| Click to Post a New Message!
Page | | | | [ 5 ] | | | | | |
| | |
|
Generator set up ideas wanted
Murf,
"Want proof, put on some heavy leathe gauntlets, top up your life insurance, disconnect the neutral wire from a 3 prong receptacle, then plug something in and see if you don't still have 120 volts and more than enough flow to power an appliance."
If I followed this fully..one use rubber gloves that approved for such but...if you removed the neutral from a 110 circuit it should not power anything if the appliance has no defects in it. The neutral is required to complete the circuit. Now, there is still the 110 volts sitting on the power or hot leg which you did not disconnect. If anything were to complete a path the across that hot leg to a ground it will have current flow through it. A person could be the anything. For a 110 circuit to work there must be a "flow" path back and that is the neutral. This may be proving the point I think you are making on the danger of not having the neutral/ground disconnected back to power lines.
Along the line of voltage on the neutral/ground that can be dangerous. If you have voltage on your house ground, then the cabinet of your three plug machines may have that voltage. If so then if you are touching that cabinet and touch something with a different ground you may find you have current flowing. Before someone thinks this can not happen, I have seen this with a washing machine. From the cabinet to water line there was a voltage reading. This is also why washing machines use to come with ground wire that was to be connected between the washer cabinet and the water line. I don't know if they do now or not.
As long as the path can not be completed through you, you will not get hurt by touching a live circuit. Look at the birds sitting on the power line or the guys working on high voltage lines with them live. But if something completes a path through them (bird or person), it normally means death.
kt
|
|
 Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
KT, I think the part of the equation you missed was "3 prong receptacle", in this case the ground will act as the neutral because they are joined together.
The ground & neutral are joined together remember? A path is a path.
Take a volt meter, unplug a 220v. appliance and measure between L1 & L2 in the receptacle, 200 volts right?
Now measure between L1 & ground, and L2 & ground, it will read 110 volts in each case, because the neutral & ground are bonded together. Thus the ground will certainly act as the other conductor.
Best of luck.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
A quick point, there are three pong plugs that are 110 volt and also there are those that are 220 volts. I was/am assuming you are talking about 110 volts.
In our part of the world the neutral and ground are bonded together and yes current on one would be there on the other.
However, in a 110 volt applicance the ground should not serve to carry the current back to the breaker box and on to the meter and power lines, UNLESS there is a shortage in that appliance. That is the purpose of the ground. I fully agree the ground can and will complete the path but it is not suppose to be the path and is only there for a shortage.
If you disconnect the neutral wire on a 110 volt applicance circuit and it still operates, you need to disconnect that appliance and get it repaired. There is a shortage in it.
kt
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Lets look at this:
Quote from Murf
"If in ANY of those diagrams, 1, 2, 5 & 6, and with the generator running, you put a meter between the neutral line outside the house, and the earth itself, you WILL measure a potential across those two points."
Diagram 1 - generator not running - does not apply (as per your description "with the generator running" .
Diagram 2 - no connection between utility neutral and generator neutral (neutral isolated in transfer switch) therefore no capacity to generate potential between utility neutral and anything (as a result of the generator).
Diagram 5 - generator not running - does not apply.
Diagram 6 - connection between utility neutral and generator neutral (neutral remains connected in transfer switch). No connection between generator neutral and ground other than that at the service entrance. No current flowing in utility neutral - current is however flowing on the house neutral up to the point it returns to the generator. You have to have current flowing to generate a potential (One of those pesky laws of electricity). The only potential that exists is between neutral (both utility and generator neutral) and hot line of generator. Therefore no potential between utility neutral and ground possible.
So in each scenario the only way to observe a potential between utility neutral and ground is if potential is being established by something outside of the generator circuit. As a result the generator cannot establish the scenario you keep refering to. Q.E.D.
Quote by Murf
"Further, if you were to run an extension cord out some distance from the house, and again measure between the neitral leg, and the earth, you might be surprised to see just how much potential voltage & current you would find."
