Electric gurus-Generator input ?

[grantgoold]

To all you electrical gurus. I have a large 18kw diesel generator that has two 110 volt output poles. I tested both poles and they are putting 110 volts under idle. I also have a generator panel on top of the box with several external electrical plugs available. One plug is for 220. There is no wiring diagram but the internal schematic has one large red wire that connects to the 220 volt receptical. I also have another single large black wire that wires directly into the 110 receptical and powers several downstream 110 plugs. My question is this. I will be running one 110 hot line into the bus through the automatic switch.  I wanted to plug the panel 110 wire onto the remaining 110 pole so I have external power should I need it.

That leaves me with the 220 volt plug not connected.

The question, can I connect both 110 poles together into one line and then connect the 220 single wire to those combined poles?



If this is not clear enough, I can scan the generator output schematic and send it should more information be required.


Thanks in advanced for any help you can provide.


Grant

[Nick Badame Refrig/ACC]

Hi Grant,

The question, can I connect both 110 poles together into one line and then connect the 220 single wire to those combined poles?

NO, you will short the field and ruin your gen. If you want a single 220v leg, most generators have a terminal for that.

Grant, can you run both legs to your panel box and split them from there? That's how most of us do it.

You should have 2- 120v legs, 1- Nutral, and 1- ground to run to your transfer switch. From there, run them to either your panel or inverter.

Hope this helps
Nick-

[Hartley]

Not enough information.

You really need to find out what brand and model the generator head
is and what diagrams may be available.

From your limited description it sounds like some kind military or industrial
unit. The next problem is you stated "at idle".. This cannot be right
unless it is actually a 1200 or 1800 rpm generator. It might sound like
it's at idle but may not really be.

Take pictures of all of the ID Plates and engine and post them, We will
find an answer hopefully before you electrocute yourself or burn something up..

Dave

[grantgoold]

Here is more description of the setup. The receptical box on top of the genhead has one 240 volt plug, one 12/240 volt plug (30 amp breaker inline before plug) 3 120 volt plugs (one with a 30 amp breaker, 2 with 20 amp breakers). There is no schematic or identication label for the receptical box. The 240 volt single red feed wire goes directly into one side of the 240 volt plug. The black feed wire goes to the other side of the side of the 240 volt receptical. Leaving the 240 volt on both sides with the hot wires is one wire that goes to the 120/240 volt receptical and the other to the 30 amp 120 volt receptical. It appears that the rest of the 120 volt recepticles are daisy chained to the first 30 amp 120/240 receptical.

The neutral wire goes to the first 30 amp 120/240 receptical and then daisy chains to the remainer of the recepticals.

The deutz generator has a Leroy Somer alternator (genhead) from Marathon Electric. The Valley power repair facilty provided me with the attached schematic. It show that I have  a "low zig zag-single phase (parallel) connection. I have scanned the electrical connection scehmatic provided by the deutz repair facility as the set up on the genhead. The diesel motor has been set to run at 1800.

I hope this helps. Perhaps I have now figured it out myself. One 120 volt leg (red wire) goes to one side of the 240 volt receptical and the other (black wire) 120 volt goes to the other side. I can also connect the house 120 volt line to one of the 120 poles to provide power to the automatic transfer switch. I am not sending 2 hot leads to transfer switch as the power cord first runs through an industrial auto reel (rated for 48 amps continuous).  So at this point I only have one 120 volt lead wire to power the internals of the bus.

I hope this is enough information to confirm my plan.

[Nick Badame Refrig/ACC]

Hi Grant,

I'm going to try and post some diagrams for power wiring.

Hummm, I thought I had more but, maybe on my other computer..

Nick-

[JohnEd]

I like Nick's diagram.  Looks like what I have seen all my life.  Still, I learn every day that I have missed SOOOO much.

Can anyone enlighten me on why one of the 120 legs has two pairs of windings?  Or, how can you get two different 220/210 volts and two different 120/110 volt  outputs?  I am sure it all makes sense with the proper explanation.

