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Generator set up ideas wanted
Murf, I have a question. If I run a generator with a transfer sw. that does not break the nuetral then it can backfeed the neutral and cause a shock. In reverse of that if I don't have a generator and I turn off my main disconnect and do not break the neutral then I can get shocked in my own home. Tell me how it can work one way and not the other. If so, why do I not get shocked when I turn off my breaker to work on my house wiring?
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Generator set up ideas wanted
First of all, the term 'backfeed' is very misleading. "It can create an unsafe voltage potential in the neutral conductor." is a more appropriate way of saying it.
"In reverse of that if I don't have a generator and I turn off my main disconnect and do not break the neutral then I can get shocked in my own home." No, without a second source there is no possibility of a voltage potential being generated.
The problem is potential between the neutral / ground conductor and true ground, the earth or some second source to ground.
Unless your house has a dirt floor you have no worrys.
Best of luck.
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Generator set up ideas wanted
Unless your house has a dirt floor.
Makes me think. Here concrete floors are popular due to high ground moisture. So, there could be a possible problem with bare damp concrete or tile floor, correct?
Also, when you have flooding (not anything like New Orleans) but say for your house only, any ideas?
Sort of on this line, something that concerns me greatly is small children with plugged in cords. Their fingers are small enough to have the plugged still making contract in the outlet and their finger making a bridge across the hot and neutral prong on the male plug. Not a good situation. If you have small children, be sure your outlets don't let the plugs slip out part of the way due to being worn or strain on cord.
Let's keep them safe also. With Christmas lights they are looking at cords at lot right now.
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Generator set up ideas wanted
How can the current from a power co. not backfeed the neutral if all I did was turn off the breaker?
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Generator set up ideas wanted
It is not 'backfeed' per se, it is a potential in the neutral / ground conductors, without a second path it is an open circuit.
If you managed to get between the neutral in your house and true earth ground, yes the possibility exists. That is one of the reasons for GFCI circuits where that is possible, like around plumbing or outdoors.
Best of luck.
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Generator set up ideas wanted
We live in an underground home with concrete floors. Ok, I can understand that it can be unsafe to not break the neutral on incoming or outgoing electric power. I have an air compressor that when wired for 220v. at two other locations had about 30 volts on the air comp. it self. I could not run a ground from the comp. to the panel without poping the breaker. When I moved to my present location and wired it up I expected to find voltage on the comp. To my supprise I did not and then I grounded the comp. and it did not pop the breaker. The motor is a 220v single phase made in 1956. The only thing that I did different was to switch the wiring to reverse the motor because at my present location it ran backwards. I never have understood why switching the wires around allowed me to ground the comp. Should this be a new thread?
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Generator set up ideas wanted
It sounds more likely that the problem was the wiring in your old place.
On an A/C motor it reversed directions when you moved it? That means the power supply was reversed also. That explains why you blew a breaker grounding it too, you would have been putting a live wire to ground.
Lucky all it did was blow a breaker ........
Best of luck.
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Generator set up ideas wanted
I don't think the wiring in any of the places this motor has been used (4 that I know of with 3 different owners) were faulty. The person that owned it before me took it to a motor shop and they told him it was meant to be wired with two leads and not grounded. That would be a neutral and a hot on 115 and two hots on 230 which is what the motor is rated at. The motor or pressure switch has no provision for a ground. To reverse the motor you switch leads 7 and 8 no matter if it is wired for 115 or 230. Apparently it has never had to have been reversed before as it was obviously hooked to the same two phases to run, at least the motor wiring appereared to have never been tampered with. I put a 120v 40w bulb between the comp. and ground so I could tell if it was hot to ground when I turned it on. It never shocked me and I do not believe the wiring in any of the places it was used was wrong. All the places were wired to code. I have posted a question on a motor forum to see if anyone knows why this motor acts the way it does. I have wondered about this for years and been watchful of it as well to avoid a shock. I do not like ungrounded motors, etc. and the thought that a generator could cause a hot lead on the power lines is unsettling. I have the intention of using a standby gen. at my home/shop and the local power co. will be involved with the installation when I do it.
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Generator set up ideas wanted
"I put a 120v 40w bulb between the comp. and ground so I could tell if it was hot to ground when I turned it on"
I could be totally confused in following all of this but have a few questions: Did you find voltage before you install this test light? If not it probably is coming through the test light. A meter is safer. You can also get small indicator lights that would allow much less wattage through than your 40 watt bulb.
Having very little three phase current experience, could that have been where you hit the motor running backwards?
Unless I am way off, even if a motor was not made for a ground wire, you should always be able to hook one to the motor frame and it not cause any breaker to trip. Now if you were hooking it to the 110 terminal on the motor itself I think you would find a problem and would trip breaker.
Please, do post here what you find for fact if you will.
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I did not ground it when I used it in Missouri but when I brought it here to Ky I decided to try to ground it and everytime I grounded it to the panel it poped the breaker. Remember that I did not have to reverse the motor direction at that time. The voltage from the motor case to ground was about 30v. So, far a safety warning I put a 120v 40w bulb between the case and the ground wire. I knew the bulb would not light up untill there was sufficient amperage to overcome the resistance of the bulb and then I had better not touch the motor as that would indicate an internal short that could be dangerous. No one but my son and I were ever around the comp. The reason I did not pursue it when I moved here is because it is now grounded. It has an internal protection and a circuit breaker. What I do not understand is why I could ground it when I reversed the motor. That has been puzzleing me since I hooked it up this year.
I have posted a question on eng-tips.com and also sent a question to A. O. Smith motor corp. I will post the replys here.
Just so everyone understands, When the motor is wired to run in one direction the motor housing is hot and cannot be grounded. When it is wired to run in the opposite direction the housing is not hot and can be grounded.
Now, from past experience with motors if a winding is shorted to the case then it shows up no matter what direction or voltage it is wired for. That is why I don't understand this motor and have been carefull with it.
Currently it is wired for 220v and is grounded. If anyone is interested it is an A. O. Smith 2hp 1ph 115/230v motor model# C1224N4AAA. It is a large heavy motor.
I may disconnect all the wires and check them to ground but, in it's current setup it is safe and I have no intention of replacing it. If it shorts out as wired it will kick the breaker and I will be forced to replace it or have it rewound.
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Gas Generator Weather Protecti
12-18-2005, 22:08 
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