240v -vs- 120v equipment wiring?

From an electrical standpoint, when a choice of line voltage is offered, motors will run better (cooler and more efficiently) at higher voltages as opposed to lower voltages.

At a lower voltage for a given HP, you are going to have higher running currents and possibly dramatically higher starting currents. Copper (I^2R) losses are proportional to the square of the current, so if the motor is driving any kind of load, these I^2R losses will be higher. The voltage drop of the circuit (expressed as a percentage) will be higher for the low voltage circuit. Whether this is significant or not depends or your setup, the length of the lines to the genset, etc.

The high voltage option for the same HP offers you lower running and starting currents.

Beachcomber

Well, not really. Think about it. In a dual voltage motor (120/240, for example), the windings are arranged in parallel for low voltage, and in series for high voltage. When the windings are in parallel, each winding is connected to the line, and draw a commensurate amount of current. The line current is the sum of the two winding currents. When the windings are in series, the windings each draw the same amount of current, but do it at twice the applied voltage. No matter how you connect them, the winding current is the same, hence the copper and iron losses are the same. That is the whole point of dual voltage motors, the performance DOESN'T change on either connection.

Take a look in a motor catalog. There is only one efficiency rating, regardless of the connection. There is also only one code letter. The code letter is a measure of the apparent power drawn by the motor under starting conditions.

This is all true enough, but applies only to the wiring leading to the motor, and not the motor itself. The motor, when properly connected, doesn't know the difference between the high and low voltage connection.

As the OP states, the decision is primarily about convenience and the size of cords, breakers and switches. Assuming good engineering practice is used, the tools will perform just as well on either voltage.

If your generator will be connected to all of it's loads by cord and plug there is no issue other than convenience. If the generator will be used to energize any home wiring then you must wire it as 120/240 to avoid overloading the neutrals of multiwire branch circuits. If it will power only specific circuits and you know that they are all 120 only then suit your self.

On Thu, 02 Jun 2005 08:19:57 GMT Beachcomber wrote: | |>>

|>> Any ideas on how best to wire this genset? |>>

|>240 to a transfer switch or a stand alone breaker panel. the breaker panel |>will allow you to operate 240 or 120V equipment and lights. |>

|>

|>

|>> What are the benefits of running the tools at 240v, smaller wires for |>> power cords??? |>>

|>> -- | | From an electrical standpoint, when a choice of line voltage is | offered, motors will run better (cooler and more efficiently) at | higher voltages as opposed to lower voltages. | | At a lower voltage for a given HP, you are going to have higher | running currents and possibly dramatically higher starting currents. | Copper (I^2R) losses are proportional to the square of the current, so | if the motor is driving any kind of load, these I^2R losses will be | higher. The voltage drop of the circuit (expressed as a percentage) | will be higher for the low voltage circuit. Whether this is | significant or not depends or your setup, the length of the lines to | the genset, etc.

Changing a motor to operate on different voltages like 120 vs. 240 involves changing paired windings to be either parallel or series. In series the net impedance will be 4 times that of parallel. The current in each winding, and the voltage drop across each winding, will just be the same.

Where there might be an issue is in any connection wiring which is used to feed power to the motor. But the motor itself effectively operates the same either way. What you are referring to is a change in voltage given a constant winding. Running a motor wired for 240 with 120 volts would have severe consequences, like not even starting and drawing locked rotor amps indefinitely (or until something burns out).

He didn't mention if the genny can be wired for 240 with a center-tapped neutral. Never *assume*. If it can't support a neutral, and he wants some

daestrom

Look at my text above, I did say it can be wired for 240V@43.5Amps, if I didn't make myself clear, Yes, it can be wired with a center tap at 240V, but the documents that came with the genhead state that in in order to see the full 87 amps at 120 volts I would need to wire it a certain way and not have the option of 240V, or could wire it for 240V, and have two legs of 120V but at only half the current rating for each leg and still have

| Look at my text above, I did say it can be wired for 240V@43.5Amps, if I | didn't make myself clear, Yes, it can be wired with a center tap at 240V, | but the documents that came with the genhead state that in in order to see | the full 87 amps at 120 volts I would need to wire it a certain way and | not have the option of 240V, or could wire it for 240V, and have two legs | of 120V but at only half the current rating for each leg and still have | 240V for load that require it.

