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Experience:  29 years as a Licensed Electrical Contractor in Illinois, 5 year college Electrical Instructor, Former Electrical Inspector, Diploma in Digital Electronics, Former Illinois Licensed Home Inspector
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# I am splicing into an existing circuit in my attic, and before

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I am splicing into an existing circuit in my attic, and before I hooked any of the wires up, I turned the power back on and measured the voltage. The hot to neutral is as expected, about 123-124 volts. But the hot to ground is about 30 volts, and the neutral to ground is about 20 volts. So I'm thinking I must have a bad ground somewhere in the circuitry leading to that wire. Now I've discovered that that entire circuit has similar voltage readings (at all the outlets I've tested). Other circuits I've tested are fine. So, what kind of wiring problem would lead to those voltage readings, and what is the best way to figure out where this is mis-wired?

Hello.....my name is XXXXX XXXXX I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!

1) I always recommend to start at the source and work your way downstream.

2) Test the voltage at the circuit breaker. From the breaker hot to the neutral bus bar, you should read 120 volts. From the breaker hot to either the equipment ground bar or to the load center metal enclosure, you should read 120 volts. From the neutral bus bar to the load center metal enclosure, you should read 0 volts.

3) If you have recently replaced or removed any switches, receptacles or splices on this circuit, this is also a good place to measure. Double check the neutrals for loose or faulty splices.

4) A neutral to ground voltage reading of 20 volts suggests a loose or faulty neutral splice somewhere in the branch circuit. Neutral to ground voltage should = 0 volts.

5) You can also try the Wiggle Procedure shown below to determine if you have a loose or faulty splice at one of the branch circuit receptacles:

Wiggle Procedure

You have a circuit with dead outlets and maybe some dead lights on it or you're experiencing flickering on a circuit. You will need a 2 wire voltage tester to check the outlet. A Multimeter or a Volt/Con are suggested. I prefer the Volt/Con because there are no settings to make, it does continuity and is audible. Success begins with knowing what you're looking for.

1] No voltage reading between the hot and the neutral or ground indicates an open hot.

2] No reading between the hot and the neutral but 120V between the hot and ground and 120V between the neutral and ground indicates an open neutral.

3] No continuity between the neutral and ground - Check for tripped GFCI device first

4] If all the branch circuit breaker are on you have a bad connection on the hot or neutral wires. The usual cause is a bad connection, either a termination on a device or connection in a wire nut.

Over the years I've found the easiest way to locate the opening needing examination and correction is to wiggle the devices.

5] The first step in this exercise is to get a lamp to act as an alert. Make sure the lamp works and in the on position. You may also use something like a vacuum cleaner or blow dryer, for an audible alert. Don't use anything electronic, like a radio.

6] Plug it into a dead outlet.

7] Now with a cube tester or any plug you will need to go to all the dead outlets and any live outlets in the area, insert the plug and wiggle the device side to side slightly. Watch the test lamp or listen for the other alerts as you wiggle the devices.

If the loose or bad connection is present the wiggle action may make it contact briefly and the lamp or the other things will alert you . Having found the suspected outlet all that is left is to correct the bad connection.

If the device is a push back wired device, this probably is the cause of the circuit failure. All wires must be terminated under the screws. Also you should never put more than one wire under a screw.

This troubleshooting procedure works in most cases and won't have you open boxes un-necessarily.

Keep in mind that the problem is in one of two places in the circuit, either in the first dead outlet or the live outlet just ahead of it.

Hope this helps.........If you have any additional questions, let me know and I'll be glad to answer them for you.

Otherwise, don't forget to rate me before you log Off.

The next time you have an electrical question, you can also request for me at: http://www.justanswer.com/home-improvement/expert-your-electrician
..........Thanks..............Kevin!

Customer: replied 3 years ago.

Thanks for your reply. Please can you give me some more information: The ground to neutral and the ground to hot are both not what they should be. The hot to ground should be 120 volts, but it is actually 30 volts. But the hot to neutral is normal. So, this can't be just a bad neutral connection, as you suggest. It must be something else or something in addition to that. I just don't know what.

