Neat control cabinets / control panel wiring?  - Page 1
Forum section: electronics / projects

author: conducteur
author_rank: Regular Contributor
timestamp: April 02, 2016, 09:43:36 pm
content: I want to learn how professionals build their control cabinets. What are the do's and don'ts when it comes to building a cabinet and connecting everything in it? Which basic rules should I apply in order to obtain a good result? Are there "rules" where to place different parts? Are there "rules" when to use Din rail connector terminals an how to order them on a piece of din rail? Are there other guidelines i should follow ?I ask this, because i"ll start working on the new cabinet to control my CNC machine this or next week and want to get a proper, neat, safe & reliable result. (for my project, only few parts are on a Din rail).This is what i call a neat result:http://asdllc.us/wp-content/flagallery/panels-photos/internal-bus-field-terminal-wiring.jpg

author: Rerouter
author_rank: Super Contributor
timestamp: April 02, 2016, 10:00:28 pm
content: The biggest rules I follow are1. Maintain physical seperation between high and low voltage systems (generally 50v dc or 75v ac,)2. Isolate fast or noisy (high current) signals from small signals.3. Label every wire, if you want to use a code, then print out an index and stick it inside the cabinet.4. Ensure no connections are hanging, that everything is supported where possible,For mounting and layout, it comes down to the situation, I work on trucks, so it involves more vibration

author: sarepairman2
author_rank: Frequent Contributor
timestamp: April 02, 2016, 10:28:03 pm
content: don't try to save on wire length.neat = more materials used then absolutely necessary.also, make it easy to disassemble. leaving a loop of cable that is tightened with a zip tie so a subassembly can be removed is and electrically disconnected in a ergonomic position is nice. you will thank yourself when you need to modify or repair it if you have slack.this goes to say, unless its made to a stringent requirement don't try to cram everything in super tight. neat also tends to mean over sized. unless you want to engineer the shit out of it.(i.e. think about how much a pain in the ass it is to disconnect things like old VGA connectors on the back of a computer when they have no slack so you cannot pull the computer out).DIN rail mountable things are nice.

author: rstofer
author_rank: Super Contributor
timestamp: April 02, 2016, 10:32:26 pm
content: Black for power wires, Red for control wires (switches, relay logic, PLC logic and such), Blue for signals (I'm thinking about DC kinds of things).Note the abundance of Panduit. That's the secret! In the old days we had to lace those harnesses with waxed twine. Some time in the late '60s, we moved to TyWraps but it just wasn't the same. OTOH, relacing a harness just to add another wire didn't make a lot of sense either. Panduit! That's the secret!Plenty of wire space between the Panduit and the components.Wire labels on horizontal wires read left to right regardless of which side of the terminal block it is on. Vertical labels should all read in the same direction - pick top-to-bottom or bottom-to-top and stick with it. I don't care which way I have to tilt my head to read the labels as long as it's always in the same direction.Tooling permitting, heat shrink labels are better than the tape style. Some tape style have a length of clear tape to cover the label - preferred over the style you can get at Home Depot.It's kind of Euro-centric but those folks use crimp-on sleeves at the wire ends so that the sleeve is clamped by the terminal screw, not the individual strands. I kind of like this.http://www.iec.ch/about/activities/standards.htmNotice that almost every component, other than the transformer, is touch-free. You couldn't get bit working on that panel if you tried! I'm surprised there isn't a cover over the transformer. That's a very nice panel. US components don't emphasize touch-free - particularly for contactors and motor starters. IEC is a nice system

author: German_EE
author_rank: Super Contributor
timestamp: April 03, 2016, 08:56:39 am
content: Some additions:Inputs on the bottom and outputs on the top, or vice versa if you want but don't mix inputs and outputsAdd an emergency stop buttonAdd one or more indicator lights showing that the panel is live.If you have more than a couple of contactors then label them all according to function. The same applies to fuses and circuit breakers.If your panel has a swing out door with controls on the front you will need to clamp the wire loom at both ends. Why? We had a run of panels with weird intermittent failures that were traced to the wiring loom bending at the wrong point when the door opened.Leave space inside the box for you to rest your multimeter.

author: mikerj
author_rank: Super Contributor
timestamp: April 03, 2016, 09:47:22 am
content: Quote from: rstofer on April 02, 2016, 10:32:26 pmPanduit seems to manufacture of a huge range of cables and cable management products (not heard of them before), so do you mean split sleeving, braided sleeving or something else?

