Electrical question again please

I have been watching these topics, trying to avoid being "bubba", so now it's my turn to ask, lol.

Putting up a new building right next to my existing garage. Power comes from the house 200 amp box via overhead 3 wire.
Existing garage has a 100 amp service box.



Mast is installed in the new building along with the following box.



Here is what the inside of that new box looks like.



Along with what's printed on the inside of the lid.



Now my questions...

(1) Do I need a ground rod and if so where do I attach the copper ground wire?

(2) Existing garage has its own ground rod attached to the neutral terminal bar..is that correct?

I have the wire, rod, and clamp, but am not going any further with this till I am clear on where I finish up.

Also have the overhead wire in place (temporarily) to run my air compressor inside the new building. This line will become the source for power to the new building.

What I need to do is keep my air compressor in service while I finish the new building.

The air compressor will have its own 40amp circuit, see pic.

Thanks in advance.

This can go a lot of different ways. IF you attach
at the top of the existing mast over the existing
garage you only need 3 wires down to the new
panel. In this case the ground rod will connect to
the ground/neutral bar.
However if you take power out of the existing
garage panel then you need to take 4 wires to the
new panel, 2 hots, 1 neutral(grounded conductor),
and 1 ground(grounding conductor). In this case
you will need to remove the bonding screw and
strap that connects the neutral bar to the box,
visible in picture 3. Now you will need to supply
a separate ground bar that attaches to the back of
the inside of the box. This is where the ground
rod and ground wire from existing garage hook to.
The existing neutral bar in the new panel is now
the dedicated neutral so no grounds are to be
hooked to it.

Hopefully John T or someone else that is qualified
will chime in and mention anything I may have
missed. I get tired of typing easily and usually
am a person of few words anyway so my answers tend
to be shorter than some who go very in depth on
answers.

Your panel better be speaking spanish otherwise you have Line A and Line A. What no French , how are the Canadians gonna buy that ?

Farmer, glad to hear youre seeking out help instead of letting Bubba engineer it lol Lets take this one step at a time:

WHAT YOU ALREADY HAVE

1) Under the old code a 120/240 volt Single Phase Three wire service sub panel in the garage could legally be fed (subject to a few other requirements) using ONLY 3 wires, 2 UnGrounDED Conductors and 1 GrounDED Conductor (Neutral) in which case the Neutral would be bonded to a proper GroundING Electrode such as driven rods etc. Its treated as another Separately Derived System.

2) The later code required you to run 4 wires, 2 Hots, Neutral, Equipment GroundING Conductor in which case the Ground buss and Neutral busses are kept separate and isolated.

SOUNDS LIKE YOUR UNDER THE OLD 3 WIRE CODE TO THE GARAGE

If that's so and you want to leave it as is??

Id treat the new buildings panel as a current code legal sub panel fed from the garage (its treated like a main panel in this situation). That means you run 4 wires,,,,,,,Since every buildings (if new building is separate) electrical service still requires grounding, for that sub panel its ground rod would wire to the Equipment Ground Buss. If the new building is a part of the garage or an addition???? You wouldn't need another ground rod at its sub panel.

CONSULT LOCAL AUTHORITY as what they say counts NOT me or Bubba or anyone else lol

I guess the difference is if the new bldg. is a garage addition or a new separate building as far as if a new ground rod is required. If same buildings no additional ground rod (building service already has one), but if a separate building yes you need another grounding electrode.

SORRY I HAVE TO RUN so no time for a better detailed explanation but I will check back later tonight and add to this if necessary

John T Too long retired electrical engineer and rusty on latest codes so no warranty but I will check back later

Well, looks like you guys agree with each other.
I am still a little confused as to what to do.

I was hoping I could wire up the box in the new building, taking power off my breaker inside the old garage....seems like that's not the way to go with this...

Am trying to keep this simple, and use what I have, but will that mean buying something extra to install inside my new box??

Keep pounding away on this and I may get it yet.

I don't want to change anything that's done in the old garage or overhead if I can avoid it.

The new building will be mainly used for storage, and housing my air compressor. Most of the SHOP work will be done in the old garage.

Air lines are buried underground between the two buildings, with new termals inside the new garage, in case I need to make use of a larger uncluttered (for now) area.

Greg K and others of the same theme have the better solution using a four wire supply, a floating neutral and a pair of ground rods.
Those overhead triplex electrical supplies can wreak havoc by causing tingle voltage shocks to livestock.

A new ground bar only costs $5-10 and mounts on the 2 raised bumps in any of the 4 corners of the new panel. There should not be any changing inside of the old garage since with the new 4 wire setup the ground and neutral will terminate on the same ground bar in the old panel in the garage. The interesting issue would be the overhead needing another conductor added. They make an overhead quad cable for 3 phase but you will need to identify which one is used as the neutral.

If you don't know anything about electricity, it would be a whole lot safer to hire an electrician to come out and wire it for you. Might keep you and somebody else some day from getting fried.

Sorry, I got home too late last night but here I am again finally with more thoughts:

I see no reason why you cant take power out of your Garage panel (if that's your choice) to the new building PROVIDED the garage panel has sufficient ampacity and will accept a 2 pole breaker big enough to supply the new building loads????????? THATS A BIG PROVIDED!!!!! So don't have a calf Billy Bob

RECALL if the Garage was fed off the house main panel, under new code it should have been fed with 4 instead of only 3 wires, while if grandfathered in or under old code, 3 sufficed.

