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douglee25 01-12-2011 09:08 PM

Wiring Bridgeport Mill in Shop
 
I'm wiring a Bridgeport Mill in my garage shop. The shop has a single phase, 220v subpanel (ground and neutral unbonded). The mill has a 3 phase, 1 hp motor. There is also a digitial read out and work lamp on the mill.

Here is my initial plan....

Wire from the panel via a DPST 20 amp breaker to a 2 pole siemens disconnect (LNF222R). Wire from the disconnect to the VFD enclosure and then from the VFD to the 3 phase motor. The VFD will convert 1 phase input to 3 phase output.

I plan to wire from the VFD to the motor with SOOW wire.

Questions....

1. Can I wire directly from the panel to the disconnect with SOOW wire as opposed to Romex? I know the disconnect technically is not needed in a 'home use' situation because technically the breaker already provides a means of disconnecting the machine. I felt with a disconnect close by, it gave me the ability to isolate the machine without running all the way to the other end of the shop.

2. The ground must be carried from the panel then to the disconnect then to the enclosure and finally to the motor, correct? The disconnect itself does not have a ground lug (2 pole disconnect - no gnd or neutral) so I would need to add a lug for that. Is that all correct?

3. Although the mill motor does not require a neutral, can I utilize the unused neutral in the SOOW or romex from the panel to power the receptacle for the digital read out and lamp? Is it acceptable to double tap the disconnect on the load side for the feed to the receptacle? If not, I either will need to add a transformer or I can easily add another receptacle on the wall just for the dro and the lamp.

Please advise.

Thanks again.

Doug

mpoulton 01-13-2011 12:41 AM

Quote:

Originally Posted by douglee25 (Post 568899)
1. Can I wire directly from the panel to the disconnect with SOOW wire as opposed to Romex?

No. The permanent wiring between the panel and the disconnect must be a code-accepted wiring method for that purpose, and SOOW is not. Romex (NM cable) is fine, or you can run conduit and pull individual THHN conductors. If you use NM, you can use either 2-conductor or 3-conductor w/ground cable. If you use 2-conductor, you will re-mark the white conductor as black and use it for the other hot, with no neutral. Using 3-conductor cable will give you a neutral, which is more versatile and probably a good idea.

Quote:

2. The ground must be carried from the panel then to the disconnect then to the enclosure and finally to the motor, correct? The disconnect itself does not have a ground lug (2 pole disconnect - no gnd or neutral) so I would need to add a lug for that. Is that all correct?
The disconnect will have some means of bonding the enclosure, probably just a green screw. You should not have to add a grounding bar.

Quote:

3. Although the mill motor does not require a neutral, can I utilize the unused neutral in the SOOW or romex from the panel to power the receptacle for the digital read out and lamp?
I think so. As long as your breaker is a double-pole 20A, I think you can use it to supply that 120V load. There might be some type of code rule against combining a 240V load or fixed equipment load with a receptacle on the same circuit - but it's not an unsafe installation and I would do it if it were my shop. Someone may be able to chime in with a more authoritative NEC-based answer.


Quote:

Is it acceptable to double tap the disconnect on the load side for the feed to the receptacle? If not, I either will need to add a transformer or I can easily add another receptacle on the wall just for the dro and the lamp.
You almost certainly cannot put two wires under one lug on the disconnect. However, you can "pigtail" the connection instead, using a short length of wire from the disconnect lug and a wire nut to connect it to the two load conductors.

Suggestion: Instead of using a disconnect and a separate receptacle and VFD all mounted near the mill, why not simplify this. Install your new 20A circuit with a 4-conductor L14-20 twist-lock receptacle near the mill. Mount your VFD and receptacle right on the mill, and connect with a cord and twist-lock plug. The twist-lock replaces the disconnect, and mounting your VFD and receptacle on the mill is more compact and self contained and avoids NEC issues.

frenchelectrican 01-13-2011 01:16 AM

Quote:

Originally Posted by douglee25 (Post 568899)
I'm wiring a Bridgeport Mill in my garage shop. The shop has a single phase, 220v subpanel (ground and neutral unbonded). The mill has a 3 phase, 1 hp motor. There is also a digitial read out and work lamp on the mill.

Here is my initial plan....

Wire from the panel via a DPST 20 amp breaker to a 2 pole siemens disconnect (LNF222R). Wire from the disconnect to the VFD enclosure and then from the VFD to the 3 phase motor. The VFD will convert 1 phase input to 3 phase output.

Ok just read on you will get the answer there.


Quote:

I plan to wire from the VFD to the motor with SOOW wire.
Is this bridgeport have single or two speed motor in there if that the case if you wired up the VSD just hook up to the high speed side and leave the low speed unconnected { you may have to check the nameplate to make sure the connectons is correct }

Quote:

Questions....

1. Can I wire directly from the panel to the disconnect with SOOW wire as opposed to Romex? I know the disconnect technically is not needed in a 'home use' situation because technically the breaker already provides a means of disconnecting the machine. I felt with a disconnect close by, it gave me the ability to isolate the machine without running all the way to the other end of the shop.
Short answer is no you can not use the SOOW cable from the breaker box to disconnect switch you have to find a others means like NM cable or MC cable or in Conduit. any one of the metholds will meet the code without issue.

The other thing is you will need a disconnect switch if you are not in sight of load centre and you will see couple more details in a bit.

Quote:

2. The ground must be carried from the panel then to the disconnect then to the enclosure and finally to the motor, correct? The disconnect itself does not have a ground lug (2 pole disconnect - no gnd or neutral) so I would need to add a lug for that. Is that all correct?
A small ground bussbar will do the trick for this purpose that is only couple Euros for it and majorty of all the disconnect devices I have ran into they will have a provations for hook up the ground conductors.

