3 phase riddle - home workshop 3ph wiring

[86turbodsl]

Ok, electrical gurus.

Looking for ideas on how to run 3ph in my shop. 40x64, combined wood and metal shop. For obvious reasons, i've decided to place woodworking tools and welders in opposite corners of the shop. The really big power suckers are in the corner right next to the 200A main panel. I also have a 50HP rotary phase converter with a pony start which goes right next to the main panel. The 10HP air compressor is also 3ph and is right next to the phase converter.

I had planned to add a small 3ph breaker panel near the phase converter, and my general plan was to run dedicated breakers for loads which can be on at any time regardless of what is going on in the shop, such as compressor.

Then to save some money on wiring, i would run a "buss" of 10ga three phase around the perimeter of the shop, to run additional loads which are point of use, and would typically be the only load being used by a person at any one time, such as a 5hp radial saw, or a 5hp table saw, or jointer, or whatever.

Each machine would be connected to the buss with it's own fused disconnect to protect that machine from overload. There would also be a breaker protecting the buss lines at the capacity of that line to prevent meltdown.

Anyone see any difficulty in this plan? I think it's similar to the copper buss bars that factories use, but without all the cost. Everything would be in conduit.

Thoughts?

 

[slice]

Your question maybe goes beyond the avg homeowner. Sounds viable but a master sparky would answer the best.

 

[Slowgsr]

is this 3ph 480v ?

(We have 600v in Canada)

Your idea is not to code but would work.

 

[930dreamer]

Can't help, but would like to see some pictures of the 50hp converter. I have a 30hp but don't have it installed, just the small 10hp for now.

 

[Strouty]

Oh, this sounds like FUN! 50 HP is a little undersized if you ask me.

I would run a panel for sure, then just do dedicated circuits for the machines. It is definitely smart to keep the big machines close. I bet you can find some used 3 phase stuff floating around at reasonable prices.

 

[_Dock_]

One thing to keep in mind is that if your running a phase converter from a home shop is that you will be creating 240 volt 3ph not 480v. Make sure your machines have dual voltage motors and that you do your load calcs based off of the nec motor fla at 240 volt. Current requirements will be higher at the lower voltage.

I don't see any major problems with your plan but there are some details that would need to be payed attention to regarding your plan.

 

[86turbodsl]

Strouty,

The problem with dedicated lines for each machine, is I have a LOT of them. And they are all over the place. In the wood area, we have a 5hp RAS, a 5HP table saw, a 10HP planer, a 1HP RAS, a 5HP jointer, and a 5HP shaper. In the OPPOSITE corner, i have a 2HP bridgeport, 1.5HP drill press, and a spot for a lathe. Also a big plasma, and a 3PH BIG mig welder. Future plans include a big dust collector at some point too. And you never know when i'll find a good deal on more vintage industrial iron. I would be looking at a LOT of conduit running around the outside of the shop.

All loads are 240V delta wired.
All motors are wired correctly, most are dual voltage.
I'm pretty solid on how to hook up machines on 3ph, not really very up to code on 3phase building wiring though. I have a suspicion that code wants all machines individual breakers AND disconnect at each machine, but not sure on that. I guess i could call a sparky, but he'll want to do the work then and my bank account probably can't stand industrial quality work at home.

I can wire about anything, but don't always know the codes.

The 50HP was because that was the cheap big idler i found. I really only needed a 30HP or so to start the compressor. The pony was so i didn't brown out the neighborhood.

 

[86turbodsl]

930dreamer, i don't have mine installed yet either. I have a 10HP installed at the moment that runs one machine at a time on an extension cord until i get the shop properly wired. That's why i was asking all these questions. I should really start a shop build thread i suppose.

 

[Norcal]

Set panels near groups of machines so branch circuits can be run from them.

 

[wyliesdiesels]

Definitely do a 3-phase panel.

Remember, the generated third leg is the stinger and is 208v to neutral or ground. Don't try to run any 120v equipment off of it...

I have limited experience with rotary phase converters. Youre most likely gonna need a disconnect on the line side of the converter. As far as wire and breaker size, I think speedy petey or Norcal can best answer that...

Any equipment requires an individual disconnect if the breaker panel is not visible at the machine and more than 50' away...

How large is the pony motor?

Are u planning on hardwiring all the machines that will be on the same branch circuit or will u be using outlets?

Will u be running several of them at once?

is this 3ph 480v ?

(We have 600v in Canada)

Your idea is not to code but would work.

In the US, we have several flavors of 3ph- 120/240v delta, 208Y/120v 'wye', and 480Y/277v 'wye'...

 

[A_Pmech]

What you propose is not a bad idea. I've seen many such setups in industrial buildings, usually using a multi-hole lug on the supply side of they safety switches.

 

[Strouty]

I figured you would chime in with 50HP, anything less than that wouldn't even get your attention. Any compressor updates?

