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Forum topic by SweetTea posted 06-08-2019 02:29 PM 729 views 0 times favorited 45 replies Add to Favorites Watch
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SweetTea

430 posts in 1055 days


06-08-2019 02:29 PM

Need some help on adding a RPC to my shop. I will be picking up a used 25hp RPC that will power 5 machines in my shop. None of the machines will be powered at the same time. I have a 10HP wide belt, a 7.5hp table saw, a 10HP dust collector, a 5HP shaper and a 1hp feeder. I haven’t checked out the RPC yet because I don’t have it in front of me, but I was wondering if I should get a separate box with breakers and wire each machine to the box then run one circuit from the box to the RPC? I was planning to run 2 gauge wire from the main panel to the RPC and use the same wire possibly from the RPC to the box that I have the machines wired to. Would that work or is there a better way of doing this?

Could I use 12/3 romex for the 5HP shaper and feeder, then 6/3 for the 10HP sander and the 10HP dust collector and then 10/3 for the 7.5hp table saw?

Any help would be great.


45 replies so far

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ibewjon

604 posts in 3188 days


#1 posted 06-08-2019 04:29 PM

You don’t list voltage, I am guessing you have 240. Yes for the panel for the output of the rpc , each motor needs the proper breaker. 12 ok for the 5 hp. 10 ok for the 7.5. 8 good for the 10. I hope you don’t plan to use Romex in place of cord, and cord would be 12/4 or 20/4 because the ground is counted as a conductor, where Romex is 12/3 w/ ground. Romex is not allowed by NEC for exposed usage, and dangerous because romex is easily damaged and not flexible. And there will be 2 machines powered at once, so start the DC first, then a tool. Then the feeder. So actually 3 machines.

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SweetTea

430 posts in 1055 days


#2 posted 06-08-2019 04:50 PM


You don t list voltage, I am guessing you have 240. Yes for the panel for the output of the rpc , each motor needs the proper breaker. 12 ok for the 5 hp. 10 ok for the 7.5. 8 good for the 10. I hope you don t plan to use Romex in place of cord, and cord would be 12/4 or 20/4 because the ground is counted as a conductor, where Romex is 12/3 w/ ground. Romex is not allowed by NEC for exposed usage, and dangerous because romex is easily damaged and not flexible. And there will be 2 machines powered at once, so start the DC first, then a tool. Then the feeder. So actually 3 machines.

- ibewjon

Ok thanks for the reply. I wasn’t planning to use romex, but rather 12/3 and 10/3 and 8/3 ect. That has three wires and a ground and it will be in conduit. I will have 240 out of the breaker box and into the RPC. So you are saying that I can have a box on the output of the RPC with a breaker for each machine and the appropriate sized wire going from the box to the machines? What kind of box should I use? A standard 3 phase breaker box with the appropriate 3 phase breakers? Never dealt with 3 phase equipment. The 10HP dust collector is 25amps on 240v so that would get a 30amp breaker and the same for the sander. I would use conduited 8/3 wire going from the 3 phase box on the output of the RPC to the machines. The table saw is 17 amps at 240v so I would use a 20amp breaker and 10/3 conduited wire. Then so on. Does this sound reasonable? Any suggestions on specific 3 phase breaker boxes for this setup? It would need to have at least 10 spaces. Also, what sized wire should I use from the RPC to the main panel? I was thinking 2 gauge copper with a 70amp breaker as it is a 25hp but i don’t have the specs in front of me so I will have to double check.

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ibewjon

604 posts in 3188 days


#3 posted 06-08-2019 05:06 PM

Square D is the only brand I will use. QO type breakers. You will need breakers x 3 = spaces and spares for the future. I would get a 30 circut with a main breaker. Main depends on output of rpc. I have not done one in years since vfd’s came out. What is output amps of rpc? And I would have starters with overload protection on each motor if you do not. Have you priced vfd’s compared to rpc?

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SweetTea

430 posts in 1055 days


#4 posted 06-09-2019 12:03 AM



Square D is the only brand I will use. QO type breakers. You will need breakers x 3 = spaces and spares for the future. I would get a 30 circut with a main breaker. Main depends on output of rpc. I have not done one in years since vfd s came out. What is output amps of rpc? And I would have starters with overload protection on each motor if you do not. Have you priced vfd s compared to rpc?

- ibewjon

VFD’s would be very expensive. There is a guy in Canada that makes custom VFD’s at good prices but it’s still too high compared to the cost of a used RPC. I think he quoted me $800 for a VFD for my sander and $185 for the feed motor with $80 and $60 shipping and he said they have to be shipped separate. I would imagine my dust collector would be $800 + $80 as well. My table saw VFD was $500 + $60 and my shaper is $250 + $60 and feeder would be $185 + $60.

