3 Phase to table saw

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  #1  
Old 03-20-13, 01:40 PM
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3 Phase to table saw

Hello, I could use a little hwlp with wiring a table saw. Just bought a place that has 3 phase in shop that used to be a machine shop. I'm decently accomplished with nost things electrical but 3 phase is new to me. I think it is a delta type but could use confirmation. I get 120 V ground to A and C, Nothing ground to B and 240V A to C. It does have a grounding/neutral bar. All breakers were removed (but one) and wires are unlabled but run to various places in shop. They only used black white and green individual conductors so its a real pain to try to id correct circuits. I believe I have located a circuit which went to an outlet labled 30A 3 phase that I would like to power a 3 phase Powermatic 66 table saw I picked up. The saw has the corresponding plug wired to it. I hooked up the remaining 30A breaker like I thought made sense (Blacks to A and C positions and white to B) green ground was already hooked to bar. However, saw will try but wont start. I have same voltages to switch that I have at breaker, but no go. confused more by wiring diagram for 240V 3 phase 5 hp saw. manual has 3 wires (L1, L2, L3, plus ground) but all 3 lines are labled as 240V. Mine are only 120V to ground on L1 and 3. 240V measured across 1 and 3.
What am I doing wrong? Please help.
thanks
 
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  #2  
Old 03-20-13, 03:15 PM
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Holy Crap! I am a bit surprised that that panel has not exploded in your face with how close that uninsulated lug is next to the B phase! This needs to be corrected ASAP before continuing on. You could easily have a phase to phase short which would really make for a bad day! What are the red wires and why are they double lugged on the line side of the breaker?

Is this a service directly from the the power companies drop, or does it come from another panel?

With a three phase service you should read the following with your meter, assuming it is a Delta high leg, and not a wye/star service:
A to B 240 volts
B to C 240 volts
A to C 240 volts
A to neutral 120 volts
C to neutral 120 volts
B to neutral 208 volts <---High leg!!!

The readings you posted to not jive with the readings you should have. You need to check this out and see if you really have three phase there. Your motor is trying to start but can not because it is single phasing, you are missing one leg of the three phase. Your saw needs three hots with 240 volts between each and a ground. No neutral is required.
 
  #3  
Old 03-20-13, 04:03 PM
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saw will try but wont start.
If the three phases of a 3-phase service are not connected to a motor in the right order, the rotation of the motor will be reversed. Not all motors are prepared to do that.

Sorting that out requires a meter that shows rotation. From the look of the double-lugging on the feeders for this panel plus the question you're trying to answer, I'd call an experienced commercial electrician. An HVAC technician with experience with 3-phase units might also be able to help you.
 

Last edited by Nashkat1; 03-20-13 at 11:18 PM.
  #4  
Old 03-20-13, 07:04 PM
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Please take all the readings that I posted earlier and post them here. (A/B, A/C, B/C, A/N, B/N, C/N, A/G, B/G, C/G) It might be possible that you may have a corner grounded delta.
 
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Old 03-20-13, 08:01 PM
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Where exactly in MO are you located, what power company do you have there? Is this a 3-wire or 4-wire service to your shop?
 
  #6  
Old 03-20-13, 10:03 PM
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Yikes!

I'd seriously get someone to re-feed that main. As was said, I'm surprised that hasn't gone POW trying to work around it with those bare lugs. Where is it being fed from, it looks like the wires just go through a knock out with no conduit or bushing.

As for voltage, did you check for voltage at the main? It could be a blown fuse before the main breaker. You mention checking each leg to ground, and getting reading on two of the phases, not the 3rd. I'd check phase to phase too.

I agree with the single phasing of the saw. A phase is missing.
 
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Old 03-21-13, 04:42 AM
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Just another nickel's worth.....have this service disconnected immediately until a proper upgrade on wiring can be made. I had to catch my breath when I saw no hub connection and bare splices. I question, too, the double input on phase three. Something just isn't right, and may fall outside the realm of DIY.
 
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Old 03-21-13, 07:04 AM
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I don't think it's a double input, I think it's a makeshift feed-thru setup. Since it's on A-C, I'd bet those go to a single phase subpanel somewhere else in the shop.. Lets just hope that there is a OCPD somewhere before this..

Considering all the other crap that's wrong with those pics, OP mentioned that he has no reading B-G where it should be reading 208v. So my guess is there's a fused disconnect somewhere feeding this panel that has the B fuse blown.
 
  #9  
Old 03-21-13, 07:59 AM
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I hear you

First thanks for all the responses...I thought I might be hollering down a well and would never hear back.

I agree It looks a mess, I was shocked (figuratively) when I opened it up. It sits right next to another single phase panel that looks relatively OK except for some of the things they did (ie. using 2 seperate breakers to pull legs for a 220 run... unlabled of course) Elec really was a mess all over ...taped splices, cut ends of runs, open boxes, etc...the usual but I've pulled it all out and re-done it but this "3 phase" however, does have me worried.

That said, some specific replys:

I will get a commercial guy in here, I glad it looks as odd to me as you guys. that said it did operate a metal shop for 30 years.

I find no other panels, switches, pull outs, etc related to this box anywhere. the riser conduit from the service meter on pole is directly on the outside of this box.

I cannot figure out the extra wires lugged to A and C. I just accepted this was how the Osage Valley Electric does it in South Kansas city. I will put in a call today.

I knew I wasn't getting a high leg delta so thought maybe a type of corner grounded type based on readings I got. maybe B phase is unintentionally grounded somewhere between the panel and pole....100 ft of underground probably not in a condiut. Again I'll have to call Osage Valley Elec.

