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Generator set up ideas wanted
There are dozens of permutations of fuel and gen setups. The cost of each generated kilowatt is likley to get incremantally higher the fancier your system becomes (different fuel types stored inside or out, electric starting options etc) We all like to think that we are rugged and independent enough prepared to face an entire winter without any outside provided infrastructure (utility water roads etc) but in reality those winters dont happen to any but a very very few. And for the few where they do happen you can bet they are not talking about a 6500 watt generator set ups and debating fuel types. Get yourself a 6500 kW set and 50 gal of gas which you can use in the car next spring when you have not used it all up. Your generated kW cost will be as low as possible (still astronomical compared to bought power from the utility). I think of it this way - self generated power is the most expensive power I can buy - therefore buy the absolute least amount of it I can possibly do with. I have a portable 4000 kW set that I plug into the dryer outlet (bad me I dont have a transfer switch!) AFTER flipping the main. I can run the bare essentials - furnace, well pump and a few appliances by regulating which circuit breakers are turned off and on. And yes I am fully aware of the danger of not having a transfer switch.
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Generator set up ideas wanted
The internal wiring of the generator determines the type of transfer switch needed.
1) Generator with neutral not bonded to ground (usually frame of the generator) = 2 pole transfer switch - hot lines are switched but neutral is to remain solidly connected with utility (unswitched).
2) Generator with neutral bonded to ground (usually frame of the generator) = 3 pole transfer switch - hot lines and neutral are switched in transfer switch.
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Generator set up ideas wanted
Forgot to provide the reference.
Link:
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Generator set up ideas wanted
Murf, in my citation which you quoted:
"If you install a single phase TS, remember that the neutral to ground bond needs to be isolated just as a subpanel would be.
--------------------
Pierre Belarge
Instructor & Industry Advocate"
Pierre is refering to the neutral to ground bond INSIDE the generator - not as you suggest the neutral to ground bond at service entrance. He compares the neutral to ground bond INSIDE the generator as being similar to a neutral to ground bond in a sub panel.
So with all due respect your comment:
"Notice the word "isolated" ? What he is saying is that if you do NOT have a three pole TS, you need to isolate the neutral to ground bond. In other words, with a single phase TS, you must mechanically break the neutral / ground bond, a neutral switching TS does it for you."
where you mistakenly interpret the neutral to ground bond as that located at the service entrance is not correct.
There are 2 basic generator grounding wiring types:
1) Generator with floating neutral - neutral not bonded to ground at or inside the generator.
2) Generator with bonded neutral.
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Generator set up ideas wanted
Grinder and of course other interested readers:
Here is a very well written article that discusses this very issue and provides very comprehensive easy to understand wiring diagrams. They show when a transfer switch that switches neutral is needed and when one that does not (as Grinders electritian has indicated) it required.
Link:
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Generator set up ideas wanted
Grinder - it depends on your generator. Look at the specific wiring for the generator you have (will buy). If it is floating neutral - use a double pole transfer switch (two hot lines) but leave neutral connected at the service entrance. If neutral is bonded to the frame at the generator use a transfer switch that disconnects the neutral. In my experience it is cheaper (much) to isolate the neutral to ground connection in the generator than is is to buy the transfer switch that switches neutral but you will have to reconnect it if you use the generator for anything else but powering the house. Print off the reference I posted above and identify what setup (8 different scenarios are provided) you have and apply the correct connections. Get an electritian to verify you have the correct set-up.
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Generator set up ideas wanted
Murf and others still interested, I have to post a rebuttal to Murf's last post. This will be my last on this subject.
Read and understand the article I posted. There are situations (it depends on the wiring of the generator) where the transfer switch is required NOT to switch the neutral. In these cases the neutral remains connected to the utility. Not only is this safe it is required by code.
All this talk of backfeeding the utility (and presumably killing a lineman) is really not relevant here. Backfeeding is not possible even if neutral remains connected in the transfer switch (as is sometimes required) if the hot lines are switched (as required in all situations) and neutral is grounded at one location only (service entrance). As a minor asside on this issue I challenge any readers out there to demonstrate how a circuit could be completed that could injure or kill a lineman when the neutral line remains connected to the utility and connections are made according to code.
The main point here is that the decision to switch the neutral in the transfer switch is dictated by how the generator is wired. It is over this point that Murf and I disagree, I worry that Murf's prominent and regarded stauts on this forum (and deservedly so!) will lead readers to conclude that the neutral must be switched in all situations in a transfer switch that switches utliity and generator power. His advice is correct but only in situatins where a bonded neutral generator is used. Grinder's electritian has indicated that in the cases he (she?) is familiar with the neutral remains connected and we can assume that this is safe and would pass inspection. It also implies that there are many floating neutral generator in use out there, mine being one of them.
If you have a floating neutral generator AND you switch the neutral in the transfer switch you have created the scenarios detailed in diagrams 7 and 8.
Quote (from the web link I posted above - BTW it's referencing the CEC or Canadian Electrical Code but the situation in the US is the same for point of this discussion):
"If we try to connect a generator with a floating neutral using a 3-pole transfer mechanism and switch the neutral conductor, Diagrams 7 and 8 show this circuit. In normal conditions (Diagram 7) the load is powered from the utility and the neutral is connected through the generator panel neutral and bonded in the service entrance panel. Everything looks okay.
But in stand-by power mode (Diagram 8) the load is fed from the generator and the generator neutral has been switched. Therefore the neutral bond has been removed from the system. This would be a violation of CEC Rule 10-106 that requires AC systems to be bonded to ground.
These Diagrams show that a 3-pole transfer mechanism switching Line 1, Line 2 and the neutral conductors would result in a circuit that does not comply with the rules of the CEC. In stand-by power mode, a circuit exists in which the system voltage from the generator could float on each phase. In the most extreme case 240Vac would appear on one phase and 0Vac on the second phase, potentially resulting in damage to any 120Vac equipment operated in the home."
