Control Panel Design for Beginners Pt. 2: Layout

What's up Automation Nation and welcome back to the channel. Today's video is going to cover how to design a layout for an industrial electrical control cabinet. A layout, especially when dealing primarily with low voltage components, has a lot of best practices and common conventions, but not a ton of actual laws that must be followed. So use this video more like guidelines than actual rules. And if you missed how to generate a bill of materials for your controls project, you may want to consider watching that video first, as we'll use the bill of materials from that video in this specific layout, but it's not totally necessary if you're just here for the concepts covered in this video. Once you've identified what size of electrical cabinet you plan on using, be on the lookout for a few different dimensions. For example, I'll be using this 24 inch by 24 inch panel from Vivor, but that 24 by 24 dimension is the external edges of the box. But I need to hunt down the dimensions for the mounting plate specifically, which is the surface I actually get to mount my controls hardware to. That gives me the outer dimensions for my mounting plate that I can start my layout from. So these are the starting dimensions that we can drop into our CAD software. As we jump into this side of the tutorial on the computer, I'm going to be using an electrical schematic software called CoFaso, and the CoFaso team has agreed to give anyone interested in following along a six month free trial license by emailing CoFaso at CoFaso.com and mention code LeMasterTech6 to request your free six month trial. So if you'd like to follow along with this example or dabble in your own projects, be sure to take advantage of that. The concepts we're covering today regarding layout will be fairly similar regardless of electrical package. I've actually had to get scrappy for some customers before and build cabinets very quickly and I've used PowerPoint to make panel layouts in the past. So don't worry too much if you have a different software in mind. The layout concepts will be universal. The main point of a panel layout is to create a dimensionally accurate plan showing the physical positioning of all components in your control cabinet. So you have a package to hand a builder or technician or even just the source of truth schematic for you to follow yourself as you build it. Typically found near the very beginning of an electrical drawings package. And even though they're high level and not as critical to the functionality of your cabinet as the actual wiring diagrams, still a super important design document. And just like everything in engineering, there are good designs and bad designs that can be technically functional. So let's review some of the guidelines to make a good one. Let's start by dropping in a grid of DIN rail and wire way. We're going to ring the outside of the mounting plate on all sides by wire way. And it's not crazy to only do this on three sides so that you could get some extra length for DIN rail, but that would extend some of our wiring runs unnecessarily to go the long way. And in general, having these external wire ways is a good idea. So you always have a clean path to route your wiring, but you leave plenty of space in the middle for your components. So the second infrastructure type thing we want to lay down is DIN rail. So let's drop two long lateral runs of DIN rail, kind of equally spaced in the remaining gap of the cabinet. And typically you want to take the largest component you think could get dropped on a DIN rail section, add some buffer space above and below it so you can easily get wires connected and clip the objects onto and off of the rail itself. And in my case, I can use the S7-1200 PLC or my power supply dimensions to see this spacing will work for me with a pretty healthy margin. Now we'll just drop one more wire way section between the two DIN rail sections. And for all my wire way, I'm going to use inch and a half, which is a very standard size in the U.S. for smaller cabinets. And this stuff comes in many flavors and sizes. So if you have thicker cables or a main chase where you expect a very full wire way, just size it up. There are actual tools online to help you anticipate max wire load in a wire way and try to keep the total percent full less than 70% full for control voltage or less like 50% for higher AC voltage applications. But typically people just oversize a little bit and try to leave room for future expansion. In any case, this gives us a nice clean wire way and DIN rail framework to start adding our components onto that will really speed up the rest of the layout process. Different CAD software will have different features for actually snapping components to the DIN rail, while some like CoFaso rely on the user to do that specific alignment. And one quick note here, lateral runs of DIN rail are the most common to see because you're not going to have to fight gravity trying to slide your stuff off of the rail all the time. But you can use these end terminals which screw down and bite onto the DIN rail to be able to hold up components if you think you have an optimized layout that would use vertical DIN rail runs. I think vertical DIN rail is usually unnecessary if it's a preference or a style thing or a specific customer designer site wants it. Just keep in mind you could have slipping components if not properly secured on the ends. So now let's move into component placement and one pretty major golden rule is try very hard to separate AC power from low voltage DC signals from network communications. Ideally have them in different wireways whenever possible and if they do have to share try to keep them separate with dividers and extra spacing between the runs. And if you must cross AC and DC wires, cross them at 90 degrees to reduce noise from electrical coupling. Now in my cabinet today I'll have just 120 VAC coming into the cabinet and feeding into a power supply and everything else being designed here will be nice and easy 24 volts DC. But it is very common to have motor contactors or VFDs with higher voltages, often 3-phase 480 VAC in the US or even higher in the same enclosure as your controls components. And so extra steps should be taken to keep all AC runs separate from all DC runs in those sorts of cabinets. And a brief mention here for standards and codes everyone's favorite topic. NFPA 79 is the National Fire Protection Association's application safety standard for conductor color guidelines, grounding, disconnect requirements, and is very closely intertwined with National Electrical Code or NEC 70. Additionally UL 508A is the build standard that dives into component selection, spacing, wire