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Old 07-07-2018, 08:55 PM   #1
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First time working with plc , mcc , controll panells motors on production floor ,

I’m just curious the way that the plc system was engineered was from the controll boxes to the plc system we would have to pull around 16-18 control conductors thhn ,s

Their are a lot of controll boxes at least 40 ,

So we had a lot of pulles labeling etc .

Witch a lot of the reals would run short at times and was a pain pulling .
I thought it would be easier if the plans would call for like a 16 pair
Cable tray wire assemble were your pulling like one cable that has many thhn conductors in them so this allows you to buy a master real and do less labeling and cutimg etc .

Also don’t plc system know use Ethernet cable that’s what my Forman said .
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Old 07-07-2018, 09:31 PM   #2
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Honestly it comes down to cost and your labor is peanuts compared to the cost of the hardware. Wire is cheap in standard rolls and nothing in industrial is standard so multi-core never seems to have the right amounts of wires.

On some panels we do use Ethernet but that means one com conduit and one power conduit so we are already looking at one extra conduit.
Plc back plane is about $800, power supply is about $1000, com card is $1800. Thats making a 50 wire pull seem like a cheap option.
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Old 07-07-2018, 09:41 PM   #3
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First off the conduits would have to be larger if tray cable was used. the junction boxes you speek of are they large area type boxes with several terminal points or small boxes that only pick up a couple of devices.
In the process control business it is common to have a 30 or 36 pair tray cable going to a area junction box from a DCS computer . Then several 2 conductor cables going to individual instruments from the area junction box. Most instrumentation wiring is shilded 2 conductor 18.
When using tray cable and area junction boxes they would always have spairs in the multi-pair cable.
If you are just working with field switches and no process control transmitters unshilded control witing in conduit will be fine. if you miss somrthing or add comething they can always pull in a couple of new pairs.

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Old 07-07-2018, 09:56 PM   #4
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To be honest I’m not exactly shure what type of controll panels they are

I know they have relays and switches in them , some controll Silinoids , airboxes , censors , lights etc ,

I was just wondering instead of bringing like 20, 16 awg thhn

Sometimes it’s spec out to just run one cable tray assemble or two

The control panels have terminal blocks that you land your conductors on and then you land same numbers on the plc terminal blocks .

Theirs plenty of room in the enclosures .

Not shure if I have enough info
But this is my first time working with
This equipment just curious .
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Old 07-07-2018, 10:26 PM   #5
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Originally Posted by Switchgear277 View Post
To be honest Iím not exactly shure what type of controll panels they are

I know they have relays and switches in them , some controll Silinoids , airboxes , censors , lights etc ,

I was just wondering instead of bringing like 20, 16 awg thhn

Sometimes itís spec out to just run one cable tray assemble or two

The control panels have terminal blocks that you land your conductors on and then you land same numbers on the plc terminal blocks .

Theirs plenty of room in the enclosures .

Not shure if I have enough info
But this is my first time working with
This equipment just curious .
The plc controls things. In this case the things its controlling are mounted in cabinets outside the mcc. You are adding the wire between them.
It may seem complicated in the beginning because you are looking at the big picture of lots and lots of wires. If you remember its just one wire a lot of times then its not that complicated.

Pulling lots of small gauge wires is a skill. I hope you have some old hand on site that can show you the basics.
Things like shaking the wire to remove the knots rather than trying to pull the knot which just makes a bigger knot.
Gently pulling the wire of the roll rather than snatching on it, etc
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Old 07-08-2018, 12:28 PM   #6
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Often times the decision of whether or not to use what’s called “Fieldbus” (Ethernet, Profibus, DeviceNet, etc.) vs “hard wiring” is made by people who are generally afraid of letting go of hard wired controls in the first place. In other words they have only just become comfortable with the concept of a PLC at all, let alone wiring to and from it using a network that they can’t see working or not. The reality is, hard wiring between I/O racks is proven to be the more expensive option when labor is properly considered, and less reliable when you consider the likelihood of mistakes and the time it takes to find them.

