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Gentoo · Sep 24, 2007, 11:18 PM

Allright, I have been talking to a few contractors for the work I need, and each one gives me a different story! Please help clear this up.

1. Electrician "A" says that all I need is a GFI on the line and I will be safe from shocks, and can plug in any 3 wire appliance I want.

2. Electrician "B" says no, he needs to run a separate ground wire to each outlet to ground them, and I can have a GFI if I want as well.

The more I read about this, the more confused I get... :o

What will happen to me if I plug a 3 wire item into a GFI protected 2 wire system? What will happen to the item? (Not work, blow up, etc?)

Electrician B quotes me $3,300 to "Add grounding protection to home. Numerous holes will have to be cut to accomplish this task. We will limit these holes as much as possible. Change all outlets out to grounded outlets"

What about the light fixtures? Do they and the light switches need to be grounded as well? Does the oven, or the range?

tkrussell · Sep 25, 2007, 02:33 AM

Having 3 wire cable is the best. But electrician A is correct, that using GFI devices to protect outlet circuits is allowed. And can use 3 wire receptacles on the 2 wire GFI protected circuit.

A GFI detects a ground fault and will trip. An equipment grounding conductor allows fault currents to flow to cause a standard breaker to trip in the event of a fault. Both do the same job in different ways.

Ground fault devices actually work better since they are designed to trip over 5 milliamps of fault flow. A standard breaker relies on solid low impedance grounding of the circuit to insure the breaker will trip, current may need to flow to a higher level to cause a breaker to open.

Must use the "No Equipment Ground" labels that are provided with every GFI receptacle on the 3 wire outlets connected to a 2 wire circuit.

Electrician B is only correct about running an equipment ground for NEW cable extensions to an existing circuit. It is not allowed to add a third wire to every existing outlet. Ask him to show you where his plan is allowed by code?

Existing lighting fixtures do not need grounding. Nor do switches. Existing installations do not need to be brought up to new code. Of course, any grounding that can be added is a plus. Any major remodeling will require new wiring in that area.

Ungrounded switches can be protected by using nonmetallic plates with nylon screws. Many inspectors require this to eliminate any exposed metal that may become energized.

Gentoo · Sep 25, 2007, 06:37 AM

So what will happen to say, my computer if I plug it into a "no equipment ground" GFI outlet? Will it short out or not work?

I know that nothing *needs* to be brought up to code. But can I get electrocuted trying to change the light bulbs on a fixture if it is ungrounded?

KISS · Sep 25, 2007, 06:55 AM

Surge protection may not work properly therefore I would recommend a whole house surge protector. Connections between grounded devices that use ground as a common wire, damage could occur between devices. e.g. A USB printer attached to a desktop computer. Isolated hubs can fix that.

Change your lightbulbs using a wooden stool or step ladder with one hand in your pocket and your fine. You can use GFCI breakers on these circuits as well.

tkrussell · Sep 25, 2007, 08:38 AM

If the fixture was energized, unless your on an aluminum ladder in water on a grounded surface, nothing can happen to you.

Of course, changing a lamp should be done with the switch off, even if the fixture is grounded. Lamp breakage or damaging a socket is possible changing any lamp.

If a fault develops a GFI receptacle will trip.

Kiss has a good suggestion to use a whole house surge protector, which is a good idea for anyone with power issues.

Another device that works well to protect computer equipment is a UPS backup.

donf · Sep 25, 2007, 08:50 AM

Hey Gentoo,

It sounds like you have more than a healthy respect for what electricity can do to a person if she gets ticklish.

Might I suggest a book that I've seen at the "Big Named Hardware Chains". Its by Black and Decker and it's the "Complete Book on Household Wiring" This will give you a pretty good theory of what actually going on as well as current levels of code and plenty of pictures to show you how to do things.

I've recommended the book before to others who did not want to be embarrassed by knowing almost nothing about electricity but didn't want to actually do the work for themselves. Generally you can find the books at the front of the store.

