Panel design

[Jnelson]

Just to bring back a point from above...

Fuses or breakers make no differnce, the point I was trying to make was install some type of current interuption on as much of your I/O as possible. Trying to troubleshoot a panel with 300 I/O points and 1 fuse off the main control transformer makes everyone happy.

 

[testsubject]

Some panels are built so "tightly" that 99% of the view shows devices while visible wiring accounts for only 1% of the view. This is usually because ductwork is placed so close to termination points.

I've seen wire-leads that extend no more than 1/2" to 3/4" directly from the duct to the termination point... barely enough room for a wire-number label, and just barely big enough for a finger-hold. I know some builders that use a hemostat to insert wires into terminations.

I agree with you on this Terry. With me, it is not about looking pretty and tight though. I am fighting against cost. My boss is getting upset because I am trying to increase the size of our enclosures for the very reasons you stated: giving more room for the installers and maintenance to work in. This drives up the cost of the enclosure.

I am standing strong on this issue but he is fighting me on it. Eventually he will see that I am right and give in.

Bob

 

[LadderLogic]

Oh boy...

I wish I did not have to squeeze too much stuff in my panels. Not least because quite often it is me who has to dive in there in order to reconnect a wire.

I would curse and yell although I know it was my freaking design. But I have to fit in the limited room under the machine base - period. No exceptions.

With that said, I do appreciate a wiring guy who has a feel for the right way of tie-wrapping the wires: not too close, not too far, not too tight, not too loose. Just right to look neat and to be able to pull out a spare easily when necessary...

 

[Eric Nelson]

I've seen wire-leads that extend no more than 1/2" to 3/4" directly from the duct to the termination point... barely enough room for a wire-number label, and just barely big enough for a finger-hold. I know some builders that use a hemostat to insert wires into terminations.

I'll remember to splurge and stick a pair of hemostats in the literature pocket of the next panel I send to you, Terry...

Although I am guilty of some of the items Terry mentions, I DO hear from the guys who maintain my stuff. From those who have had to make modifications, all I've heard is "What a pleasure it is to work on" and "You should see some of the **** other guys build". I'm sure there are those who dislike my panels, they just don't tell me... :nodi:

The assumption, on the part of many designers/builders is that nothing can go wrong... after all, it was their design or their build!

Of course, we all know that "Murphy is alive and well in every human endeavor!"

Of course, this is true, but more often than not, it's the field devices that fail, since they are 'exposed'. I make an extra effort to keep the field devices simple to replace. Manifold mounted valves with integrated coil connections, quick-disconnect cabling on all sensors, etc. makes replacement easy.

beerchug

-Eric

 

[paulB]

drawings

Is anybody knows which standards define wiring diagrams, wiring schematics, and point to point wiring diagrams. What should be depicted on each these documents? What are the differences between these documents?
Thank you.

 

[akreel]

Re: drawings

What should be depicted on each these documents?

As much as possible without becoming unreadable. Plus, if you're going to name an object on a drawing, the label attached to it in the panel should be the same!


Here are some things I've learned about drawings that come in handy:

1. Try to show information in one place. Searching your drawing set, just to change a value or reference can be a pain.

2. Don't be afraid to create new drawings in order to unclutter old ones. Sometimes details deserve their own page. I've also found that one-line diagrams are a better place to make comments on wire gauges than schematics are.

AK

 

[martyh]

2005 NEC

Has anybody looked at the 2005 NEC yet? I was just curious because
on the website:
http://www.nfpa.org/Catalog/product...005SB&src_pid=&link_type=category&src=catalog

It states:
"All-new Article 409 introduces rules for industrial control panels."

I was just curious what this entailed.


Marty

Edit: I found this article that gave a little more detail: http://www.ul.com/tca/spring04/news.html

 

[elevmike]

ASME A17.5 covers elevator control panels so that's what we follow. To be honest, it's the only dedicated control panel spec/code I was aware of. Looking at the UL link, it seems like it's still in a class all by it's self.

Comment: judging from the photos on this forum, most other panels wouldnt meet the critera set by A17.5.

Comment 2. I just recived a sample "screw-less" terminal today from AD. We have a controller vendor who uses these also. Neither me or my field guys are in love with them. The wires go in the top and cover the terminal markings which are mounted on the side, makeing them double hard to see. IMHO I think they make the panel look messy also.. What's the general consensous??

Mike.

 

[Jnelson]

What's the general consensous??

Have Casey post a poll...

 

[Terry Woods]

JNelson said...

"Nothing in the world drives me more crazy than looping wire back and forth multiple times in the wire duct. It makes a huge rats nest of tangled jargon that makes me irritated."

Are you suggesting that I suggested that? I recall saying something like...
"...the standard was to make a double-loop in the wire by wrapping the wire around your thumb twice before making the termination..."

If you interpret that to mean "...looping wire back and forth multiple times..." then... I can only wonder... how fat are your thumbs?

