NEW SHOP NEED ELECTRICAL HELP

[Mike67]

You need to know the size to properly size your breaker. Also you need to take into consideration voltage drop...which increases with distance. If your over 150' you may need to derate.

 

[XMAN JR]

You need to know the size to properly size your breaker. Also you need to take into consideration voltage drop...which increases with distance. If your over 150' you may need to derate.

Yea its around 15 ft from house to 1st garage around 30 ft from 1st garage to 2nd. The wire that's already under ground will not fit 50 or 60 amp breakers at least the ones I found That's why I need to use a 100 amp breaker

 

[Don Frelier]

You can put in a box at each end and reduce the wire size down to what your breaker size is.
There is no problem code wise having wire that is larger than the breaker size in the middle of a run.
But you do need to be careful with connections for aluminum & copper.
Voltage drop is not an issue at these distances.

 

[XMAN JR]

You can put in a box at each end and reduce the wire size down to what your breaker size is.
There is no problem code wise having wire that is larger than the breaker size in the middle of a run.
But you do need to be careful with connections for aluminum & copper.
Voltage drop is not an issue at these distances.

The wire is already under ground & the newer style panel boxes are already in place. Just trying to use what is there.

 

[Mike67]

Yea its around 15 ft from house to 1st garage around 30 ft from 1st garage to 2nd. The wire that's already under ground will not fit 50 or 60 amp breakers at least the ones I found That's why I need to use a 100 amp breaker

Like I said earlier you need to determine the size of the wire to correctly size your breaker. The wire is sized to the load carried, the breaker protects the wire. If the wire is larger than the load that's perfectly fine, if the breaker is larger than what the wire can safely carry. That's no bueno and a fire hazard.
Also remember most of your loads are non continuous...<2 hrs, except for lights... your peak load will more than likely be significantly less...
You can go to NFPA 70 get free access to look at ampacity tables for your wire size/type

 

[451Mopar]

I used this calculator for wire size:
https://www.southwire.com/calculator-vdrop

It says for 100 Amp 220 Volt Single Phase, 1 conductor per phase (none in parallel), 30 foot run of aluminum wire in conduit, the wire size should be 1/0 AWG which is really large. about 0.325" diameter.

The wiring and having it function is the easy part, but I don't know the specific codes for out buildings? There may be different grounding / bonding requirements than say a sub panel in your basement or attached garage. Also, I don't know if each detached building requires an external shutoff? That may be more of a fire code thing?

 

[cosgig]

this is a piece of 00 or 02awg, which is 100a aluminum wire. I am guessing this is what you have, and is acceptable to run a 100a panel in your 2nd garage, especially if it’s already there. If it is already in the panel of your 1st garage and on a 100a breaker in there, you can simply buy a new 100a panel for your 2nd garage and run it into a main breaker. Although not technically legal to go from 100a to 100a, in this case I would say it can be done. Your problem may be that if you don’t have a 100a snap in breaker for the panel in the 1st garage, you may have to run a piece of #4 copper from a 100a snap in breaker in the 1st garage panel to a 100a service disconnect near that panel, to change the wire size to accommodate using the aluminum wire that’s already buried.

How about a pic of the inside of the panel in the 1st garage? That may help determine what exactly can be done.

 

[SSmoothie]

1. It sounds like you have interior wiring buried in the ground, 3 wire cable. You also have a bare neutral. And you should have a 4 wire for each feeder. Although there is an exception in NEC for a existing 3 wire feeder. You need to ground the neutral bar to the panel add the 2 ground rods at each building and land the grounding electrode wire to it on the neutral bar. Also you do not need main disconnects in the feeder panels if you have six or less disconnecting breakers in each. So if you have main lug panels no need to add mains. So your 1st feeder disconnect, will be in the house panel. Feed the main lugs in the first building then you will add a breaker in that panel that meets the wire size and load to the second building. Again no main needed on either if less than 6 disconnecting breakers. Also all new 120 volt outlet shall be GFCI protected if they are in a garage.

 

[XMAN JR]

1. It sounds like you have interior wiring buried in the ground, 3 wire cable. You also have a bare neutral. And you should have a 4 wire for each feeder. Although there is an exception in NEC for a existing 3 wire feeder. You need to ground the neutral bar to the panel add the 2 ground rods at each building and land the grounding electrode wire to it on the neutral bar. Also you do not need main disconnects in the feeder panels if you have six or less disconnecting breakers in each. So if you have main lug panels no need to add mains. So your 1st feeder disconnect, will be in the house panel. Feed the main lugs in the first building then you will add a breaker in that panel that meets the wire size and load to the second building. Again no main needed on either if less than 6 disconnecting breakers. Also all new 120 volt outlet shall be GFCI protected if they are in a garage.

