I was using a small 3gal compressor (rated 15A) in my house when I lost power to 4 outlets. I immediately thot it was a breaker so I checked, none tripped. I turned each one off and on again and power was still not restored. I pulled the outlet from the wall where I had the compressor plugged in and all the wiring still appears new, tough, like it was just installed (house is a mere 7 years old) in other words, nothing was burnt or melted within the wall of the said outlet nor did I smell anything nearby or at the breaker panel. I got my multimeter and took some measurements:
Incoming is 440VAC from outside to panel rated 200amps
12.5 ohms between the black & white wires, no voltage.
125 VAC from the white wire to ground, 60 Hz
124.5 VAC from the black wire to ground, 60 Hz
So the power is there on both wires but not connected between the two. What could the problem be? A friend suggested a faulty breaker but would there still be voltage on both wires to ground? And info appreciated. Thanks.
The resistance reading between the white and black conductor suggests some device is connected to the same circuit at a different location.
Normal voltage between the black (hot) wire to ground would seem to indicate that the breaker/wiring between the outlet in question, and the panel is operational.
The full voltage reading between the white (neutral) wire most likely will be traced to an open neutral (bad joint or connection) connection between the panel, and the problem outlet. The cause for the full voltage reading could be voltage feeding from the hot wire through some utilization device connected further down stream on the same circuit, and not able to make it back to the panel due to an open neutral connection creating an open circuit. Connecting your volt meter between the neutral and ground completes the circuit. If the neutral weren't open you shouldn't see more than a few volts connecting the meter between the neutral and ground. With the open neutral what you have is a good portion of the neutral wiring in that circuit effectively a hot conductor.
By the way I suspect that you don't have anywhere near 440 volts entering your home. It's possible but highly unlikely.
You mention 440VAC, did you possibly mean 240?? If you're in the US, that would be more likely.
Anyway, if one 'hot' from the panel to the 240VAC circuit is open, and the two 'hot's are connected together through a load (compressor or other), then the good 'hot' will read ~120 to ground/neutral as you'd expect. And the other will read from the 'good' hot, through the load (meter won't draw enough current to drive the load), to the 'open' hot and to ground. Result is the 'bad' side will also read ~120 to ground/neutral.
I think your friend could be right and you have a faulty two-pole breaker, only connecting one 'hot'. But you might check to see if the other outlets are 'upstream' of the one you opened up. If the outlets are wired in a 'daisy-chain' from the panel to the one you were using, anyone of them could have opened up one of the 'hot' leads. Not just the one you were plugged in to. If the outlets are wired this way, each one must carry the current being drawn by the other outlets downstream.
440v????? A bit high for a residence. Are you in Canada?
From your description you have lost the neutral and it has becomed energized. I suggest that you start taking the circuit apart after you have identified the correct breaker and ohm out the wires until you find the problem.
If you do in fact have 440 (typically the nominal voltage is 480 volt) I suspect it is a separate service in addition to the 240/120 volt service the other homes in your area have.
If not there would be a transformer to reduce the 480 volt service to the
240/120 used by the normal loads in your house.
I have seen three phase 208, 240, or even 480 volt services into homes where large motor loads were present such a large compressor for an organ etc., but they are the exception rather than a norm. The hoops you have to jump through in the average US jurisdiction to have such an installation are enormous.
Don't put off searching out your issue too long. If it is a bad connection causing the problem, heating at that point could cause damage to the structure.
Louis--
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This poster resides in the US, and the circuit in question is a 120 volt with a single breaker. Thus the white, or Neutral conductor.
The fact that the hot conductor reads 120 volt to ground would indicate that the circuit breaker/wire up to the point of measurement is most likely operational.
The 120 volts measured to ground from the Neutral however, points to an open circuit or bad connection between the receptacle and the panel. Some device plugged in/connected to the circuit is the likely cause of the elevated Neutral.
Louis--
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Are you really certain about the 440VAC. I would bet you have 220 (110 on each leg)
I assume you are saying those measurements were made with the circuit breaker turned off.
Something is still on the line to give the 12.5 ohms. With that low resistance I might guess it is a motor (inductive load). Or it is a faulty measurement.
That to me would indicate an open return. Check the return bus bar in the breaker box. Tighten all the screws.
You don't by chance have Aluminum wire?
If you still have something plugged into the circuit and you still have power coming in through the circuit breaker and the return path is open you will be measuring the voltage on both the black and white wires.
