3 phase breaker panel with household input and rotary sending wild leg to L3
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    Default 3 phase breaker panel with household input and rotary sending wild leg to L3

    OK so I got a great deal on a 3 phase Square D QO 200 amp panel. Got a permit for 3 phase and then Duke energy said, its gonna cost me $10,000 to hook up ( 2 more transformers and another power pole). Electrician said should be about $2000, neighbor said he paid $1700 back in 07. When I was done being pissed at the world and wanting to.... that Duke energy engineer, I decided to get started on planning on going Rotary. OK, so I am stuck with this expensive fancy shmancy 3 phase 200 amp panel. I need to know, can I run L1 and L2 to the main breaker of the panel, use those 2 lugs for 120 and 240 VAC household. Place a 240 circuit in there and send a wire all the way to the rotary and then take 1 wire from the wild leg and run that back to L3 of the panel. That way If I am not running something 3 phase no need to run that idler and second of all, I don't need to clutter the wall with another 1 phase panel. Any input guys? Gonna use a 40 HP unit. In the future will add a 20 hp idler to that. Guys think I need a 1/0 copper wire to power up that rotary?

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    Quote Originally Posted by madmachinst View Post
    I need to know, can I run L1 and L2 to the main breaker of the panel, use those 2 lugs for 120 and 240 VAC household. Place a 240 circuit in there and send a wire all the way to the rotary and then take 1 wire from the wild leg and run that back to L3 of the panel.
    Yes, that's exactly what I did back in the day. My house had the main single phase box in the attached garage and a sub in the basement. I stuck my phase convertor and 220-440 transformer down in the basement in the cement block walled well room. Then remotely controlled all of it from two control panels with one in the basement and the other rigged in the garage. (Didn't want to hear the dang things running.) And to your point, the only wires I brought back to the garage was a single wire from the manufactured leg of the phase convertor that filled the 3rd pole of the 3 phase panel, and a small three wire set out of the secondary of the transformer that fed my separate 440 panel in the garage. Ran it like that for over a dozen years. My single phase system remained separate, but that's mainly because the main box was already in the garage/shop. Your idea should work just as well.

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    If you want to draw 220 out of it you need to pay a little attention to where the 2 power wires hook up and make sure the 2 pole 220 breakers will
    land on lugs that have the single phase power. Then dont break out the 3rd cover tab next to the single phase breakers.

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    Here the deal is on new construction the customer only pays part of the build cost, but for any modifications you pay 100% of the cost. I just installed a 120/240VAC 3ph High Leg Delta as a new service and my cost from the power company was right at $3000. Not sure why you think you are stuck with the 3 phase panel you still need the panel and quite frankly if the shop is large enough to need a 40HP rotary you are going to need or least want quite a few circuits. A typical 42 slot panel will only provide 14 3ph circuits so it very easy to max it out. I have a 42 space panel board in my new but rather small shop and its already full and I haven't moved in yet. I'd put in a single phase panel and wire all the lights and single phase outlets to it along with the rotary feeder. Then you don't have to worry about the high or waste spots in the very expensive 3 phase panel.

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    Quote Originally Posted by Rob F. View Post
    If you want to draw 220 out of it you need to pay a little attention to where the 2 power wires hook up and make sure the 2 pole 220 breakers will
    land on lugs that have the single phase power. Then dont break out the 3rd cover tab next to the single phase breakers.
    buddy of mine got me thinking about that. Yes there will be a few spaces skipped because I am not getting true 3 phase.

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    The biggest breaker you can put in a 200 amp QO panel is 100 amp. A 100 amp breaker is not enough to feed a 40HP RPC to capacity and mucho undersize for 60 HP. If you use a breaker to turn the rotary on and off that breaker will fail quickly.

    The 200 amp main is bolted to the copper bus bars. Crimp lugs on a pair of 2/0 wires and BOLT them straight to the bus bars. Run these out of the panel to a fused disconnect. Feed that into your RPC.

    I tried 1/0 copper on my 50HP RPC and it would get hot running heavy loads. I went to 2/0 and use 3 40HP contactors in parallel to start and stop it.

    I have tripped the main 200 amp breaker on mine and clamped it at 177 amps single phase for 20+ minutes. Good enough for me.