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2016, 10:21:57 am
content: With a panel you will use internally a solid core wire, not a stranded one. Take all those wires that lead to the outside to a single ( or two) series of DIN rail terminal strips, numbered along, so you connect to the outside world via flexible cords. Use pin ferrules on all flexible cord ends, either the crimp on style with a separate pin, or the slip over ones. For high current use appropriate crimp on lugs, preferably the open ended types so you do not have to undo captive screws ( and lose them) to put a wire end in.For inverters use the correct spacing, and providing they are all supplied from the same breaker, use a line reactor and connect the power buses internal to them, so recovered energy on one drive stopping will be used on another drive operating. Use shielded cabling on the outputs, and connect the shielding correctly. This reduces induced noise in the rest of the cabinet.For the panel with a door, the trailing cable joining the door to the frame must be made with flexible stranded cords, and must run along the hinge side from bottom to top , with a mounting on the door side ( large P clip with a sleeve grip on the cable of a soft flexible rubber) and a similar mount on the top at the panel side. Then have a terminal strip to terminate the ends, and add an extra 5 cords in the bundle for spares and expansion without needing a new loom. Have an earthing conductor as large as the incoming supply conductor( so if your incoming is 16mm this will be 10mm to withstand breaking current) with a good firm mounting to the frame each side. Use spiral wrap on the trailing bundle to keep it flexible without damage.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: April 03, 2016, 03:19:41 pm
content: also, having wiring diagrams fixed to the inside of the box (i.e. glued to the cover) is a very good idea.the situation came up before that we open something up and then spend half the day looking for documentation someone may or may not have made 10 years ago.another good tip is to leave excess wire so current can be measured with a clip on current meter easily.

author: Monkeh
author_rank: Super Contributor
timestamp: April 03, 2016, 03:41:07 pm
content: Quote from: mikerj on April 03, 2016, 09:47:22 amI think he means the slotted trunking.

author: dom0
author_rank: Super Contributor
timestamp: April 03, 2016, 04:36:22 pm
content: Quote from: SeanB on April 03, 2016, 10:21:57 amAt least here it's pretty much standard to use stranded wire for this, because it's much easier and faster to route, even when having to add a wire ferrule to all ends

author: kolbep
author_rank: Frequent Contributor
timestamp: April 03, 2016, 05:35:09 pm
content: The main thing is to plan ahead.Take time to draw out the diagram.Then layout the parts (keeping the logical things together), then think about it.Only once you are sure it is neat, and that you have enough room (and space to add more things- YOU WILL THANK YOURSELF LATER!)Then as you wire, take your time, and tick off each wire on your diagram as you connect it.Make sure you leave lots of excess slack in the Slotted Trunking. Also Stranded Cable is a Must between the front door (if you have switches/etc), and also stranded wires between components (in the Slotted Trunking). Ferruling the ends of the stranded wire is a good idea.Also, it is always better to number the wire ends, and then to put the same numbers on the diagram (and Keep the diagram in the Panel). It is a waste of time going to site to fix a fault, and finding that you left the diagram at the office, or having to get the people to run the place to hunt around for the diagram for you, or having to reverse-engineer what you have done previously.Here is one (the neatest one), of several panels I recently did at a local nut processor. - This is before I installed the Labelling.They are all Direct-On-Line starters, so it is not too complex.You can see that there are only 10 starters, but you can see it is a large box I used (to allow for expansion). I also installed the additional Trunking and Din rails for future expansion (Saves time and mess later),also I drilled an additional 10 off 22mm Holes in the front of the panel, and put in blanks. That just means that in the future if they want something added, it just means putting the contactor/overload in, and then putting the Illuminated Start/Stop combination button in, and wiring it up (some spare cores in the loom to the door would have been better). But this way, when something is added, we do not have to come and Drill/Grind, etc, as this this a food processing (nut) factory, you absolutely CANNOT have any iron filings, etc going around whilst they are processing.

author: Stonent
author_rank: Super Contributor
timestamp: April 03, 2016, 08:31:58 pm
content: I tend to see lexan or acrylic panels being mounted in front of locations that are susceptible to accidental touching of higher voltage connections. Most commonly in fuse blocks and transformers.

author: calexanian
author_rank: Super Contributor
timestamp: April 04, 2016, 12:23:07 am
content: In my Electrical control and Industrial Electronics classes in college the instructor would grade not only on correct practices in out installations but good layout with an emphasis on logical flow and serviceability. You could do everything right and still fail if it did not have an easy to understand layout that the next guy that came along could easily understand.

