Designing Electrical Panels Not Panelbuilder

I new to this forum and new to designing panels. Is there any references (books, Web Pages, etc.) that I can look at to design an electrical panel. I talk with many different engineers and get many different answers. High voltage at the top, processor at eye level. Then I see processors at various positions in different cabinets. Circuit breakers vs fuses. I know about wiring colors for AC, DC, GND, etc.; but how do I determine what is needed in a panel?

Practice!

I think others here will agree that panel layout is a matter of doing it so many times it makes sense to do it that way. As far as web sites or books on the subject, probably not other than some few that may touch on the idea. In general you will find these things to be true among others:
1. The more heat the thing generates, the closer to the top of the panel it should be, to keep from adversely heating other components above it. Especially avoid excessive heat on electronic devices, i.e. plcs, drives, controllers, etc.

2. Nearly all I/O wiring is placed at or near the bottom of the panel to facilitate connection within the panel. Some terminal strips may be located on one side or the other in a vertical orientation.

3. Separation of HIGH VOLTAGE and LOW VOLTAGE wiring inside the panel and to and from the field will also dictate the placement of equipment and the terminal strips.

4. Cooling the panel is dependent on just how hot a location it will be in and how much heat will be generated inside the panel. Often times just regular convection cooling is enough but there are times when fans are added to produce the desired temperatures.

5. I suppose there should be this idea of preference of the designer and layout person. There will be some placement of items based on developed patterns from experience to some degree. That is what makes all panels unique and thus hard to describe. They tend to develop based on some basic truths and from there, often times, just plain "happenstance".

If you have lots of time......

NEMA

Something else to consider....

If this control panel is going onto an existing piece of machinery, i.e. a control retrofit or upgrade, then make every attempt possible to keep the terminal blocks for field wiring in the same general location as the existing wires.

I try to layout my components onto the subplate with the above guidelines in mind, but I also try and keep the components arranged to isolate my AC power from my low level DC signal wiring.

Re: Practice,

What if you havn't had any?

Next month I'm moving over to the US (NJ) and yes I can design a panel that anyone in Europe will understand:

Black - Phase - (that's 220V) (hot)
Green/Yellow - Earth (Ground)
Violet - +24Vdc
White - 0Vdc (not Ground)
Orange - voltage fed from external source

CE marked - UL cert.

A guide would be usefull before I connect the ground wire to the 0v of the PSU!

Is there such a thing?

Come on over mate!

Paul, you are welcome here and you are as ready to work here as you would be anyplace else. The list below from your post is close to our UL/NEC requirements. You should study up on the NEC(National Electrical Code) which is part of the NFPA code for our stuff here. I am sure you can find some good guides if you search Google or Yahoo or the like.

Black - Phase - (that's 220V) (hot) for our residential/commercial single phase we use two black that are 220V between them. Also, a ground wire is brought to the service entrance as well which is both grounded and connected to the center tap of the transformer providing the 220V.
Green/Yellow - Earth (Ground) We just use Green.
Violet - +24Vdc or here some prefer Red for any +DC wire and Black for the -DC side of the supply.
White - 0Vdc (not Ground) Here we use the white as the neutral of our 120V systems and it is connected to that ground above from the 220V system. But, we also require a separate ground conductor which is not part of the load handling circuit.
Orange - voltage fed from external source. Orange here gets used especially with the Brown and Yellow wires in our 480VAC 3 Phase systems.

Thanks Randy for your reply, it makes me a litle less nervous.

Last month I talked to an electrical engineer over in NJ for an hour or so. He took me around his plant, maybe the colours (colors) are different but everything else is so similar.

Same S**t different continent



There is only one thing that worries me.

It's those things you put on the ends of wires.

30 years ago we called them SCREWITS.

2 weeks ago I removed the last of them from my house lighting circuits. How do you test, how do they perform compared to other terminals?

Why do you spell colour so badly


Cheers,
Paul

Over here we call them wire nuts, and they absolutely should not be on any internal panel wiring!

One neglected area is adequate space between panel walls and field terminal connections. 4" is minimum, more is better.

The UL-508 standard has some general guidelines on wiring etc.

Your color code is a little different from common practice in the US. See this link for discussion: http://www.plctalk.net/qanda/showthread.php?s=&threadid=1415&highlight=color+code

Beg to differ, Lefty...

I agree that, aesthetically, wire-nuts suck... especially in a newly built control panel. But... why else were wire-nuts invented? If not for use in a "Junction Box", then where?

A Control Panel is a BIG Junction Box (a Terminal Box is a junction box too). That's the only place where wire-nuts are allowed!

Last time I looked, wire-nuts were not allowed in condulets! (although we ALL do it!) ...something about a fill-factor or some-such.

Besides, wire-nut connections are just as valid as terminations... they (at least the U.S. ones) do have the U.L. seal.