Measured voltages are as follows: (A/B 121v, A/C 243v, B/C 121v, A/N, B/N, C/N, A/G 121v, B/G .7v, C/G 121v)

I'm measuring to ground using the ground bar. there is no seperate neutral bar this seems to be the main panel not a sub of some sort.

I agree I just dont have the juice to the saw. I calculate NO 240v to ground leads.

Now I am bummed and thinking I wasted a bunch of $ on a 3 phase saw thinking I had 3 phase. Probably have a bunch more tied up in getting it re-done and functioning. I should have just ditched this whole panel when I opened it up

Thank you very much for all of your input

MP
 
  #10  
Old 03-21-13, 08:18 AM
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No.....that is not how a power company wires things. For the most part.....that wiring would not be theirs. They supply TO the meter and you supply the rest.

Logic would suggest that that wiring does not come directly from the meter or CT cabinet.
 
  #11  
Old 03-21-13, 09:29 AM
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Its very odd that you're getting 120v on A-B and B-C.. That almost suggests that it is a single phase service and they are using the B buss as the neutral (which is illegal and incredibly dangerous as it means the neutral is switched - also could explain why there are whites landing on breakers). If it were a corner-grounded delta with the B phase grounded, you would have 240v across A-B, A-C, B-C, A-N, and C-N. B-N would read 0 since B is grounded.
 
  #12  
Old 03-21-13, 11:20 AM
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just met with power company and found out I dont have 3 phase even run to meter. Don't know what the heck is going on. Three phase box, , breakers, outlets and conduits to equipment stations but nothing coming in anymore. They thought maybe at one time years ago there was three phase but no more. I suspect when it was removed, they lugged into the A and C leads to feed the adjacent single phase box. That's why it looks so odd.

Anyway no 3 phase for my beautiful 3 phase 5 hp Powermatic table saw. looks like I'm shopping for a new single phase motor.

Bummed.

Thanks for time and thoughts,
MP
 
  #13  
Old 03-21-13, 11:23 AM
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P.S JerseyMatt...you were on the money
 
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Old 03-21-13, 11:31 AM
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Thanks for the update, sorry it didn't pan out the way you wanted.
 
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Old 03-21-13, 01:04 PM
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If you can get your hands on a cheap used 3 phase motor with at least 7.5-10hp, you can build a rotary phase converter - which will allow you to generate the 3rd phase in-house.. That'll probably even be cheaper than trying to find a 5hp single phase motor... Plus then you can run other 3 phase equipment too.
 
  #16  
Old 03-21-13, 02:07 PM
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Just had a thought that previous owners may have brought 3 phase in to panel using a rotary converter. Why would electric company ever have taken down a 3 phase transformer after going to the trouble to put it up? Who knows? there are a couple dead heavy gage wires poking here and there which I havent traced to anything yet. Rotary converter may have been AND be just the ticket.
 
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Old 03-21-13, 05:09 PM
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I agree with Matt. Add a rotary phase converter, or a static phase converter, and utilize that nice saw you have.
 
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Old 03-21-13, 06:45 PM
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Just curious did you ask the electric company the cost and feasibility of getting 3 phase?
 
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Old 03-21-13, 07:58 PM
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Originally Posted by Landscraper View Post
Just had a thought that previous owners may have brought 3 phase in to panel using a rotary converter. Why would electric company ever have taken down a 3 phase transformer after going to the trouble to put it up? Who knows? there are a couple dead heavy gage wires poking here and there which I havent traced to anything yet. Rotary converter may have been AND be just the ticket.
Given the way it is set up and the colors used, that's very unlikely. White is not used in 3 phase circuits at all because there is no neutral. You only see white on the 120 or 277v single phase circuits. I doubt the electric co took down a transformer, more likely one never existed to begin with. Look at where the cable comes to the overhead mast.. I bet you see three wires - two insulated wrapped around the bare support/ground (called triplex). If that's the case, there never was three phase service to that building. It was just wired half-assed and there was a 3 phase panel laying around that someone decided to use.
 
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Old 03-21-13, 08:09 PM
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Sometimes a neutral is required for some 3 phase equipment that requires it. Just so happens we just wired some VAV boxes that use 480 volts for some heaters, and 277 for the fan motor. Not saying it is common, but it does happen.

Also, a neutral can be switched, or put under an overcurrent device, as long as the ungrounded conductors are disconnected at the same time as the neutral.
 

Last edited by Tolyn Ironhand; 03-21-13 at 08:37 PM.
  #21  
Old 03-21-13, 08:32 PM
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Also, a neutral can be switched, or put on an overcurrent device, as long as the ungrounded conductors are disconnected at the same time as the neutral.
Yep, gas pump circuits come to mind.
 
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Old 03-21-13, 10:41 PM
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Yeah I get that, but with that setup there is the potential to land a neutral on a single pole breaker on the B phase, which IS illegal and deadly... Which is besides the point that the panel is being used contrary to its listing...
 
  #23  
Old 03-22-13, 12:11 PM
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White (neutral) isn't really "used." It just happens to be a conductor color they ran (in individual conductors) to outlets. From outlet wiring disections it wasn't a neutral it was a power lead... technically a red. The whole shop (on three phase side) is wired this way. I think they just ran what they had.

That said... I will look for a converter or make one up.
Thanks Again
MP
 
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Old 03-22-13, 01:09 PM
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It's illegal to use white or gray as a power lead. 3 phase is either brown/orange/yellow or red/black/blue.

I still firmly believe there was never actually any 3 phase equipment there, even a phase converter. Bolstered by the fact that the electric company told you that there wasn't even 3 phase to the premises.
 
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