6 years ago I was told by a carpenter that the breaker box had 208 volts in it and that that used a neutral as one leg. I told him that there was no such animal as 208 and that 220 was made from two phases of 120 and there was no neutral "leg" on a 220 plug.  Harrumph harrumph, what does a carpenter know.  Without Paul Harvey you most probably know how that turned out.  Yes Mary Jane, 208 volts do exist as a box voltage and by golly, it is a single phase THAT IS DROPPED IN FROM A TAP IN THE FRIGGEN HV TRANSFORMER

There was a saving grace though cause I looked it up in the NEC and that great BOOK had this comment about "208".A)  It comes from a separat tap in the HV trans.  B)  It does have a neutral leg and it is single phase C)  It is a "industrial voltage" and should never be encountered in domicile applications.  D)  It was phased (no pun) out years ago and was only ever popular in the North East.  And me having my hands in a domicile box being inspected in Orygun and not even the "north east" part of the state at that.  So there is a lot to learn, I guess.

So what is that diagram with all the double windings about?

John

[boogiethecat]

Grant,  Your generator is wound with what's known as 12 wire connection, and it's basically a three phase generator.  Right off the bat, hooking it up as yours is  so it produces single phase power is a compromise- and as such, this connection hookup makes it only a 9KW generator.
Basically if you were to wire it as a three phase generator and thus create (and be able to utilize) three separate 120 volt circuits that share a common neutral, you could draw 6KW from each circuit, totalling 18kw.
But when you wire it to be a single phase machine, all you're going to get is  two circuits: hot-neutral-hot, and you can draw only 4.5KW from each one totalling 9kw.

Per your diagram,
you get one 120 volt, 4.5KW circuit from neutral to T1/T7, and a second 120 volt, 4.5KW circuit from neutral to T3/T9, and you can get 240 volts @9KW if you hook from T1/7 to T3/9 as you've already figured out.  Because T1/7 is 180 degrees out of phase from T3/T9, you cannot hook the two circuits together  to get a heftier single circuit.  That said, I believe that  you could disconnect the T11/5 -> T4/10 junction, and instead hook T3/9 to T4/10, T6/12 to T8/2, and T5/11 to T1/7 to get a single 9kw 120 volt circuit between the T3/9/4/10 junction and the T5/11/1/7 junction, although I've never heard of anyone doing it.  If anyone out there has an objection, please chime in....

John, all of the "double windings" are there so that by reconnecting those 12 wires in various ways, you can create different voltages and phase styles from the generator, depending on your needs.  For example, Grant's generator could be hooked up to be a 120/208 three phase machine, or a 240/416 three phase machine, or a 120/240 single phase machine as it now is.  It all depends on how you hook all those coils together.
The only sad part of this style generator is that if it's used in the single phase mode as Grant is doing, you only get half of the power that the generator set is rated at.  This makes for either a very reliable machine because its engine never gets fully loaded, or it could be viewed as a generator with too large an engine, because the job could have been done with half the horsepower and a lot physically smaller machine...

This is a pretty good webpage that explains everything, and why you can't get your full 18KW unless it's hooked up as a three phase machine-
http://www.anoldman.com/modules.php?name=News&file=article&sid=21

There is a little link on that page that you might miss, called "how generators work" and it goes into a good explanation of what I mentioned above.
It's:   http://www.anoldman.com/modules.php?name=Articles&page=generator.html

In fact there are a lot of little "understanding ____" links on all of this guy's pages, usually at the bottom (and easy to miss) and if you follow them all you'll get quite an education on phase, AC power, etc

Richard- we miss you!!

[Hartley]

Grant,

Looks like with the info that you provided the answer came very quickly
from some of the other Guru's of the board.

Generator head wiring can be confusing, But easy to understand once you
have the base diagram available. I can imagine the confusion due to it being
a 3-phase head. Those throw most people because the hookups to outlets
and internal wiring in some connection boxes uses the "Chaos Theory".

The best part here is that you can reconfigure the head as long as you follow
the diagram and remember that you will be converting from 3-phase output to single phase.