Then JNelson said...

"I would much rather pull in a whole new wire than deal with a mess of wires that someone has pulled out of the wireway twisted, turned, intertwined, ect. The time it takes to install a new wire is worth it to me, rather than pushing the duct cover back on with a 2x4."

Sounds to me like you are contributing to the need for the 2x4... or maybe a 4x4 by this time... no?

Then JNelson said...

"Trying to troubleshoot a panel with 300 I/O points and 1 fuse off the main control transformer makes everyone happy."

You are kidding... aren't you?

If you aren't... you don't really do troubleshooting, do you?

If you use a single fuse for outputs then that fuse has to be sized to carry the maximum load.

That means... for example... if the fuse is sized for 10-amps then that one single output transistor, or that one single 2-amp output relay, that is connected to a shorted load is going to experience... oh..., let's call it "stress". (Can you say "smoke-test" or "contact-fusing"?)

Additionally, if the single fuse blows all you know is that one of your 300 I/O has a problem.

If you are using a brick-type PLC, then, when you finally find that particular I/O point, you might have to replace an entire module!

Yeah... after all that, I can see how one fuse makes everybody happy.

I say... if you aren't using the PLC Outputs to drive opto-isolators, fuse every single PLC Output individually! (Use indicating fuses... the kind that glow.)

Many of the larger PLCs provide a single, replaceable, on-board fuse for various numbers of actual outputs. Again, this fuse must be sized to handle maximum load... 4, or 8, or 16 outputs at a typical load of 1/4 amp each requires 1, 2, or 4-amps (plus margin). If an output is rated at 2-amps... how many times will that output suffer the pains of a blown fuse when that fuse is intended to protect the set of outputs... not just one. A 2-amp output developing 3-amps will not be protected by a 4-amp fuse.

If you are using the PLC Outputs to drive opto-isolators then fuse each opto on the source side (Again, use indicating fuses... the kind that glow.)

That... will keep everybody happy!

The dollars lost in down-time while searching for the culprit of a single blown-fuse scenario will pay for the extra hardware and construction time.

---

Bob,

I feel your pain. Have you considered using some of the Laws of Thermodynamics to justify a larger cabinet?

Each device in your cabinet produces a certain amount of heat. In order to dissapate the heat effectively, without resorting to fans or coolers, the cabinet needs to be of a particular volume.

I don't have the formulas... but I do seem to recall that Tom Jenkins posted them once.

---

Ladderlogic said...

"But I have to fit in the limited room under the machine base - period. No exceptions."

Do you remember, or have you ever heard of, "QUASAR"?

They made the first "MODULAR" TV Chassis. Maybe you could develop a way to "pull that panel" and work with it on a bench. It can't be too big if it is under the machine.

Maybe you could use an interior panel that is somewhat smaller than the box. Something like this...

                +---------------------------------------+

                |                                       |

                |  c   +-------------------------+  c   |

                |  o   |                         |  o   |

                |  n   |                         |  n   |

                |  n   |                         |  n   |

                |  e   |                         |  e   |

                |  c   |                         |  c   |

                |  t   |                         |  t   |

                |  o   |                         |  o   |

                |  r   +-------------------------+  r   |

                |                                       |

                +---------------------------------------+

Terminate your field wiring at the "connectors". Then us a jumper-arrangement (ribbon-cable?) to connect the field terminations to the panel connectors.

When you need to work on the "stuff" you pull the ribbons, turn a few twist-locks and pull out the interior panel.

---

Then, in response to...

Of course, we all know that "Murphy is alive and well in every human endeavor!"

Eric said...

"Of course, this is true, but more often than not, it's the field devices that fail, since they are 'exposed'."

I totally agree that the vast majority of failures occur out in the field. And I agree with your philosophy in that respect. But you miss my point.

You, Eric, and many others, build single purpose systems. From your point of view, and reasonably so, the designs of these systems are essentially fixed... rigid.

OF COURSE, there is no reason for you to design your system for any expansion that the end-user might develop and install.

However, once in the field, in the hands of capable technicians and developers, these systems are subject to changes... that is only one of the Murphy references... as in... yeah, it's great, but what if...

But that is not where I was going. I was talking about maintaining the "innards" of the control panel. I wasn't kidding when I made the reference to wiring as if building circuit-boards. I've seen shops that run wires like violin strings... tight!

That... was my point.

---

paulB asked about...

"...wiring diagrams, wiring schematics, and point to point wiring diagrams..."

Depending on your definition of each of these items, each can be seen to over-lap the other.

If properly annotated, a wiring-diagram can show point-to-point physical-routings, connections, and a schematic, all in one. Of the three, the schematic is the hardest to see.

Again, if properly annotated and expanded, a point-to-point wiring diagram can show routings, connections and schematic, all in one. Again, the schematic might be hardest to see.

Wiring schematics, of course, provide the best view of the schematic. However, this method is the farthest from the actual physical layout (including routing and connection points).

