Panel Building Help

I am building a small control panel and need advice. I am looking at using one of the breakers in the link below

http://literature.rockwellautomation.com/idc/groups/literature/documents/td/140u-td004_-en-p.pdf

The 125 amp frame is the smallest I can get that uses cable operated handle which I want and already have the panel for so we don't have to buy it. The bucket feeding this circuit is a 50 amp breaker so is this ok ?

The control panel will feed a drive and plc in the cabinet and will go out and feed another small control panel. All added together it will not be much over 36 amps so the 50 amp bucket will work but is the 125 amp breaker ok? My wire does not need to be 125 amp size so what can we do?

I had plan on getting the breaker that has 2 lugs one to feed the cabinet and the other to feed out to the second cabinet.

Tim Ganz said:

I had plan on getting the breaker that has 2 lugs one to feed the cabinet and the other to feed out to the second cabinet.

Click to expand...

Or would a seperate distribution block be better?

If you are feeding your panel out of a 50 Amp bucket the protection there should be rated to match the downstream cable. You don't have to have a breaker on your panel, a switch will do also followed by a fuse or breaker to protect each circuit following i.e. one to match the drive and perhaps a 10Amp one for the PLC requirements and another 10 Amp feed going to the other panel.

The short answer is the 125 Amp breaker is ok on a 50 Amp circuit provided it's linited to the cable rating further back.

I want to do this right and the 50 amp bucket will have a breaker for 50 amps which is factory installed in the bucket but we already have the 125 amp breaker in stock I just need to get the cable and operator for it so I figured I would use it.

But a knife of fused disconnect would be ok also correct?

Now that it is determioned that the 125 amp breaker downstream of the 50 amp bucket is ok would it be a industry no-no? I don't want to do something foolish I just thought I would utilize what we already have if possible.

This 125amp breaker is the smallest thing AB that is cable operated. We try not to use the rotary type at all here as my boss hates them.

Will doing it as I have planned harm anything as far as arc flash ratings?

Nothing stopping you from using that breaker as a "disconnect" means only. If the upstream protection is 50 amps then fuse the panel at 50 amps after the "disconnect device" not breaker in this case! Of course it is not good practice, but the primary thing you need to do is protect the cable between the feeder and panel. You could also size the feeder cable between the bucket and panel for 125 amps +25% but the cost of that would be stupid vs putting in a 50 amp fuse block after the breaker and clearly identifying the breaker is solely a disconnect means.

In reality that breaker is way too much money and would be poor practice, put a disconnect switch with a fuse block in your panel to protect the cable, size the feeder cable to 60 amp, no choice 50 or 60 amps is #6 AWG depending on length. Fuse the panel @ 60 amp after the knife switch to protect the cable, but it will trip the 50 Amp feeder bucket in a true fault so you just have to do a reset that rather than replace the fuses.

Not sure what that 125 amp breaker cost but would guess close to $1,000? We have been using Bussmann CCP units. These have fuses / disconnect and you can get an accessory cable actuator. Looked at a bill of material on a recent project. the following parts: CCP-3-60-CF (CCP unit), CCPHM-F4-6CF13R (4’ Cable Actuator) TCF 60RN (fuses). Cost about $460. Just a thought.
Link to Buss website

http://www.cooperindustries.com/con...sconnects/ccp-family/cubefuse_up_to_100a.html

BTW: I am not a sales person and have no connection to Buss. just a satisfied customer.

Hi Tim,

Sorry mate you need to RTFM


too easy
the setting range is well within you goal current

Don't confuse the frame size of the breaker with the breaker rating. You can get a 50 amp breaker that is the same frame size but rated for only 50A.

Also you can find Cutler Hammer cable operated breaker disconnects at Automationdirect.com for substantially less money. If if you add an extra B to your AB (ABB) you can buy very good and IMO, more robust cable operated breaker disconnects, also for less money.

TConnolly said:

Don't confuse the frame size of the breaker with the breaker rating. You can get a 50 amp breaker that is the same frame size but rated for only 50A.

Click to expand...

Yes, and you need to think about coordination in the even of a fault which breaker do you want to trip first? You can get a 15a breaker in that frame size or modify the cable operator bracket to fit about any MCCB with a lever on the front. At least in Okieland that's still legal.

