Service to Outbuilding

[Anonymous]

Let me see if I get this right. If I want to run electrical to my outbuilding approx 130' away from the house I should at a minimum use a 30 amp double pole breaker at the main panel, run 4 wire #8 to the building, install a main lug panel with a maximum of 6 breakers, isolate the ground and neutral at the sub panel and install a ground rod at the outbuilding which will be connected to the sub panel ground bar with #6 wire. Load at outbuilding is only 4 plug in shop lights and 5 receptacles. IS this the minimum installation or am I missing something?

[Wgoodrich]

You are off a bit. See below for options in your original design that is allowed.

Then as for minimum yes and no. Yes the mininmum service FEEDER allowed to serve a panel containing an overcurrent device [aka breaker or fuse] is 30 amps.

No the minimum power that you are allowed to run to that accessory building is a 15 amp BRANCH CIRCUIT serving that building.

Definition of a branch circuit is that wire that is installed AFTER THE LAST OVERCURRENT DEVICE. [aka breaker or fuse].

Key point is you may install either a 15 or 20 amp BRANCH CIRCUIT with a snap switch that disconnects all ungrounded [aka hot] conductor as long as you have NO OVERCURRENT DEVICES INSIDE THAT ACCESSORY BUILDING. If you install an overcurrent device in that accessory building then you have a FEEDER serving that accessory building and not a branch circuit. The NEC states in 225 of the NEC that the smallest feeder allowed to serve a building is 30 amp rated. The smallest branch circuit allowed to serve a building is 15 amp rated branch circuit.

YOU SAID;
Let me see if I get this right. If I want to run electrical to my outbuilding approx 130' away from the house

REPLY;
240 Volts may be installed approximately 250 feet without concern for voltage drop.

YOU SAID;
I should at a minimum use a 30 amp double pole breaker at the main panel,

REPLY;
Yes 30 amps is minimum feeder allowed to serve a panel but limited to only two breakers or fuses in that panel. If you increase beyond 2 breakers or fuses then you must increase feeder size to a minimum of 60 amp feeder.

YOU SAID;
run 4 wire #8 to the building, install a main lug panel with a maximum of 6 breakers,

REPLY;
4 wire I take it you mean two hots a neutral and an equipment grounding conductor. You have a choice of installing 3 wires to a panel in the accessory building from the main building being two hots and a neutral and no equipment grounding conductor if you have no noncurrent carrying metallic path between the two buildings. You have a choice to include a 4 th wire being an equipment grounding conductor with that feeder to a panel in the accessory building from the main building if you so desire even if you don't have a noncurrent carrying metallic path between the two buildings but this would be voluntary such as you suspect in the future you may install a noncurrent carrying metallic path between the two building.

You are required to install 4 wires in that accessory building with a panel from the main building being two hots a neutral and an equipment grounding conductor if you have the noncurrent carrying metallic path such as a metal water pipe installed between the two buildings.

YOU SAID;
isolate the ground and neutral at the sub panel and install a ground rod at the outbuilding which will be connected to the sub panel ground bar with #6 wire.

REPLY;
Yes isolate the neutral bar from the grounding bar and isolate the nuetral bar from the metal case of that accessory building panel IF you have a noncurrent carrying metallic path requiring an equipment grounding conductor ran with the feeder or even if you voluntarily install that equipment grounding conductor with that feeder for any reason.

No you must marry the neutral bar and equipment grounding bar same as one entity electrically connected to each other in that accsessory building panel if you do not install the equipment grounding with the feeder between the two buildings and don't have a noncurrent carrying metallic path between the two buildings.

EITHER WAY WITH OR WITHOUT AN EQUIPMENT GROUNDING CONDUCTOR YOU MUST INSTALL A GROUNDING ELECTRODE [AKA NORMALLY GROUND ROD] AT THAT ACCESSORY BUILDING.

The grounding electrode conductor installed between the ground rod and the accessory building panel must be connected to the equipment grounding bar inside that accessory building panel. However you are a bit off on your wire size. The NEC states that a made electrode may be served with a maximum size of a copper 6 awg grounding electrode conductor. The NEC does allow a smaller grouding electrode in 250.66 tables allowing the smallest grounding electrode to be installed being an 8 awg copper as the smallest grounding electrode conductor.

Then 250.32 states an exception that if you install a branch circuit to serve that accessory building then that branch circuit must be with an equipment grounding conductor with that 15 or 20 amp branch circuit installed between the two buildings then that branch circuit in that accessory building does not require a ground rod at that building. This no ground rod is allowed not to be installed at that accessory building ONLY IF THAT ACCESSORY BUILDING IS SERVED BY A BRANCH CIRCUIT. This means no overcurrent devices [aka fuses or breakers] installed in that accessory building. YOu must have a form of nonfuse main disconnect [snap switch or nonfused disconnect] to be able to shut off all ungrounded conductors [aka hot conductors]

YOU SAID;
Load at outbuilding is only 4 plug in shop lights and 5 receptacles. IS this the minimum installation or am I missing something?