But bean counters often look at it like this: you, the electrician, are going to be employed ANYWAY, whether you are pulling those wires or not, so they don’t actually COUNT your labor and look only at the hardware cost. It’s a false economic premise however because the better way to look at it is that you the electrician could be doing something ELSE that contributes to productivity if you didn’t have to pull all of those wires. And as far as troubleshooting later, a well designed Ethernet network will actually TELL YOU exactly where a problem lies, rather than you having to waste a lot of time eliminating other possibilities to find it.

But unfortunately this is still all too common. So in the mean time one thing you can do as the electrician is to ALWAYS pull at least 20% more conductors in a bundle than you need. That covers 10% unexpected growth and 10% failure of conductors. More would be better of course, but that’s tough to get the cheapskate bean counters to buy off on.
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Old 07-08-2018, 02:28 PM   #7
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These days we mostly just pull an ethernet cable and a 24vdc cable to remote junction boxes that will contain a lot of I/O and put whatever manufacturer or flavor I/O adapters necessary inside. Pretty thankful not to have to mess around with a jillion conductors to every remote junction box.

I favor Ethernet/IP over the other protocols because it's becoming more and more the de facto standard, you can use standard ethernet switches to route traffic, cat 5/6 cable is cheap, and electricians are already familiar with how to route and terminate it properly.
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Old 07-08-2018, 04:30 PM   #8
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Often times the decision of whether or not to use whatís called ďFieldbusĒ (Ethernet, Profibus, DeviceNet, etc.) vs ďhard wiringĒ is made by people who are generally afraid of letting go of hard wired controls in the first place. In other words they have only just become comfortable with the concept of a PLC at all, let alone wiring to and from it using a network that they canít see working or not. The reality is, hard wiring between I/O racks is proven to be the more expensive option when labor is properly considered, and less reliable when you consider the likelihood of mistakes and the time it takes to find them.

But bean counters often look at it like this: you, the electrician, are going to be employed ANYWAY, whether you are pulling those wires or not, so they donít actually COUNT your labor and look only at the hardware cost. Itís a false economic premise however because the better way to look at it is that you the electrician could be doing something ELSE that contributes to productivity if you didnít have to pull all of those wires. And as far as troubleshooting later, a well designed Ethernet network will actually TELL YOU exactly where a problem lies, rather than you having to waste a lot of time eliminating other possibilities to find it.

But unfortunately this is still all too common. So in the mean time one thing you can do as the electrician is to ALWAYS pull at least 20% more conductors in a bundle than you need. That covers 10% unexpected growth and 10% failure of conductors. More would be better of course, but thatís tough to get the cheapskate bean counters to buy off on.
Been to a few places to remove as-i buss networks and install basic hardwired controls due to reliability issues.
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Old 07-08-2018, 06:10 PM   #9
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Been to a few places to remove as-i buss networks and install basic hardwired controls due to reliability issues.
We use a little ASi-i bus where I'm at now, and it's absolutely my least favorite industrial networking solution. I can't say there have ever been any reliability issues. I just hate everything about it.
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Old 07-09-2018, 12:48 PM   #10
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Yes, As-I was a flash in the pan component interface network promoted by Siemens and their wannabes, it was supposed to ease the transition from hard wiring to networking but really, it made things worse for a lot of people when support for it and product compatibility flagged. I did some cool projects with it, but I now regret it because the parts to fix or add to them are already getting scarce. The thing that will eventually displace As-I and other sensor or actuator focused networks like it will be I-O Link, which is based on Ethernet media so the hardware is the same as any other Ethernet based network. But it’s still growing in terms of availability here in the US as mfrs struggle to catch up.