 

[Slowgsr]

240v 3ph panels are not that expensive compared to 480/600 stuff.

Be aware to meet code your equipment will require a starter for the motor load, sized properly, with overloads and a local disconnect. Unless that stuff is on the equipment, or the motors have built in thermal protection.

It will be expensive to do it properly.

Fyi I'm a licensed electrician, and hold a masters. I have been licensed for 11years (minimal amount of time compared to my dad)

Just remember, there's lots of ways to get a job done correctly.

 

[86turbodsl]

Definitely do a 3-phase panel.

Remember, the generated third leg is the stinger and is 208v to neutral or ground. Don't try to run any 120v equipment off of it...

I have limited experience with rotary phase converters. Youre most likely gonna need a disconnect on the line side of the converter. As far as wire and breaker size, I think speedy petey or Norcal can best answer that...

Any equipment requires an individual disconnect if the breaker panel is not visible at the machine and more than 50' away...

How large is the pony motor?

Are u planning on hardwiring all the machines that will be on the same branch circuit or will u be using outlets?

Will u be running several of them at once?

All 3ph equipment gets a disconnect at the machine, regardless of how this gets run. One man shop, i can't see any machines getting used simultaneously. The pony motor is 2hp. cap start. It's connected through a clutch. Nothing gets run off the 3ph other than 3ph motors. Thats why i thought this idea could work good. Using the fitch williams converter plans, and the converter is protected/disconnected at the main panel. I will be hardwiring anything on the 3ph lines. No disconnects. Hubbell plugs get expensive. My machine shop upgrade at work, (i was the industrial engineer) we spent about 17k wiring in 208 and 480V machines. 2 bridgeports, a lathe, a Fadal 4020, shear, plasma table, surface grinder, tig, mig, and bandsaw. Get's expensive real quick.

 

[86turbodsl]

I figured you would chime in with 50HP, anything less than that wouldn't even get your attention. Any compressor updates?

LOL. Probably true. Compressor hasn't moved since i tore it apart. I located rings in Hastings, the big cylinder will get sleeved, high side looks ok. Replacement disc valves, and i'm relocating the tank up on top of pallet rack with a remote drain. The compressor head stays on the floor next to the converter and main panel.

 

[86turbodsl]

Set panels near groups of machines so branch circuits can be run from them.

Ugh. If i do that, i have to locate 2 panels and run large gauge to both of them.

 

[theoldwizard1]

The 10HP air compressor is also 3ph and is right next to the phase converter.
.
.
.
... my general plan was to run dedicated breakers for loads which can be on at any time regardless of what is going on in the shop, such as compressor.

If you can down size the compressor motor to a single phase motor you will save on your monthly electric bill. I can not imagine any "hobby" shop needing that big of a compressor. This is the one load that will likely get the most run time in a month. Any phase converter is less than 100%, rotary phase converter are much worse than electronic phase converters.

If it is not a "hobby" shop, then you should be able to get 3 phase from the POCO.

 

[930dreamer]

930dreamer, i don't have mine installed yet either. I have a 10HP installed at the moment that runs one machine at a time on an extension cord until i get the shop properly wired. That's why i was asking all these questions. I should really start a shop build thread i suppose.

Here's the 30hp idler running;

 

[86turbodsl]

930, if that was running unloaded, the amperage seems high. Has it been balanced?

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[930dreamer]

Running unloaded.

 

[wyliesdiesels]

I think Subpanels is a better way to go than 'bussing' it. It will probably cost u the same as running a bus around the shop with individual disconnects.

Used 3-phase panels in good condition can be had for a good deal!

 

[Steve from Socal]

The amperage into the converter is going to be about 1.73 times the 3 phase amps, NSTAFL, that third leg is not magically created. Are you sure the poco is going to be OK with that? You won't be drawing full current in the idler but, your 200 amp panel may be a bit light for the set up.

I would think about a smaller idler for say the 10 HP and under stuff. You may want to look into an inverter based converter like Phase perfect.
http://www.phaseperfect.com/

Steve

 

[wyliesdiesels]

The FLC for a 50HP motor is 130a so that would be about 225a input minus a little because its idling no load.

 

[86turbodsl]

You guys need to think in terms of energy not current. full load current on a 50hp motor is indeed about 130A per leg, but wattage consumed will not be that. Current on an idling RPC will be the load from connected machines, plus some losses for heat and bearing resistances. Power input to the device still has to follow Joule's law. Multiply by 1.73 to get single phase current. Typically idlers in this range should pull about 40-50amps. A data point for a 20HP idler is about 20A.
I will look into reducing the motor size on the compressor, but the min rpms on that pump is 350, due to being splash lubed. I'm not sure i can go any lower on motor hp to get the lower speed. That pump also was used on 15HP compressors as a data point. Ideally i'd use a VFD, but a VFD that could run that compressor would be $1000 or so.

