 100 amp wire for a 40-50 amp service?

So, the system should be designed such that the breakers protect the wire. After all, the purpose of the breaker to to keep you from overloading the WIRE. If you overload the wire, it gets too hot. That's the whole point.

So overrating and underrating things is a bad idea. If you want a 50 amp service (and it isn't 100 yards long or something crazy) get a 50 amp breaker for the main out in the shop and 50 amp wire. If you're running 20 amp circuits throughout the shop, get 20 amp wire and 20 amp receptacles. Match everything and be done with it. (Very long runs will deal with voltage drop and other factors. So you may need to go up a size to account for that. But several sizes is not needed.)

You don't need a factory installed main breaker. You can get a panel with no main and simply snap in a 50 amp breaker. Run the wire from the house to the 50 amp breaker. It will feed the rest of the panel and also protect the wire going back to the house.... which will also be protected by the breaker in the house feeding the shop. Ask a licensed electrician about when and how you can get away without a main at all in the shop (if you so choose).

Short version. Match everything and the system will operate properly. Start underrating and overrating and it becomes more of a crapshoot.

 

[BlackGun]

Honestly, not a lot. But that's because of the content, not the delivery.

I'm a machinist, but I can do a few other things, as long as they are relatively simple (electrical, mechanic, carpentry, fabrication). This project is the biggest electrical to date and although my helper talks like it ain't nothing, he's not here and I'm trying to work on it while I have the time. Nothing is mounted or connected to anything at this time. I'm sorta in limbo.

As for the wire running from the house to the shop, it's this:

2-2-4 Stephens Aluminum Triplex URD Direct Burial Cable

600V Underground Distribution Cable. Sold by the foot.

www.wireandcableyourway.com

And I have a spool of 12-2 for inside the shop.

I'm not sure what to do or what to purchase now.

First you don’t need a main if the breakers are less than 6 and rated as switching breakers. But forget this as I would put the main in so you don’t need to go back to the house.

 

[BlackGun]

Second issue. A #2 wire in Uf underground cable will not fit in the terminal screws of a 50 amp breaker.
You have big enough wire for a 90 amp main shop breaker IF the house panel can support 90 more amps. And that wire will fit under the screw lugs. How many amps is the main breaker in the house? Heat pump and the two breakers sizes? Electric water heater and breaker size? Well pump and breaker size? Electric range? See why you need a qualified licensed electrician? Not a wire puller either. A pro.

 

[kcult]

Why were you told to get 100 amp wire for a 40-50 amp service?

I can't tell you why I was told that, but I trusted the source and went with it. Should I not use it? And if I can/do, what's the risk? Although it's not covered up with dirt or run inside the shop, it is in the house and in the trench.

So, the system should be designed such that the breakers protect the wire. After all, the purpose of the breaker to to keep you from overloading the WIRE. If you overload the wire, it gets too hot. That's the whole point.

I'm showing more ignorance here, but if the wire is 100A, would a 50A breaker trip before overloading the wire?

So overrating and underrating things is a bad idea. If you want a 50 amp service (and it isn't 100 yards long or something crazy) get a 50 amp breaker for the main out in the shop and 50 amp wire. If you're running 20 amp circuits throughout the shop, get 20 amp wire and 20 amp receptacles. Match everything and be done with it. (Very long runs will deal with voltage drop and other factors. So you may need to go up a size to account for that. But several sizes is not needed.)

The length of the run from the house is about 120ft.

You don't need a factory installed main breaker. You can get a panel with no main and simply snap in a 50 amp breaker. Run the wire from the house to the 50 amp breaker. It will feed the rest of the panel and also protect the wire going back to the house.... which will also be protected by the breaker in the house feeding the shop.

I'm starting to understand, but I'm having trouble visualizing the 50A feeding the rest of the panel in lieu of a main breaker. Plus, my wife is on the phone with one of her nurse buddies and they are bitching about work and I can't focus!

Ask a licensed electrician about when and how you can get away without a main at all in the shop (if you so choose).

There are several at work. I'll do that. Thanks.

Short version. Match everything and the system will operate properly. Start underrating and overrating and it becomes more of a crapshoot.

I certainly don't mind doing the work, but it's painfully obvious that I gotta be spoon fed the details. Dang.

I appreciate the info.

 

[BlackGun]

---

Buy a 12 circuit small panel with no main breaker.
Buy a double pole breaker for the main. If the #2 wire will fit under a 60 ok. Most likely not. More like 70 which is not found often in big box stores. Mount that breaker in the house and one in the first two spaces on the left side in the building panel. Circuits 1 and 3.
Two hot blacks or black and red in the breaker terminals. White wire to neutral bar. Ground bare wire to grounding bar terminal. Note: neutral is floated when fed from the house.

 

[LeeMajors]

Exactly what I said and did myself

First you don’t need a main if the breakers are less than 6 and rated as switching breakers. But forget this as I would put the main in so you don’t need to go back to the house.

---

Buy a 12 circuit small panel with no main breaker.
Buy a double pole breaker for the main. If the #2 wire will fit under a 60 ok. Most likely not. More like 70 which is not found often in big box stores. Mount that breaker in the house and one in the first two spaces on the left side in the building panel. Circuits 1 and 3.
Two hot blacks or black and red in the breaker terminals. White wire to neutral bar. Ground bare wire to grounding bar terminal. Note: neutral is floated when fed from the house.

 

[kcult]

---

Buy a 12 circuit small panel with no main breaker.
Buy a double pole breaker for the main. If the #2 wire will fit under a 60 ok. Most likely not. More like 70 which is not found often in big box stores. Mount that breaker in the house and one in the first two spaces on the left side in the building panel. Circuits 1 and 3.
Two hot blacks or black and red in the breaker terminals. White wire to neutral bar. Ground bare wire to grounding bar terminal. Note: neutral is floated when fed from the house.

Thank you! You too @LeeMajors

Actually, thanks to everyone that replied. I feel like I've learned something.

 

[BlackGun]

Hey man. Yesterday I was doing some plumbing repair on a tub that a faucet was dripping. I took the hot water handle off, the stem, and cartridge. Not ever seeing one like it ,I squatted down and looked into the shower wall to see what was there. A spring and valve seat shot out of the peep hole and almost took my eye out. Faucet repair ain’t my thing but I do my own repairs.

 

[LeeMajors]

Thank you! You too @LeeMajors

Actually, thanks to everyone that replied. I feel like I've learned something.

I don't think I am that far. If you find you need some help. Just holler

 

[RetiredUSNChief]

My question is, is there any danger in using the box with the 100A main if the conductors are coming from a 50A breaker in the house? If that is a problem, what options do I have? I haven't run across a box, yet, that has a spot to use a regular 40A breaker as the main.

Good question.

First of all, I seriously doubt this is in accordance with Code. I'd have to look it up to find the relevant section, though.

Breakers are installed on the principle of selective tripping. This means you have a large main breaker and progressively smaller breakers between the main breaker and the final load breaker. The intent is the smaller breakers supplying the loads trip before the larger breakers back up the line trip.

It's mighty inconvenient when the extension cord on your drill develops a short and your wife suddenly discovers herself in a dark house because the main breaker tripped instead of the load breaker for the circuit you were on.

"Is there any danger...?"

Technically, no, so long as your wiring is otherwise correct. It just means if you trip the 50 Amp breaker for your house you'll have to go back to your house to reset it.

But it will not pass inspection.