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Thread: Powering tools via a generator

  1. #1
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    Powering tools via a generator

    More specifically, 220v tools. And in light of Rob's jointer problems.

    The 220V 30 amp 4 prong outlet on my generator has a label that identifies it as having a floating neutral. My first issue is to get the tablesaw working. It requires a 220V 30 amp source. Starting amperage is reportedly closer to 18-20 amps. But what is deal with a floating neutral? I Googled it but I am still in the dark - pardon the pun.

    Bottom line, will the saw run properly and safely (for the saw) or will I blow something? Who can I take it to, if I must, to resolve this.

    The saw is a 15 year old Grizzly 1023 3HP. The generator is an almost new Coleman Powermate PM0497000 powered by a Honda GX390. The PP is wired for a 30 or 50 amp 220v source. I can plug the saw directly into the generator if need be.

    The second tool I would someday like for this to run is the Jet 1642 with the electronics. But that is a dragon to slay on another day.

    Tell me what you know or what you would do to resolve this issue. Would like to making sawdust next week. Thanks.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  2. #2
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    Carol, As my electrical knowledge is mostly self learned, I have rune some 220v motors from my Miller welder/generator and had no problems, but these were not electronic variable speed either, just straight old ac motors. My gen puts out 29 amps @ 220 volts, so similar to yours.

    I have even run a couple times with no neutral wire, just the 2 hot legs. Probably not the best idea, but it worked then, not to be repeated though.

    If you have the correct plug, and wire it in accordance with diagrams, it should work. I think I would provide a ground rod hookup, in any case, just for safety sake.

    Others more edumacated in this will correct me.
    "You got to learn from the mistakes of others. You won't live long enough to make them all yourself". (Author unknown)

    "Time flies like..... an arrow,,,Fruit flies like..... a banana." Groucho Marx

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  3. #3
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    You wouldn't think electricity would have to be so dang complicated would you

    I think I have it mostly figured out and am pretty sure you should be a-ok. I would personally plug the saw in and make sawdust

    Here's how I understand it - I am not an electrician and this is getting well on the edge of my knowledge curve.

    The "floating" neutral means that there is no bond between the neutral and the ground and definitely no ground from the generator to the earth. This is essentially irrelevant for 220V applications where you don't have the neutral in play at all.

    In general the floating neutral MAY actually be slightly safer in common use because there is no path from the power source to the surrounding earth you have to short out one of the hot wires to the other or to the ground or neutral. Think of it roughly this way if you have a battery you can touch either side with no problem, its only when you connected the terminals together that you get sparks. The situation with your generator is roughly equivalent, the two hots are out of phase (and thus have potential) and there is also potential from the hot lines to the neutral and ground connections. In most cases the generator body is "the ground" though so if its in contact with something you can still form a circuit (long version of saying "don't put the generator in a puddle of water with you in it and then grab a hot wire").

    About half way down this page is about the most useful diagram I could find of floating vs bonded neutral setup: http://www.screenlightandgrip.com/ht...ad_Rating.html FYI that also talks about how you have a really nice power source with the Honda as well


    The VFD issue may make my head explode if I try to figure it all out; there are soo many variables. I would say that you have a really good chance of it just working as your generator is rated for something like 5x the expected load so it likely has enough umph to put up with the variable load the VFD puts on it. The only other possible problem I could see is if the VFD doesn't like the wave form but as its a newer generator I suspect that it is very likely to be fine.

    A really nice overview of generators and vfd issues is here (albeit at a much larger scale ): http://www.trane.com/commercial/uplo...019en_0106.pdf

  4. #4
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    Thanks, Tony. That is a beginning. Good news for the tablesaw. I kinda figgered the lathe would need the power conditioned and even with a ground rod connection, there may be a problem. Hope some more sparkies weight in.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  5. #5
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    Quote Originally Posted by Tony Baideme View Post
    I have even run a couple times with no neutral wire, just the 2 hot legs. Probably not the best idea, but it worked then, not to be repeated though.

    If you have the correct plug, and wire it in accordance with diagrams, it should work. I think I would provide a ground rod hookup, in any case, just for safety sake.
    I think you meant "no ground wire" While they may look similar and often go to the same place they actually have different purposes and in 220v only use you don't hook up the neutral just the ground but there should be no current going over it unless something bad has happened This generator does have a four wire hookup on the 120/220 outlet (2 hots, 1 neutral and 1 ground) for the case of the saw you really only need the 2 hots and the ground. The neutral would only be useful if you wanted to add a 120v load (i.e. a situation light) to the same circuit.

  6. #6
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    Wow, Ryan! The links hurt my brain! And you are right, examples are at a far greater scale than what I am trying to do. Thankfully the lathe is a much later project.