sizing, and short circuit current rating or SCCR calculation, panel markings, and more. And similarly but not to confuse you individual components can be UL listed or UL rated but that does not make the entire electrical cabinet UL listed. That requires actual validation and a lot of extra work but that's all fairly out of scope for this video just know those are some codes to go track down if you're going to do a lot of this. Some customers will give you firm requirements to follow one or all of these in their contracts but more than that it's just good practice to make safe cabinets and avoid doing dumb electrical things. So let's go ahead and place our first component and it's kind of natural to start with that power supply which we'll place in the bottom left of our layout. To make the total AC wiring inside our cabinet as minimal as possible. This power supply is the only thing in my cabinet that'll be using AC power and in 480 cabinets this would usually be in-feed power coming into a large fused contactor switch connected to a door disconnect so you can kill power from the exterior or a Meltric connection like these so you can fully de-energize the cabinet without entering or sometimes both. But for a nice 120VAC cabinet we can get away with just a circuit breaker next to our power supply. We'll drop in one 120VAC neutral terminal, one ground terminal, and a 10 amp circuit breaker right next to our power supply and this will be our overcurrent protection for the power supply and therefore the whole cabinet. This will be the only little isolated zone where hazardous voltage exists within this cabinet. In many plants and much larger cabinets you have power in-feed typically coming in in the top of enclosures and so a common convention is to see top to bottom zoning in your layout logic where you might see the top of the cabinet be where the main power disconnect lives and in the middle zone you'll see your AC to DC power supplies and some other control components like PLCs, relays, I-O modules, and communications components in the middle body of the enclosure. And as you get to the bottom of the cabinet your terminal blocks for landing field I-O will be down there. We won't be following this convention exactly but I will be keeping it in mind as we build our simple layout for sure and it's useful to know about. Now on the upper DIN rail above the power supply let's go ahead and drop in our PLC and our PLC I-O modules and here's a good chance to talk about importing device information and macros from equipment manufacturers into your drawing schematic software. For a panel layout all that really matters for part positioning is a dimensionally accurate rectangle which is why I said before even PowerPoint is feasible for layout but more detail is more useful and having a detailed drawing of your components also provides extra clarity for the team building the panels. Every software package is slightly different and Eplan and Cofasso both use a system called macros although the way they integrate them is slightly different. Macros are reusable part drawings that you can drop into your layout and AutoCAD has a similar idea with its blocks but again each platform is slightly different but in general you get the necessary part information for CAD integration right from an OEM website so let's walk through one specific example with a Siemens part number. If I want this specific PLC added to my drawing set I can go to Siemens website, enter that part number, go to the specific page for it, go to drawings and downloads, engineering files and I see the macro file right here and Siemens has sort of optimized their macros for Eplan compatibility so they call it out as an Eplan macro but it's actually able to be used and integrated into most drawing package software tools. So we'll grab that Eplan macro from the website and head back to Cofasso. In Cofasso if I go to project and import I can see it gives me the option to import a macro so I select that but I see the suggested file types called out don't match what Siemens just spat out at me which was an EDZ file. EDZ files actually contain a bunch of part information in them again mainly formatted the way they are with Eplan in mind but we can unzip them and find the .ema files which are what we need. Since an EDZ file may not be recognized as something you can unzip with Windows by default you might want to grab a tool like 7-zip so you can force an unzip and if you'll be doing a lot of this sort of work I suggest making yourself an easy to find macro folder where you can organize parts by equipment manufacturer and keep them organized as your macro library will be ever expanding. So with that PLC macro unzipped I can go back to Cofasso and import the EMA file then go into Cofasso symbol editor tool make sure it looks good I can see the terminals and overall design look good but the exterior rectangle is missing and fortunately this is super easy to add and we'll use the dimensions image from Siemens website to make sure we get the exterior dimensions right and if we save that symbol and go back to our layout page we can now select the macro and we see we have a good looking dimensionally accurate PLC ready to add to our layout. Now let's drop in all the IO cards we identified needing in our last episode called out in our bill of materials. I already grabbed all the macros and followed the process we just saw for the PLC macro to speed up this process. There is not actually a rule about ordering these on a Siemens S7-1200 PLC because they communicate with each other via these low voltage backplane connectors and they can be ordered in any order. You just have to make sure that you match this order in the drawing when you build it out in the code since the order in programming tools has to match the order it's actually built in in the real world. Much of the classic IO in factories is still chassis based so in this case you may have called out racks and slots and channels for different devices already in your IO lists and you need to make sure to order them accordingly. But for us I can add these cards in any order and just need to make sure I map them the same way in PLC programming later. Many backplanes do still have max sizing and power distribution guidelines so make sure you don't exceed max number of total cards typically eight for these style of modular IO systems or maximum expected current draw such as loading up with relay output cards because those 5 volt relays inside the cards will be drawing non-trivial amounts of current through the backplane connection. So you can pause and investigate specific requirements for your flavor of IO if need be but for now let's continue on with the layout. Now