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-   -   Testing an Installation: Accidental Grounds and Continuity (http://www.diychatroom.com/f18/testing-installation-accidental-grounds-continuity-37849/)

Bocolo 02-08-2009 12:27 AM

Testing an Installation: Accidental Grounds and Continuity
 
Hello,
I have been reading on this subject lately and need to make sure I understand what I am reading. Your help and time as always is very much appreciated.

When you test for accidental grounds. Power is off, you test from hot leg to ground on all outlets and light of continuity tester should NOT come on. Correct??

When you test for continuity (this is the one that gets me), You temporarily jump the hot leg and the neutral at the panel, turn on the breakers and test each outlet between the hot and the neutral wire and the light of the continuity tester should come on. Is this correct?

For some reason the statement of pigtailing the hot and neutral together and turning the breakers on does not feel right to me. I can understand wirenutting them together and testing the hot and neutral as that would make it similar to touching the two ends of a wire with your tester since you have created a loop. What am I missing here? Why is it that some part of my brain is telling to look into this further? Also, I am assuming that if the above is correct there cant be any fixtures installed? Anyway, can someone share their knowledge with me and explain this for me a bit more? Again, thanks for your time and help.

220/221 02-08-2009 02:17 AM

Quote:

When you test for accidental grounds. Power is off, you test from hot leg to ground on all outlets and light of continuity tester should NOT come on. Correct??

Keep in mind that:

A) The neutrals and grounds are tied together at the service panel.

B) There is continuity from hot to neutral in most any load that is plugged in/turned on.

c) Continuity may be present from one leg to another if 240v loads are conected.

Quote:

When you test for continuity (this is the one that gets me), You temporarily jump the hot leg and the neutral at the panel, turn on the breakers and test each outlet between the hot and the neutral wire and the light of the continuity tester should come on.
I don't understand the purpose of such a test. If you jumped the hot to the neutral and turned on the breaker, sparks would happen.

Bocolo 02-08-2009 06:58 AM

Thanks for your time. This is exactly what I am thinking. Unless what I read meant that this is a new installation on no outlets are wired. If that is the case would this test work? Or simply put, what is the correct way to test for continuity? Thanks again.

bobelectric 02-08-2009 07:52 AM

I got you now. That's how I sometime I.D. circuits. Panel not hooked up to power company yet,Put in jumper to short receptacle,Check what breaker is 0 ohms to ground.Easier with telephone toner.

Bocolo 02-08-2009 08:41 AM

Thanks for your time. So, you think that is the case? There is actually no power and this test is done before anything is connected? Thanks again.

AllanJ 02-08-2009 10:00 AM

Before connecting the neutral to the neutral bar and the hot wire to the breaker, you should be able to use your multimeter or ohmmeter and quickly test the branch circuit for continuity and also for lack of hot/neutral, hot/ground, and neutral/ground shorts.

Some folks, alas, omit that step and energize the circuit first and if it works when lights, etc. are plugged in then they assume the circuit is OK.

Yoyizit 02-08-2009 10:41 AM

???
 
Before closing breakers on a new installation, with everything off, put a 100W incand. lamp across each breaker, one at time.
A downstream short circuit will light the bulb to full brightness, without sparks and drama.

Once the shorts are cleared, you can check that you actually get power to outlets and appliances.

There is continuity (8Ω and more) and there is continuity (0.5Ω and less); the first is normal for an across-the-line load.

Bocolo 02-08-2009 12:03 PM

Forgive my ignorance. How do you get the lamp to illuminate if everything is turned off? What exactly do you mean with putting the lamp across each breaker? Have patience please just trying to educate myself. Thanks for your time and input.

nap 02-08-2009 12:22 PM

Quote:

Originally Posted by Bocolo (Post 227088)
Forgive my ignorance. How do you get the lamp to illuminate if everything is turned off? What exactly do you mean with putting the lamp across each breaker? Have patience please just trying to educate myself. Thanks for your time and input.

don't feel bad. I have been doing this professionally for too many years and yoyo has me confused on his test as well. Maybe after the coffee kicks in I will see it but right now I'm going Huh?:huh:

Yoyizit 02-08-2009 12:40 PM

Quote:

Originally Posted by nap (Post 227097)
don't feel bad. I have been doing this professionally for too many years and yoyo has me confused on his test as well. Maybe after the coffee kicks in I will see it but right now I'm going Huh?:huh:

Use one of these to bridge the breaker
http://images.lowes.com/product/conv...64481000md.jpg

Maybe you should not do this. . .:huh:
Instead, you could turn on each breaker one at a time, and if one doesn't hold then you have a short that needs to be tracked down. Tracking shorts is another post.

Bocolo 02-08-2009 12:46 PM

Yes, I was wondering about bad grounds and continuity. Thanks for your time.

nap 02-08-2009 12:57 PM

Quote:

Originally Posted by Yoyizit (Post 227105)
Use one of these to bridge the breaker
http://images.lowes.com/product/conv...64481000md.jpg

Maybe you should not do this. . .:huh:
Instead, you could turn on each breaker one at a time, and if one doesn't hold then you have a short that needs to be tracked down. Tracking shorts is another post.

let me explain what I think you are doing:

connecting one end of your light socket to the breaker and the other to the wire feeding out to whatever. You then turn on the breaker and if the light lights, there is a ground connection (short) allowing a return path.

Yes? If not, please be more descriptive in your test method. I'm always open to others ideas. God knows I don't know everything and I try to learn from others.

Yoyizit 02-08-2009 04:06 PM

Quote:

Originally Posted by nap (Post 227115)
let me explain what I think you are doing:

connecting one end of your light socket to the breaker and the other to the wire feeding out to whatever. You then turn on the breaker and if the light lights, there is a ground connection (short) allowing a return path.

Yes? If not, please be more descriptive in your test method. I'm always open to others ideas. God knows I don't know everything and I try to learn from others.

No, the bulb takes the place of a blown fuse or a turned-off breaker. If the bulb lights full brightness with a turned-off breaker there must be current flow due to a downstream short, and if nothing is turned on there shouldn't be any current flow.

An outlet is a Voltage Source, and just like a car battery, if you [short] a [voltage] source, infinite [current] flows and bad things happen. To get around this we use circuit breakers.
Another way around this is to use an incand. lamp, which acts somewhat like a Current Source. A flourescent lamp ballast also converts the voltage source outlet into a current source (which the tubes prefer).
A lot of things (motors, relays) prefer current sources but they are harder to make.

A current source is the "dual" of a voltage source.
If you [open] a [current] source, it produces infinite [voltage] and bad things happen.
A lightning bolt, with it's presumably high resistance and high voltage, might approximate a current source.

The wiki links on these concepts are not so good, otherwise I'd post them.

Where a current source ends and a voltage source begins is hard to say; you have to understand the idea of internal resistance.

nap 02-08-2009 09:21 PM

At the moment, I would rather not get in to your explanation of voltage and current, just tell me where you are hooking up the leads on the lamp socket to test as you suggest.

AllanJ 02-09-2009 03:57 PM

After connecting the neutral and ground wires of that branch circuit to the respective bars in the panel and before connecting the hot wire to the breaker, clip one lead of the test lamp to the circuit hot wire and the other lead of the test lamp to the breaker screw.

Now when you turn on the breaker, if there is a short, the short current will be limited to what the lamp draws and the lamp will light up.

Things plugged into the branch circuit while you are doing this test may also cause the test lamp to light up depending on what those things draw in terms of current.


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