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North American 10HP RPC - Questions about load center

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
If you're saying your lathe is single phase 240, it wouldn't hurt a thing to take those two single phase leads out of any box you like. No RPC needed.
 

Adair Orr

Aluminum
Joined
Apr 11, 2006
Location
Seattle
I should clarify. My single phase panel is not in the shop. It is my main 200 amp service for my home.
My supply source for my RPC is the same outlet that supplies my lathe. Ideally I'd like to preserve single phase power to the lathe and have the RPC hardwired so that I can have this 3 phase load center (that will only ever power 3 machines, never simultaneously). If the RPC is not on, and I have wired a single phase circuit from the 3 phase load center, then it is my understanding that I will be out of luck. I don't know how else to make branches in this system.
 

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
I should clarify. My single phase panel is not in the shop. It is my main 200 amp service for my home.
My supply source for my RPC is the same outlet that supplies my lathe. Ideally I'd like to preserve single phase power to the lathe and have the RPC hardwired so that I can have this 3 phase load center (that will only ever power 3 machines, never simultaneously). If the RPC is not on, and I have wired a single phase circuit from the 3 phase load center, then it is my understanding that I will be out of luck. I don't know how else to make branches in this system.

I think I get what you're after. The drawing is a little confusing. Go back and read what I think was my first post about only bringing back the manufactured leg of the RPC to feed you new 3 phase panel. That's the same as you need here. Leave your lathe outlet as is. That or stub it out the bottom of your 50 amp single phase disconnect. BTW, all these fuse size questions? Remember that you are fusing to protect the wire. Nothing else. Size accordingly. Those numbers are in countless electrical how to books.

Forget about T1 and T2 in your RPC box. Just have them be L1 and L2. Have them go the shortest possible route to your new 3 phase panel. They can be used and or pass through your phase convertor box. One problem I have is it's not clear how you start and stop your RPC. There is no input to the RPC shown other then two leads ending blindly in a box labeled phase convertor. Where's the switch? The 50 amp disconnect?

I don't know... if we were standing in your shop we could probably have this figured out in about two minutes. Remember you can do your connections of nearly any type inside any box you like. Only one wire NEEDS to come OUT of your phase convertor, although there is also nothing wrong with 3.

Right now I think I'm confusing more then helping. Sorry. The day has gotten long.
 

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
Hi Adair, What a difference a little sleep will make.

Your drawing is almost there. I mostly suggest to eliminate the whole area in the upper right of the drawing.

Supply Side:

1) 2 pole 50 Amp fused (breaker) circuit from house to...
2) 50 amp or more rated un-fused Disconnect in shop - to...
3) L1 and L2 lugs in your new 3 phase Load Center.

3 Pole 3 Phase Panel:


4) 2 Pole Breaker feeding Lathe Outlet.- Must use positions connected to L1/L2
5) 2 Pole Breaker feeding RPC- Must use positions connected to L1/L2
6) Return wire from Manf Leg Terminal in RPC to L3 Lug of 3 Phase Load Center.
7) Remaining positions in Load Center open for the rest of your remaining Machine Tools.

I'm assuming your RPC has its own On/Off capabilities as most do. If not, add a starting system outside and separate from the Load Center. But still feed it as described above.

Of course Grounding needs to be included.

The breakers will act as your individual Service Disconnects for when a machine needs work. The Main Disconnect of course for when the whole System needs work.

Seeing as most machine tools are not moveable in the day to day, and they also all have their own on/off capabilities, it is of no value and not typical to wire machine tools to plugs of any kind, In short, they are usually hard wired. Save your money on plugs and do just that.

There has been little mention of how your shop has lighting and other single phase stuff. How is the shop currently supplied? How far from the house? Buried cable? What's there now. Just curious how any 120v single phase stuff is playing into all this. You know... the dreaded white wire stuff.

