Wiring Practices in Panels

[lgray66]

Hello,
I recently had to design and build panels for a piece of equipment we built. The machine did not allow much room for controls, so I wired the remote I/O wires directly to the field I/O modules (Terminator I/O from Automation Direct), no terminal blocks. I also didn't have room for wireways, so I bundled the wires as neat as I could, and intended to do a final cleanup after installation. Due to the proximity of AC and DC I used shielded cable on all signal wires.
When the customer received the equipment, they complained about poor workmanship in the panel, and are insisting it be replaced. They also are requesting we replace the Automation Direct components with Allen Bradley. They did not provide us with specifications, and did not request AB when the machine was ordered.
Since I don't have access to UL 508A, or NFPA 79 (although I've put in three requests), my questions are: Are the panels as bad as the customer says? They claim all AC and DC must be run perpendicular to each other, is this the case? Do I have to use terminal blocks and wireways? Are there any reliability issues with Automation Direct components?

Thanks,
Larry

 

[hacksaw]

Ouch!

NFPA and UL are standards organization. you can buy a set of standards, but you'll not likely get any interpretations.

Discount PLC will give most people heart burn simply because they do not guarantee that they still be providing spare parts ten years from now.

Panel wiring is always a grey area. That is why layout drawings from the purchaser or at least signed-off or approved by him is essential. I know of no code that governs panel wiring and have seen some really scary (high risk) designs.

Generally you can expect to find voltages of all levels and types within a panel.

Ultimately, you have a contract dispute with between a customer and a panel shop. It is not the first.

Either he directed you to design the panel or he had you to build it to his specification.

To the extent that you can check off compliance with the purchase contract you are clear.

The supply of the plc is a grade of product issue in the eyes of the designer.

good luck,

 

[pablo02]

If the customer did not specify AB, then the selection is yours -- we have used the same PLC's you provided (couldn't justify the expense for AB) overall, they have worked out admirably... the engineer who did the work indicated that he uses them for all his jobs except when the customer specifies others -- he indicated that you needed to put a good surge suppressor on the front end, but other than that they have been very reliable...

Other than than that, I can only echo 'hacksaw'...

 

[artym]

I think Hacksaw has summed it up:

Unless the customer required that it be built using certain components or wiring practice, you are OK unless you did something really poorly, or unsafe.

(looks do count a little bit!)

I had some trouble with a senior engineer when I first started about the wiring practice, size and standards for a panel. I built the proto on a 2 sq ft, panel and bought a half dozen 4 sq ft panels & enclosures for the deliverables.
He bought huge 20 sq ft panels & enclosures to lay them out to the JIC standards!

(A lot of industrial controls are/were built to (or at least close to) JIC standards; Joint Industrial Council.

They required that every line coming to/from a panel go thru a term. block, & lots of other stuff. It's required by some customers, and very good in some applications.

I suspect that your customer expected something that looked like an old JIC panel, but I've seen a lot of well- built newer stuff that doesn't look like that.

On the plcs, I got some registered letters a few years back regarding Automation Direct PLC bugs, but that may just mean they are acting responsibly and forthrightly.

Some customers require AB ONLY for future support as hacksaw noted, and standardizing.

Possibly your customer is just trying to establish a position to haggle price. That would be pretty sleazy, but it happens.

Again, if he wanted specific components or practices, it should have been BEFOREHAND.

 

[marshg]

It's a good idea to use runway (panduit) for just about every panel. That away you can cover up wiring and it looks better. We have used it in every panel we've built.

I would reccommend you using terminal blocks also. That would make the panel look better as well. You won't have 5 and 6 wires hanging off the power or common of a power supply. This may save problems later on with loose wires. You can get the screw type or the clamp type. I would reccommend spending the extra money (especially on a big project) to get the clamp type. They are much easier to wire (all you have to do is stick your screw driver in one slot and the wire in the other!). You could possibly save a lot of time during install and startup (which may justify the extra cost).

Running Wire:
- You need to seperate all AC and all DC.
- Sometimes this is not possible. In these circumstances, you should NOT run them in parallel.
- You should use a program at the beginning of your project, such as AutoCad, to layout your panel to the exact dimensions and place your components. Remember to keep AC and DC seperate. This will also allow you to size you panel appropriately. I've had to go up a couple of panel sizes bigger than what I thought. This saved a lot time and heartache.
- Go out of your way to make sure that you keep AC and analog DC signals seperate. You will run into problems if you cross them.
- Before you even start wiring, it is a good idea to layout all of your components on the panel like you have in your drawing. This will help you visualize your wire runs and may prevent a mistake made during your original layout concept.
btw...I really don't think that running a few 24VDC or a steady DC wires w/ some AC wires will hurt. Its that we try to avoid any potential problems.