One problem I have is that I don't know in what order the circuit is wired. Can you tell me whether circuits are normally wired with a single incoming hot - neutral - ground cable, which is then connected in serial to each part of the circuit? If that is the case, how can I figure out which receptacle or fixture is first in the circuit? If I can figure that out, then I can test the first one, then the second, until I find out where the problem starts.

Thanks.

1) Normally when measuring voltage from neutral to ground, it indicates a loose or faulty neutral connection. Your issue may also have a loose or faulty hot connection.

2) Did you measure the voltages at the panel? If so, were they normal measurements? If you are unable to measure normal voltages at the panel, then the problem lies within the panel either at the breaker or a hot, neutral or ground wire loose termination. If the panel is good, then you know the problem lies downstream from there.

3) All 120 volt circuits are wired in parallel. Hot connects to a downstream hot, neutral connects to a downstream neutral and grounds to grounds.

4) Not knowing the order of how the circuit was originally wired is always the million dollar question. I always start at the source, ie the main electrical panel. If you can measure proper voltages there, then you know the problem is downstream from the panel. Troubleshooting this type of problem is a matter of locating and isolating and can be very time consuming since you don't know the order as to how the original electrician connected the devices and/or splices.

5) Every branch circuit has 3 possibilities. Any box whether it is a receptacle, wall switch, ceiling fixture or a splice box is considered as either a "Home Run", Middle of the Run or End of the Run. A Home Run is only 1 box or device and terminates at a box directly originating from the panel. A Middle of the Run is multiple downstream boxes or devices from one another. An End of the Run is the last downstream box in the circuit.

6) If you are unable to measure the correct voltages at the attic splice box, your problem is either in that box or upstream from that box (closer to your main electrical panel). I try to visually check out the next most logical box where the circuit would be spliced into and try to narrow it down from there. Often, this involves opening other splice boxes, receptacles, wall switches and/or ceiling fixtures. Loose wires and/or faulty splices can be anywhere. If no problems found in the attic location, logically work your way back.

Attics boxes are often used as access to the bedroom/hallway/bathroom/closet areas below. Check all receptacles in these areas. Turn labeled breakers ON/OFF and map out the rooms. Make a diagram of each room showing the receptacles, lights and switches. Map the devices with the breaker number and isolate all box devices. Your attic area may have other splice boxes that are buried underneath insulation.

7) Often, electricians will use a toner to trace out the wires due to the complexity and time consuming effort this can involve in locating where the branch circuits were spliced or connected too. If your house was wired using metal conduit, this becomes somewhat easier, since you can tug on the wires and listen to where they go. If the house is wired in Romex, you won't have the luxury of tugging on wires since the Romex is stapled to the 2 x 4's.

Customer: replied 3 years ago.

Hi, and thanks for your additional help. The voltage at the main panel appears to be correct, although I cannot tell which neutral wire is the one connected to this circuit. Is the only way to tell which neutral and ground are the ones for that circuit, to trace them up to the cable as it emerges from the panel box? It appears to be a pretty messy panel box.

So, from what I understand, the only way to figure this out (if the main panel has the correct voltage) is to check the wiring at each fixture, switch and receptacle on the circuit. One other question: How can I test whether the ground is properly connected, without using the neutral or hot wires to test it? Is there a good device that tests whether a ground is really grounded?

Thanks. Sorry for the continued questions, but I just want to make sure I understand everything before I sign off on this question.

1) No problem on the questions. I'm here to assist you and happy to answer them.

2) OK, so the panel voltage is good. I assume the house is wired using Romex? If so, trace the hot wire from the breaker to the knockout where the Romex comes into the panel. Then you can see the neutral and the bare copper ground wire. The Romex color insulation for a 15 amp breaker will be white, for a 20 amp breaker, it will be yellow. That is the easiest way to determine which neutral or ground you have for your subject circuit. Inside the panel you should see some white or yellow insulation coming in from the knockout. Trace it back.