we can take the network switch and we can throw it down just after the PLC module or if we want to leave easy room for adding more IO modules in the future we could slide the PLC and all the IO modules to the right and drop our switch to the left. There's no real rule about where to place this but since the switch will pretty much always be connected to your PLC near the PLC is a normal convention. And again trying to make sure to keep your network communications separate from any AC or higher current draw signal wires is always a good idea. And dealer's choice if you want to put some over current protection for this switch and this PLC right next to the modules either smaller circuit breakers or fused terminal blocks or if you want to do that with some centralized power protection. My case I've always enjoyed the convention of all my circuit breakers and fused terminal blocks being grouped together so I'm going to go back down next to my power supply and drop in some terminal blocks for power distribution. Some of the fused terminal block variety and some just regular so I have some nice shared terminals where I can create a whole rail of available 24 volts and a whole bunch of spare zero volt terminals as well. Next to these I'll drop a bunch of relays since any equipment requiring higher current draw or control of AC components from my DC cards will need relays. Then next to the relays I'll basically fill the remainder of the row with terminal spaces for IO terminals. And I'm not going to worry too much about counting total terminals right now or calling out whether these need to be single tier, double tier, triple tier, quads because there are so many flavors of terminal blocks. But this convention of having power distribution terminals, relays, and IO terminals each in their own dedicated zone so to speak is really what I want to call out here. Of course it's always a good idea to plan for 20% spares for all of these relays, power, and IO terminals and in case of expansion and unexpected pivots you'll be glad you have these. With this being a lower voltage cabinet I don't need space for larger components like motor contactors or VFDs but these are often more space hungry and require AC voltage. A few things to keep in mind if you need to add a lot of these it's recommended if you can to put higher voltage stuff in its own enclosure so you can service the low voltage control signals while the panel is live without needing to deal with hazardous voltage and arc flash dangers. If you can't do that for whatever reason you need to tie the high voltage power in the cabinet to a disconnect so you can make the cabinet safe to enter and lock out and tag out before entry. In terms of layout VFDs and higher current consuming components especially those running on higher voltage AC circuits tend to give off a lot more heat and you may need to incorporate heat dissipation such as door or side fans or even panel air conditioning. There are plenty of tools online to help you calculate expected heat put off from the panels and remember the environment they're going in will be a factor too because a hot panel in a cool room where it's being built won't reach the same temperatures as a hot panel in a hot factory floor so try to expect the worst. For our low voltage control panel we don't have to worry about heat generation as much so we won't be adding fans or air conditioners but again keep in mind those can also void the environmental ratings of your enclosure unless you get similarly rated components and install them in the proper rated methods. To speak briefly about grounding standards and guidance because I sort of just glossed over that when we Larger panels typically standardize around a grounding bar convention where a strip of metal with many terminals gets bonded to the mounting plate the panel and the door and this is where you land all your ground hubs for components and in the event of any stray hot wires this makes them touching any metal on the cabinet have a path back to ground which should cause a ground fault that draws enough current to trip your over current protection prevent potentially explosive events. Since this is a smaller panel I'm using a slightly easier to install convention of using just grounding terminal blocks only. These are special terminal blocks that combine electrical contact on their two sides with electrical contact to the DIN rail they're clamped onto through the back and when you use these it's extremely important to verify that you have good bonding so use a multimeter to verify that the door the mounting plate the back body of the panel and everywhere you're expecting ground has continuity because getting your grounding right is critically important for safety. Now last couple of fast tips for today's video I didn't add end terminal blocks to every spot in my layout you might want them but you can basically plan that between every distinct zone of stuff and on your ends you'll likely want some of these components with no purpose other than to hold stuff in place on the sides. Additionally I might do component swaps with some of these things called out as Siemens components shown here for Amazon off-brand components or stuff I have on hand of similar functionality. As for my home builds the savings are a few hundred dollars and I know how to make these replacements without risking safety or violating a customer's preference but I'm using Siemens macros for representative locations and overall dimension sizes. And last thing for now one good convention to know about as well some panel overviews will have a huge terminal block strip shown as one rectangle on the overview sometimes labeled with something just like TB1 or TB2 for terminal base and they create a supplementary detailed TB1 or TB2 page where they can zoom in on the actual terminal scene there since it's very hard to get good clarity on what your terminals are actually composed of on a high level overview of a big cabinet drawing. So other than that in the next few videos we'll get more into actually creating the wiring schematics show how to design network and power drawings as well as sensor to IO card schematics then we'll actually build the cabinet together. I hope you found this intro to creating a good panel layout helpful as a starting point. This is obviously a very broad field I'm sure to have missed some elements in there so feel free to add your thoughts and input to the comments below and share with the community. As always thank you for watching don't forget to leave a like on the video and subscribe to Lemaster Tech if you found it helpful and let me know what you want to see more of on the channel in the comments below. Thanks and we'll see on the next one.