****! Where the hell did I leave that damned wire stretcher?

Lets not get into a whole "Wire nut is great, Wire nut sucks" debate, all I realy wanted to know is "is there a techy skills shortage in the US as well as the UK?"

Will I be a house husband or will I be a controls/systems engineer again?

And I must ask again "why do you spell colour so badly?"


Seriously though,

I'm a somewhat nervous about moving to your interesting country. I enjoy ny work now I just hope I still will in the US.

My coleagues at work say there won't be a problem getting a job;

just remember the phrase:

"You want fries with that!"


B-)


Paul

The cabinets I design are usually 2-3 door.

I put the high voltage on the right, by the disconnect. Usually the entire first door section.

I/O terminals are in a vertical row down the left side of the cabinet. Our wires usually exit via a 6X6 wireway out the top or bottom left of the cabinet. Then the wires have a straight shot to the terminals.

Between the terminals, I create a kind of "ladder" of panduit. Two veritical wide pieces with smaller horizontal. I try to follow a logical progression downward- fuses at the top for 120V which are usually feeding the devices below (relays, power supplies, etc.) Then the PLC rack(s). This usually pusts them at about eye level.

Below that are the 24V devices.

Finally the very bottom is usually empty. However sometimes servo or variable frequency drives end up there. (But not at the very edge) If I have an air conditioner, the ouput of is usually blowing right on them. If I don't, by placing them at one side on the bottom will encourage a good convection flow.


Regarding wire nuts- many years ago (before my time), we used them to connect motors. After one slipped off and neary electrocuted an engineer, we switched to ring terminals and screws wrapped in tape. Not a failure since.

Marrettes are definitely a no-no in a control panel. I can just see trying to test a few connections with my meter and hold it at the same time without terminals. The trouble is I've seen it done and it makes me want to cry. Panelbuilding is an art, there is good, and bad, even if it meets code.

As far as using marrettes in a Peckerhead (Motor Termination Box), they work great if you wrap a little tape around them to help resist vibration.

Paul, if you come to Canada, we still spell colour your way. As far as colours go, Canada is pretty basic, our 3 phase is all Red, Black, Blue no matter the voltage, no brown, orange, yellow here. I understand your confusion about all the colours. I had to hook up a gas-fired turbine (Jet Engine) generator in the North West Territories that was Half-Built in Quebec and Finished in Texas and the wiring looked like crayola got a hold of it. Very colorful and confusing at first. (Not as bad as the Russian Motor Starter though....)

Another thing in panels I forgot to mention is to Read the installation instructions for the equipment you are installing. I've seen a lot of PLCs without adequate space for convection cooling as stated in the manual. I guess maybe only the maintenance guys care if it craps out after a year because of inadequate cooling........

Personally I think you will easily understand what differences there may be as far as wire color (colour). Randy made valid points about heat factors etc but alot depends on what is going into the cabinet.

I would suggest that drives (which are heat generating items) be place towards the top, anything that has a display or readout in middle or towards the top. Actually do your best to keep ANY item that may need to be accessed for troubleshooting etc away from the BOTTOM of the panel if AT AL POSSIBLE.

EVER had to sit on the floor to troubleshoot? Its a pita. I prefer the vertical mounted terminal strips vs the horizontal strips at bottom for the above reason.

Basically think about the panels you have had to work in when troubleshooting, then determine the weaknesses they had for that purpose. Avoid those situations if possible.

NOW to another aspect of this subject...coming to work in the US. Not long ago there was a thread from someone living here that was from India. This person was an Engineer I believe and seemed capable. The issue/problems he had was not with ability but with the VISA system.

This is the thread:http://www.plctalk.net/qanda/showthread.php?s=&threadid=3695

I am not familiar with the rules/laws involved with people working here that are from another country but you may want to THOROUGHLY reseach the subject.

ALSO on this subject you may want to research the housing and cost of living aspect. New Jersey is a high cost of living state, housing cost is very high. Gasoline (Petrol) is higher. Food costs are higher.

Just points to ponder. Good luck.

paulbroughton said:

Same S**t different continent

Click to expand...

Exactly! If you are competent in the UK, I doubt you will have any problems 'adapting' to our methods.

Just don't come to NJ. I have enough competition...

beerchug

-Eric

P.S. to Ron. Wow, I forgot about that infamous thread...

I think that was the only thread that Phil officially 'closed' without simply deleting...

Basically I'll add that you should purchase the NFPA 79 booklet and study it from front to back. It has examples pictures of panel layouts and everything you need to know about building a panel.

Also, you don't always have to build to UL standards. Most companies DON'T require it in the USA.

If you build for UK, makre dang sure you understand the IEC specs. Building panels in the UK is alot tougher if you have to ship overseas.

The NFPA 79 booklet is your best bet, I promise!
http://www.nfpa.org/Codes/NFPA_Codes_and_Standards/List_of_NFPA_documents/NFPA_79.asp