TConnolly said:

Also you can find Cutler Hammer cable operated breaker disconnects at Automationdirect.com for substantially less money. If if you add an extra B to your AB (ABB) you can buy very good and IMO, more robust cable operated breaker disconnects, also for less money.

Click to expand...

I agree except for the stainless steel washdown type of operators, too much black iron inside the square d brand i have been replacing, although NEMA 4x rated, they are not repairable when any major linkage rusts away.

In dry locations and for that small frame size theirs and cutler hammers are simpler to put together and work fine.

It took me four hours to figure out how to combine the bits and pieces for the 600amp stainless a/b disconnect with cable operator I recently had to install. It has a some plated parts, mainly the spring and cable glands, but they are accessible and easy to replace every few years, but all the leverage handle and frame parts are stainless.

I thought 125 amp was the lowest I could buy becuase that what the AB config tool said below (the big link / very bottom of post).

In the manuals it looks like different sizes for the H frame. Also according to another document http://www.ab.com/en/epub/catalogs/12768/229240/229254/305540/3087073/ the part number the configurator gave me is for a molded cases switch rated at 125 amp. this is located at the bottom of the page in the link above. Is the molded cases switch just that a switch but not really a breaker?

Also in the link above why are some of the 1 pole and 2 pole breakers fixed on the thermal trip and the magnetic trip so much higher that the current rating of the breaker? like a 15 amp 2 pole breaker has a fixed thermal trip and a magnetic trip of 500 amps?

I guess i need someone to help me understand how the therma; and magnetic trip are so different? I thought magnetic trip was like a dead short and thermal is gradual up to the rating like 15 amps on a 15 amp breaker?

Also why do they a have a breaking capicty at 50Hz and a Interrupt rating at 60 Hz

I am really having a tough time understanding this chart and would really be appreciative of some detailed help with it.

To not what OkiePC said what would be the best way for me to coordinate this so the panel breaker would trip before the MCC? The breaker in the MCC bucket will be 50 amps? do I need to buy a breaker with a lower amps? Will that handle coordination?




Rated
Current
In [A] Thermal Trip [A]
Ir = In (Fixed) Magnetic Trip [A]
Im = 10 x InBreaking Capacity (50 Hz)
Icu /Ics [kA] Interrupting Rating (60 Hz)
[kA] Cat. No. 220…240V 380…415V 500V 690V 240V 480V 600/347V 15 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C1520 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C2025 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C2530 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C3035 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C3540 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C4045 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C4550 Fixed 500 85 43 40 30 — — — — 85 35 22 140U-H3C2-C5060 Fixed 600 85 43 40 30 — — — — 85 35 22 140U-H3C2-C6070 Fixed 700 85 43 40 30 — — — — 85 35 22 140U-H3C2-C7080 Fixed 800 85 43 40 30 — — — — 85 35 22 140U-H3C2-C8090 Fixed 900 85 43 40 30 — — — — 85 35 22 140U-H3C2-C90100 Fixed 1000 85 43 40 30 — — — — 85 35 22 140U-H3C2-D10110 Fixed 1100 85 43 40 30 — — — — 85 35 22 140U-H3C2-D11125 Fixed 1250 85 43 40 30 — — — — 85 35 22 140U-H3C2-D12



Product Number: 140U-H6S3-D12
Link: http://raise.rockwellautomation.com/raconfig/validate.asp?pid=140U-H6S3-D12
Photo: http://raise.rockwellautomation.com/raconfig/rtcache/jpg/140uhfrm.jpg
Quantity: 1
Description: Molded Case Switch, H-Frame (up to 125A), 60...69 kA

Done a lot of reading and I still don't understand where you would use a pure magnetic breaker? I guess I need thermal magnetic.

Is the molded case switch not a breaker? The description leads you think it's not but what is is missing that would make it a switch and not a breaker?

Tim Ganz said:

Done a lot of reading and I still don't understand where you would use a pure magnetic breaker? I guess I need thermal magnetic.

Is the molded case switch not a breaker? The description leads you think it's not but what is is missing that would make it a switch and not a breaker?

Click to expand...

in a power feed system you may have several 'tapoff' buss bars of different currents
these tapoffs do not use thermal overload only magnetic.
Also
in some cases a magnetic trip may not be wanted with an extreemly high stall current.