# Double 220 plug in for mill and grinder



## Brett (Feb 20, 2020)

I’m hoping someone can help me out here. I just finished making a 2x72 belt grinder that is powered by a 220v 30 amp VFD.  I also have a grizzly mill that is powered by 220v 30 amp. I’d like to have the 220 extension cord that hangs down from the ceiling above both of them power them both but not at the same time. I’d like to have a box I can mount that has two plug ins on it but then has a DPDT switch to control both plug ins. That way I could have both machines plugged in at the same time but use the switch to power the grinder or to the mill or center for off. I also would like this because the vfd for the grinder doesn’t have an off switch. It has to be unplugged to turn off. Wondering if this is even possible. Did some research but can’t come up with much. Thanks for any help.


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## FOMOGO (Feb 20, 2020)

Something like this, but in a 30 amp version. https://www.bluesea.com/products/9077/AC_Rotary_Switch_-_OFF_+_3_Positions_240V_AC_65A


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## markba633csi (Feb 20, 2020)

Brett: This is not a great idea for a couple reasons:
A) Turning off the belt grinder by opening the connections from the VFD to the motor would likely blow up the VFD- you would need to turn it off at the VFD itself.
B) Similar situation with the mill- possible damage to the VFD if you were to switch the loads with the motor still coasting down and VFD on

Most folks have a dedicated VFD for each motor/machine with no switches between motor and VFD output
-mark


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## Bi11Hudson (Feb 20, 2020)

FOMOGO said:


> Something like this, but in a 30 amp version. https://www.bluesea.com/products/9077/AC_Rotary_Switch_-_OFF_+_3_Positions_240V_AC_65A



That looks to be the optimal solution. The only input I can make is to go with the higher current rating. It (used to be) general practice to use larger contacts than the rating of a machine to ensure longevity. If the load is switched while off, the damage to contacts is minimized. But my experience is that there is always an unexpected exception and things get switched under load

There is a slight degradation of contacts every time they are cycled. Very slight, but over time can add up to trouble. The closer to maximum capacity a contact is operated, the more likely the damage to occur. It isn't really exponential, but that is a good way to describe it.

My opinion, based on 50+ yrs experience, is to use the heaviest contact you can find space for and forget about maintenance. Which usually doesn't happen anyway, it's usually "corrective maintenance". (Fancy name for repairs)

This is assuming you want to switch the line side of the VFD. The load side of the VFD is not a good idea in that each motor has to be tuned into the VFD. There are other foibles to operating a VFD into an open circuit, however quickly, that I am not qualified to comment on.

.

.


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## pontiac428 (Feb 20, 2020)

The only way I know how that would work legally is to install  a double throw safety disconnect switch rated for the full load of your machines on the wall, and run two drops to your equipment from there.  It's bulky and rather expensive.

I've run double 220v outlets on one cord, that part is doable; it's the switching that would get wonky.  Putting a switch on the grinder (either with a new VFD or by restoring function to the master power on the grinder) would probably be the better choice.

@Bi11Hudson:  Ha ha, corrective maintenance.  In the Army, we called it unscheduled maintenance.


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## RJSakowski (Feb 20, 2020)

A transfer switch used to switch between mains and auxiliary power could be used. 








						Reliance Controls 60 Amp Utility / Generator Transfer Switch TCA0606D - The Home Depot
					

This 60-Amp, double-pole manual transfer switch is for use with any 125/240V generator up to 15,000 running Watts. Ideal for switching a 60A service or subpanel from utility to generator power. This economical



					www.homedepot.com


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## RYAN S (Feb 20, 2020)

Hi fellow Minnesotan! For my mill, lathe and sg, I have one 220 volt 30 amp circuit that has three separate female plugs in line. Each plug has a cord going to a separate VFD for each machine. I only run one machine at a time.  None of my VFDs have an “off” mode, they are all  left on and basically sit dormant with only the screen using power. I know some people are not a fan of this method. From talking to the tech dept for the VFDs, it is not a concern to simply leave them on and not running. It is like my microwave, I never unplug it or turn it off.
Ryan


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## hman (Feb 21, 2020)

Here's a switch that's claimed to be rated for 63 amps, bargain priced at $27.39





						Baomain Universal Rotary Changeover Switch SZW26-63 660V 63A 3 Position 3 Phase: Amazon.com: Industrial & Scientific
					

Baomain Universal Rotary Changeover Switch SZW26-63 660V 63A 3 Position 3 Phase: Amazon.com: Industrial & Scientific



					www.amazon.com
				





You'd wire L1 (in) to terminals 1 and 3, L2 (in) to 5 and 7.  Grinder wired to 2 and 6.  Mill wired to 4 and 8.  Terminals 9,10,11,12 not used.

