Electrical Safety – Easy Ways to Trace a Home Electrical System

A sub panel must have the neutral and ground isolated. Panels come with a very long, rather thick (about 1/4 x 20) green bonding screw that connects the neutral bar to the can in the case of a primary panel. You don't get a neutral from your utility, you create one with that bonding screw.

Sub panels should be fed with 3 insulated conductors of appropriate size, and a ground that need not be insulated (but can be, if you want). So the first part of your question is, yes, that sub panel must be grounded, but the grounding conductor should be attached to the can using a ground lug, not by landing it to the neutral bar.

Sub panels must also have a fused disconnect, which means they need to be fed from a breaker, and there can't be anything else on that breaker. Don't double tap. You have two options here:

• Increase the size of the existing sub panel
• Put in a new double pole breaker in the existing sub panel and use that to feed your new sub panel. Land the circuits you had to pull out of the existing sub panel into the new one.

As others have noted, you need to watch your loads. If all you need are a few convenience receptacles or a lighting circuit, you should probably be o.k. (hard to tell with what you've given).

Either way, get an amprobe and look at what each incoming phase is pulling in your existing sub panel prior to doing anything. Make sure everything is on when you do. If it's only pulling 25 - 30A on average, you should be o.k. to add a small 8 circuit sub panel. Since it's directly in the line of sight with the existing sub panel, the new sub panel need not have a main breaker since the means of disconnect is right next to it.

A six to eight circuit sub panel runs about $80 without breakers, they typically start at 50A, but you don't have to feed them with 50A. You could feed it from a 30A breaker if all you want are convenience receptacles and lights.

Here is an amprobe being used:

_{(source: amprobe.com)}

Do that on your sub panel first (one phase at a time) just to be sure you have room to add more. If not, you need to replace your existing sub panel, and an electrician is really your best bet there.

Another good thing to do is measure the draw of the circuits you'll have to move to the sub panel in order to make room for the breaker that will feed it. Obviously, you want to move the circuits drawing the least to the new panel in the end. Some re-arranging might be needed to make that happen.

Since this is a garage, take care what you connect to the sub panel. If you are going to be powering something like a compressor (or anything else with a decent sized motor), carefully consider the locked rotor amperage when determining the load. It will be printed on the motor.

Finally, if any of this sounds overwhelming, call an electrician. If you get into any kind of trouble, call an electrician.

That explanation doesn't really make any sense to me personally. The neutral bus bar in your main panel should be bonded to the ground bus bar so in effect, all neutral wires in your house are grounded.

The third prong in a typical three prong outlet is known as the equipment ground. This is a safety feature that should cause your breaker to trip if an electrical fault inside of an appliance causes the metal body of the appliance to become energized. The equipment ground protection however is a safety feature for YOU so that you won't be electrocuted in the case of an appliance fault. It doesn't and shouldn't make any difference at all do the proper functioning of an appliance.

If an appliance you (recently purchased, older appliances may not have the same quality standards!) purchased has only a two prong plug, then it is essentially assured to not be an electrocution hazard in the case of an electrical fault, or it is not capable of having such a fault.

So basically what I am saying, the appliance you are talking about would never have been grounded anyway if it has a two prong plug. Grounding has nothing to do with the failure of your appliance.

You must have misheard because perhaps the tech support person meant to say "Ungrounded Neutral" which potentially could be a problem for sensitive electronics. The neutral (connected to the center tap in the main panel) can and does carry an electrical charge, so the neutral bus bar should be grounded to the outside through the use of a grounding rod to bring Neutral to Earth Ground.

If your home was built in 1959 then it is possible that the grounding rod was never placed deep enough into the earth to provide proper grounding, or perhaps it rusted away over time. How far the grounding rod needs to go depends highly on the region you live in too. I used to live in a home built in 1958 and had a similar problem. A qualified electrician would be able to fix this for you, or an adventurous DIY'er.