I found part of the problem. the 1st outlet on this circuit where the main feed comes to the outlet and feeds the rest of the circuit I found the
*black* wire musta got hot and burnt to ground where it took a chunk out of the ground wire and burnt the end of the black wire in two. Naturally, I cut the bad parts of the ground and black wire off and re connected with the same problem. Turns out, the wiring from the 1st outlet to the last is fine. I jerry rigged an extension cord (dangerous I know but without proper testing equipment, the hillbilly way is best!) and stuck the wires that feed the rest of the circuit into the plug in end of the cord, plugged the other end of the cord into a working outlet and wah lah, it works. Now, I'm left with the problem from the main feed wire feeding this circuit back to the box. I got the multimeter and took some more measurements:
Black wire to ground = 125VAC White wire to ground = 0VAC Black wire to white wire = 0VAC
Black wire to white wire resistance = open (tested with breaker on and off) Black wire to ground resistance (tested with breaker on and off) = open-breaker off/jumpy-breaker on White wire to ground resistance (tested with breaker on and off) = open
I have an electrician coming tomorrow to check into it. Hopefully the wire is good and something happened in the box.
In response to those who are wondering about the 440V incoming, I have two boxes in the garage. one is a box, same size as the next with a label that says "440VAC Disconnect main prior to servicing" and it has 2 breakers, a main and one slightly smaller looking one. Right beside it is the one for the house with all the lighting, etc on it and looks like one 3" pipe connecting the 2 panels. I know the previous homeowner ran some pretty hefty equipment in the garage but I have no idea what. I know that I do not have any such equipment that operates at that voltage. The previous owner had this house built and I assume he musta went thru hell to get such voltage into this house.
Yep. My bad. Was fixating on the 440VAC and jumped to a 240V load. You're right, if the neutral reads ~120, he has an open neutral between the outlet and the panel.
But I still think he should look at the other three outlets that 'lost power'. Bet one of them is between his outlet and the service panel, and that is where the neutral opened. Seen a few 'daisy-chain' outlet strings where the problem was in one of the boxes 'upstream' of where it is first noticed.
When the electrician comes have the voltage read at the two panels. If your house panel is fed from the "440v panel" you don't have 440v to your house unless there are two service drops/meters, or a transformer in-between the two panels.
Unless there are two drops, or a transformer connected to your "440v" service, there is no way to supply the 240/120v house panel.
I suspect what you have is a 240v 3 phase service with the center tapped phase providing the Neutral, supplying the house panel through a breaker in the service panel.
Let us know how it turns out.
Louis--
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Did you measure this? If so where did you place the meter leads. I know you have repeatedly said 440VAC is accurate - I am asking for specifics of how you measured it.
Which specific black and white wires? The same two wires as you mention below?
That is absolutely wrong. The white wire must be at
0 volts with respect to ground at the service panel
Incorrect conclusion - the power is there on the black wire. The white wire should be at 0 volts with respect to ground, and there should be ~120 volts measured from black to white.
The white wire is not "electrically white". That means it is not grounded conductor as it is required to be. It sounds like the white wire is disconnected in the panel and you made the measurements with that wire disconnected. For us to answer exactly (ie, without terms like "sounds like") we have to know exactly where the meter is connected for each measurement.
By the way, I'm merely repeating some of what Louis Bybee said - just in a different way.
I'm still betting on an open neutral. With all loads unplugged, the resistance between hot and neutral is infinite/open. So the voltage between hot and neutral is zero. This fits your description. The only thing to figure out is *where* it opened up. If the wiring from first to last outlet 'is fine' (meaning you have continuity of the neutral), then it must be between first outlet and panel, or inside panel. The white wire for this circuit may have burned off the neutral bus or been loose to begin with.
If you're not comfortable about taking the cover off the panel, wait for your electrician tomorrow. Tell him what you've found so far and let him/her take it from there.
I agree that the return is not grounded. Probably open at or near the breaker box. Since he measured 12.5 ohms between black and white (at the outlet he was using), it appears there is still something connected in the circuit. That would explain how the voltage is appearing on the white wire.
In response to those who are wondering about the 440V incoming, I have two boxes in the garage. one is a box, same size as the next with a label that says "440VAC Disconnect main prior to servicing" and it has 2 breakers, a main and one slightly smaller looking one. Right beside it is the one for the house with all the lighting, etc on it and looks like one 3" pipe connecting the 2 panels. I know the previous homeowner ran some pretty hefty equipment in the garage but I have no idea what. I know that I do not have any such equipment that operates at that voltage. The previous owner had this house built and I assume he musta went thru hell to get such voltage into this house.
The electrician just left and the problem resided in the breaker box at the breaker. He said the neutral wire musta been weak where it was spliced in before and had been pinched so he respliced it and all is working now. He also replaced the breaker stating that it should've tripped in this event. I asked him to open the 440v panel to read voltage and he was leary of it but he did read the inputs coming from it into the house panel. He said there were two seperate legs of 240v coming into the house breaker box from the
440v panel, one leg goes to the A/C unit and to the clothes dryer, the other leg goes to the furnace and the stove range. He said there may have been
480v in the panel at one time if the previous owner was using it but chances are it was disabled when the owner sold the house. There was a capped port on the 440v panel as if something ran out from it at one time. the main and the single breaker on the 440 panel has no effect on the house panel so the electrician turned them off and locked the box.
Thanx a t> I was using a small 3gal compressor (rated 15A) in my house when I
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