I hope some of this helps instead of confuses. I'm still leaving the wire and fuse sizes up to you. It all changes depending on the type of wire and wiring you do. Conduit? Cable? Cord? Some ampacities change depending on how many wires in conduit etc.- etc. I'm betting most of your stuff will be in the 10 - 6 awg range.
 

Adair Orr

Aluminum
Joined
Apr 11, 2006
Location
Seattle
This is excellent, I would never have thought of arranging things in this sequence. I've updated my drawing again to make sure I am understanding you correctly. To answer your other questions first:
  1. My shop 120 is all supplied from my house breaker panel. All wiring is in the walls, including the (3) 50 amp outlets I put in place for my welder and two power hammers. Lighting is the same. The shop is the ground level of a tiny three story home.
  2. I expect to run everything in rigid conduit. I think I have my wire gauges all figured out now.
  3. Yes, the RPC panel came from North American Phase Converters and has an integral power switch. They have been very helpful and I have read good reviews of their control panels.
Below is my updated diagram incorporating your recent comments. I think my only question is how to ground the RPC panel. Thank you for all the problem solving. It's enlightening.
 

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13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
Well shoot... looks good to me. Nice drawing! I think you've got a System. Conduit in the walls. Sounds like my old system. Good luck with this.

One last idea for maybe later. You could stick the RPC in the basement next to your Main Panel and run that L3 all the way up to the shop, straight thru the Disconnect and to L3 of your load center. Only thing you'd need is a remote start setup. It's great not having to listen to the RPC when you're trying to think about heavy detailed machinist stuff.

Oh wait... small three story... shop is ground floor. Never mind. :-)
I'll leave the idea there in case others happen to be working on something similar.
 
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Adair Orr

Aluminum
Joined
Apr 11, 2006
Location
Seattle
I've attached a floor plan of my shop. The load center and RPC are shown in red on the wall behind behind the lathe and shaper. There is a utility space behind that wall where I will put the idler motor. The wall is insulated so that should address the noise issue.
 

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604Pook

Cast Iron
Joined
Sep 14, 2022
@Almost Retired

Why the angry? It's a 100amp three phase panel rated for 240v max. He is pulling 3 phase loads off it. He is wanting to feed it from a 50amp cct, and he doesn't need to use the neutral or even need to tie one in to it. It will 100% function without any issue feeding his three phase loads.
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
Location
Ontario Canada
This is excellent, I would never have thought of arranging things in this sequence. I've updated my drawing again to make sure I am understanding you correctly. To answer your other questions first:
  1. My shop 120 is all supplied from my house breaker panel. All wiring is in the walls, including the (3) 50 amp outlets I put in place for my welder and two power hammers. Lighting is the same. The shop is the ground level of a tiny three story home.
  2. I expect to run everything in rigid conduit. I think I have my wire gauges all figured out now.
  3. Yes, the RPC panel came from North American Phase Converters and has an integral power switch. They have been very helpful and I have read good reviews of their control panels.
Below is my updated diagram incorporating your recent comments. I think my only question is how to ground the RPC panel. Thank you for all the problem solving. It's enlightening.
well...... problem with the wiring.
i own pretty much that RPC
first problem is the lines all over. the NAPC panel has 2 lugs, one ontop of each for the 3 phase.
so the input has to go fully through the panel.
so it would come into the garage, go through the pull down shut off, then go into the phase coverter, L1 and L2
the other L1L2L3 will have the bottom lug set go to the motor, then top lug set go to the 3Ph panel. just creates a wiring mess.
if you want a 1PH panel, by code it needs to be separated. they are under $100. much cheaper then a pull down switch plus fuses which can be $200.
 