I used to picture stuff in my mind, But I seem to be having "power failure" lately so the schematic or diagram is the better bet.

Dave....

[boogiethecat]

I modified my above post to include the following:
Someone may want to enlighten me or comment...

Per your diagram,
you get one 120 volt, 4.5KW circuit from neutral to T1/T7, and a second 120 volt, 4.5KW circuit from neutral to T3/T9, and you can get 240 volts @9KW if you hook from T1/7 to T3/9 as you've already figured out.  Because T1/7 is 180 degrees out of phase from T3/T9, you cannot hook the two circuits together  to get a heftier single circuit.

  That said, I believe that  you could disconnect the T11/5 -> T4/10 junction, and instead hook T3/9 to T4/10, T6/12 to T8/2, and T5/11 to T1/7 to get a single 9kw 120 volt circuit between the T3/9/4/10 junction and the T5/11/1/7 junction, although I've never seen or heard of anyone doing it.  If anyone out there has a comment or an objection to this scheme, please chime in....

[Nick Badame Refrig/ACC]

I modified my above post to include the following:
Someone may want to enlighten me or comment...

Per your diagram,
you get one 120 volt, 4.5KW circuit from neutral to T1/T7, and a second 120 volt, 4.5KW circuit from neutral to T3/T9, and you can get 240 volts @9KW if you hook from T1/7 to T3/9 as you've already figured out.  Because T1/7 is 180 degrees out of phase from T3/T9, you cannot hook the two circuits together  to get a heftier single circuit.

  That said, I believe that  you could disconnect the T11/5 -> T4/10 junction, and instead hook T3/9 to T4/10, T6/12 to T8/2, and T5/11 to T1/7 to get a single 9kw 120 volt circuit between the T3/9/4/10 junction and the T5/11/1/7 junction, although I've never seen or heard of anyone doing it.  If anyone out there has a comment or an objection to this scheme, please chime in....

Hi Boogie,

Great info...  The 9kw single 120v connection between T5/11 to T1/7 would work as long as the gen head is set up for
3Ph low leg. If it's set up for 3Ph with a high leg, then he would have a single 230v curcuit at the same terminals.
I guess it depends on what the generator was used for in it's younger years.

Nick-

[grantgoold]

The genset was originally set up to handle two large AC units on piece of mining equipment. The unit was never installed and an employee purchased the unit during a bankruptcy auction. The unit would not start but would turn over. I got the unit from the employee who needed to pay some bills (looking to sell his mci8 originally).  I gambled and bought the unit for pennies on the dollar. I took the genset to the dealer and he found the sabotaged part that was missing, put in the part and for $45 the unit runs without issue. It has now about 2 hours of total run time.  It is actually nice to know that I have so many options with this unit!

We have set up the exhaust system and very pleased with how much noise reduction has already been accomplished. Now to build the quite box!

Thanks again for the input. I knew the guru's could help out.

Grant

[Sean]

Great discussion, and I see my good friend Gary has already answered well the original post.  However, with all due respect to John, I want to correct some misinformation that arose during the discussion:

...
6 years ago I was told by a carpenter that the breaker box had 208 volts in it and that that used a neutral as one leg. I told him that there was no such animal as 208 and that 220 was made from two phases of 120 and there was no neutral "leg" on a 220 plug.  Harrumph harrumph, what does a carpenter know.  Without Paul Harvey you most probably know how that turned out.  Yes Mary Jane, 208 volts do exist as a box voltage and by golly, it is a single phase THAT IS DROPPED IN FROM A TAP IN THE FRIGGEN HV TRANSFORMER

There was a saving grace though cause I looked it up in the NEC and that great BOOK had this comment about "208".A)  It comes from a separat tap in the HV trans.  B)  It does have a neutral leg and it is single phase C)  It is a "industrial voltage" and should never be encountered in domicile applications.  D)  It was phased (no pun) out years ago and was only ever popular in the North East. ...