    I also may have to think about how to power the 110v circuits if I have to by-pass the breaker box. That hurts my head, too. Obviously, if the genset can power the breaker box and the saw can run through that as intended, life will be much easier. Everything worked when I was plugged into a 30 or 50 amp RV park pedestal. If the genset rated at 7.5K can duplicate that, I will be a happy camper.
    Last edited by Carol Reed; 10-27-2013 at 02:52 AM.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  7. #7
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    Quote Originally Posted by Carol Reed View Post
    Wow, Ryan! The links hurt my brain! And you are right, examples are at a far greater scale than what I am trying to do. Thankfully the lathe is a much later project.

    I also may have to think about how to power the 110v circuits if I have to by-pass the breaker box. That hurts my head, too.
    Hah, well you are basically setup for it with only "minimal" work. The 120/220 outlet on your generator has all four connections you need so I would think about putting in a small panel and then outlets downstream from that in the trailer and just hook the generator up to the breaker panel. When you do that (this part I'm at least vaguely familiar with ) you want to hook the ground and the neutral up to the connection from the generator but NOT to each other inside the panel (this may require removing a bonding strip from the neutral bus to the ground bus in the panel as for normal house installations they are bonded). Essentially you are wiring a "subpanel" in this case so the rules for that should apply. You would wire an "outlet" (inlet really I suppose) on the feed side of the panel so that the cord has FEMALE connectors and the panel inlet has MALE connectors (thus you don't have exposed hot connectors if you hook the cord up to the generator first).

    You're looking for something like this as the inlet box: http://www.homedepot.com/p/Reliance-...2#.UmyBnSQikwk
    You would hook it up to the generator with something like this (which you probably have): http://www.homedepot.com/p/DEK-Unive...4#.UmyB6SQikwk
    Size the panel based on number of circuits not load so probably a 60 or 100 amp panel would give you enough flexibility.
    The outlets downstream can be just standard outlets.

    One caveat for the other circuits, for portable installations like trailers romex isn't a great idea (moderately ok if everything is tightened down good, all screw connectors, etc..) but stranded copper in conduit would imho be much better. Its also a pain to use romex in conduit (I don't think NEC even allows it anymore except for some exceptions for short "feed" runs or something) because of the conduit sizing rules for heat and I wouldn't want exposed cables so you'd want to either have to put it behind walls (bleh) or in conduit which devolves back to stranded.

  8. #8
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    Ryan, here are some pictures of what I already have done. This is the breaker box. It has a separate ground bar as spec'ed by the sparky at Home Depot. You can see it in the lower right of the box. The neutral bar is above the bus bar.

    It is fed by an RV 50 amp cord and 50 amp plug. A 30 amp/50amp adapter is also available. I could run a separate ground from the ground bar to earth ground. I haven't looked at the genset closely enough to know if I could do that to earth ground as well.

    Click image for larger version. 

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    The outlets are all 4 plex boxes with 2 separate circuits in each box.

    Click image for larger version. 

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    And I did use Romex, because I had it on hand. But I stripped the exterior insulation to run it in the EMT.

    The next project is shop lights. They will be on two circuits switched separately. I need the tablesaw to make the shop lights.
    Attached Thumbnails Attached Thumbnails 50 Amp Cord.jpg   some plugs.jpg  
    Last edited by Carol Reed; 10-27-2013 at 03:34 AM.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  9. #9
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    So things I'm pretty sure about first:

    You have the breaker box wired correctly
    You should be able to use the 220 outlet just fine
    The 50a/50a cord should be fine, I was somehow under the misapprehension that the generator was 30a for some reason..

    The floating neutral thing is a mess and I don't have a coherent answer. I'll try to talk to some of the sparkies at work on monday but I'm not overly hopeful on them helping a lot as its somewhat outside their realm of expertise.

    I can say definitively that OSHA requires the neutral/ground bond at the generator: https://www.osha.gov/OshDoc/data_Hur..._generator.pdf
    My copy of "RV Electrical Systems by Bill and Jan Moeller" (which is otherwise a pretty good book - yes I have a lot of books ) was no help on the generator side but did confirm the breaker box wiring.

    This article was somewhat helpful: http://www.fohonline.com/current-iss...er-part-2.html - in particular the section on "“Floating Neutral” Generators" - I don't know if the powermate falls under the "some small inverter generators do not hold their neutral at ground potential, but rather have the hot +60V RMS to ground, and the neutral -60V RMS to ground. These generators cannot have a neutral to ground bond, and are only intended to operate cord- and plug-connected equipment." category but would bet not as its more high end.

