Three Common Electrical Options
How are you handling your electrical control panels? There are quite a few options on the spectrum. You can purchase a standard empty enclosure and do all the work yourself. You can hire a third-party contractor to build your control panel, deliver, come onsite, and wire it up. There are many points in between. We’d like to talk today about what those options are and some best practices you can use to come up with a cost-effective way to get the electrical control panel solution you need.
You purchase an off-the-shelf standard sized stock enclosure. You purchase all of the different components: drives, a PLC, power supplies, fuses, DIN rail, panel duct, ethernet cable, glands, mounting plates, etc. Your team uses hand power tools to make cutouts, openings, and access points in the enclosure. Your team drills and taps holes and starts installing components. After some amount of work, your team will begin to do the actual electrical wiring – both wiring the control components and wiring to power.
Hire a third-party contractor. They will fabricate the enclosure. They will create the openings to your drawings and specifications. They will install components. They will do the wiring.
#3. PLUG AND PLAY
This is an inbetweener. It is not as hands-off as an outsourced option, but some of the involved work from a DIY option is taken off your plate. You order a custom enclosure. You provide a rough idea of what components will be involved. You receive a partially finished panel – an enclosure with some amount of DIN rail, duct, pre-drilled & pre-tapped holes, and components pre-installed. Your team can complete the wiring.
Many end users in the world of automated manufacturing take advantage of the PLUG AND PLAY Option. It allows them to move the pre-fab and pre-install work that isn’t in their wheelhouse off their plate. It keeps the critical work under their supervision and control. They are not entirely reliant on a third-party contractor, which helps them manage in house maintenance and upgrades.
Basic Considerations for Your Control Panel
Your control panels are typically trying to do two things, (1) provide and control the flow of electrical power to equipment, typically electric motors; and (2) control how your equipment operates within the framework of your DCS, distributed control system. That means making sure any safety devices you have on your plant floor properly talk to your control panel which in turn will talk to a motor to shut it down as required. That also means that your control panel can talk to your enterprise and production systems to communicate what is happening at the machine and equipment level. This lets production personnel gather data to monitor and improve your manufacturing processes.
When you are installing a new control panel, there is a lot to consider. Your manufacturing and engineering teams will have to consider what the overall function of that panel is. In this section, I’d like to look into the actual considerations for how the panel itself will function as a piece of electrical equipment.
- We’ll assume you have a pretty standard control panel with some drives to control some motors
- Your fictional panel will also have a PLC/HMI so a machine operator can control those motors
- Your panel will use 480V three-phase incoming power
- Your panel is going to be installed in an area that gets washed down
(think, machine oils or food & beverage production)
So now we have this panel concept. Once you know where it is going to go, one of your first steps should be a first pass on the physical limitations for a panel. Enclosures are typically available as wide as 48 to 60 inches and 10 to 12 inches deep. You are going to need to do a basic back panel layout and it won’t be good if you start designing for 48 inches of allowable width and then find out something that big won’t fit on your factory floor. We want to avoid those “D’oh” moments.
Physical Considerations for Your Control Panel
After a physical assessment of floor space, you can move on to the basic physical considerations for the inside of your panel. The panel will need to house drives and a PLC and a few power supplies, some fuse block options, panel duct, and more. You might know exactly which drive you want. If that is the case, you can determine actual dimensions. Example: PowerFlex Drive 25C-B017N104 is a 5HP 200-240V drive. We know that this device, Frame B, is 3.43 inches wide x 7.09 inches tall x 6.77 inches deep. If you want to mount 4 of those drives inside your panel now you know that you can safely fit all four on one “row” of your back panel layout. Want to learn more? You can use this tool from Rockwell Automation. Don’t have a 2D or 3D design background? If you have basic knowledge of the electrical control side of your project but do not have a formalized way to verify physical builds/designs, Horizon Solutions can create design files on-demand for you and your team as a service.
Back Panel Layout Checklist
Let’s talk about a back panel layout. This can be considered the map of where components will go. In typical cases, I consider a back panel layout to be 2-dimensional, i.e. flat. Meaning we don’t stack components over one another, depth wise. You can do that, but that would be a whole ‘nother blog post. Even though we consider it flat, the panel is typically installed vertically. Imagine a map poster on a wall in your office.
We’re trying to realize a panel that delivers the power required to equipment, keeps your people/plant safe and communicates correctly with your control systems. To do all of that we want to go down this checklist:
- Double check physical fit of overall panel footprint on the factory floor (see above)
- Double check physical fit of componentry, actual sizes (see above)
- What material will your enclosure be? Three common options:
- regular “mild steel” **most common
- stainless steel
- a non-metallic composite
- Review other physical considerations
- Heat dispersal (drives)
- Mounting options – drilled & tapped holes
- The weight of components and how they are mounted
- Strain relief for the cord(s)
- Confirm field entry; i.e. where does the power come IN to the panel?
- Confirm knockouts and mounting options
- Where is power going OUT? What is it going to?