Your original post did not make it clear a neutral could be supported. If the wiring coming out only supported a 2-wire system, then it would not have. But since it does, that is generally the way to go because you get both 120 volts (no grouping of loads larger than 43.5 amps) and 240 volts. IMHO, the more things that can run on 240 volts the better, NEC 210.6(A)(2) not withstanding.

From the original message:

I can change the genset to run at 120v@87amps only or can wire it to have

That implies two 120 VAC outputs that can be wired series or parallel. If they are connected in series for 240 VAC, how hard can it be to connect the pair of wires where you connect them in series to the neutral?

Maybe not hard to do physically, but then there was the question of whether the manufacturer intended for that mode of operation.

For example:

I think it was good of a couple guys to flag up the 2-wire 240V vs 3-wire

On Fri, 03 Jun 2005 01:10:46 GMT Michael A. Terrell wrote: | snipped-for-privacy@ipal.net wrote: |> |> On Thu, 02 Jun 2005 22:01:21 GMT SomeBody wrote: |> |> | Look at my text above, I did say it can be wired for 240V@43.5Amps, if I |> | didn't make myself clear, Yes, it can be wired with a center tap at 240V, |> | but the documents that came with the genhead state that in in order to see |> | the full 87 amps at 120 volts I would need to wire it a certain way and |> | not have the option of 240V, or could wire it for 240V, and have two legs |> | of 120V but at only half the current rating for each leg and still have |> | 240V for load that require it. |> |> Your original post did not make it clear a neutral could be supported. |> If the wiring coming out only supported a 2-wire system, then it would |> not have. But since it does, that is generally the way to go because |> you get both 120 volts (no grouping of loads larger than 43.5 amps) |> and 240 volts. IMHO, the more things that can run on 240 volts the |> better, NEC 210.6(A)(2) not withstanding. | | | From the original message: | | I can change the genset to run at 120v@87amps only or can wire it to | have | 240@43.5amps. | | That implies two 120 VAC outputs that can be wired series or | parallel. If they are connected in series for 240 VAC, how hard can it | be to connect the pair of wires where you connect them in series to the | neutral?

No, it does not imply that at all. It tells me there are two 120 volt windings that can be in series or parallel. It does NOT tell me there is more than 2 wires coming through the generator control box. It can be a generator where the winding configuration is apart from the feed connections. A generator with a circuit breaker would be configured on the line side of that breaker, and utilized on the load side. It may be easy for you to see that your generator really can do 120/240 OK, but going on a description that doesn't say there are 3 wires available, and doesn't say "120/240", I would not (then) make such an assumption.

Consider a three phase 12-lead generator. There are a lot of ways it can be wired up for a lot of different voltage and phasing configurations, including 66% single phase (double delta). But one thing I have found that is not easy to do is 3 separate 120/240 volt systems, even though there are 6 windings (2 per phase angle). I could configure it so each phase is done with 2 windings in series and the center taps all connected together as a common neutral, and grounded. But this would involve SEVEN wires. It's unknown if the voltage regulator could handle this at all. The terminal space is not there to feed that power out without a lot of modifications.

Without me getting into too much detail : I figure if i had more 120v equipment to connect than 240v my choice would be obvious., even then as per your load requirements a 240 outlet is needed., (since all machines will not likely be on simultaneously) Go with the dual mode configuration not the 240v one.

It seems dubious by what the others have concluded here that a 240v configuration would leave the 120v needs well covered, because of the neutral constant not present as with dual mode or 120v stand alone, you only have 1 best choice for your set-up/equipment. [120/240 VAC] =AEoy

says just that.

