Could you please cite the code reference that says that you cannot install a ground rod on a sub-panel. They are required for separate buildings and are used for lightning protection. They cannot be bonded to the neutral in a sub-panel.
John Grabowski
There is no limit to the number of rods or other electrodes you use, only a limit of one main bonding jumper where the neutral gets tied to the grounding electrode system. In fact, if this sub panel is in a separate structure, another electrode is required.
A subpanel should be connected with FOUR wires (two hots, separate neutral, and ground).
The neutral bar in the subpanel must be isolated from the ground bar (the ground and neutral must not be connected in the subpanel).
You can use as many breakers in the subpanel as you wish (as many as the panel supports anyway). However, you need to determine what the typical total load of all those branches will be. For example, will you be running two or three machines at the same time?
If your expected load is less than 60 amps, you can use 6 gauge wire to supply your subpanel. It should be protected by a 60 amp breaker in the MAIN panel.
In the subpanel, you would protect each individual branch with appropriately sized breakers (15 amp for 14-gauge wire, 20 amp for 12 gauge wire, etc.).
If you overload an individual branch, the corresponding breaker in the subpanel will trip.
If you load multiple branches at once (i.e. 18 amps on four branches), you'll trip the breaker back in the main panel, even if you don't necessarily overload an individual branch in the subpanel.
If the subpanel is in a detached building, you must add a grounding rod at that building (NEC 250.32(a) I believe).
Multiple grounds are fine (ground rods, buried metal water pipe, rebar in the foundation, etc.) but all grounds must be bonded together with wiring.
Anthony Watson
"why is there always enough money to do something over, but never enough to do it right?"
That was my interpretation too. Ground at avery distribution panel, but only one ground to neutral bod (as close to the main service entrance as possible)
I believe if the sub panel in an outbuilding has more than six slots it also needs a main disconnect - either a main switch or (more commonly) a main breaker -
You can have more than one ground, but a separate ground at every subpanel is not required either.
A main breaker is required in a detached structure if there are more than six breakers in the panel.
If the subpanel is in the same building as the main panel, I believe the breaker in the main panel qualifies as the disconnect even if you have more than six breakers in the subpanel.
Regardless, I prefer having a main breaker in a panel. If there's an electrical issue, or you want to make changes, you can just kill the whole panel instead of trying to figure out which circuit you're on. It's also safer working in a panel when you can kill the main breaker and disconnect all power from the panel.
When I built my pump house back in 1991, I thought the electrical inspector said the limit was four breakers max without a main. Either he was wrong or the codes have changed. In any case, I have a small panel in the pumphouse that connect directly to the meter (not a subpanel). It has a double-pole breaker for the pump, and a couple small breakers for lights and outlets. There's no way to cut power to the panel if I need to replace a breaker or something. I've done work in the live panel, but it's not something I would recommend. If you slip with a screwdriver or something you have NO overcurrent protection.
Anthony Watson
Back when they differentiated a "lighting and appliance" panelboard, the limit was 2. I think that was prior to the 2002 or maybe 2005
ire to supply a panel with 4 breakers (20A each)? Do you have to consider t he possible use of all of the circuits carrying the maximum load? Thanks!
y given time. Will you be running machines constantly or intermittently? You do not have to total up the rating of the individual circuit breakers.
ning protection is a good idea.
It is an attached garage (poorly wired) sharing a circuit with living, and dining. I want to extent (6-6-6-8) about 35' and use a 4-breaker box. Put e xisting receptacles on their own, and add a couple circuits for power tools . Cheapest source for cable was .80/ft, but they wanted $18 shipping! I thi nk HD is a little over $...I'll have to check them out.
Usually HD/Lowes will be competitive with any other deal you can find unless you have an account at a supply house and get the discount.
If you have extra slots in your main panel, you might want to compare the costs of just running four individual circuits from the main panel. Four 12 gauge Romex cables would probably accomodate what you're needing.
You might pay slightly more for the cables, but you wouldn't need a subpanel, or the extra breaker in the main panel.
Just something to consider.
Copper is heavy, so it's usually cheaper to buy it locally. Home Depot has a more limited selection, but their prices are hard to beat if they have what you need.
Anthony Watson
Thanks for that...I could get away with running 2 circuits (#12) from the main box and that would be a solution. Is handy to have the breaker in the garage, but not necessary. Good thought!
...the panel is cheap, and I have the main panel breaker...I will need the 6-6-6-8, and a couple 20A breakers. I will try to go with a sub panel...it won't be that much more expense.
...unless the sub-panels are each in different buildings.
I decided on separate wires from the main box (3 circuits + existing light circuit). One circuit for existing outlets...and two for power tools, using #12 NM. Thanks for all the info!
I'm glad you found a solution that worked for you. Thanks for letting us know how it turned out.
Take care,
Anthony Watson
I was having difficulty finding 6-6-6-8 aluminum SER cable, locally...and (as you said) shipping charges are prohibitive.
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