The rated power would give you a good operating margin (per *Bi11Hudson*). I'm just not absolutely sure I believe that current rating, especially given the low price.  _Caveat emptor_.


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## machPete99 (Feb 21, 2020)

Just make yourself an extension that has 2 outlets on it and only turn one machine on at a time.
My whole shop is on one 220 feed.
Worst case you might have too many things running and blow the breaker.
You probably don't want to try to get a single VFD to power multiple machines, you should use a separate VFD for each machine.


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## Brett (Feb 21, 2020)

Thanks everyone for the answers. Lots of good info. I just want to clarify a couple things. I’m only running on VFD on my grinder and it is only used to power the grinder. Basically right now I have an extension cord that hangs down from the ceiling. My grinder and mill sit below it back to back. When I want to use the mill I plug it in and use it. When I want to use the grinder I unplug the mill and plug in the grinder and when I’m done I could just unplug it. My idea was to have the extension cord from the ceiling go to a box that would have two outlets on it. With both machines plugged into those outlets. With having a switch on the box I could have it in the off position when I’m not using either machine. When I wanted to use one simple turn the switch to power the outlet that machine is on. Hope that makes sense. I think that rotary change over switch may be the answer.


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## talvare (Feb 21, 2020)

I would use this type of safety switch for your application: https://www.eaton.com/us/en-us/cata...ols-systems/double-throw-safety-switches.html

Ted


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## matthewsx (Feb 21, 2020)

Brett said:


> Thanks everyone for the answers. Lots of good info. I just want to clarify a couple things. I’m only running on VFD on my grinder and it is only used to power the grinder. Basically right now I have an extension cord that hangs down from the ceiling. My grinder and mill sit below it back to back. When I want to use the mill I plug it in and use it. When I want to use the grinder I unplug the mill and plug in the grinder and when I’m done I could just unplug it. My idea was to have the extension cord from the ceiling go to a box that would have two outlets on it. With both machines plugged into those outlets. With having a switch on the box I could have it in the off position when I’m not using either machine. When I wanted to use one simple turn the switch to power the outlet that machine is on. Hope that makes sense. I think that rotary change over switch may be the answer.



I have to say it sounds like you're making it too complicated with the switch IMHO. Since you're using an extension cord and not hard wiring anything into your panel it shouldn't be any kind of a code violation to have two outlets at the end of your cord. Since you won't be using both tools at the same time you shouldn't be drawing any more power than either tool can use, rate the wire for max amp draw of one tool and use an appropriate breaker on that circuit and you should be fine.

I'm familiar with the Blue Sea stuff from my marine electrical training, it's top notch and would totally recommend it if you needed a switch. Also familiar with transfer switches from my standby generator days and they would do the job too. I would not recommend the cheap Chinese switch from Amazon just on principle, this isn't the kind of application to try and save money on.

But, I don't really see any need for a switch at all. The VFD will only draw any significant amperage when it's running your grinder motor, otherwise it's just using line voltage to power the control board. If you really want to get fancy do like I did and put a sub-panel at the end of your extension cord and use regular breakers but that's just an extra expense. Spend the money on tools instead

Cheers,

John


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## markba633csi (Feb 21, 2020)

I just re-read your first post- now I understand- but- your VFD must have a power switch or standby mode of some kind, does it not?  As John mentioned above, in standby it should not need to be disconnected from the power line, since it draws only a tiny current.  But yes, you can add a main switch for it if you want to turn it off completely.  So you really just want to build a split outlet with a switch on one side for the VFD- I assume your mill has it's own power switch


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## Brett (Feb 23, 2020)

markba633csi said:


> I just re-read your first post- now I understand- but- your VFD must have a power switch or standby mode of some kind, does it not?  As John mentioned above, in standby it should not need to be disconnected from the power line, since it draws only a tiny current.  But yes, you can add a main switch for it if you want to turn it off completely.  So you really just want to build a split outlet with a switch on one side for the VFD- I assume your mill has it's own power switch


The VFD doesn’t have a power off switch. When it is plug in it is on and the fan is running too which is why I don’t want to leave it plugged in. The mill is kind of the same way. When it is plugged in the light on the mill is on showing power going to the mill. Probably not a big to leave that on since it’s just a power light but my ideal plan would be this. Use a splitter at the extension cord for the ceiling. Plug in both machines but have some kind of inline switch on each machine plug wire so the power could be completely cut off from the machine. Something similar to this. 
	

		
			
		

		
	



I’m having trouble finding an in-line cord switch that is 250v 20 amp though. Not sure what to do. May just be stuck plugging and unplugging the machines.