Once again, you show that not only can't you "Think outside the box", but once more you prove that you ARE the box. The OP is building his own power plant. If there is no way to bring a third wire out of the generator let him say so. Once again you analyze things way past where they need to be. Is you are using a 240 VAC output you should be able to ground the center tap for the safe operation around a work site. He stated that he could wire most of his tools for 240 VAC, so he should. You don't have to worry about balancing the load on the two windings, and the few 120 VAC tools or work lights shouldn't force you to wire everything for 120 VAC.

The more of your off the wall posts that I read the more that I know that i would never hire you to change a light bulb, let alone do real electrical work. You sound like the two EEs from the base's power plant that I ran into at Ft Greely, Ak. The government finally approved, and delivered a large 208/220 VAC through wall air conditioner for the transmitter and control room at the TV station. Two EEs come out to the station to take a look at the three phase breaker box mounted on a relay rack a couple feet from the AC unit and informed me that there wasn't enough power available to hook it up. Without taking the cover off the box it was obvious that only one phase was in use because there was a row of single pole 20 A circuit breakers, one in every third slot. So, I had 100 amp 208 VAC that had nothing connected to it. I called on of the GIs who did their grunt work and talked him out of the 30 amp breaker, some wire and conduit and installed it myself. When they came back to prove it couldn't be done, it was running, and the three phases were in better balance than before.

You can come up with a thousands reasons why nothing can be done, without asking for more information while others use simple logic to find a safe and reasonable way to do it.

Why do you always try to complicate things? Why do you want to toss in a three phase setup when the OP clearly stated he had a 120/240 source. Only in your mind can it become a multiple voltage three phase haywire.

Hey Mike, Don't mind Phil too much I think he's got a little Drain Bamage from exposure to Nucleonics };-)

=AEoy

|> | I can change the genset to run at 120v@87amps only or can wire it to |> | have |> | 240@43.5amps. | | says just that. | |> It tells me there are two 120 volt |> windings that can be in series or parallel. It does NOT tell me there |> is more than 2 wires coming through the generator control box. It can |> be a generator where the winding configuration is apart from the feed |> connections. A generator with a circuit breaker would be configured on |> the line side of that breaker, and utilized on the load side. It may |> be easy for you to see that your generator really can do 120/240 OK, but |> going on a description that doesn't say there are 3 wires available, and |> doesn't say "120/240", I would not (then) make such an assumption. | | | Once again, you show that not only can't you "Think outside the box", | but once more you prove that you ARE the box. The OP is building his | own power plant. If there is no way to bring a third wire out of the | generator let him say so. Once again you analyze things way past where | they need to be. Is you are using a 240 VAC output you should be able | to ground the center tap for the safe operation around a work site. He | stated that he could wire most of his tools for 240 VAC, so he should. | You don't have to worry about balancing the load on the two windings, | and the few 120 VAC tools or work lights shouldn't force you to wire | everything for 120 VAC.

Actually I really am thinking outside the box, because I have NOT limited myself to a singular way of thinking. I really do know there are generators that can be wired for either 120 or 240 volts that _cannot_ provide a dual voltage Edison style center tapped 120/240 volt system. I was not making any assumption one way or the other about _your_ generator because I know of these possibilities.

But you are making assumptions about my knowledge ... and you got it wrong.

Most people with as dual voltage Edison style center tapped 120/240 volt generator would have described it as "120/240" volt in reference to it having the feed for a neutral. You didn't.

| The more of your off the wall posts that I read the more that I know | that i would never hire you to change a light bulb, let alone do real | electrical work. You sound like the two EEs from the base's power plant | that I ran into at Ft Greely, Ak. The government finally approved, and | delivered a large 208/220 VAC through wall air conditioner for the | transmitter and control room at the TV station. Two EEs come out to the | station to take a look at the three phase breaker box mounted on a relay | rack a couple feet from the AC unit and informed me that there wasn't | enough power available to hook it up. Without taking the cover off the | box it was obvious that only one phase was in use because there was a | row of single pole 20 A circuit breakers, one in every third slot. So, | I had 100 amp 208 VAC that had nothing connected to it. I called on of | the GIs who did their grunt work and talked him out of the 30 amp | breaker, some wire and conduit and installed it myself. When they came | back to prove it couldn't be done, it was running, and the three phases | were in better balance than before.