- What types of cables are going OUT? Do they need shielding?
- Investigate possible sources of electrical noise
- Consider power isolation
- Review power and devices; i.e. low power / high power
- Some devices can be located near to each other, some can not
- A general best practice is to put high power devices by like devices
- A general best practice is to put low power devices by like devices
A lot of those checklist items talk about modifications to enclosures.
Do you need holes, knockouts, square cutouts, or other modifications?
Best Practices for Electrical Control Panels
Some further detailed thoughts on the checklist above:
Heat dispersal. Drives create heat. You can use fans on the drives to move air to cool them down. You can also use heat sink devices. You can even use heat sink devices that mount externally on your panel. This keeps the heat out of your panel. If your panel gets too hot, the heat can damage other electronic components. This is a very important topic and you can learn more here. Most drives will come with very specific published user guidelines about space, i.e. how much space to leave above or below or behind the drives to ensure they are properly ventilated which will help keep them properly cooled. In our example, the panel we are using a PowerFlex Drive 25C-B017N104, a 5HP drive. For this device, there are published minimum mounting clearances.
Minimum Mounting Clearances. First, we have to assume that you will mount the drive upright on a flat, vertical and level surface. Then, you can refer to Publication 520-TD002B-EN-E, the PowerFlex 527 AC Drive Specifications, a 44-page technical data document. RE: minimum mounting clearances, you can jump ahead to page 16. This page shows five different configurations in which you could mount two or more drives. For each array, the document recommends a minimum of 2 inches of clearance from the bottom of the drive unit.
More about heat dispersal. Heat rises. The temperature is higher at the top of a panel versus the bottom regardless where you mount the heat generating devices. The question is where to mount the heat sensitive components. The more sensitive components would be better low. If it is a drive panel with no PLC mount the drive as low as possible because it is a heat generator and is heat sensitive. If it has a PLC in it I would mount the PLC low and drive high, as typically a PLC is more heat sensitive. PLCs and drives are heat sensitive. The lower the better. Most other components are not as sensitive.
Thermal management. Sometimes, if you have a lot of devices inside a smaller enclosure, it might get hot. Or sometimes, you might have a control panel that has to run extra hard when the ambient outdoor temperature is in the 90’s in the summer. It is also quite common to have a control panel in use on a hot manufacturing line that creates or processes hot materials such as rubber or glass. You could consider this “even more about heat dispersal” but really – at a certain point we’re not truly dispersing heat. You will have to use a solution like an air conditioner. There are also scenarios where you need to heat the panel, like outdoor or refrigeration panels.
Triple check physical fit of componentry. There are many types of 3D modeling software out there that one could use. A few we like are SolidWorks and Inventor. Most engineering departments will have access to something like AutoCAD. You already double checked, so the digital triple check before you start drilling holes can be a worthwhile step. Using 3D modeling software can also bring together all the benefits of programs like ProposalWorks and files from enclosure manufacturers (like Hoffman). You can do some searching, build a file, create an output and confirm a nice tidy fit. All without ever leaving your desk. We already mentioned earlier in this post that if you don’t have a solid 2D/3D layout background, but DO have a basic knowledge of the electrical control side of the project we can create design files on-demand for you and your team as a service. This allows you to focus on what you do best while we help you verify the physical (mechanical) aspect of your design.
Is this a stainless steel enclosure? Stainless steel enclosures are very common in wet environments – water, chemicals, machine fluids, cutting oils, etc. Stainless steel (SS) is designed to be resistant to corrosion, which makes it a natural choice to house a control panel in a plant that requires wash-down. Example: food & beverage manufacturing. The same properties that make SS resist corrosion also make it very tough to cut and machine properly. The PLUG AND PLAY Option we discussed above is a natural fit for SS enclosures. Let Horizon Solutions machine those difficult HMI cutouts for you. We can do it quickly and cleanly, saving you time and money.
Power coming into the panel. Identify what your incoming power requirements are and verify that all of your back panel components are rated for that power. If they are not, provide the appropriate measures (transformer, power supply) to convert the incoming power to the voltage needed.
Circuit protection. Provide appropriate protection for downstream devices using fuses or circuit breakers. Keep in mind any overall SCCR (Short Circuit Current Rating) requirements for the entire system. SCCR does require calculations, which can sometimes be complex.
If you have detailed technical questions about your specific panels, feel free to ask us in the comments section below. If you’d rather reach out to our team privately, you can contact us any time.
Want to Learn Even More About Control Panels?
Horizon Solutions will be hosting a series of six events in May/June of 2018. These Smart Manufacturing Expo events are a great opportunity to talk shop with the experts. You can see, feel, and touch both enclosures as well as many of the devices that will go on the back panels in your facility. These events are certainly a good fit for anyone that has to use, design, or specify control panels in a manufacturing environment. Attendees will also learn how to modernize your production environment, increase access to critical information, and improve employee safety. There is no charge for this event, continental breakfast and lunch are included, pre-registration is required, seating is limited. Reserve your seat today.