 

[A_Pmech]

Typically idlers in this range should pull about 40-50amps.

At a very low power factor.

 

[Strouty]

You guys need to think in terms of energy not current. full load current on a 50hp motor is indeed about 130A per leg, but wattage consumed will not be that. Current on an idling RPC will be the load from connected machines, plus some losses for heat and bearing resistances. Power input to the device still has to follow Joule's law. Multiply by 1.73 to get single phase current. Typically idlers in this range should pull about 40-50amps. A data point for a 20HP idler is about 20A.
I will look into reducing the motor size on the compressor, but the min rpms on that pump is 350, due to being splash lubed. I'm not sure i can go any lower on motor hp to get the lower speed. That pump also was used on 15HP compressors as a data point. Ideally i'd use a VFD, but a VFD that could run that compressor would be $1000 or so.

I am switching my compressor over to single phase because I decide it was not worth the effort and power usage of a rotary phase converter and the VFDs that were reasonably priced were still out of my price range. I found single phase motors that fit the bill. I have seen a brand new 15 HP single phase motor in a catalog for about $1,300 and it was made by baldor. I thought that was very reasonable considering the effort it would save. I ended up with a 10 HP single phase, but everything is still in pieces right now.

 

[86turbodsl]

I will need am rpc anyway, but you bring up a good point. We should look at power usage on these things and if it makes sense a single phase motor would be an easy swap. Ive heard 10hp 1ph motors are fussy and unreliable though.

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[InterpreDemon]

86 - You should read your own writing, "You guys need to think in terms of energy not current."

You don't have to change the motor, just change the motor sheave to bring the pump RPM down to 350-400 RPM and the power consumed will drop proportionally and, if you are now running 600-800 RPM, significantly. You can further reduce the power draw by dropping your pressure from 175 to the minimum needed, like 125 or so and add more receiver capacity if needed. When running an RPC, which ain't that efficient anyway, you might as well stretch out the duty cycle on your compressor, which by running more continuously at lower power will reduce motor starting issues elsewhere in the shop... in fact it may even contribute some VARs to your grid. Between the sheave and lower pressure I bet you can cut your current in half, at the very least get the motor load down to 75%. See if you can find the performance graphs for the motor, if a Baldor they are on-line, and that will show you the target you are aiming for.

All that will happen if you put a 1PH 10hp motor on it without changing the sheave is you will have an overloaded 10hp motor, whereas if you just change the sheave you will have a very happy 3ph motor loafing along.

 

[86turbodsl]

Interpredemon,

You are correct, i can lower current by slowing the motor down. I think i mentioned further up that i think the pump is running pretty slow already, so that avenue may be out. I had already planned to lower cut out to about 125, and see what duty cycle looked like. The accepted method to drop compressor HP is to downspeed. What i could get out of that is unknown. I don't believe it's likely i can find the motor curve. It's a 1960's motor. Not a baldor or anything modern. It's probably not inverter duty rated either. I don't agree however i would have an overloaded 10hp single phase motor if i used one. The compressor is already rated at 10hp. HP is HP, no matter how you get there. I'll look at the current with a clamp on ammeter when i get it fired up.

 

[Steve from Socal]

Out of curiosity is your meter a "smart" meter or analog? I have to think the X-former to your house and others not going to have the KVA for summer loads with a 50 HP idler.

If the compressor is your only hard starting load and, everything else 5HP and under I really wonder about the choice in RPC idler. Why won't a 10 or 15HP idler suffice? All the wiring and devices for an RPC that size are cheap as dirt on ebay.

Running home brewed buss bars is another head scratcher? Why? Wire is not expensive in comparison to copper.

Steve

 

[InterpreDemon]

86 - I'm not talking about slowing down the motor, only the pump, which is the device that consumes the power and establishes demand based upon the combination of RPM and pressure. Slowing down the motor gets you nothing but a less efficient, hotter running motor.

Without graphs on the motor, you can go about it another way. First determine the sheave/rpm ratio between the motor and the pump, then assuming the motor was properly sized originally and is running at rated power, measure the current and calculate the real power in the present configuration. If the current is in-line with the nameplate FLA data (assuming you still have a legible nameplate) at 175psi, which it should be for any commercial grade constant duty compressor, you can assume it is running at about 1725 RPM and calculate your pump RPM from the ratio determined earlier (or measure it directly if you have a tach). If it is drawing more than 100% FLA, find the reduced pressure at which it is at the proper FLA, which in any event should be your cut-off without a sheave change... unless you have high current regardless load and a possible power factor correction issue too complex to deal with in this post. In any event I'm betting that if the compressor is as originally configured and, considering it came from an era when they designed such equipment as an investment instead of a source of replacement/repair revenue, it will probably be running at rated power or less due to wear in the pump, and the pump RPM will be somewhere between or above 500-600, meaning you will be able to cut it down by at least a third with a smaller motor sheave and, with lower pressure easily get down to 10hp or lower.