The house was built in the 50s not sure when they rain the under ground wires. The 3 wire coming from the house to the first garage is the same type of wire going from the first garage to the second garage.

 

[SSmoothie]

This should work but not code compliant. Your panels are probably not listed to have 100 amp breakers in the the lower section, it would be on the label on the side of the panel. I would suggest lowering it to a 50 amp. Also I would wrap black electric tape and cover your neutral conductor except were the connection is made. And I do not see we’re the neutral bar is grounded (connected) to the panel. I see a hole in the upper right corner of the neutral we’re a bond screw would fit and screw to the back of the panel to make a connection. Or you can add a “L” shape lug with a bolt and nut on the panel and run a wire jumper to the neutral bar.

 

[SSmoothie]

I see a solid copper wire, looks like number 6. Make sure it is connected to a ground rod. Code now is 2 rods 6 feet apart. So this insures you have a fault path to ground when you have your neutral bar and panel box connected if a connection fails.

 

[dadsbee]

Just remember, electricity is not a hobby.............

 

[XMAN JR]

This should work but not code compliant. Your panels are probably not listed to have 100 amp breakers in the the lower section, it would be on the label on the side of the panel. I would suggest lowering it to a 50 amp. Also I would wrap black electric tape and cover your neutral conductor except were the connection is made. And I do not see we’re the neutral bar is grounded (connected) to the panel. I see a hole in the upper right corner of the neutral we’re a bond screw would fit and screw to the back of the panel to make a connection. Or you can add a “L” shape lug with a bolt and nut on the panel and run a wire jumper to the neutral bar.

The solid copper wire is going to a ground rod. I have to install a second one. Didn't know I needed 2. I would replace the 100 amp breaker with a 50 or 60 breaker but the wire is to big & will not fit into them. I don't want to dig up that wire if I don't have to.

 

[kiwigtx]

With AC power nothing is ever wired in series.

Most people who are not in the trade don't understand the difference.

My advice for wiring is to bite the bullet and pay a pro.....don't play with electrical wiring if you don't know exactly what you are doing.
Amateur wiring leads to either fires or injury/death.

Biggest thing to remember is the Validity of your home Insurance should a catastrophe occur.....think about that when you're playing with stuff you're not qualified or experienced in playing with.
That's my positive input for the day. (A DC term)

 

[kiwigtx]

Just remember, electricity is not a hobby.............

Exactly, and it's not learned in an afternoon.

 

[SSmoothie]

You can down size the wire by using a connector called a SPA (aka a mechanical butt splice that has either Allen head or flat head screws) and tape it up with black tape the same thickness as the wires you are splicing to as to not have any of it exposed. With the ground rods you would add another ground rod connector to the first rod a jump a number 6 copper to the second ground rod 6 feet away.

 

[MiradaMegaCab]

I believe the #6 bare ground wire must be one continuous piece (no splices) originating from the panel looped through the 1st ground rods connection and then ending at the last ground rod, for each individual panel.
Yet again, I believe two ground rods are required for a 200a panel.
I believe one ground rod is acceptable for a 100a panel.....

But as mentioned earlier as being that this is an “existing” installation, I’d stick with the term “existing “ for future inspections or the sale of your house.

 

[cosgig]

Straight from Big Al.....take the wires coming in to the box in the 2nd garage, nip off a few strands until it fits into a 60a breaker, use the 60a breaker as the main shutoff. It is not legal to go 100a to 100a, the breaker is only meant to protect the wire, which a 60a will in this case, and you don’t need more than 60a in either garage with no 220a circuits, even tho 60a will easily handle 220a circuits. This is a legal setup, and would pass inspection, and your insurance company.

Big Al is well versed in all areas of electrical, hydraulics, HVAC, plumbing and construction. He was the plant manager at Ann Arbor Machine for over 35 years, and has his master license and journeyman’s status in all areas. I tend to trust him on all things.

 

[SSmoothie]

Ground rods required-NEC 250.53 A1-A3 unless you meet the exception. If the panel is existing and installed and inspected and approved when one rod was required no second rod required but when when you alter or new two rods required. Or other means such as a ufer, water pipe in the ground 10 ft or more etc. NEC 250.64 A-F go to (C) Continuous 1-4 (3) Bolted connection. And tell Al he can not trim conductor down to size to fit breakers, you will be interrupting the listing of the manufacturer and they will not stand behind there product once you alter it.

 

[beanhead]

Call someone that's well-versed in your local codes and practices. Remember...the NEC is a MINIMUM requirement and the 'authority having jurisdiction' has the ultimate say, and can (and often does) supersede the NEC.
There's some sound advice here but also some real head-shakers...