As far as chosing which manufacturer's components to install, you really need to have that specified in your quote. If they don't specify, you should make it known to the customer what their getting. If they approve and then go back, you will have documentation. This will allow you to justify charing them above the specified quote for the new components and engineering hours (this should be included in you quote also). Beware, if you charge them, the customer may decide to get rid of you and hire someone else. If this customer is giving you tons of business, then you may want to consider negotiating with them and eating part or all of the cost. Otherwise, I would charge them. As a rule of thumb that we keep at our company is to use AB when the customer doesn't specify.

 

[jbartos]

Suggestion: If the Customer is used to certain quality, material manufacturers, inventory items, etc. it will try to procure it one way or other. Therefore, it is a good idea to do a little leg work before the actual design and building of panels is performed. Surf for panels specification and pictures on internet might also help.

 

[jbartos]

Suggestion: A suitable software for a panel design might be considered. E.g., visit

http://www.elecdes.com/elecdes.htm

http://www.cim-team.com/e3_panel_c.html

http://www.cadtek.com/e3/e3seriest.asp

etc. for info
Also, visit

http://www.cleanrivers-pdx.org/tech...Standards Manual/Adobe Acrobat/App_D_2003.pdf

http://www.waukeshaelectric.com/ref_library/pdf/service/Worldbox.pdf

etc. for more info

 

[afterhrs]

lgray 66,
for the most part I agree with Marshg.

It would be easy to say that I would not have built the panel without the proper guidelines, however, I think we have all been victims of the clashes between business and ethics at one time or another. In the end, it is up to
to everyone to put the company in the best light, but it has to start at the top and trickle down. LEADERSHIP BY EXAMPLE!!!!!
If you have requested the proper documentation to do a job and have not recieved before you were directed to proceed, then I would hold the company responsible for not providing you the proper industry standards to do the job.
As far as the panel goes, if the company calls in the electrical inspector, and he rejects the whole panel, then you have no choice but to do it over. Your only recourse would be if the customer said it did not have to meet the National Electrical Code and you have that in writing.


Good luck!!!
Afterhrs

 

[advidana]

Check your contract, what does it say and go from there. It would be wise to comply with some types of standards if your are building electrical panels.

 

[skills]

There is nothing in what I've read above that suggests any NEC code violations, so that's not at issue here.
AC and DC and Signal wires should intersect perpendicularly whenever possible to negate mutual inductance. I do this when power or switching lines run within 3" of each other. Some don't and it isn't a RULE or LAW that you do.

It sounds to me like your customer wants something for nothing and I've seen it before.

Direct Logic stuff is superior to AB logic controls in most measurements of reliability that I've performed here in the shop. I've melted down AB plcs doing what a DL205 is
happy to do.

If you customer is willing to shell out the bucks for a changeout, then go for it, if not- let him take his shenagins elsewhere.

Lastly, I don't believe that cabinet wiring practices are
standardized by any form or regulation. I stand to be corrected though.

Doesn't 'terminator I/O' have removable teerminals? I thought so and I always see people wire field wiring directly to them. That is the purpose and intent of using them.

Fire your customer, He is playing games with you, I think!!!

 

[xnuke]

Here's access to a draft of NFPA 79:

http://www.nepss.org/NFPAtc79/draft_NFPA79_2002.pdf

I don't know how long it will be there, since I don't think it was meant to be posted on the Internet. (I didn't post it, I found it by doing a Google search on NFPA 79 Draft.) The actual release is only $35 US or so, so I recommend buying an official copy.

xnuke

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[EddyEE]

You can avoid this in the future by providing drawings for customer's approval prior to ordering of major components and manufacturing (I thought this is a standard practice here in the U.S.?). Of course this will incur overhead cost but the bottom line is better product and protection against that kind of customer.

Regards.

 

[buzzp]

I have not used Automation Directs PLCs but have used several other items. They all performed well with no problems. AB does have high quality parts (in most cases) but they charge way too much, in my opinion. Look at their fuse blocks. The ones with LED indicators if the fuse is bad, these from AB are junk and they charge around $15 for one and Automation charges $4.
If your customer wanted AB parts it should of been in the spec. Or they should of negotiated this after your submittal was reviewed. As far as wiring, I have not seen your panel. In my designs(OEM use only), I try to limit terminal blocks for every wire if access is allowed with a probe to the part that the wire connects too. Terminal blocks, in my opinion, are another point of failure. Now if changes are expected (upgrades) in the future then terminal blocks could reduce running new wire for your customer. I imagine if the panel is installed by the customer that they would prefer all connections to be made by terminal blocks. One note, solder all wire leads to reduce loosening of connections.

 

[lgray66]

Hello,
Thanks for all the replies, they were very helpful. We've agreed to make them a new larger panel using the existing components. We've made it clear that if they want to change to AB it will cost them. The customer agreed they should have provided specifications, and we agreed that we should have got the schematics approved. Overall, it was a learning experience for myself, and I will never let the situation happen again.

Thanks Again,
lgray66