 

[theoldwizard1]

We should look at power usage on these things and if it makes sense a single phase motor would be an easy swap. Ive heard 10hp 1ph motors are fussy and unreliable though.

Buy a new Baldor. $1,000 +/-

If you old motor is in decent shape, you should get about $500 for it.

 

[theoldwizard1]

... just change the motor sheave to bring the pump RPM down to 350-400 RPM and the power consumed will drop proportionally ...

If he does that, he can use a 7.5 hp single phase.

 

[InterpreDemon]

That's true, but he is going to be running that big RPC anyway, so why not just buy a new sheave and keep what he's got... a simple, reliable motor without capacitors or centrifugal switches to worry about. As I said before, that big old compressor with doubtless plenty of inertia might actually help start other motor loads when it is running.

 

[Strouty]

Is the compressor the biggest load and motor? Or is there something bigger? I agree 50 is a big RPC, but it is cool.

 

[86turbodsl]

Strouty, the rpc was sized while on the practical machinist forum. Rule of thumb is 3x for a compressor. The 50hp idler was found local for really cheap. I never saw a 30hp locally for less than megabux.

I will reply to the others in a while. Cooking dinner...

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[Strouty]

I keep forgetting to ask, what is your 86 diesel?

 

[86turbodsl]

Out of curiosity is your meter a "smart" meter or analog? I have to think the X-former to your house and others not going to have the KVA for summer loads with a 50 HP idler.

If the compressor is your only hard starting load and, everything else 5HP and under I really wonder about the choice in RPC idler. Why won't a 10 or 15HP idler suffice? All the wiring and devices for an RPC that size are cheap as dirt on ebay.

Running home brewed buss bars is another head scratcher? Why? Wire is not expensive in comparison to copper.

Steve

Steve,

There's a story here. Dad worked for the power company as an engineer. He got me an internship when i was in college for engineering. I ended up doing engineering special projects in the area. Fast forward almost 15 years, i started building the house we're in now. Called for service, and the engineer showing up knew me. Knew my dad, etc. It was like a reunion. I told her i was running "big motors" out in the shop. She smiled, said ok, we go on with life, service gets installed. Finish building the house, and one day a service truck shows up. Yanks the 10KVA transformer off the pole and puts in a 50kva. It's a giant can hanging off the pole. I'm the only guy on it. I'm good. It pays to have connections. And i have 400A service to the house. 200A to the shop.

The compressor is the big load. For now. I have thought about home businesses though and one thought was a 15HP CNC mill. So i'm a little oversized. Maybe.

The original question wasn't about homemade buss bars, it was about running wire around the outside of the shop used "AS" a buss bar. It was more the idea. Not planning any copper bars. THHN in conduit.

 

[86turbodsl]

86 - I'm not talking about slowing down the motor, only the pump, which is the device that consumes the power and establishes demand based upon the combination of RPM and pressure. Slowing down the motor gets you nothing but a less efficient, hotter running motor.

Without graphs on the motor, you can go about it another way. First determine the sheave/rpm ratio between the motor and the pump, then assuming the motor was properly sized originally and is running at rated power, measure the current and calculate the real power in the present configuration. If the current is in-line with the nameplate FLA data (assuming you still have a legible nameplate) at 175psi, which it should be for any commercial grade constant duty compressor, you can assume it is running at about 1725 RPM and calculate your pump RPM from the ratio determined earlier (or measure it directly if you have a tach). If it is drawing more than 100% FLA, find the reduced pressure at which it is at the proper FLA, which in any event should be your cut-off without a sheave change... unless you have high current regardless load and a possible power factor correction issue too complex to deal with in this post. In any event I'm betting that if the compressor is as originally configured and, considering it came from an era when they designed such equipment as an investment instead of a source of replacement/repair revenue, it will probably be running at rated power or less due to wear in the pump, and the pump RPM will be somewhere between or above 500-600, meaning you will be able to cut it down by at least a third with a smaller motor sheave and, with lower pressure easily get down to 10hp or lower.

I miss-spoke. I meant slow the pump down. Not the motor. I understand the concept. The original motor is 1750ish rpm. The pump is getting rebuilt. It will be as hard to start as ever, minus the drop on psi. As i said, i plan to drop to about 125 and evaluate duty cycle. I will be doing some significant sandblasting at times. Dad has a couple of big 2 stages and his runs constantly sandblasting. I bumped my compressor up a bit to avoid his issues.

 

[86turbodsl]

I keep forgetting to ask, what is your 86 diesel?

My 1986 F250. Love that thing. Reliable as the sun.
Planning to upgrade eventually, but probably put the 86 sheetmetal on the new one just cause i love the look so much.