author: SeanB
author_rank: Super Contributor
timestamp: April 04, 2016, 05:50:49 pm
content: Quote from: dom0 on April 03, 2016, 04:36:22 pmI did an apprenticeship in industrial Instrumentation, where solid panel wire was demanded, and no such luxury as slotted trunking, you had to do the bends and straight runs with no crossovers, and lace it all up with waxed lacing twine ( still have 2 rolls of it as well, along with the needles, plus another roll of bootmakers twine I use for stronger bindings that will be varnished after manufacture) at the exact same spacing, all knots being exactly on top of the bundle. Was time consuming, but still i try to get wiring looking like that even using trunking and cable ties, as i hate knitting in a trunk.Had a compliment from an inspector on a house, he muttered the wiring I had done was too neat for it to have been done by a registered electrician. Something about using cable ties, and routing the wiring in a bundle down the centre of the roof, and 90 degree branches off as opposed to a tangle of knitting as I had found it. I do tend to buy cable ties not as packs of 10 or 100, but as boxes.Not going to comment on what I think of domestic alarm installations, where it seems they only get issued a single roll of the thinnest wire and 5 tubes of glue for any installation, and are expected to return the roll and glue unused.

author: conducteur
author_rank: Regular Contributor
timestamp: April 05, 2016, 08:29:22 am
content: Thank you all! Very useful tips!There's one (silly) question that's left unanswered. For my project, 230V (earth, ground and line) comes into the case i've ordered. (first parcel with components will arrive today at home).The 230V goes to the main on/off switch. After that switch, the 230V needs to be distributed to different parts in the case (like the 24V DC PSU). (same for the 24V output for the TinyG controller board, a relay , the vfd and a fan)What's the best way to do that? Are there any "rules" when it comes to ordering the din rail terminal blocks? Is the "most logical order" the way to go?

author: bookaboo
author_rank: Frequent Contributor
timestamp: April 05, 2016, 09:04:00 am
content: Quote from: conducteur on April 05, 2016, 08:29:22 amGood practice is to group and seperate power and signal connectors physically. There wil almost certainly be regulations for this for where you are based, personally I like to use these as a seperatorhttp://uk.rs-online.com/web/p/din-rail-terminal-accessories/0425314but theres thin plastic dividers that do the same job. Also use seperate star point wiring for heavy loads and signals (i.e. dont daisy chain your 0V for sensors, micros etc. from the 0V of a solenoid or contactor just because it's physically close by.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: April 05, 2016, 09:24:10 am
content: You can use the DIN rail terminal blocks to distribute power. Whichever manufacturer and type you use should make something like this:http://uk.rs-online.com/web/p/din-rail-terminal-accessories/0425320/Which commons neighbouring terminals together.I'd recommend using vertical dividers between L, N and E to reduce the risk of shorts. (and Green/Yellow terminal blocks that connect through to the DIN rail for the earth)If you;1. Have a proper drawing with all the wires numbered2. Label the wires appropriately with cable markers e.g. RS 557-0173. Mark them off the drawing with a highlighter pen as you install them4. Use bootlace ferrules5. Use slotted trunking and expandable braid (e.g. RS 170-5447) for flexible sections e.g. to a dooryou will not go far wrong and it will look the business and work first time.

author: SL4P
author_rank: Super Contributor
timestamp: April 05, 2016, 09:51:43 am
content: A good starting point is not unlike good schematic layout!Large broadcast facilities set a pretty good example...https://www.google.com.au/search?q=broadcast+rack+cabling&espv=2&biw=1286&bih=735&source=lnms&tbm=isch&sa=X&ved=0ahUKEwicrLignPfLAhWCOKYKHX-1BgcQ_AUIBigB

author: dom0
author_rank: Super Contributor
timestamp: April 05, 2016, 10:08:27 am
content: Quote from: DenzilPenberthy on April 05, 2016, 09:24:10 amIf he has lots of single-phase AC stuff there are newer terminal blocks which combine N/L/PE in a single width unit (less than a cm), with PE automatically contacted and the neutral contact to a common rail with a switch.E.g. Wago 2003 / 2005.

author: conducteur
author_rank: Regular Contributor
timestamp: April 05, 2016, 10:36:21 am
content: If i don't forget one, i have 4 single phase 230V devices in the cabinet.

author: SL4P
author_rank: Super Contributor
timestamp: April 05, 2016, 11:07:58 am
content: Quote from: conducteur on April 05, 2016, 10:36:21 amGood point.Keep the necessary separation for electrical regs, and interference requirements.