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Shop electric questions?

blazinzuk

blazinzuk

Buzzbox voodoo
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Need to run power to the shop, yes I am making progress.

Wire I have is good for 150 amps. It is 2/0 2/0 #1. So my plan is to put a 125 amp breaker in my current panel. Then run it to a 100 amp panel in the shop.

So 2 questions. If I get a 125 amp load center and I upgrade my main panel, can I switch the subpanel main fuse to 150 amps at that time?

Should I just get a 125 amp subpanel. My thinking is if the shop has 100 amps then at worst it will pop the 100 amp breaker before the 125.

The reason for the 125 amp breaker in the main panel is it takes less space than the 150.

I had a 100 amps in my old garage. Never had an issue but my wire will be capable of 150 amps I wanna be able to upgrade if I ever need too
 
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To tell the truth, I'm not totally sure of what you are saying. Not enough to give you an opinion anyway. Its too important a question for guesses.
Also, I am not a fan of a sub size ground, even though it might meet code in some cases.

But, the most important thing, is for you to reread your last sentence very carefully!!!!!
I really do not want to get involved in that!
 
Nice catch. Lol

It's hard to explain because I don't know proper terms.

My current breaker box has 4 spots open.

I need to run power to my shop.

My plan is to install a 125 amp breaker in the current breaker box.

Then a 100 amp subpanel being fed by the 125 amp breaker in the main box.

My wire is sufficient for the amp load.

If I buy a 100 amp subpanel such as this

square-d-main-breaker-box-kits-hom2448m100pcvp-e1_1000.jpg

Can I at a later date swap out the 100 amp main fuse for a 150 amp main fuse.

In that situation I would of course swap the 125 in the main power breaker box also.

If I only plan on running a 100 amp subpanel for now, should I run a 100 amp breaker in the main power breaker box or the aforementioned 125.

Is that more clear?
 
If it were me, I would place 125 breaker in main panel. Then place 125 sub panel with out a main breaker.
I have three sub panel on the main. 2 are 100 amp and one is 70 amp. none of the sub panels have a main breaker in them. The 70 amp sub panel is tied to my 13.2 kilowatt solar system. All the panels passed county electrical inspections. The main panel is has 200 amp main breaker, which was changed to 150 amp when the solar system was installed. County and Electric company approved.
 
My reasoning for running a smaller main breaker in the subpanel is well, personal comfort. If it blows I don't have to go outside to reset it
 
Well it is your shop and i was just offering what i have , that has worked for 32 years. In that time i have never tripped the the main breaker of any of the sub panels. My main panel has over 500 amps of breakers in it. The point I was making is that you don't need two main breakers. If it makes you feel safer, that is all that matters. I am not trying to ruffle any feathers. When I am running off the solar , the whole 3300 sq ft house is on a 70 amp breaker. At the same time putting power not used by house back into power grid through that same 70 amp breaker.
 
Oh no feathers ruffled at all.

I appreciate the advice .

In my old shop I only tripped my main breaker a couple times and it was ( both times) a large piece of metal severing a power cord. Usually the welder.

It's not a long walk to the main box. But it gets further the more below zero it gets lol.
 
Don't bother going out and looking tonight, but when you get a chance, look on the wire and see what style it is, UF, THHN, ect. and what temp rating it is. 60 degree C, 75, or 90.
And, what is more important, how much wire (length) is there going to be between the boxes?
The ampacity of the wire, per size, is dependent on the temp rating.

But, where a lot of folks make a mistake is by going by only the ampacity rating of the wire. Voltage drop enters into it too.
You could hook a foot of 10ga wire up between a breaker and a load. Throw a 150 amp load on it, and it would smoke pretty quick.
Change out that for a piece of 2/0, throw on the 150 amp load and it would be fine.
So, you know that 2/0 can handle 150 amps. And the NEC charts mostly agree with you. Grab a big spool of wire, and proceed to wire up a panel 1500 feet away. Throw on that 150 amp load, and suddenly you only have about 200 volts instead of 240.
You have to allow for resistance of the wire.
There are charts that show that.

Found one.

http://www.electrician2.com/calculators/vd_calculator_initial.html
 
Fordum said:
Don't bother going out and looking tonight, but when you get a chance, look on the wire and see what style it is, UF, THHN, ect. and what temp rating it is. 60 degree C, 75, or 90.
And, what is more important, how much wire (length) is there going to be between the boxes?
The ampacity of the wire, per size, is dependent on the temp rating.

But, where a lot of folks make a mistake is by going by only the ampacity rating of the wire. Voltage drop enters into it too.
You could hook a foot of 10ga wire up between a breaker and a load. Throw a 150 amp load on it, and it would smoke pretty quick.
Change out that for a piece of 2/0, throw on the 150 amp load and it would be fine.
So, you know that 2/0 can handle 150 amps. And the NEC charts mostly agree with you. Grab a big spool of wire, and proceed to wire up a panel 1500 feet away. Throw on that 150 amp load, and suddenly you only have about 200 volts instead of 240.
You have to allow for resistance of the wire.
There are charts that show that.

Found one.

http://www.electrician2.com/calculators/vd_calculator_initial.html
Click to expand...

I honestly don't remember the letters on it xhhw I think.

The run is 135 ft voltage drop was figured at 3% I was told 5% is the acceptable range. I will be with in that.

It took me a couple months to get a couple electrician guys over here to ok the wire.


I never asked about hooking it all up cause I thought I'd have to pay someone to do it.

Of course then I tried too. 4 no shows to give me estimated cost, 5 flat out no we are too booked up for a job that small and several just not returning my calls I am trying to do it myself

It seems hooking it up is easier than I thought.

Oh cable is buried in 3" schd 40 grey conduit, at a 3' depth. Grounding rod will be driven in to the proper depth also.

I just wanted to check my thinking on the 125 amp vs 100 amp stuff. See if I was way off base or not
 
You can swap out, depending on the panels. Most panels now a days you can not swap mains. You need to be careful depending on what the panel in your house is. I remember vaguely from my install about the sub panel not exceeding a certain percentage of the main panel. That being said I upgraded my 150A 30 space main panel to a 40 space 200, then ran a 100A breaker feeding the 100A in the barn. You need two ground rods driven flush, and spread 6 feet apart. Make sure its a 3 wire feed plus ground. 135 feet is about the same as my run from panel to shop. I did 3% voltage drop. The inspector just made sure I used No ox on the wire, and that I labeled everything. I highly suggest picking up a ptrouch labeler for 35 bucks and labeling everything. In my opinion buy the 125A panel for the shop and be done. Hell you can use a 150A panel if need as its just a service disconnect. You will always trip the breaker in the main panel first unless its a direct short. Xhhn i aluminum so make sure you use no ox on all connections. Also re tighten after a few months.
 
Eric - I did almost exactly what you’re talking about when setting up power between the house and the shop. Power comes into the shop at 150A, and the house is on its own 125A “slim” breaker. Some 50’ of 4 conductor aluminum power cable feeds the house and its own 100A panel, which is plenty for us.

Recognizing your power flow is house-then-shop, that’s just good management of your priorities. Your plan makes sense to me. I’ll reiterate the advise to uprate the wire, and also add that I put each quad outlet on its own 20A circuit...for reasons.

David
 
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