When I do drawings (which I do often), I do a Schematic Drawing, a Routing Drawing and a detailed Point-to-Point Drawing. Each drawing makes references, to one degree or another, to the other drawings.

I believe that a "complete drawing set" includes each of these drawings. Each provides a particular benefit.

And since I'm the poor sot that uses these drawings, I know who to blame when they don't provide what I need.

For LARGE SYSTEMS...
As far as multiple-page drawings, I've found that the German method of coordinating the drawing and the wire-numbers works pretty well. That is, wire-numbers include schematic page number followed by wire number as depicted by particular hard-wire rung number followed by specific wire-number.

The caveat is to start Page-numbers at Page-10.

For example, wire-3 from rung-number-16, on page 14 would be wire number 141603 (that is, Page-14, really page-4, Rung-16, and wire 3.)

Of course the number scheme would have to be tailored to accommodate the maximum number of specific wires on a rung, the maximum number of specific rungs on a page, and the maximum number of pages.

This scheme accommodates 99-pages, 99-rungs-per-page, and 99-wires-per-rung. That should be enough to handle any drawing... even in size 4 font.)

If you find a wire labeled as 141603 you would go to the drawing, turn to page-14 (really page-4), look for rung-16, and find wire-3.

 

[Eric Nelson]

You, Eric, and many others, build single purpose systems. From your point of view, and reasonably so, the designs of these systems are essentially fixed... rigid.

OF COURSE, there is no reason for you to design your system for any expansion that the end-user might develop and install.

However, once in the field, in the hands of capable technicians and developers, these systems are subject to changes... that is only one of the Murphy references... as in... yeah, it's great, but what if...

It's true that our machines are single purpose. We don't have a 'product line' per se. Each machine is custom from the ground up, though my panel designs tend to get re-used for similar machines. I would say that the majority of our machines never get changed, yet I still allow for it.

I usually provide contacts for handshaking to upstream/downstream equipment, even when I'm positive they'll never get used. Same goes for spare I/O. ALL spare I/O extends to the terminal strip, and quite often out to different points on the machine. For instance,

• A few spare I/O to the operator terminal in case and extra PB or pilot lamp winds up being needed in the future
• Fully populating the indicator light stack even when there are only a few lamps on it

Plus there's always a handful of spare wires in each cable or pull, most often landing on a terminal as well. I actually do this mostly for ME, because customers have a tendency to ask for last minute additions, right before the machine ships!...

beerchug

-Eric

P.S. I'm quite certain that cousin John was being facetious with his 1 fuse / 300 I/O remark...

 

[LadderLogic]

Terry:

This is kind of the way I am getting around. The panels are assembled on a bench - with all the cables attached to them. Moreover, lately I have been avoiding any field-wireable cables whatsoever: everything is connectorized through and through. I am particularily fond of Turck's little breakout modules - 10 pico connectors per module let me snap prox cables in easily. Not cheap, but considering time saved on wiring well worth it.

Once the panel build is complete, they are mounted inside the cabinets under the machine base, the cables get unwrapped and pulled through the slots machined in the enclosure walls (well, I am blessed that I don't have to build for dusty, oily or explosive environment). Then it is just plug'em, dress'em and play. Well, at least that's an idea.

Still, once a while I have to do a change or to fix a mistake on a panel that has already been installed in the enclosure. That is when it really hurts.

 

[Rick Densing]

In addition to the normal schematic stuff- we do a connection diagram. All field wired devices are grouped by machine section and labeled with wire numbers.

I remember once talking to a guy from Via about a way of automatically generating these and he had no idea what I was talking about, though I know a lot of other people do it, too.

 

[pstephens]

Wire Color Standards

He everyone,

Not to interrupt the flow of the discussion here, but I’ve got a couple of questions about panel wiring color standards. Most of my experience to date has been with panels that have a 3-phase supply /control transformer, and AC-only PLC’s, so I’ve not encountered many examples of my current project.

1) My understanding is that red is generally used for the hot side in AC control circuits that operate at less than supply voltage. Is this correct? If it is, what would be the convention where the supply voltage is 110V single-phase? Would you use black for the hot side of the control circuit? This seems unnatural.

2) It is also my understanding that blue is used for the ungrounded DC control circuit wiring, such as 24VDC. I’m wondering what color should be used for the DC common. I’ve read that white with a blue stripe is often used, but I’ve not been able to find it anywhere. Should you just use white? This doesn’t seem right, since they are not electrically equivalent. Or are they?

Anyone have any insights to offer?

Paula

 

[Rick Densing]

You are correct in your assumptions.

I would use red even with a 110V supply.

You can get white with blue stripe wire. I'll check with our purchasing agent. I think you can get away with white- but remember in both cases the conductor needs to be grounded. If it is not- use blue. Like you I have a problem with plain white for DC.

Refer to NFPA 79 standard for electrical machinery.