OK, most of the foregoing is just plain incorrect; at a minimum, it's confusing.  John, I'm not sure what note you are talking about in the NEC, but I certainly can't find it in my copy (although if you give me a section number, I can probably clarify it).  You are correct, though, that it is not commonly used in residential applications.

208 volts is an extremely common voltage in the US (the entire US, not just the Northeast).  It happens to be the phase-to-phase voltage on a three-phase wye power system, where the phase-to-neutral voltage is 120.  This is the single most common system for providing 120 volt outlets in office, commercial, and light industrial buildings.  I can go into great detail about why, but it is really not relevant here.

As I discussed in my seminar last week, what RVers need to know is that a "50-amp service" involves two hot legs, a neutral, and a ground.  If those two hot legs are derived from a single-phase system (which, in turn, is really just one of the three phases of utility power dropped to the customer through a transformer), then the voltage between them will be a nominal 240.  The "neutral" in this system is a derived entity that happens to be the center tap of the secondary transformer winding, which means that the voltage between either hot leg and the neutral will be half that voltage, or 120.  (There is, therefore, no such thing as a system with 120 and "220" -- it's either 110 and 220, or 120 and 240, or maybe even 115 and 230.)  The neutral is grounded at the transformer, which gives some people the impression that 240/120 is a "two-phase" service with the phases 180° apart; if it helps you to think of it this way, I won't stop you.  (And, yes, there are neutrals on many 240-volt receptacles -- all range outlets have them, and most codes now require dryer outlets to have them, too.)

If, however, the two hot legs are two of the three phases of the aforementioned three-phase wye service, the hot-to-hot voltage will be 208, and the hot-to-neutral voltage will be 120.  Many commercial RV parks, some state park campgrounds, and virtually all truck stops supply their pedestals from such a system, and so it is absolutely not uncommon for you to find this voltage on the road.

Since most appliances and systems on an RV are 120-volt only, most of us will never even notice the difference.  However, if you have any 240-volt appliances, you will.  The good news is that virtually every appliance made for "240" is actually designed to run fine on 208 as well, because it is so common.  But heating appliances, such as cooktops and clothes dryers, will produce only 75% of the heat on 208 that they can produce on 240.  Expect your pasta and your undies to take longer.

An exception might be motor-driven appliances such as air conditioners.  If you are using, for example, marine Cruise-Airs or residential mini-splits, you might find that there is a switch, jumper, or terminal post that needs to be connected differently for 208 vs. 240.  (But not necessarily -- some will work just fine on both, perhaps with a reduced output on 208.)

For the intellectually curious -- if all your loads are 120, you'll get the same usable power from a 208Y/120 system as from a 240/120 system, 12,000 watts.  On a single-phase system, if you actually drew exactly the full 50 amps on each hot leg, the legs would be completely balanced and the neutral current would be zero.  On a 208 three-phase system, if you drew 50 amps per leg, the neutral return current would also be 50 amps, because that is the "imbalance" among the three legs of the system (one of which is not connected to the coach).  The designer of the park has arranged the pedestals such that, on average, all three phases will be balanced for the park as a whole (actually, this is more or less an automatic side effect of filling up your three-phase panel with two-pole breakers).

If you had a single hot-to-hot load of the same amperage, say an oven drawing the full 50 amps, you'd get less power out of a 208-volt system than a 240 -- 10,400 watts vs. 12,000 watts.  In practice, however, since heating appliances are resistive, and the resistance of the appliance is fixed, an oven which would draw 50 amps on 240 (which would mean a resistance of 4.8 Ohms) would only draw 43.3 amps on 208, for a load of just 9,013 watts.

Incidentally, the mathematics of the neutral currents is the reason why I tend to jump on folks here who suggest that a 50-amp, 4-wire service is really only a 120-volt service, and that the hot-to-hot voltage is irrelevant to an RVer.  If you find a pedestal with a 50-amp receptacle (NEMA 14-50R) and measure 120 between each hot and neutral, but zero volts between the hots (don't laugh -- I've seen it), the receptacle is unsafe and should not be used.  The neutral in such a connection will be carrying the sum of the hot currents, rather than the difference, and you could easily end up returning 100 amps through terminals and wire built only for 50 amps.  No breaker will trip, however, since the hot currents will be within limits, and there is no breaker in the neutral.  Hot-to-hot voltage should always measure between 208 and 250 volts.