End quote.
I cannot put is more straightforward than Schneider Electric has already done. It's a technical issue and hard to understand. It's also the reason that many 2 pole transfer switches are sold and used with confidence and saftey.
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Generator set up ideas wanted
Murf you certainly have an enormous amount of conviction here. I said I would not reply but I can't resist.
Murf, in the following quote:
"When you introduce an inductive source like a genset, then use the ground wire as a current carrying conductor, you just amplify the problem."
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. I don't see which one that is?
And in this excerpt:
"No, that's exactly my point, the neutral & ground are permanently bonded together, and even bypass your meter that way. As long as there is electricity in the house, you are creating a VOLTAGE POTENTIAL outside of your house in the grid as well unless you disconnect the ground wire between the grid and your house, leaving of course, the ground rod as part of your houses circuit."
It would help me understand if you could simply illustrate the completed circuit that could electrify our "many times dead already" lineman. For example: Hot (L1) to load to neutral to lineman to neutral to powerstation to L1 = completed circuit = dead lineman or as the case may be dead linechick. Could you also indicate between which two specific entities this "VOLTAGE POTENTIAL outside of your house" exists. For examle: a 220V potential between utility neutral and utility L1. Please indicate which code compliant diagram (in the web link I posted) you think the generator would produce the voltage potential in the utility lines you keep refering to.
And in this quote:
"Everybody seeems to forget one small detail, the ground & the neutral in your house are bonded together, and the neutral is a load carrying 'leg' of any circuit, therefore there is a (up to) 220 volt potential in your ground circuit."
In this comment between which two specific entities are you indicating the 220V potential exists. For example a 220v potential between ground and L1 or between neutral and L1.
Many thanks
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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.
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Generator set up ideas wanted
"If you do not have to cut the neutral, then if all a disconnect cuts is the two power legs, what is the difference in using a disconnect switch and cutting off the main breaker?"
Electrically speaking there is none (provided your generator is of the type that would require a transfer switch that did not switch neutral) - unless you want to argue about the direction of electricity flow in the circuit used to connect the generator (like a welder or dryer plug) and the suitability of that setup. The reason that transfer switches are used is so that it is physically impossible to connect the generator to the utility supply (on the hot legs). Accidentally connecting generator L1 and L2 to utility L1 and L2 is extremely dangerous (as I am sure everybody is aware of by now). In addition to connecting the generator to the house supply, transfer switches mutually isolate the utility supply and vice versa when the utility supply is reconnected - they isolate the generator, accidential connection is made impossible.
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Generator set up ideas wanted
Thanks for identifying the error there - I misspoke (typed) in that bit of the response - it was however not material to my main point. However your comment is revealing for another reason:
"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)."
In diagram 2 Generator neutral and utility neutral are connected, but the connection is through the ground wire even though neutral is isolated in the transfer switch. So EVEN IF the neutral is disconnected in the transfer switch there is still a connection between the two (utility neutral and generator neutral) and this is code compliant. It still supports the position that isolating neutral in the transfer switch is dependent on the wiring in the generator.
"All of a sudden they invented one-way wires?"
These statements dont help the discussion - it's not clear what you mean by this.
"As soon as you power your house you will have potential in both the neutral & ground wires, period."
Please be specific tell us potential between what and what. As in potential between house neutral and utility L1.
The statement I made:
"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..."
And your question
"So it's illegal now to run an extension cord outside of your house and set down an appliance with a steel frame and a grounded case, like a battery charger for your vehicle?"
There are three wires in the extension cord. L1 (hot), neutral (also called the grounded conductor) and ground (also called the equipment grounding conductor). Neither L1 nor neutral are permitted to contact ground (including euipment frame and grounded cases) at the appliance or in the cord. This would be a fault current. In the residence neutral is bonded to ground at one point only (the service entrance).
Please be more specific:
"The whole (potential) problem is in having a voltage potential in a supposedly "dead" circuit."
Having a voltage between what and what - and how do you propose this potential is generated (sorry about the pun).
In any case - I beleive I have provided a comprehensive set of diagrams that illustrate when and when not the neutral needs to be isolated in the transfer switch. Anecdotal evidence contributed by members of the forum suggest that there are code compliant installations where electritians have installed transfer switches that do not switch neutral and since we can assume that these were inspected we know that the authorities are satisfied that these installations pose no additional risk to our linemen out there. While some of us may have installations where neutral is required to be switched in the transfer switch - others do not. My entire point was to illustrate that automatically installing a transfer switch that switches the neutral leg is neither code compliant or safe in EVERY situation. As is eloquently demonstrated by the set of 8 diagrams, it depends on the wiring setup inside the generator (Bonded Neutral vs floating neutral).
Happy generating
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Generator set up ideas wanted
I am sure Schneider Electric of Toronto Ontario consider their Application Note on Stand-By generator panels to be just some theory they have dreamed up.
Anyway I think this thread has outlived it's usefulness, I am satisfied that no linemen are going to be fried on my account and that's good enough for me. For those of you who are still unsure, well you figure it out - or better yet pay your electritian to do so for you. It might be fun to survey the forum members and find out who has what setup (switched vs. unswitched neutrals) and see what the common ground (sic.) is for each type. Good discussion, I am glad there are folk out there who are passionate about life and dont have to resort to shameless name calling and the like, they are a dime a dozen on other forums.
Cheers Ann
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You can not change direction of a single phase ac motor just by switching hot and neutral. The great majority of single phase motors are induction type motors. For most of these switching the leads for the start windings will reverse rotation. These are usually red and black, or they may be numbered 5 and 8.
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