That being said and if you choose to leave it (garage) as is (3 wires) Id treat it as a Separately Derived Source and in that case (like used to be done) I WOULD BOND THE NEUTRAL AND GROUND BUSSES TOGETHER (may or may not have to mount a ground buss) same as at the house main panel. If it were under the new code and treated as a sub panel off the houses main panel, the Neutral and Ground Busses would be kept separate and isolated.

With the 3 wire feed to the garage, the Neutral needs bonded to a proper Grounding Electrode (such as a driven rod or rods etc) via a usual No 4 bare copper wire GroundING Electrode Conductor and that bond is usually at one of 3 places: 1) Up at the weatherhead riser where aerial Neutral splices to Neutral down the riser pole: 2) Inside the meter base (but you have none there): 3) Inside the panel to the Neutral Buss.

FINALLY to be under the new code and if you feed the new building out of the garage panel if theres enough ampacity and a big enough breaker available

ID DEFINITELY FEED THE NEW BUILDING WITH 4 WIRES AND TREAT THE NEW BUILDING AS A SUB PANEL in which case you run 4 wires (for 120/240), Two UnGrounDED hot phase conductors, One Neutral Grounded Conductor,,,,,,One Equipment Grounding Conductor and at the new buildings sub panel the Neutral and Ground Busses are kept separate and isolated.

Finally every buildings electrical service requires grounding, so if the new building is a separate structure you need another GroundING Electrode (driven rod or rods etc) but in this case (4 wire feed) its connected to the Equipment Ground Buss instead of the Neutral as I understand it (but Im rusty on new codes remember)

AGAIN it depends on if you leave the garage as the old 3 wire (will still work) and if you feed the new building out of the garage and if the new building is considered as a separate building or not so don't let Billy Bob have a calf as the above depends on those differences so may or may not be right depending on some facts.

Nuff said, remember not being there and unsure of the new structure and if its separate or not and unsure of the house to garage wiring and unsure of latest codes NO WARRANTY

Soooooooo consult with local authority and utility providers and/or current practicing professional electricians (more familiar with later codes them myself) instead of myself or Billy Bob.................

Got it?? Questions??

John T

Thanks John, you're better at explaining this stuff than I am.

Thanks but not sure I agree, its just that as an attorney after being an engineer I'm bad to use a lot of words lol I just cant help myself. Often fewer words is best to help a lay person understand grrrrrrrrrr

John T

Thank you John T. and Greg K.

A couple facts before I ask my next questions.

The new building is separate from the old garage by about 5'.

Current box in the old garage is 100 amp with a place for up to 60 amp breaker to run my new garage.

CODE means nothing in this area I live, at least no one else is going to give me grief if this isn't done buy the book. I have talked to the power company friend of mine who is also an electrician. Also to a local electrician, who is planning on coming over tomorrow to see what I have.
Over the phone with him this morning, Jason says I can tap into the 3 wire line at the top of my mast and run it over to the new building, bypassing the old garages breaker BOX. In this case I may need to get a different box for the new garage, that has a main breaker already installed.
I guess maybe I jumped the gun with the box I purchased and installed, WTH it's only 35.00 I guess.
At any rate I am trying to avoid doing the 4 wire run between the buildings as that would then require me to install a 4 wire cable to my air compressor.....grrrrrr...already have a 3 wire on hand for that.

And I now understand what's the deal with the neutral and ground busses....but this new box I have installed now only has a neutral buss....with a screw to tie the buss to the box if need be, in this case it will be connected and the #4 copper wire will also be ran to the neutral buss from my NEW ground rod....

Having said all this, I know you want to throw the book at me, lol, but why won't this work with a 3-wire overhead to my new building IF I replace this box with a 100amp box and breaker?

(quoted from post at 12:15:43 06/04/14) Thank you John T. and Greg K.

A couple facts before I ask my next questions.

The new building is separate from the old garage by about 5'.

Current box in the old garage is 100 amp with a place for up to 60 amp breaker to run my new garage.

CODE means nothing in this area I live, at least no one else is going to give me grief if this isn't done buy the book. I have talked to the power company friend of mine who is also an electrician. Also to a local electrician, who is planning on coming over tomorrow to see what I have.
Over the phone with him this morning, Jason says I can tap into the 3 wire line at the top of my mast and run it over to the new building, bypassing the old garages breaker BOX. In this case I may need to get a different box for the new garage, that has a main breaker already installed.
I guess maybe I jumped the gun with the box I purchased and installed, WTH it's only 35.00 I guess.
At any rate I am trying to avoid doing the 4 wire run between the buildings as that would then require me to install a 4 wire cable to my air compressor.....grrrrrr...already have a 3 wire on hand for that.

And I now understand what's the deal with the neutral and ground busses....but this new box I have installed now only has a neutral buss....with a screw to tie the buss to the box if need be, in this case it will be connected and the #4 copper wire will also be ran to the neutral buss from my NEW ground rod....

Having said all this, I know you want to throw the book at me, lol, but why won't this work with a 3-wire overhead to my new building IF I replace this box with a 100amp box and breaker?

Click to expand...

I'm not sure why a single phase 240V aircompressor needs four wires?
That breaker box isn't right with one buss bar. There should be a ground bar and a separate neutral sitting on an insulator to isolate it from the ground system.