Note, by the way, that all code provisions of the NEC relating to RV's explicitly specify 208Y/120 alongside 240/120 as allowable voltages, and the required labeling on a 4-wire 50-amp inlet must include both voltages in the wording.

Hope this clears up some confusion.

-Sean
http://ourodyssey.blogspot.com

[boogiethecat]

Just a quick addition to Sean's post, I was told (and it makes a lot of sense) that the reason there are both 208 and 240 is more or less this- money.
(and Sean is totally correct- there is just as much 208 floating around in the country as there is 240...maybe even more)

Industrially, 240 volts (delta) systems power a lot of 3 phase motors and 3 phase equipment, but being that 240 is a "delta" connection, you can obtain 120 volts for office lights etc from only two of the three phases involved.  So if you use a lot of 120 volt stuff on a Delta system, you'll eventually unbalance the system to the point that the power company will not like it.  But the largest portion of Delta power is used for three phase equipment, not office stuff.....  Being that in the end it's all about balancing the loads between phases, 240 delta is OK for industrial applications even though operating 120 volt stuff on it creates a small compromise.


On a less industrial basis, for example hotels, commercial and light industrial, 120 volt things are more common than three phase machinery, and because of this, the "Wye" connection is used, and "wye" gives you 208 volts.  On a wye system it's possible to completely balance all the 120 volt stuff you'd ever want to hook up, and also operate three phase equipment.

So the question is, why even bother with Delta being that is is almost always a compromise, and not just use Wye which is best for all worlds?

It's simple. Copper=money. Out on the telephone pole, you see big transformers (endearingly called pole pigs) that drop high distribution voltages down to 120/208/240/440 etc.  These contain a lot of copper and cost a lot of money.  Turns out that a delta system only requires two of them, while a wye system requires three.
So it's simply a matter of economics, not much more... it costs less to create a Delta system, so when you can get away with it, why not!!!

On another note, an interesting thing about voltages vs various countries.  Again, this is something that was told to me a long time ago by an old engineer who worked at navel Electronics Lab here in San Diego... it is interesting and makes sense:

The question, why out of all the world (who is pretty much either on 120/60hz as we are, or 240/50hz as is most of Europe and everyone else)
ok, why is Japan 100 volts 60hz? It's a really weird voltage, and japan is the only country!

The answer apparently is, that back in WW2 we bombed all of their generation capability before we did anything else.  When it was all over, they were left without power to rebuild.  We proceeded to run cables from our ships to their shores and provide "temporary" power to them.... but the cables were so long that there was a large voltage drop, and by the time the power got to them it was only 100 volts! So they rebuilt using that voltage, it became their standard, and the rest is history.
May be true and may not, but it makes sense... anyone know for sure?

[skipn]

   Oops   "telephone pole" must be narrowback jargon....

   Wouldn't say that around a lineman or a power company person   :0

    Just being a brat

    Skip

[Sojourner]

Thank you for Grant to post this strange generator for motorhome used. Now we learn it a 3-phase design.

Thank you to both boogiethecat and Sean for well written reports about the electrical voltage, load, phases, history and applied to RV in general. This should be in Wiki file.

FWIW
I am so glad you guys came to the rescue on this Grant's post because it gotten me confuse until I have seen the "Low (voltage) Zig Zag" schematic. Now I wish Sean would post on this because he can explain must more clearly and complete with his great grammar then I can. I need to go back to school to learn grammar with my state of art hearing aid.

Well He answers it! Praise the Lord!

I truly enjoy this MAK's BB and his crew to say the least.

FWIW

Sojourn for Christ, Gerald

BTW...I hope anyone that appreciates these acknowledgeable "bus nuts" of whatever subject would chime in with their appreciation. After all we need to keep them to rescue us.