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    Quote Originally Posted by madmachinst View Post
    OK so I got a great deal on a 3 phase Square D QO 200 amp panel. Got a permit for 3 phase and then Duke energy said, its gonna cost me $10,000 to hook up ( 2 more transformers and another power pole). Electrician said should be about $2000, neighbor said he paid $1700 back in 07. When I was done being pissed at the world and wanting to.... that Duke energy engineer, I decided to get started on planning on going Rotary. OK, so I am stuck with this expensive fancy shmancy 3 phase 200 amp panel. I need to know, can I run L1 and L2 to the main breaker of the panel, use those 2 lugs for 120 and 240 VAC household. Place a 240 circuit in there and send a wire all the way to the rotary and then take 1 wire from the wild leg and run that back to L3 of the panel. That way If I am not running something 3 phase no need to run that idler and second of all, I don't need to clutter the wall with another 1 phase panel. Any input guys? Gonna use a 40 HP unit. In the future will add a 20 hp idler to that. Guys think I need a 1/0 copper wire to power up that rotary?
    What Garwood said matters.

    Modified 100 A, here, but...

    - I'm at about HALF your "normal" of 40 HP even when.. the third supplementary idler is put onto the line. And one-quarter or less, normal running. Just downsized one planned idler by 2 HP to assure that I stay within bounds.

    - I only have a max load of around 8 to 10 HP.

    Because.. it is a staggered-start / triple-idler array, that is as often:

    - "pick any ONE"

    as it is:

    - "pick any TWO",

    - almost never "pick any THREE", and even then only to improve balance or hard starting, not to be run "sustained" load all that high. (1.5 HP to 8 HP).

    ... so...I can "get away with" the "QO" "plug-on" breakers.

    Better way in your situation is to utilize that panel for medium LOAD distribution?

    But put the "heavy" stuff onto heavier switchgear.

    Fused disconnects? Not my cuppa. I like "common trip". A lot!

    See also Bolt-on "QOB" and Unit-mount "QOU".

    Short-ton of documentation and "FAQ" examples right on the Schneider website, BTW.

    PS: Schneider say the Plug-on QO is good to 100A, 3-P?

    Wellll.. it's true enough, but... we've only been "married" to QO in our family.. and USACE, & Telco projects - since "QO year ONE". 1955. I was but a ten-year-old "apprentice". Dad was already 24 years an Inspector, NACA and USACE.

    So...

    How high is worst-case "ambient" temp were yah run 'em?

    ANY pole-count, lesser is wiser, yah like 'em to live long and not pester.

    Only so much it is reasonable to ask a spring-clip to sustain, hour after hour, day after day, before the Phenolic holding it goes wonky from long-term slow cooking heat, even if the metal is still good for it. EG: "Usually, but not ALWAYS" tough-enough.

    That's why QOB exist, also?



    Damned few failures, many locations, many long years.

    But we've stayed "married" to "QO", easily as much because we din't get greedy as it has been the "QO" being good value-for-money.

    2CW

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    so clearly I need to get a separate disconnect box for the 40 Hp Idler. How many amps you think I need?

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    Quote Originally Posted by madmachinst View Post
    so clearly I need to get a separate disconnect box for the 40 Hp Idler. How many amps you think I need?
    If it is your ONLY idler? Have a look at the nameplate "FLA", then "do the math" (online) for the higher Amperage you'll need off the input feed of just ONE phase where it expected three.

    ISTR my Phase-Craft operated 10 HP Weg wants 55 A out of the single-phase panel, wudda been happy with 30 A if fed utility-mains 3-Phase for use as a motor-not-idler?

    ISTR the 10 HP Phase-Perfect is almost the same. Around 55A single-phase feed for around 29 Amp three-phase out to the load side.

    250 Amp single-phase, 2-pole breaker for your one? Only 200 A?

    Check your actual figure.

    Then-also "fudge upward" for box space, conduit size, and max wiring Ampacity, but breaker it for the lesser actual it will need.

    "Just me" but whether 2 -pole for the 1-P feed, or 3-pole for the 3-P loads, it is never fuses, always "common trip" circuit breakers, and always separate, and NOT fused disconnects.

    I like the lockable "rotary" type for the lighter goods, big old 600-Volt-class Square-D lever-operated for the heavier stuff.