REPLY;
If those 5 receptacles are for general use without any KNOWN fixed load but convenience outlets only then you may install a 12 or 14/2wGrnd UF underground branch circuit cable serving a 15 or 20 amp branch circuit to that building and no overcurrent device [aka fuse or breaker ] is to be installed in that accessory building and no ground rod is required. YOu must have a snap switch or nonfused disconnect to be able to shut down your accessory building within that accessory building and you would need your 15 or 20 amp breaker protecting that single branch circuit installed in the main service panel inside the main building.

You mentioned a maximum of 6 breakers in that accesory panel. You have a choice of installig a main disconect most commonly a main breaker in that panel and you may have many branch circuit breakers in that panel if you like. If you so desire to install a main lug only panel without a main then the NEC limits you to 6 sweeps of the hand to shut off all breakers in that panel to use those branch circuit breakers as you maximum of six main breakers in that accessory building.

HOpe this helps

Wg

[Anonymous]

This makes more sense. In your opinion is this installation as per code.

Branch circuit breaker in Main: 20 amp double pole
Wire: 130' 10-3 with ground
disconnect at entrance point in detached garage
In building:5- 15 amp receptacles on one leg (gfi protected)
and 2 15 amp receptacles(lights) and outside light on other leg

Questions: 1) do I still need to install a ground rod? 2) SInce I have 110 volts on each leg is it still possible to install a 240 volt receptacle?

Thanks for your invaluable help

[Wgoodrich]

The NEC in 250.32 states "branch circuit". It does not designate whether 220 volt or 120 volt or mulitwire branch circuit. Yes you may install a 20 amp rated breaker to a 10 awg 30 amp rated set of wires to the garage to address any voltage drop concern then reduce back to the 12 awg 20 amp inside the garage and split into two 20 amp 120 volt general lighting branch circuits whether that be receptacles or lights.

Yes you may install a 20 amp 220 volt receptacle if you tap into that multiwire branch circuit before that 220 volt multiwire branch circuit splits into the two 120 volt runs of lights or receptacles. This 220 volt 20 amp wire may serve a 220 volt a/c unit. Just make sure you are not trying to run more load than 20 amps 240 volts can carry or you will be tripping that breaker inside that main house panel.

DO NOT INSTALL ANY BREAKERS OR FUSES IN THAT ACCESSORY BUILDING AND TRY TO CALL THAT A BRANCH CIRCUIT. If breakers or fuses are installed in that accessory building then you no longer have a branch circuit you then would have a FEEDER that must be wired under the feeder rules requiring the ground rod and other rules that apply.

This 20 amp 220 volt multiwire branch circuit meets the definition of a branch circuit therefore your grounidng will be served by the main house and no ground rod is to be installed at that accessory building but only if NO BREAKERS OR FUSES ARE INSTALLED IN THAT ACCESSORY BUILDING. Remember that breaker in that house must be sized no more than the smallest wire on that circuit. If you install 10 awg wire using the branch circuit exception then you are required by the Code to still reduce to 12 awg max to connect to any 15 or 20 amp receptacle or switch. This brings your breaker in the house back to maximum size of 20 amp.

You are not allowed to serve more than one power source to that accessory building. This forbids you trying to install two branch circiuts using that exception for branch circuit to accessory building.

You may install a 20 amp 220 volt double pole breaker in your house then install 15 or 20 amp GFI receptacles in the accssory building but only if you install those 15 or 20 amp GFI receptacle that are 120 volt rated after or downstream of that place you split to two 20 amp 120 volt circuits. A GFI will react to any white wire that is being used as a shared neutral serving two hot lines. The GFI won't work on a shared neutral. The 120 volt GFI must be installed and fed by a 120 volt black and white where the white only serves that one black. This GFI is then to be installed on the load side of where you split to two 120 volt lines only.

YOu may also install a 20 amp 220 volt GFI receptacle in the house to serve both split 120 volt runs. A 220 volt double pole GFI will monitor both hot lines individually using the shared neutral. This is a different design than the 120 volt receptacle.

Be aware a 220 volt double pole GFI may not be your best choice if you plan to run a window a/c unit. a/c units use a hermetic motor that will show leakage on the white wire that isn't really there but because a hermetic motor has the windings bathed in the liquid that is pumps by heat transfer. This cause a GFI to often trip even on a new hermitic a/c motor or refrig.

Also if you have a fridg then install your GFI on the load side after the fridg so that GFI does not read the hermetic motor in that fridge.

hOpe this helps

Wg

[Anonymous]

Good. This is great help. Thank you so much. I was getting some contradicting info and this clears everything up. If I ever get a fridge in there I'll drink a cold one to your health!

Cheers!

[Wgoodrich]

Sparky110, good luck with your project.

Wg