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
well...... problem with the wiring.
i own pretty much that RPC
first problem is the lines all over. the NAPC panel has 2 lugs, one ontop of each for the 3 phase.
so the input has to go fully through the panel.
so it would come into the garage, go through the pull down shut off, then go into the phase coverter, L1 and L2
the other L1L2L3 will have the bottom lug set go to the motor, then top lug set go to the 3Ph panel. just creates a wiring mess.
if you want a 1PH panel, by code it needs to be separated. they are under $100. much cheaper then a pull down switch plus fuses which can be $200.
Maybe things are different in Canada, but I see nothing wrong with what he's got going. Not exactly sure what is meant by two lugs on top of each other in the PC box. If that means the incoming and outgoing (if there even is such a thing in AC circuits) single phase connections share parallel lugs in a direct pass thru sort of fashion, then that's electrically no different from what his drawing is doing. Besides... feeding the RPC out of the 3 phase panel allows him to fuse it down with a breaker and run smaller wire then the heavier supply feed. I ran my RPC home system for over a decade wired pretty much like the OP has in the drawing. No problems at all.

As far as the need for a single phase box, he already has one in the house feeding the garage. I'm in a commercial space now where a single 3 phase panel (which looks just like the OP's only much taller) in the shop services every type of single and 3 phase connection a person can imagine. It even used to be a High Leg box, until the building changed over to 208 when both the neighbor and I wanted another 400 amps each. Same box is still being used fulfilling all needs. (Except the extra 400)

Lastly he really doesn't need a fused disconnect, as the incoming feed is already fused at the single phase house panel. In reality, when the two pole disconnect is off, the 3 phase system is also completely off.

I mean... I don't hold an electricians license, but I have wired tons of stuff without ever letting the smoke out, or putting anyone or anything in danger. I'm game for whatever satisfies the OP's needs and the authorities.
 

Adair Orr

Aluminum
Joined
Apr 11, 2006
Location
Seattle
I am the furthest thing from an electrician imaginable, but I tend to research things until I have full confidence that all is going to be safe. I put this diagram past a technician at NAPC who said the diagram was sound. I updated the drawing again, tying to tidy up all the wiring. He said it was fine to pull the T1 & T2 from two legs of the 3 phase load center, then supply the manufactured leg back to the L3 bus.
I'm in the process of mounting the components on a board to test the system. I'll report back here if I learn that something I've done was a poor decision. I will have a local electrician review this before it goes hot.

Wiring_Diagrams-for-Rotory-Phase-convertor V.jpg
 

SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
Personally, I would connect the L3 from the RPC back to the panel to a three pole breaker together with L1 & L2. This ensures that if you have the RPC breaker off to do work on the RPC or due to a fault, the RPC is completely isolated from supply. Otherwise, you have fun race conditions where e.g. the RPC breaker trips, but the lathe was running and continues supplying L3. You open up the RPC to inspect assuming that since the breaker is off, it's dead. L3 gets you. Similarly, someone pushes the start button on the lathe while you're working on the RPC with that breaker open. Lathe backfeeds through motor windings and livens L3.

If you accept that you're going to need to open the 60A disconnect to work on the RPC, then you may as well not have a 2-pole breaker for the RPC and just double-tap the panel lugs in a compliant fashion (there may be top and bottom lugs on the panel?). Overcurrent protection is provided by either the upstream supply breaker and/or a motor overload in the RPC controller.
 

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
Looks like Someone has some ideas. :-)

I see where you're coming from and your points are valid, but it would have to be a long shot group of events to get caught up by it, especially by someone who I think mostly works alone and is aware of the potential, even how likely or unlikely it would be.

The 2 pole breaker feed to the RPC allows smaller wire and allows his single phase lathe to remain running should he need to do something with the RPC concurrently.

The only time you could start another machine with the RPC disconnected would be if another 3 phase machine of larger HP was already running. If the RPC is out and no other machine is running, no 3 phase machine will start. (Likely this is already understood) It will growl and make horrible complaining noises. Whether a 3phase machine of higher horsepower or starting load would start over an already running smaller one would have to be seen. I'm a little doubtful, and wonder about more motor complaining should it be attempted.

In the many years I ran a system of similar design, it never was a problem. A simple bit of awareness will go along way to keep the OP safe.

Interesting stuff to think about nonetheless. Looks like more then one way to skin this cat.
 

SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
The 2 pole breaker feed to the RPC allows smaller wire and allows his single phase lathe to remain running should he need to do something with the RPC concurrently.
True, although a 3-pole breaker would give those same advantages (at higher cost). I'm not sure that you're gaining much in wire size going from probably a 40 to 60A breaker. Depends on distance from panel to RPC.

The only time you could start another machine with the RPC disconnected would be if another 3 phase machine of larger HP was already running. If the RPC is out and no other machine is running, no 3 phase machine will start.
The issue is that while they won't *successfully* start, the contactor would still pull in, livening L3 via the motor windings. Granted, it should be *close* to neutral potential, and that's mostly an issue if you have someone else that wants to use the tool, and doesn't check to see if the RPC is running first.

*shrugs*. I'm paranoid.
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
Location
Ontario Canada
problem with the most recent picture is you are now back feeding the breakers with the RPC. that's why the panel for the RPC has 2 separate lug spots for 3ph wires output. as the input side doesn't have the caps on it and only the output side is wired that way.
power supply and power distribution needs to be separated. this way if one leg drops out, it will shut down the unit and not burn up machines down stream by single legs missing. also makes for a cleaner sine wave form being direct to the motor on all 3 legs to keep the phase shift in sync.
 
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SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
power supply and power distribution needs to be separated. this way if one leg drops out, it will shut down the unit and not burn up machines down stream by single legs missing.
Fair call, but given the desire to run single-phase equipment without the RPC running, this requires a second panel or new home runs. I think it's been debated further upthread.

also makes for a cleaner sine wave form being direct to the motor on all 3 legs to keep the phase shift in sync.
Absolute BS for mains frequency AC with wavelengths of literally thousands of miles/kilometers. Phase shift from lightlag is something that can be ignored even by utilities. Volt drop from extra conductor impedance can occur, but would be difficult to measure on a balanced three phase system, let alone have a significant impact on a system with an RPC that's inherently miles from being perfectly balanced.

That said, you've reminded me of something I hadn't considered. All conductors in a given circuit need to pass through steel rings/holes/conduit together, or you get eddy current heating causing volt drop, excess heat, and power wastage. So your L3 from the RPC needs to go back to the panel in the same conduit as the L1 & L2 supplying it.
 

13engines

Stainless
Joined
Jun 30, 2015
Location
Saint Paul, MN
I tend to agree with Something that phase is not a problem. It would be a fun experiment for the OP to wire the RPC up as drawn, (and paying attention to what Something said about eddy currents) and wiring it up in what one can call the "normal" way shown in the artwork in post #37 by BT. I'm thinking the OP's machines will not be able to tell the difference in starting characteristics or running performance.

And let's not forget... he showed his drawing to North American and they okayed it. And I'll say it again... I ran my system for years like the OP has drawn without trouble. That included starting a big 24" G&E Shaper that had a 7 1/2HP motor that matched that of my RPC. My single Manufactured Leg return lead from the house basement to the shop 3 pole panel was close to 70 ft. long. (Main panel in shop, RPC fed from house sub panel in basement)
 
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Adair Orr

Aluminum
Joined
Apr 11, 2006
Location
Seattle
This is a great discussion, thanks all for participating.
This panel will power three machines, never simultaneously. The single phase lathe and the three phase power hammers would never be run together. My shop operates as a "clean space" and a "dirty space" depending on whether I am forging or tinkering with machine tools. If there was a way to further isolate the supply power or a different way to branch a single phase circuit I would. 13engines is correct that I work solo in my shop. I would not allow anyone around these machines without my own supervision, mainly because they all have the capacity to remove limbs.

The only option I can think of is to have the RPC fed from a receptacle at my 50 amp outlet. That would allow me to either plug in my lathe or the RPC. I wish there were some kind of device that would let me toggle between the two.
I can't repower the lathe with 3 phase because I just got done wiring in a motor, cutoff, and drum switch. That was an electrical nightmare for me.

-Adair
 








 
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