    My gut reaction is that you probably want the neutral-ground bond back at the generator. If it was me, I would call up a service center and describe the use and ask what the proper configuration is and if they can change the generator for the RV/trailer use case: http://www.powermate.com/servicecenters.php Its only vaguely possible that they'll be helpful but it can't hurt to try. I would leave the breaker box with the bond disconnected though because you don't want that connected if you hook up to grid power (as you will be tying off of an existing box which will already have a ground-neutral connection and loops there are bad no nos). If you do decide to re-add the bond and the powermate people are unhelpful you can make a special cable that does it inside the cable which is probably about as good (I think the rvdoctor guy linked below describes how).

    Some other comments/notes since I was reading stuff:
    The bigger problem with romex (since I was re-reading some of that advice in the books I only vaguely remembered from the last time I looked at them) in portable installations is that larger copper wires work harden over time when "flexed" (vibration from the road can suffice to cause this eventually) and then break. The RV Electrical book (and "The Bus Converters Bible" that sits next to it... yeah books..) both recommended "boat wire" which is pre-tinned stranded wire. You have to use crimp connectors or solder the ends though so it is more of a pain than solid. If you aren't moving the trailer much its likely not a problem as there are a lot of old RV's with romex in them it looks like... and most of them haven't burnt down yet

    If you haven't I'd cross check all the 110v circuits with a circuit tester:
    http://www.homedepot.com/p/Klein-Too...9#.Umy17yQikwk
    You don't need the GFCI testing capability, but its within a buck or two of the one that doesn't have it so.. yeah. tools!
    The 220 circuits are nominally harder to mess up (or at least you're suppose to be paying closer attention when you install them ).

    If you're ending up using a lot of questionable campground power the RV electrical book suggested upgrading your testing setup to something a like this:
    http://www.idealindustries.com/prodD...?prodId=61-165
    because it also alerts you to over voltage power and some other conditions that can ruin your camping adventure. They have basically a whole chapter on detecting and correcting bad campground power so I'm guessing its a pretty common issue (or at least used to be the book is from 95). The rvdoctor links below show how to do some more complex/complete testing with a simple ampmeter and handheld hot/cold tester.
    And it gets worse - some old campgrounds did stuff like this: http://www.rvdoctor.com/2001/07/frie...gary-mike.html
    some good advice here: http://www.noshockzone.org/rv-electr...0%93-hot-skin/
    and more here http://www.noshockzone.org/category/rv-safety/ (pages 1 and 2)
    (note that he recommends the neutral-ground bond be established as well).

  10. #10
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    I will weigh in here with what I know and have discovered.

    It was my intention to do exactly as you are contemplating/planning.

    So I have made a small panel to supply electricity both 220v and 110v to my temp shop due to the current mains supply being unable to provide for my needs.

    The issue that one needs to get ones mind around is there is a vast difference between powering a static load to powering a dynamic load.

    This is where the problems come in. Starting a motor and running it without any load is not as big a deal as when it is loaded with a belt and some mechanism it is expected to drive right from start up. Think of this like resistance.

    There is also a big load placed upon the motor when the machine is then used to perform its intended operation ie cutting wood or in my case jointing wood.


    Now if you compare a motor say to switching on the lights, in both cases when the switch is thrown, you have a load, the huge difference is the lights do not require much current and secondly they in the case of the good old filament bulb will still glow at all sorts of voltages.

    Motors are a different animal. The magnetic field setup is created by a winding which is a particular gauge of copper with specific amount of insulation on it. All of this is designed with specific intentions regarding voltage requirement and current requirement. They tolerate variables but only for short periods and if continuously subjected to stress at some point the weakest point is going to show itself.

    So presenting the motor with the proper voltage and the correct current at this voltage is the issue.

    So theoretically when you look at these generators and you consider the loads, what you find is in theory they should work out and in a static calculation the capacities all look fine as in my case where I have 3 times the power and 2,5 times the current requirement.

    The problem is understanding motor dynamics. The huge winding that is in a motor is essentially a very large inductor. Its also essentially putting a short across the mains. When you throw the switch there is a huge inrush of current into the inductor to create the magnetic fields required for the motor.

    The higher the HP naturally the higher all these currents are. I say all because most of the motors we are using do not only have one winding. In order to get the motor turning they have a start winding and a running winding. Both are in circuit when the motor starts except that in the case of the start winding it has a capacitor in circuit as well to change the dynamic load of the winding.

    Note we are talking here about a very complex subject called impedance. Impedance is the load of a "complex circuit" that is no longer just resistance but includes taking into account the capacitive nature of the load and the inductive nature of a load. These components change the load and bring into play an element which has to do with the phase angle between current and voltage.
    Unfortunately we cannot calculate these parameters for a given motor because they do not provide these values in a specification for a typical motor. The only component you do know is the elements like the run capacitor and the start capacitor.