Also, never be afraid to ask a question. Better to prove you don't know what you are doing than to illustrate it for the world to see!

Gentoo · Sep 25, 2007, 03:07 PM

OK now even MORE confused!

What I really need to know is if I should spend the money to have the outlets grounded. I was planning on running new lines to where my computer is anyway. But my laptops, which move around the house with me use a 3 prong plug. I can't afford to fry them because they are not connected to the correct outlet.

KISS · Sep 25, 2007, 08:00 PM

Laptops will be fine unless you connect them to something else with a 3 prong plug without isolation.

USB uses ground. Ethernet is isolated. Modems are typically isolated.

Something like this: UISOHUB4 - USB Optically Isolated 4 Port Hub will safely connect USB devices.

Here's what happens. Things like computers and those little power supply bricks generate high frequencies. One way to keep them from radiating into the environment is to shield them (enclose the device in metal) and attach that metal to ground. No ground. It may cause minimal interference and may not be detrimental.

The problem comes in the filter design in the AC line. Since it may have capacitors from L1 and ground and N to ground, it can raise the potential of ground. In fact I've seen 70 VAC because an outlet had a bad ground. There was a ground that was good and a ground that was bad. Two different devices or one on and one off, you can't guarantee what potential ground will be raised to with respect to another device.

I just checked by 3 terminal brick and there is a connection from the third prong to the DC input of the laptop. I can't easily check anything else. That in itself makes me suspicious.

Logic levels of USB is 5V. If you exceed that by 10% or so, the logic devices could be history. I wish I had a spare USB cable to canibalize.

Ethernet typically has isolation since it's transformer coupled.

Modems should be OK too: http://assets.zarlink.com/AN/MSAN_15...ote_Sept06.pdf

Here is a way too technical discussion: Chapter 10: Noise Reduction and Isolation

USB will be the major troublemaker.

Gentoo · Sep 25, 2007, 08:25 PM

Thanks, you really seem to know your stuff!

I think I'm just going to bite the bullet and pay to have the outlets grounded as well as run a new line for my computers. tkrussell, I don't know how the electrician plans to do the job. I was very clear that I wanted grounded outlets in the home, and he is a licensed and bonded electrician, so I assume he knows what he is talking about.

What will happen if say, he doesn't know what he is talking about and he decides to just run a single ground wire to each outlet? If this is against code (and I think it is) where does that leave me, the homeowner?

tkrussell · Sep 26, 2007, 02:50 AM

Be very clear that you want new cable, and not just a ground wire installed.

Have him give you a written scope of work and estimate that spells out exactly what will be done and with what type of materials.

Be sure he applies for permit and inspection.

Stratmando · Sep 26, 2007, 06:47 AM

Since most of the cost will be labor, you may have him use #12 with a 20 amp capacity,
The only thing worse than upgrading, would be to upgrade to #14.
Another thing on grounding boxes and fixtures, if a live wire comes loose in a box and touches ground, it will trip breaker, not become live.
New construction and remodel require 4 wire range and dryer outlets. This separates the neutral and ground. The neutral carries current, the ground does not.(Unless a problem)

KISS · Sep 26, 2007, 06:51 AM

If you don't do it right when it comes time to sell your home and there is a home inspection and they catch it, you'll have to do it then before you can sell.

labman · Sep 26, 2007, 07:22 AM

Yes, no sense living with a problem and then paying to fix it after you move out. As tkrussel said, you don't have to add a ground. But if you do, you can pay to have it done right, now or later. That is part of the reason I have spent much of the week cleaning up my breaker panel by adding a subpanel as part of installing an interlock and back feed breaker for a generator, see https://www.askmehelpdesk.com/electr...se-123290.html

I though if I had enough 10-3 with ground left over, I would replace the old dryer cable. I wa pleased to find that the 1970 original already was 4 wire. If I hadn't spent so much tine here I would have the project done and my grass mowed.