The RPC that I am buying is $500 so it would be much more economical. Planing on getting a 30 space Square D 3 phase panel which is $275 and each 30 amp 3 pole breaker is like $175 and the 20amp 3 pole breakers are $75 each. The wire is not going to be too bad as I have a buddy that gets 20% off at my local electricians supply house. I will be using conduited wire.

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SweetTea

430 posts in 1055 days


#5 posted 06-09-2019 12:10 AM

My 10HP wide belt sander and 10HP dust collector each list 25amps at 240v which is what they will be wired at, so would a 30amp breaker be ok or should I go with a larger breaker?

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ibewjon

604 posts in 3188 days


#6 posted 06-09-2019 12:57 AM

Do you have magnetic starters with overload protection on each tool? How do you plan to turn each tool on and off?

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SweetTea

430 posts in 1055 days


#7 posted 06-09-2019 01:07 AM



Do you have magnetic starters with overload protection on each tool? How do you plan to turn each tool on and off?

- ibewjon

I have them on my table saw, and shaper. Would need to purchase new ones for the dust collector, and wide belt sander. I must admit I don’t really see their purpose from a functional standpoint. If there is a 3 phase panel with independent breakers connected to each machine and then the panel to the RPC, wouldn’t the factory on off switch be fine?

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ibewjon

604 posts in 3188 days


#8 posted 06-09-2019 02:58 AM

What type of switches? Are the original switches magnetic with overload protection? The overload heaters in each phase in the starter protect the motor. The overload heaters are sized closer to the actual amperage draw of the motor, protecting the motor, but also the wiring because the breaker is sized large enough not to trip on startup current.After being an industrial electrician for over 40 years, and electricity being dangerous, I only do things the safe way. Safety is not always cheap, but I am not getting hurt, and will not advise anyone to take any shortcuts. The vfd will replace a starter, so they are not as expensive as they look. Take out the panel fed by the rpc, and there is more savings.

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SweetTea

430 posts in 1055 days


#9 posted 06-09-2019 10:32 AM



What type of switches? Are the original switches magnetic with overload protection? The overload heaters in each phase in the starter protect the motor. The overload heaters are sized closer to the actual amperage draw of the motor, protecting the motor, but also the wiring because the breaker is sized large enough not to trip on startup current.After being an industrial electrician for over 40 years, and electricity being dangerous, I only do things the safe way. Safety is not always cheap, but I am not getting hurt, and will not advise anyone to take any shortcuts. The vfd will replace a starter, so they are not as expensive as they look. Take out the panel fed by the rpc, and there is more savings.

- ibewjon

Any idea on what size breaker I should run for my wide belt sander and dust collector? They each list 25amps at 240v so I was thinking 30amp breakers and 8 gauge conduited wire. Would that be ok?

Also, what size and type of wire should I get for wiring the RPC to the main panel and then the RPC to the 3 phase subsequent panel that will feed the machines?

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ibewjon

604 posts in 3188 days


#10 posted 06-09-2019 02:45 PM

What is the output of the rpc?

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Greg66

30 posts in 53 days


#11 posted 06-09-2019 04:45 PM

In many states you can only legally do your own work on your primary residence that you own. If you have insurance on this shop they can deny any claim if any electrical work is done without a permit and inspection if it’s required by the local regulations. This varies widely across the country. I would encourage you to look into the legal requirements before doing any work to make sure you are not jeopardizing your insurance coverage.

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therealSteveN

2876 posts in 969 days


#12 posted 06-09-2019 05:29 PM



In many states you can only legally do your own work on your primary residence that you own. If you have insurance on this shop they can deny any claim if any electrical work is done without a permit and inspection if it’s required by the local regulations. This varies widely across the country. I would encourage you to look into the legal requirements before doing any work to make sure you are not jeopardizing your insurance coverage.

- Greg66

Goes with my default “electrical questions” answer of asking a Licensed electrician, and then verifying with your insurance agent. I also point out, that in most cases you have 3 phase at the road. Most power companies will do the install, and it can be pricey, then you will be on a secondary service with a monthly meter charge. BUT, big “but” your insurance will be good, at least on that electrical hook up.

-- Think safe, be safe

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ibewjon

604 posts in 3188 days


#13 posted 06-09-2019 06:54 PM

Totally disagree with ” three phase at the road”. Rarely in a residential area. And yes, always get an experienced electrician. Many states have no license. That is why I only post information from a reliable source, like the NEC. And few power companies do the install. They may send a contractor they work with.

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SweetTea

430 posts in 1055 days


#14 posted 06-09-2019 07:35 PM

No inspector in my area as this is the very rural south. Plus this is my shop and I am not worried about the insurance. I am not a professional electrician but I am confident that my work won’t cause any fires. My buddy that is a licensed electrician will be assisting. I am just trying to gain a better understanding of what all I will need and how to implement it.

Don’t know the output of the RPC as I don’t have it in front of me.

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ibewjon

604 posts in 3188 days


#15 posted 06-09-2019 08:04 PM

Output determines wire size

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