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## markba633csi (Feb 23, 2020)

I'm sure you can find a beefy enough switch- keep looking
might be some $
You could always wire up a contactor and a light duty switch to do the job


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## Chewy (Feb 23, 2020)

Simply put a 30A DPST wall switch in the circuit. You can put it on the feed to both items or just put it in series with either one or both.  I have two switches at the mill .  One is the switch above (20A) to power the mill.  The other is the standard SPST  wall switch to power all the 110V outlets  and DRO.  I flip both on to use mill and both off when I walk away.  Been that way for a couple of years.  I also wired the wood lathe VFD that way for wife.  Been that way for about a year.  If the switch is not available at big box store, go to electrical supplier. Around $10  from memory.   Also using this on air compressor contactor.  Kills power to both sides of contactor and that also kills power to contactor coil. 

Here is HD # for 30A
*            Model # R62-03032-2WS        
            Store SKU #589535        
            Store SO SKU #162677        *


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## Bi11Hudson (Feb 23, 2020)

If the plug(s) to be loaded are difficult to get to, as in over, under, behind, or otherwise obstructed, I concur with your general idea. The difficulty arises with the "switch" carrying load current will require running either large wire some distance *or* the switch being also located also in a difficult position.

I offer two possible solutions, the first of which is an extension cord of suitable size brought out to an easy to reach location, with a switch (if desired) located in the enclosure at the end of the extension. It _would_ make things easier to plug or un-plug with this remote so the need for a switch would be minimized. A little extra length on this extension would allow it to be moved to the desired machine.

The second, more complex, solution is to use Air Conditioner relays mounted at or near the existing source. They are usually low voltage relays, 24 volt coils. While they are not high current(>20A) rated, they *are cheap* and easy to acquire and replace when needed. A low power switch that would provide mutually exclusive operation could then be mounted at a convienent location. Since it is a low voltage, low current operation it would be below most codes concern. An old small extension cord with the plugs cut off would be all that was required. 3 conductor, of course~~~ for portable cable, the NEC allows the *green* wire to be current carrying.

For such an operation, a "single pole, double throw, center off" (SPDT-CO, ON-OFF-ON, or 3 position) switch would suffice. I have numerous such switches on hand, they are very common with my models. They are available at most automotive suppliers. Or if you were a stickler for better quality devices, most any electrical or electronics supplier. We're talking a couple of dollars for best case devices.

In either case, the final call is yours to make. My suggestions are just that, suggestions. I have been "finagling" similar setups for years and having been an electrician for well over 60 years (50 professionally) and am knowledgable of the safety concerns involved. Safety is the most important part of such an attempt.

Bill Hudson​


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## Brett (Feb 23, 2020)

Thanks again everyone for the tips and suggestion so far. I still haven't found an inline switch that has a high enough amp rating. What if I just did something like the drawing below.



I would have the wire from the ceiling come down into a box. Then splice the wires and hook up two 30A DPST switches. Connected to each separate switch are the outlets. Plug the mill in to one outlet and the grinder into the other. When I want to use one the machines flip the switch for the outlet that machine is plugged into. Let me know if I'm way off or if this is something that could work? Thanks in advance.


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## Chewy (Feb 23, 2020)

You drew the picture with 110V wiring.  In the old days, you could paint or tape the white wire "red" and get away with it.  The electricians that I have worked with in the last couple of years said that is a no-no any more.  You need Red/Black/Green for your set up. I do have the painted white wire in some mobile homes that use it for a hot feed.  They are 30 years old. Portable cords are a different story.

If you are running new wire, consider going to 10/4, which is red/black/white/green. The white is not used for 220V.  But you can grab either the red or black and make a 110V outlet in the same place.  Example, red/white/green.  I have a triple drop 220V/110V at the mill, wood lathe & drill press.   I used black at the drill press and wood lathe and red at the mill for 110V outlets. I have my switches at the machine because it is more convenient for me.  You can do it as you have drawn above.  Electrically it does not matter. Pay attention to the length from breaker to machine.  The guys are correct about voltage drop and maybe using relays and larger wire etc. The suggestion about low voltage relays and switch is good and I have done that in the past.  It does add some complexity to the system.  On new systems, I just went with the wall switch as the cheapest way out.


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## tq60 (Feb 24, 2020)

They make a standard lught switch that is DPSP double polarity so good for 240 volt switching rated for 20 amps.

Box store has them.

Get name brand unit.

Since it is on line side of VFD it is not acting as motor starter so contacts will be fine.

Photos if ours.

Light switch is the main power.

We added a 240 vac neon pilot to the drum switch so we know power is on 

The meter connects to the VFD 0-20 ma signal line that shows frequency or load, set to show frequency and the knob sets speed.

Added foot brake bar as drum switch over the Chuck and foot switch stops lathe 

All mounts in subframe.

The light switch works fine for 5 years now.
	

	
	
		
		

		
			











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