3) If the box is messy, and you intend on being in the house for a long time, now's the time to clean it up. When you have free time, go to Home Depot. In the electrical department, purchase a number label book so you can stick the numbered labels on all of your hot wires and neutrals within the panel. This takes awhile, but down the road, you'll be thanking yourself that you took the time to label and identify your hot and neutral circuits.

4) Yes, you are correct. If the voltages are all good inside the panel, then the problem lies downstream (away from the panel). Unfortunately, the problem can be inside any wall receptacle, switch box, ceiling fixture or wall lighting fixture. Try to logically work your way backwards from the attic box. If any recent electrical work has been performed such as replacing switches, receptacles, etc. those boxes should be inspected 1st since a loose or faulty wire splice may be there.

5) Inside your panel, take your 2-prong tester and measure every circuit breaker from hot to either the bare ground wires or to the panel's metal enclosure. If you can read 120 volts on each circuit breaker going from hot off of the breaker to the bare copper ground wires or to the panel metal enclosure, this means your panel is properly grounded. This is the best way to determine if you have a proper grounding system.

You can also use an extension cord to measure for a good ground. If you plug-in an extension cord into a receptacle, take your 2-prong tester and insert 1 probe into the round grounding hole of the extension cord. Take the 2nd probe and insert it to the hot blade of another wall receptacle. You should read 120 volts by doing this. Remove the probe from the extension cord ground and place 1st probe into the ground hole at the same receptacle, you should also measure 120 volts. By doing this, you will have measured hot to ground from 2 different grounded receptacles. Let me know if that makes sense?

The other way to check for a proper ground is using a 3-prong cube tester. Insert the cube tester into all of the 3-prong receptacles in this house. Look at the lights on the cube tester to determine if the receptacles are properly grounded.

Another method to test for ground is to intentionally trip a GFCI receptacle. If you insert 1 probe to the hot of a GFCI receptacle and the 2nd probe to the ground, the GFCI should intentionally trip and you have just caused a ground fault. This means the GFCI is properly wired and so is the ground. You will need to reset the GFCI after doing this test since it was tripped.

6) Most homes today have 2 grounds. 1 is from the main panel neutral bus bar directly to the street side of your metal water supply pipe. The supplemental ground is from the neutral bus bar inside the panel to the exterior 8 foot ground rod. You may only have 1 ground since many municipalities have various codes on grounding.

Let me know how you make out and we'll take it from there. Double check the attic box where you were splicing into. I assume everything worked OK prior to opening the attic box? Your problem may just be there. If uncertain, turn the breakers to OFF and open up each splice one at a time. Use a pair of lineman's pliers and make sure the twists are OK. Turn the breaker back to ON and measure/check for proper voltages. If OK, re-cap the splice and move onto the next one splice or termination. Your attic should not have that many splice boxes, probably only a few. The pull-chain for the attic light is one of them. Remember, the problem may not be inside the attic, it can be anywhere along the path of the circuit.

If you are willing to spend \$80 @ Home Depot, here is the toner/probe that many electricians use to locate and identify wires within a circuit. At the panel, the hot and neutral wire from the circuit is temporarily removed and the tone generator is installed on the hot and ground or hot and neutral. Then you go around the house at each box with the toner probe and listen for the tone generator. Once found, you can then open up the box and there is your circuit!

http://www.homedepot.com/p/Klein-Tools-Tone-cube-and-Probe-plus-Kit-VDV500-808/203015886#.Uds9svko59A

Category: Electrical
Satisfied Customers: 2778
Experience: 29 years as a Licensed Electrical Contractor in Illinois, 5 year college Electrical Instructor, Former Electrical Inspector, Diploma in Digital Electronics, Former Illinois Licensed Home Inspector
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Thank you for the positive rating............much appreciated!

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Take care and have a great day...............Thanks.................Kevin!

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