    So for this reason, a motor from one manufacturer is not the same as the other, but there is way more to this than I am attempting to simplify.

    In my case my generator connects the earth leg directly to the neutral leg within the generator. Its expected that the generator is grounded with proper ground to provide the ground leg for safety etc.

    For the motor I only need the two hot circuits.

    But the big difference between a supply from a power company and the supply of a generator is that apart from the circuit breakers in the loop at a home supply, we can essentially have "infinite" supply of current from the home source.
    The only thing preventing this is the circuit breakers along the way.

    In the house situation, the only thing likely to cause a drop in voltage is if you draw the "infinite" current through wire not capable of handling it which is going to add resistance in the loop and hence create its own voltage drop.

    Note R= x.L /a where resistance is determine by the constant x for the material acting as a conductor, L is the length of the conductor and a I the cross sectional area of the conductor.

    This is why when people wire their shops and look to do it with the lowest gauge possible they are not doing themselves or their equipment any favors. The longer the run the more copper the greater the change of a volt drop especially when you look to draw large dynamic start up currents.

    So where am I at with my tests to get my jointer working.

    Well first issue I have is blowing start capacitors.

    Now let me say this jointer worked in my old place with no problem and with a long cord I had which was suitably over rated. So I know the motor and jointer work.

    The next thing, on my initial attempts I had the same cord involved and in an attempt to remove variables after the start cap blew I have taken to a very short cord of 10 gauge wire direct from generator to the motor using the motors own output switch as a start switch for the jointer. This is not safe but its experimental intended to eliminate any possible effects of other switches inline.

    This did not solve any problem and the start cap still blew.

    Now where I have a basic problem is that the start cap is rated at 250V for a circuit of 220V. In theory this would be ok. Theory being that the voltage of a capacitor needs to be higher rating that the voltage its going to be connected to.

    The big question is just what that voltage looks like coming out of the generator. Here one needs to understand how the generator is creating this "alternating current and voltage". Its not the perfect sine wave output that your normal hydro company supplies.

    So I would be much happier with a voltage on this cap of 300v and in my next "experiment" I am planning on doing that. I have one on order from a different supplier. Of course this introduces other issues. The cap is housed in a metal housing that is designed to fit the oem one. The higher voltage cap is larger and while I have procured a larger housing for it, it will require mods to mount it.

    But lets assume the cap is ok, the next thing I have to be sure of is the generators ability to deliver the load I require.

    So an additional test I have in mind is to put a fixed load in my case a electric stove element onto the 220v output of the generator and measure both current and voltage and check that the generator can provide the claimed 5500 watts of current.
    Its supposedly rated to supply higher power for start up loads rating 6250 watts.

    But note they refer to watts not the actual current. And that always makes me suspicious. Anyone that has audio engineering knowledge will remember the big craze growing up of having a boom box that puts out more watts than his friends. We all used to refer to the labels but all missed the aspect of what kind of watts they were. Manufacturers in the case of audio equipment have abused this subject for a lifetime. You would see specs where they would say 200 watts and if one looked closely it was Peak wattage, not RMS wattage which is really the only watts that counted.

    So in order to find out where my issue is I have to sift fact from fiction in the case of the generator.

    Then there is a third component at play in my equation.

    The start capacitor is only intended to be in circuit momentary while the motor starts up. It plus its winding is designed to be in circuit to give the motor a greater burst of power to get the whole thing moving given its starting under load.
    As Don has pointed out when the motor gets to a certain point there is a centrifugal switch in circuit which is supposed to switch out the capacitor and then the motor runs on its own windings directly on the mains supply.

    In some motors the contact of this centrifugal switch takes a hammering over time with the currents involved and so burns out. This is not the case in my motor. But the switch can be "adjusted" to kick out at different points simply by adjusting where it is tightened on the shaft. Really flunky design but it has worked for decades.
    If this switch does not kick out at the right time the cap is subjected to the start current for longer than intended and hence pop goes the weasel.

    Two elements play a part here. In one case, is there current/voltage to get the motor up to speed and second is the switch kicking out when up to speed.

    All I can do is work at eliminating the variables. I have tried to find a motor repair shop but have been unsuccessful trying to find one with a dynamo. They all just bench test the motors and put them back in place and I am talking motors much bigger than my piece of junk. Makes one wonder about so called "motor repair shops" but that's another subject.

    So there you have where I am at and the detail involved in my situation and generator along with the steps I have taken and am taking to get this lot to work.

    Apologies for the long winded nature but there is detail here I don't see how to present in a tweet type post.
    cheers

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