It seems you and I do have one thing in common: we have both run into EE's that think inside very small boxes when it comes to practical power work. Now I'm glad I didn't go through EE in school (I did take a couple of EE classes while majoring in CS, to raise my GPA).

But I don't think I would want to work for you given the risk of you specifying work to do, have providing ambiguous specifications because you only know of one way those specifications could be understood, and it might be that I know more than one way (as in the case of a generator that is "240 volt").

| You can come up with a thousands reasons why nothing can be done, | without asking for more information while others use simple logic to | find a safe and reasonable way to do it.

I've learned NOT to make assumptions, especially from what people with less experience might say.

|> Consider a three phase 12-lead generator. There are a lot of ways it |> can be wired up for a lot of different voltage and phasing configurations, |> including 66% single phase (double delta). But one thing I have found |> that is not easy to do is 3 separate 120/240 volt systems, even though |> there are 6 windings (2 per phase angle). I could configure it so each |> phase is done with 2 windings in series and the center taps all connected |> together as a common neutral, and grounded. But this would involve SEVEN |> wires. It's unknown if the voltage regulator could handle this at all. |> The terminal space is not there to feed that power out without a lot of |> modifications. | | Why do you always try to complicate things? Why do you want to toss | in a three phase setup when the OP clearly stated he had a 120/240 | source. Only in your mind can it become a multiple voltage three phase | haywire.

I was giving an example for your benefit, not for the OP. But I guess it is beyond you.

Making assumptions? You give no evidence of understanding anything. You are often vague and frequently wrong. The facts speak for themselves.

Sure! just keep telling yourself that and maybe someday you will believe it. As far as writing specs, I have equipment aboard the ISS where everyone's work is reviewed at many levels and noting I wrote was ever changed. Specs that I wrote allow you to see photos from weather satellites. I did a lot of work on the Microdyne MFR LEO Earth Station installed at Wallops Island. You're full of yourself, while I'm past the stage where I have to prove myself to anyone. Been there. Done that. Wore out the cheap ass T-shirt. I served my country in the US Army, engineered at a number of radio and TV stations, and built one from scratch. All I see from you is grasping at straws. Why not take your CS and leave electricity and electronics to those who know what they are doing. The threads you have started would scare me if I had to work or live around any of your work.

An example? I see that you still suffer from delusions of adequacy. Don't worry your little pointed head! Life is short, then you die. Get over yourself.

Naw. He proves that old phrase, "A mind is a terrible thing!", "Brought to you by United Way, the best dam candy bar money can buy!"

On Sun, 05 Jun 2005 03:14:54 GMT Michael A. Terrell wrote: | snipped-for-privacy@ipal.net wrote: |>

|> Actually I really am thinking outside the box, because I have NOT |> limited myself to a singular way of thinking. I really do know there |> are generators that can be wired for either 120 or 240 volts that |> _cannot_ provide a dual voltage Edison style center tapped 120/240 volt |> system. I was not making any assumption one way or the other about |> _your_ generator because I know of these possibilities. |>

|> But you are making assumptions about my knowledge ... and you got |> it wrong. | | | Making assumptions? You give no evidence of understanding anything. | You are often vague and frequently wrong. The facts speak for | themselves.