Quote:

3. Although the mill motor does not require a neutral, can I utilize the unused neutral in the SOOW or romex from the panel to power the receptacle for the digital read out and lamp? Is it acceptable to double tap the disconnect on the load side for the feed to the receptacle? If not, I either will need to add a transformer or I can easily add another receptacle on the wall just for the dro and the lamp.
For the digtail read out is that part of the Bridgeport system or sepearted most case I know quite few peoples leave this connection seperated from the motor circuit and they do the same thing with the luminaires { that usesally get from any 120 volt circuit otherwise a transformer will be included in there }

And the other thing you can not make a double tap connection in any type of termations point unless they are listed for multi conductors so that is a fine line to cross so best to make a pigtail for it.

The other thing you will have to becarefull with VSD is if you want a motor disconnect do it on line side not on the load side otherwise some case it can damaged the VSD { I have see that once a while but not very often } This part you may want to check with your VSD manufacter details about useing the load side disconnect switch.

What brand name the VSD you have there? I may know couple details with it.

Now I know you menton unused conductor in SOOW cable my answer is don't do it due your motor is three phase you will need all four conductors anyway. and I rather keep the lamp and digtail read out seperatred from the motor circuit for very good reason.


Merci.
Marc

douglee25 01-13-2011 10:30 AM

Quote:

Originally Posted by mpoulton (Post 569018)
No. The permanent wiring between the panel and the disconnect must be a code-accepted wiring method for that purpose, and SOOW is not. Romex (NM cable) is fine, or you can run conduit and pull individual THHN conductors. If you use NM, you can use either 2-conductor or 3-conductor w/ground cable. If you use 2-conductor, you will re-mark the white conductor as black and use it for the other hot, with no neutral. Using 3-conductor cable will give you a neutral, which is more versatile and probably a good idea.



The disconnect will have some means of bonding the enclosure, probably just a green screw. You should not have to add a grounding bar.



I think so. As long as your breaker is a double-pole 20A, I think you can use it to supply that 120V load. There might be some type of code rule against combining a 240V load or fixed equipment load with a receptacle on the same circuit - but it's not an unsafe installation and I would do it if it were my shop. Someone may be able to chime in with a more authoritative NEC-based answer.




You almost certainly cannot put two wires under one lug on the disconnect. However, you can "pigtail" the connection instead, using a short length of wire from the disconnect lug and a wire nut to connect it to the two load conductors.

Suggestion: Instead of using a disconnect and a separate receptacle and VFD all mounted near the mill, why not simplify this. Install your new 20A circuit with a 4-conductor L14-20 twist-lock receptacle near the mill. Mount your VFD and receptacle right on the mill, and connect with a cord and twist-lock plug. The twist-lock replaces the disconnect, and mounting your VFD and receptacle on the mill is more compact and self contained and avoids NEC issues.

Thanks for the help. The confusion here locally on the SOOW cabling was the fact that even though it's typically used for unsupported machine connections from a junction point, if the cabling was properly secured from the panel to the enclosure, that would also be acceptable. We could not specifically locate anything in the NEC that stated otherwise. I also have NM wire available in the shop, so I agree I will just go that route.

Roger on the pigtail connection in the disconnect.

Originally I thought of using a twist lock style plug and mounting the vfd on the mill, but I decided I didn't like that idea due to the potential for swarf and other dirt to enter the vfd. Personal preference I guess. I am just going to mount a board on the wall behind the mill which will have the disconnect, vfd enclosure, and the receptacle all mounted to it.

Appreciate the input.

Doug

douglee25 01-13-2011 10:35 AM

Quote:

Originally Posted by frenchelectrican (Post 569024)
Ok just read on you will get the answer there.




Is this bridgeport have single or two speed motor in there if that the case if you wired up the VSD just hook up to the high speed side and leave the low speed unconnected { you may have to check the nameplate to make sure the connectons is correct }



Short answer is no you can not use the SOOW cable from the breaker box to disconnect switch you have to find a others means like NM cable or MC cable or in Conduit. any one of the metholds will meet the code without issue.

The other thing is you will need a disconnect switch if you are not in sight of load centre and you will see couple more details in a bit.



A small ground bussbar will do the trick for this purpose that is only couple Euros for it and majorty of all the disconnect devices I have ran into they will have a provations for hook up the ground conductors.



For the digtail read out is that part of the Bridgeport system or sepearted most case I know quite few peoples leave this connection seperated from the motor circuit and they do the same thing with the luminaires { that usesally get from any 120 volt circuit otherwise a transformer will be included in there }

And the other thing you can not make a double tap connection in any type of termations point unless they are listed for multi conductors so that is a fine line to cross so best to make a pigtail for it.

The other thing you will have to becarefull with VSD is if you want a motor disconnect do it on line side not on the load side otherwise some case it can damaged the VSD { I have see that once a while but not very often } This part you may want to check with your VSD manufacter details about useing the load side disconnect switch.

What brand name the VSD you have there? I may know couple details with it.

Now I know you menton unused conductor in SOOW cable my answer is don't do it due your motor is three phase you will need all four conductors anyway. and I rather keep the lamp and digtail read out seperatred from the motor circuit for very good reason.


Merci.
Marc

Good points. I will be using the disconnect on the line side of the VFD. The motor is one speed. Roger on the ground buss and pigtail connections. I will do some more investigation tonight.

Thanks again.

Doug

douglee25 01-18-2011 08:17 PM

Well I finished the job over the weekend. Everything works great and I have to say it turned out pretty well. I even managed to wire up the original switch to the VFD. I still have to wire a pot for speed control, otherwise I need to manually input it on the VFD.

Doug

Sorry for the slightly out of focus picture. It was taken with my cell.

http://onfinite.com/libraries/1651727/216.jpg


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