In this scenario you have violated code by establishing a connection between house neutral and ground at some point in addition to that at the service entrance, this established a paralell neutral current in the earth or equipment ground circuits, that looked like this: Generator L1 to load to neutral and back to generator with a paralell current as follows: Generator L1 to load to neutral to house grounding rod to earth to extension cord neutral (as connected via your voltmeter) and back to generator. This is a paralell neutral current in the ground hence the code violation. This current would be extremely small (high impedance of earth) and would decrease the further you connected the extension cord from the house ground rod. In anycase it's a violation of code and therefore not under consideration in our discussion regarding the potential to electrocute a lineman with the use of a code compliant generator with neutral unswitched in the transfer switch.
In response to my queston which stated:
"Using the web link I posted, would you be so kind as to indicate the number of the CODE COMPLIANT diagram in which, as you suggest, the ground wire is being used a current carrying conductor."
You state:
"Every one of them, the neutral wire in any house is a current carrying conductor, the AMOUNT of current is NORMALLY extremely low in the ground circuit though, since it takes the path of least resistance, the neutral leg."
There is no code compliant diagram where the GROUND wire (green) is being used as the current carrying conductor. In addition you state that in the house current has the opportunity to flow through either the neutral (path of least resistance) or the ground circuit (albeit a small amount). This is clearly an instance of paralell current flow and would not be code compliant.
And here
"Want proof, put on some heavy leathe gauntlets, top up your life insurance, disconnect the neutral wire from a 3 prong receptacle, then plug something in and see if you don't still have 120 volts and more than enough flow to power an appliance."
In this instance you would need to meet two conditions to power the appliance. 1) the neutral would have to be disconnected from the recepticle (deliberatley as you stated) and, 2) there would have to be a connection between neutral and ground inside the appliance (a fault). In this case the current flow would be: L1 to load (appliance motor for example) to neutral to ground (while still in the applance) to ground pin of recepticle to service entrance ground where ground is bonded to neutral and from neutral back to L1 in the generator. This does not establish a current from utility neutral to ground through our lineman. Potential in the utility neutral is the same as ground as they are tied at the service entrance (ground rod) and at every utility pole.
And in this section:
"As was stated so well by jdcman "However it is a fact that in order for electrons to flow there needs to be a path. And sometimes humans are in the path and bad things happen."
The electricity takes the path of least resistance, but it does and will travel, if one path is the neutral leg of the grid, and a second path is a linesman or other unfortunate individual, "bad things happen.".
Ask any farmer with cattle, they are about 50 times more sensitive to voltage than humans, I've seen them stand in a circle around a water trough, not drinking, because of a few transient volts from a stock tank heater or some other source."
The conditions that you describe here are no more prevelant using a generator than they are when using power from the utility. You are describing a parallel current in the ground and the utility neutral. For example, current flowing from the customer's load back to the power station on the neutral wire has the opportunity to travel along the utility neutral and in addition at some point go down the utility pole (on the grounding wire) travel along in the earth and up the next pole to return to the utility neutral and back to the power station. The use of a code compliant generator generates no current flow in utility neutral (where would it be flowing to). It does however generate current flow in the house neutral up to the point where it returns to the generator (service entrance and transfer switch).
We can easily replicate our dead lineman scenario by using the following example. You accidently sever the grounding wire traveling down the utility pole while mowing (the edge of the mower deck cuts it in two). You grab the end of the severed copper wire that runs up the pole to reconnect it (remember this is connected to the utility neutral at the top of the pole). At this point you are solidly connected to the utility neutral (through the grounding wire) and to the ground (you are standing on it). In the dead lineman example everyone keeps talking about you would get fried at this point - but we all know that this does not happen - why? Because utility neutral is tied to ground at numerous locations and by design no potential difference (of any consequence) exists between utility neutral and ground. In the home however it's different - there is only ONE connection to ground (service entrance). The scenario describing the stray voltage on farms (with the cows) is occurs in most cases because the on-farm wiring has numerous connections between neutral and ground downstream of the service entrance (a code violation). The neutral to ground connection at the service entrance is the only one permitted.
Anyway I have about run out of power (bad pun I know), hope you are all (even Murf) convinced that a unswitched neutral in a transfer switch may be required by code (depends on the generator wiring) and as a result would be safe even for our dead lineman.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Grinder Don't worry about the transfer panel you electrician install, I know the panel you are talking about . It is also one a few that Central Maine Power will accepted for approvel. The same is true for New Hampshire. I am liecensed in 3 states NH,Me,and Ma and install about 12 of these a year. No they don't switch the neutral but the uttillity companys along with the UL test this equipment. They just don't give thier aproval to equipment. And if they say to use this equipment then I use it. As for other Uttilitys or other states or countrys everyone needs to check thier local codes
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
It’s clear that there’s a lot of mysticism in the minds of folks when it comes to electricity.
