I guess in the worst case scenario if I take the alternate advise here, I would have to run the RPC in order to operate my lathe off of L1 & L2 from the 3 phase load center. I don't know how much electricity that will chew up, but I don't run the lathe that much. I suppose I could set it up that way.
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North American 10HP RPC - Questions about load center
- Thread starter Adair Orr
- Start date
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SomeoneSomewhere
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- Dec 24, 2019
The diagram in post #31 will work fine for what you want, including running the lathe on single phase power without running the RPC.
It does have the disadvantage that attempting to start three phase tools without the RPC running will fail, but you will presumably notice, hit stop within a second or two, and start the RPC.
As I said previously, I would hook the RPC to a three pole breaker including the L3 (blue) wire, but that's just me being paranoid.
It does have the disadvantage that attempting to start three phase tools without the RPC running will fail, but you will presumably notice, hit stop within a second or two, and start the RPC.
As I said previously, I would hook the RPC to a three pole breaker including the L3 (blue) wire, but that's just me being paranoid.
BT Fabrication
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BT Fabrication
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without buying a separate $100 single phase panel, you can also get double lugs and have it spit from the pull down switch.
13engines
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Come on Someone, you seriously must be joking. At what time in your life that you're in your shop and you walk up to a machine, do you not already know whether your RPC is up and running? Never... is the answer to that. It just doesn't happen. Even in my old shop where I couldn't hear or see the RPC, I always knew when it was on or not. (A little light for backup) Do you smoke a lot of weed in the mornings or something. :-)
I wonder if in his drawing #31, he could change out his 2 pole breaker for a 3 pole and run his L3 backwards (so to speak) thru the breaker, leaving the top L3 lug empty? (This may be what you're suggesting also?) I think his RPC is close enough to where he might just hook it up the "normal" way like BT is wanting him too. He and his local electrician friend will be the last call on that. I think it will all work fine either way he goes.
BT, This is a really intriguing idea! I just ordered a non-fusible switch for my primary disconnect for this system (see image below). Maybe I should use a two position load center downstream for a single 240 outlet to provide protection (see image below). If this worked I could wire the RPC and 3 phase load center as per the original NAPC instructions. Man, what a puzzle this is. I haven't even explored yet if there are additional grounding needs with all of this.
I'm trying to understand the purpose of T1 & T2 supplied to the RPC through a 3 pole breaker, while backfeeding L3 through the same breaker. Would that be to provide an interruption to all legs if something caused it to trip? I spent some cash on 2 pole breakers yesterday, but I suppose I could send the 50 amp back.
For everyone's information all of these panels fit on a 36x48 sheet of plywood that will be 6 feet away from the 50 amp outlet that I will tap into.
13engines
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Hi Adair, Yes that's exactly right. Trying to satisfy what Something was saying about the rare possibility for L3 to have AC potential, should the RPC trip the 2 pole breaker feeding it, while another 3 phase motor is still running in the shop somewhere.
SomeoneSomewhere
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As I said, I'm paranoid and used to setting stuff up for the 300lb shop gorilla. There are a lot of safety rules that are unnecessary if one assumes there is one occupant who is perfectly logical, sober, with perfect memory and a complete understanding of the entire system, and who never touches anything they don't intend to.
In the real world, breakers, overloads, and lockouts exist.
In the real world, breakers, overloads, and lockouts exist.
BT Fabrication
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a breaker likes to trip when the load is one way from the panel to the load, reversing a breaker and back feeding it is a big no no in the electrician world.
so you have a 50A single phase plug in the shop? 3 prong? ideally direct wiring most things is best
is it recessed in the wall? if its surface mounted you can run a wire from the plug to the RPC, just too many variables without seeing actual pictures of said plug and respective wiring to go with it.
as for grounding you just need to connect it all to make sure it has grounds to get back to the main panel, adding any others can cause issues. (ie ground loops)
13engines
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I call hogwash... there is no way in the world a breaker electrically knows what side is line and what is load. I'm not sure where the idea was hatched that there is a direction to AC circuits, but there is none. The only direction that exists is like in any circuit, where there will be Voltage Potential and Current Capability on one side of a Switching or Overcurrent Device and not the other. And a person could say that Potential etc. starts at the Load Center and moves out to all the devices, representing a physical sense of direction we can all relate to. Yet once the switches close, all direction is gone.
I digress... I'm sorry for mentioning it in the first place, but I do think it's a bad idea to back-feed the Manufactured Leg thru a 3 pole breaker. Mainly because it's unconventional, and leaves a high side potential in a place where no one expects it, even with the breaker off. So Adair please forget that idea. (You may have already done so which is good.) On my system I believe I ran the Manufactured leg back thru a Single Slow-Blow Buss fuse in a single holder. Remember that all the breakers and fuses are there to protect the wire and nothing else. Any other protections for motors and such are done with other devices sized accordingly.