Do you, or do you not, understand that it is possible for a generator to have only a 2-wire feed while being able to be configured for either 120 volts or 240 volts by peans of either parallel wired windings or series wired windings? I've repaired such generators so I not only understand how they work, I know they exist.

|> But I don't think I would want to work for you given the risk of you |> specifying work to do, have providing ambiguous specifications because |> you only know of one way those specifications could be understood, and |> it might be that I know more than one way (as in the case of a generator |> that is "240 volt"). | | | Sure! just keep telling yourself that and maybe someday you will | believe it. As far as writing specs, I have equipment aboard the ISS | where everyone's work is reviewed at many levels and noting I wrote was | ever changed. Specs that I wrote allow you to see photos from weather | satellites. I did a lot of work on the Microdyne MFR LEO Earth Station | installed at Wallops Island. You're full of yourself, while I'm past | the stage where I have to prove myself to anyone. Been there. Done | that. Wore out the cheap ass T-shirt. I served my country in the US | Army, engineered at a number of radio and TV stations, and built one | from scratch. All I see from you is grasping at straws. Why not take | your CS and leave electricity and electronics to those who know what | they are doing. The threads you have started would scare me if I had to | work or live around any of your work.

I do not even believe you, now. The reason is because the generators that I have worked with which would not do 120/240 volts at all were military surplus generators. YOU should have run into those. But if you are as educated as you claim, then YOU would at least under that if the feed lines only have 2 wires, then you cannot get dual voltage out of the thing. Since you cannot comprehend that, everything you are saying above simply comes across as false.

If you in fact did any of those things, it is clear you don't have the mental capacity to have done anywhere as well as others.

But I sure as hell won't leave electricity and electronics to you, since you have clearly shown that you cannot comprehend something as simple and basic as how many different voltages you can get at the same time from two wires.

|> I was giving an example for your benefit, not for the OP. But I guess |> it is beyond you. | | | An example? I see that you still suffer from delusions of adequacy. | Don't worry your little pointed head! Life is short, then you die. Get | over yourself.

You don't even know what "example" means?

Sad, really sad. You need Roy's meds even more than he does.

I've resisted ever putting anyone's name in the ignore list for my NNTP news reader. I guess it's finally time to go back to the man page and look up how to do that. You might want to do the same with yours.

Yes, and I understand how to wind the generator as well. What does that prove?

Good for you! Did you even bother to look up the specs on the ST10 gen head? It shows two separate windings and it is a crude farm grade unit made for long life and rugged service. It isn't a factory built system, so you can pretty well do what you want with it.

So, in your small mind the fact that i was in the military and worked in electronics means I had to have seen every piece of equipment ever used? The class of generators you are talking about would be Korean or Vietnam era junk. Grow up and get a life, loser! My MOS was in Broadcast, (26T20) but I did service RADAR, microwave, CATV, and numerous other systems related to my job at different bases.

No, every generator I ran into in the US Army was three phase, and permanently installed. The smallest was the 100 KW water cooled Chrysler plant at Ft Greely Ak, the largest diesel Onan ran a pair of 2 MW radar transmitters, the air conditioning and 20 radar consoles along with the other electrical loads at Ft rucker Al.

The civilian systems I've seen since then were all three phase as well, and all built by Onan. One powered a 10 inch well at a couple hundred acre nursery, another was at a nursing home, and the third was for a 5 MW TV transmitter site. I didn't have to maintain them, because they were all under service contracts, but I had to make sure they were in working order at all times.

You have a lot of room to talk when you can't even understand the basics, like how a transformer works. I feel sorry for you, Phil, but you're becoming a boor.

Yawn. Big talk from a CS. I doubt that you can even do ISP on a microprocessor without someone to hold your hand.

Example? Phil is a troll. How is that? Example. You show Phil the answer. He doesn't get it. Just like the famous out of control loop on a shampoo bottle. Lather. Rinse. Repeat. Or a roach motel. Answers go in but they don't come out.

It figures that a CS won't know how to use a simple piece of software. I already know how to filter out idiots, but I was hoping you were willing to learn rather than mouth off without doing any research. Tell me, Phil, are you really wanting to learn, or just display your bad attitude?