I agree on Ethernet I/P, it has the staying power to be around >10 years from now. Even Siemens, who has HEAVILY promoted and invested in Profibus and ProfiNet, and Schneider who was pushing Modbus TCP/IP Ethernet, have both succumbed to accepting Ethernet I/P as the future and now offer that option on a lot of their new equipment.
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Old 07-09-2018, 05:31 PM   #11
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Yes, As-I was a flash in the pan component interface network promoted by Siemens and their wannabes, it was supposed to ease the transition from hard wiring to networking but really, it made things worse for a lot of people when support for it and product compatibility flagged. I did some cool projects with it, but I now regret it because the parts to fix or add to them are already getting scarce. The thing that will eventually displace As-I and other sensor or actuator focused networks like it will be I-O Link, which is based on Ethernet media so the hardware is the same as any other Ethernet based network. But itís still growing in terms of availability here in the US as mfrs struggle to catch up.

I agree on Ethernet I/P, it has the staying power to be around >10 years from now. Even Siemens, who has HEAVILY promoted and invested in Profibus and ProfiNet, and Schneider who was pushing Modbus TCP/IP Ethernet, have both succumbed to accepting Ethernet I/P as the future and now offer that option on a lot of their new equipment.

I think the over abundance (lack of interchangeability) of different networks caused alot of places to re-think using networks just for the sake of a few wires.
Im dealing with replacing remote i/o. Due to parts being obsolete for plc5, 1336 drives, 1791 control blocks, etc its a very expensive job once you include hardware and programming.
Ethernet I/P is the only network i would consider installing at the moment. Some of hardware does not have that as a option so it will probably be hardwired for now. (at least that allows freedom from being locked to a manufactures network while the original hardware slowly dies out)
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Old 07-09-2018, 09:39 PM   #12
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Modbus has been around and became a de facto standard in spite of Modicon (now Schneider) because your average cider can write driver code in about one day. Itís that simple unlike the others. Every PLC brand supports it. All kinds of goofy hardware supports it if itís more complicated than a limit switch. It just wonít die even when Schneider moved on too.

When it comes to future proofing Modbus is future proof. It looks like Ethernet/IP is becoming the same way. Profound has wide support but not as good as the other two at least in North America. BUT when it comes to say drives the standardized packet format (70 and 71) is so limited the manufacturers begrudgingly support it but nobody programs using it. So I canít use say the generic Ethernet object in an Allen Bradley PLC and substitute say a Square D drive and expect it to just work. And I canít even do this when I upgrade from say an AB PF 40 to a PF 525 or 753 drive. The programming is all drive specific even though say Schneider supports almost an open user defined format on objects 100 and 101. Same problem with Modbus so either way I have to use a bridge to map everything around but it can be done with some pain.

I do drive upgrades all the time. If the drives are hardwired though usually I just move the wires over and sometimes add an isolation relay but thatís it. Very simple. Networking even in the same brand and even in the same product line is a royal pain no matter what.



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Old 07-09-2018, 09:57 PM   #13
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We use a little ASi-i bus where I'm at now, and it's absolutely my least favorite industrial networking solution. I can't say there have ever been any reliability issues. I just hate everything about it.
Sad thing is i really liked as-i especially as a valve interface. with a wonderware screen to show whats talking it was simple to locate a problem in a node or a splitter and with the hand held programmer it was simple to test and program.

Unfortunately it didn't do well outside in the sun and rain especially as 24vdc liked to eat the pins of the connectors, Things improved after we used gel in the connections.
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Old 07-09-2018, 10:13 PM   #14
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what we had a lot of in the motor control panels was plc, asi, relays, vfd's and contactors as they were built off site and installed.
you would see a lot of wire pulled from the conveyors to the panels.
typical for most factories but the downside is so much induced noise and feedback.
connection between plc panel and remote vfd, and low voltage contactors via ethernet and low voltage system would make more sense.
putting in small panels for contactors and vfd may be a pain, but you would be eliminating a majority of the conductors being pulled.
less voltage drop issues, and less induced noise.
and coupled to the fact that the plc /asi control panel would also be a lot smaller footprint.
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