Help adding 230v outlet at subpanel in the garage

[CobyRupert]

Everything looks good in your latest picture, except a 'grounding electrode conductor' is required to a grounding electrode (e.g. ground rod).
One rod would be ok.
As per NEC 250.66: For a #10 feeder into the sub-panel, a #8 copper 'grounding electrode conductor' from the ground bus to the rod would be ok.
As per 250.53(G), if rod encounters a rock bottom, rod can be driven at an angle of up to 45 degrees, if this is not sufficient, rod can be buried horizontally at a 2 ft depth.

 

[caps]

I just recently had a 100 amp subpanel put in my garage which is on the other side of my driveway from the house.

The contractor put in a ground rod just down from the panel on the outside of the wall. The inspector made him remove it and said that we only needed one ground as two could cause ground loops due to uneven potentials. He said something about the soil that we have here is inconsistent (layers of clay and sand). Also made him remove the short (4 Ft) ground rod that existed by the house and put in a long one (8 ft I think).

 

[GPintheMitten]

Keep in mind, if you decide to bury larger cable and if you want to get it approved, you will need to have the trench depth approved. If you go this route, when you get your permit, just ask at what stages the inspector wants to be called.

 

[s219]

You can sign up to view the NEC online for free, which is the best way to nail down requirements (though some of it is open to interpretation). Section 250 covers grounding.

The ground rod needs to have less than 25 ohms resistance to ground, which is why a lot of people recommend two rods (and they should be 6' apart, not 7' I mentioned). Unless you can test to verify the one rod has less than 25 ohms, most inspectors want to see two rods.

caps, I am surprised to hear your story, but sometimes local inspectors will override code if they have reasons. One of the benefits of grounding sub-panels in detached structures is quicker path to ground for lightning strikes. I'm not sure I like the idea of relying on the main building's ground rod for a lightning strike on an out-building.

 

[caps]

S219, There is a bit more to the story. The inspector did have some sort of meter that he used to test the ground rods when he did the original inspection. The reason I had the garage wired was to build a ham radio room into it with 220 outlets for my amplifier and welder, plus 120 for AC, heater, lights, etc.. On the far side of the garage and about 15 feet from it, I put a 50 foot rohn tower for my antennas. I put three ground rods six foot out from each leg with really heavy copper cable to each leg. Antenna feed lines run underground to my bulkhead for the connectors which also has an 8 ft ground rod directly below it. Also all six guy cables are terminated with six foot long screw in anchors. All antennas are disconnected at the bulkhead when I am not using them so there is no connection to the radios when they are not being used. All radios run off of 12 Volts except the amplifiers. Also there are gas discharge tube type lightning arrestors on each coax feedline (4 of them). The inspector came out to look at it and approved it but said that I was a bit paranoid.

 

[k0ua]

S219, There is a bit more to the story. The inspector did have some sort of meter that he used to test the ground rods when he did the original inspection. The reason I had the garage wired was to build a ham radio room into it with 220 outlets for my amplifier and welder, plus 120 for AC, heater, lights, etc.. On the far side of the garage and about 15 feet from it, I put a 50 foot rohn tower for my antennas. I put three ground rods six foot out from each leg with really heavy copper cable to each leg. Antenna feed lines run underground to my bulkhead for the connectors which also has an 8 ft ground rod directly below it. Also all six guy cables are terminated with six foot long screw in anchors. All antennas are disconnected at the bulkhead when I am not using them so there is no connection to the radios when they are not being used. All radios run off of 12 Volts except the amplifiers. Also there are gas discharge tube type lightning arrestors on each coax feedline (4 of them). The inspector came out to look at it and approved it but said that I was a bit paranoid.

He obviously hasn't seen what a strike can do to expensive radio equipment. I have.

 

[buickanddeere]

RockKnocker , Gator and others of similar thought have good advice.
No such thing as a 300amp panel.
Grounding system with two rods is required even if the inspector says it isn't.
Our inspectors here would pull the meter from the base and shut off the power. Until you protected the NMW cable supply at the bottom of the panel from mechanical damage. Only one wire per box connector. Not three cables through one connector as the top left .
Don't even think about back feeding that panel with a generator and supplying the house.
I don't know if you are trying to install equipment past your income and expense bracket . Or you are overly economical to the point of being dangerous?
Use a Generlink transfer switch in the meter base and a 7200/7500W Champion generator.

 

[Sodo]

Great info! Thanks very much for your time.

..protected the NMW cable supply at the bottom of the panel from mechanical damage.

Heres the 10/3 feeder coming into the garage from the 30A breaker(s). It goes direct up to the panel (36 inches). Plastic conduit and fittings are easy. Thanks very much for that.

Only one wire per box connector. Not three cables through one connector as the top left .

2 cables. Probably ran out of clamps. But will fix that ASAP

Don't even think about back feeding that panel with a generator and supplying the house.

Haven't thought about it but? But for the sake of education, are you referring to the 30A breaker limit (simply not enough power)? Or are there other problems? If I was powering the house I would not call any attention to my subpanel, I'd attach direct to the main panel.

I don't know if you are trying to install equipment past your income and expense bracket . Or you are overly economical to the point of being dangerous?

Not income and expense bracket but "$$$ usage and desires" bracket. And git'er done bracket too.

Do you mean dangerous that it might cause "inspection problems"? Or dangerous as in "Safety problems"? Do you have the time to clarify specifically what is dangerous here?

 

[aczlan]

Don't even think about back feeding that panel with a generator and supplying the house.

Haven't thought about it but? But for the sake of education, are you referring to the 30A breaker limit (simply not enough power)? Or are there other problems? If I was powering the house I would not call any attention to my subpanel, I'd attach direct to the main panel.

If you feed a generator into the panel, it needs to be connected in such a way that the generator breaker and the main breaker cannot be on at the same time (using a physical interlock).
Otherwise you could push power back out to the lines on the street and fry a lineman, or blow up your generator (literally) when the power comes back on.

Aaron Z

 

[Sodo]

If I was powering the house I would not call any attention to my subpanel, I'd attach direct to the main panel.

OK got it. If you hooked up a generator out at the subpanel, your "connection" out there cannot employ or work exclusively with the mechanical interlock which is a device that physically ensures the main breaker has been disconnected from the utility.

Understood that many want to power the whole house during outages. Not me, I'd power the fridge and freezer, maybe the modem, and light a fire in the stove.