The point to keep in mind is that any source, be it a AC, DC, Pulse, RF or some Arab Gen requires an output port and a return port in order for the electrons to move.
As Ann has pointed out, disconnect the Generator at the high side or low side and it’s out of the circuit. Think of your battery, both the positive lead and the gnd lead have to be connected in order for energy to be delivered.
I’m not a big code guy myself, but there is a subtle but important point that is being made, I think in sch 3 or 4. And that is, if the return for the gen is left connected to the main house circuit while the house is being powered by the public utility, the current path has the potential to be shared by the return path through the generator. In order for this to happen one would have to have the return path of the load connected to the generator while the high side is open. Why a system would be put together to allow this to happen is beyond me, but I guess it’s certainly a possibility. Mind you, the potential problem is localized to the home.
At any rate I view codes as an attempt at protecting the masses from themselves. It’s a shame, but the reality is you need some standardization because of all the unscrupulous vendors trying to take advantage of folks.
For those that are interested here’s a poor mans way of dealing with the alternative power issue, albeit not automatic and definitely not preferred by the wife.
I live in the northwest among big trees where occasional big winds or snow storms knock out the power.
I have a 10K generator that I use to power some essential stuff like the well pump, pellet stove, frig and a few lights. I don't use a transfer switch but have chosen to treat the loads as appliances. For example, the well pump is on a breaker of it’s own --- I simply break the connection between the pump and breaker, mount a 30 amp receptacle on the output side of the breaker and place a plug on the input side to the pump. (My access panel is in the garage … makes it easy to do).
I have separate outlets for the rest of the items. And yes it’s a little work to go out and start the generator, move four or five plugs but it works and is safe.
In my situation installing an automatic transfer switch for this small of a generator is just not worth the effort and cost.
One of these days I’ll get around to putting in a large diesel or propane generator and automatic transfer switch system --- it’ll make the wife happy.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
jdcman,
You have a very functional setup. A couple questions:
l. is this an automatic startup when power goes out?
2. if not, what do you do if you are not there?
I went with the 7KW, which would cover easily the stuff
you discussed and the transfer switch wasnt a big additional cost with the generac system. Plus it is
automatic. If I am gone(as I often am). It will automatically power up and keep my house from freezing or
keep my refrig and freezer going in the hot summer.
just a couple thoughts on my part
doc
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
I just talked with a local electrician who said he had installed many transfer switches and they do not disconnect the neutral. He is licensed, and they were inspected for code. He is talking current and not years ago.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
All this talk about back feeding with a generator got me to thinking.
If it is possible, then the same would be true for a resident? For instance, you want to work on the wiring of your house. You throw the main breaker. What's the difference? You could get zapped by the electric company?
I don't think it's possible, if your house is wired right and the main breaker is thrown, to electrocute a lineman Or vice versa.
From generator to breaker panel... You have neutral/ground to panel neutral/ground. L1 to L1 on panel. L2 to L2 on panel. When you throw the main, you disconnect both L1 and L2, which breaks the circuit to electric company? How the heck would/could it travel to the outside electric lines?
I'm thinking this all came about with people people forgetting to throw their
main breaker and zapping some poor unsuspecting soul. The electric companies come up with mandatory transfer switches to take care of human error.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Billy, I agree. My brother in law is a licensed PE, puts up large commercial buildings and has built power plants for major corporations. He shuts the main off at the panel and back feeds his house with his generator. No transfer switch. He states it is safe providing you shut the main off. His word is good enough for me.
|
|
Add Photo
Bookmarks: |
|
| |
|
Page | | | | [ 5 ] | | | | | |
Thread 120490 Filter by Poster:
2 | 13 | 1 | 2 | 10 | 4 | 2 | 9 | 1 | 3 | 13 | 1 | 20 | 2 | 1 | 2 | 1 | 1 | 1 |
|
()
Picture of the Day
DennisCTB
Unanswered Questions
Active Subjects
Hot Topics
Featured Suppliers
|
Gas Generator Weather Protecti
12-09-2005, 11:33 
Pics
Reply
Digg It 
Del.icio.us 