    My only fuses go inside the equipment cabinets - "semiconductor" type, and fast-acting where a DC Drive "might" benefit.

    Any fusing where there is more than one leg, one trips, the other(s) are still a shock-hazard at the least, and potentially a motor going in harm's way running on dropped-phase as well.

    "Common trip" is what it says it is - takes them all out of play when any one - or more - hits bad news.

    CB's are not really "forever" items, nor meant to be convenience switches, but "usually" once the fault is cleared they can simply be reset.

    Fuses yah may have to go-fetch or even ORDER and await replacements. Especially if you've had two hits in a row and just used up yer spares!

    Yah don't have to buy a load center with buss bars to utilize CB's.

    Stand-alones in decent NEMA box, yah use the "unit" mount ones. Square-D's are "QOU Series", for example.

    One presumes you'll have a pony-start rig to deal with as well?

    One of the reasons my rig is multiple idler, staged start, is that I only have 200A service.

    Starting even a 20 HP in one "chunk" would be more grief than I care to be bothered with. The 10 HP or any of the lesser ones - no big deal. Basic remote-control button, cap-start, of any ONE, add the other(s) later, once it is up to speed.

    And I can still "get up to" above 20 HP - or down to 3 HP - if need be.

    Unitary 40 HP idler in one, single, bucket?

    That's a tad more "dramatic" at start-up, ain't it?


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    Quote Originally Posted by thermite View Post
    If it is your ONLY idler? Have a look at the nameplate "FLA", then "do the math" (online) for the higher Amperage you'll need off the input feed of just ONE phase where it expected three.

    ISTR my Phase-Craft operated 10 HP Weg wants 55 A out of the single-phase panel, wudda been happy with 30 A if fed utility-mains 3-Phase for use as a motor-not-idler?

    ISTR the 10 HP Phase-Perfect is almost the same. Around 55A single-phase feed for around 29 Amp three-phase out to the load side.

    250 Amp single-phase, 2-pole breaker for your one? Only 200 A?

    Check your actual figure.

    Then-also "fudge upward" for box space, conduit size, and max wiring Ampacity, but breaker it for the lesser actual it will need.

    "Just me" but whether 2 -pole for the 1-P feed, or 3-pole for the 3-P loads, it is never fuses, always "common trip" circuit breakers, and always separate, and NOT fused disconnects.

    I like the lockable "rotary" type for the lighter goods, big old 600-Volt-class Square-D lever-operated for the heavier stuff.

    My only fuses go inside the equipment cabinets - "semiconductor" type, and fast-acting where a DC Drive "might" benefit.

    Any fusing where there is more than one leg, one trips, the other(s) are still a shock-hazard at the least, and potentially a motor going in harm's way running on dropped-phase as well.

    "Common trip" is what it says it is - takes them all out of play when any one - or more - hits bad news.

    CB's are not really "forever" items, nor meant to be convenience switches, but "usually" once the fault is cleared they can simply be reset.

    Fuses yah may have to go-fetch or even ORDER and await replacements. Especially if you've had two hits in a row and just used up yer spares!

    Yah don't have to buy a load center with buss bars to utilize CB's.

    Stand-alones in decent NEMA box, yah use the "unit" mount ones. Square-D's are "QOU Series", for example.

    One presumes you'll have a pony-start rig to deal with as well?

    One of the reasons my rig is multiple idler, staged start, is that I only have 200A service.

    Starting even a 20 HP in one "chunk" would be more grief than I care to be bothered with. The 10 HP or any of the lesser ones - no big deal. Basic remote-control button, cap-start, of any ONE, add the other(s) later, once it is up to speed.

    And I can still "get up to" above 20 HP - or down to 3 HP - if need be.

    Unitary 40 HP idler in one, single, bucket?

    That's a tad more "dramatic" at start-up, ain't it?

    Lady from american Rotary did some math for me and said I should be able to run the phase converter and say a few smaller items. Did she do her calculations with the phase converter only running on idle? Look at post #6 phase converter power use . The machine itself running off of this others have run it on 80 amp 3 phase sticker on machine says 125 amp. Amperage the rotary takes is really a concern fro the manufacturer not you guys. All I wanted to know is if I needed another panel or not


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