BT Fabrication
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i guess eaton breakers can by design, apparently it all depends who makes it. Only code here in ontario prohibits it though.
The most interesting part of this discussion, apart from trying to discern how to put this RPC together, is that I'm learning from all these sideline debates!
I suspect I will feed the RPC control panel L1 & L2 as BT Fabrication has recommended, without going through the 3 phase load center. This seems to be the route with the least risk and greatest assurance of success. I can also still use the breakers that already purchased.
I will have a 30 amp single phase 240 branch from the 3 phase load center to power my lathe. I will have to run the phase converter to operate it, but that will work for now. I don't use it very much.
In the future I can introduce a single phase sub-panel.
BT,
Thank you for the pointer on the ground. I just read the same advise last night. Do you have a preferred/recommended means of making the 6 AWG wire connection in a junction box?
-Adair
I suspect I will feed the RPC control panel L1 & L2 as BT Fabrication has recommended, without going through the 3 phase load center. This seems to be the route with the least risk and greatest assurance of success. I can also still use the breakers that already purchased.
I will have a 30 amp single phase 240 branch from the 3 phase load center to power my lathe. I will have to run the phase converter to operate it, but that will work for now. I don't use it very much.
In the future I can introduce a single phase sub-panel.
BT,
Correct, I have (3) 50 amp, single phase outlets around the shop, all wired NEMA 6-50 with 6 AWG. I have one at my lathe that should really be 30 amps.
Correct, this outlet is recessed in the wall. I thought I could purchase an extension box so that I can connect EMT conduit through which I would supply the L1 & L2 of the RPC. My goal is to get all my machines hardwired.
Thank you for the pointer on the ground. I just read the same advise last night. Do you have a preferred/recommended means of making the 6 AWG wire connection in a junction box?
-Adair
SomeoneSomewhere
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RCD/GFCI/AFCI breakers may or may not be suitable for backfeeding, because the electronics usually are supposed to have the power removed when the breaker is open. Some breakers have an additional third internal contact (in addition to the line and neutral) to achieve this regardless of which side of the breaker is fed.
I believe US (and CA?) code requires breakers to be bolted down if backfed, rather than being merely clipped into place, so you don't have a live breaker bouncing around if it comes unclipped. Likely unnecessary in this case as the backfed pole is only live if the other two are supplied.
DC breakers using permanent magnets to control/break the arc usually only have full breaking capacity in one direction, and some codes forbid the use of these. ABB has some cunning ones with two contacts and a magnet for each polarity.
Breakers/protection units for generators often have reverse power protection to disconnect the generator if something goes wrong and the grid starts running the generator as a motor, spinning the prime mover/turbine. I think this is basically always done with electronics.
If the breaker is off, L1 & L2 are disconnected and the RPC cannot generate L3. L3 disappears.
BT Fabrication
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6Ga size is ideally spliced together using barrel crimps as a butt connector then heat shrink over top of them to seal and insulate it. as there is a wire size limit on wire nuts which off the top of my head I think is 8 or 10 ga wire.
so either this or this.
13engines
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Fuses can be expensive. That was my reason for suggesting the latter. Also when preceded by a breaker it's redundant. But that's not the worst thing in the world. If the cost works for you no harm going that way.
Last night I finished wiring in the idler motor. I didn't have a way to torque all the lugs, I'll have to have an electrician check that out soon. I got a bit eager, tested the voltage and just fired up the system. It was exhilarating! I checked the voltage of the three legs with the idler running. Everything appeared in order so I went ahead and fired up the shaper. No problems there either. I had the shaper in it's slowest setting, shortest stroke. It came to life without complaint.
I'd like to thank everyone who helped me out with this. I'd also like to put a plug in for North American. They had great customer service and support. Clearly I didn't have a lot of confidence in the area, but I am much more comfortable with all aspects of shop wiring now, enough so that I'm going to revisit some other motor wiring that I have done in the past and set it straight.
Now I can get back to making things in the shop. Many thanks!
-Adair
I'd like to thank everyone who helped me out with this. I'd also like to put a plug in for North American. They had great customer service and support. Clearly I didn't have a lot of confidence in the area, but I am much more comfortable with all aspects of shop wiring now, enough so that I'm going to revisit some other motor wiring that I have done in the past and set it straight.
Now I can get back to making things in the shop. Many thanks!
-Adair
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