Five years of ordering motors for a food processing plant has taught me one thing: the motor is the easiest part of the order. The wiring diagram and the VFD sizing are where the money disappears. I've watched a $450 Leeson motor replacement turn into a $1,800 two-day nightmare because the wrong questions were asked before the purchase order went out.
And it was never the motor's fault. It's always the details around it.
Who I Am, and Why You Should Care
I'm the office administrator for a 150-person food processing facility. If it isn't raw ingredients, it comes across my desk: motors, VFDs, linear actuators, control components, spare parts. About 60 to 80 orders a year, roughly $180,000 in annual spend, spread across eight or nine vendors. I report to both operations and finance, which means I get blamed when the plant is down and praised when invoices are clean.
I'm not an engineer. I've never claimed to be one. But I've been at this since 2020, through the whole wild ride of supply chain disruptions, and I've written enough electrical component orders to know which mistakes are common, which are expensive, and which are both.
Start with the Wiring Diagram, Not the Price
If you're replacing a Leeson motor—or any motor, honestly—the first thing you need is the Leeson electric motor wiring diagram for that exact model. Download it before you order. Not after. Before.
Here's the catch nobody warns you about: the same model number can have different wiring configurations depending on the voltage and the production version. I learned this the hard way. We needed a 2 hp single-phase motor to replace one that had been in service for about a decade. I found what looked like an exact match. Same model prefix, same frame size. But the wiring diagram on the new motor showed a different capacitor configuration than the old one, and our electrician spent two hours on the phone with tech support trying to reconcile it.
The most frustrating part? The motor was perfectly fine. The paperwork wasn't. And nobody thought to compare the connection diagrams until the old motor was already off the wall.
Took three days to sort out. Not ideal.
So now, before any motor PO goes out, I ask maintenance to send me a photo of the existing motor's nameplate. Then I cross-check the diagram against what's actually in the motor. If they don't match, I know I'm looking at an older or modified version, and the question goes back to the vendor before any money moves.
What Size VFD for a 5HP Motor? Start with Amps, Not Horsepower
This is the question I hear from our own team constantly: what size vfd for 5hp motor applications do we need? The short answer: the VFD's continuous current rating has to be at least equal to the motor's full-load amps. The "5 hp" on the nameplate is just shorthand.
For a typical 5 hp, 3-phase Leeson motor, full-load amps run about 15.2 A at 230 V and 7.6 A at 460 V. Those values are straight from NEC Table 430.250, which is a useful reference even for non-electricians—it lets you double-check what a vendor quotes instead of just nodding along.
So would I pair a 5 hp motor with a 5 hp VFD? For a fan or pump, yes. Those are variable-torque loads, and the drive handles them fine. For a conveyor or a mixer—constant-torque loads—I've learned to step up to a 7.5 hp drive. It costs more, but it gives you current headroom and thermal margin when the motor is running slow and producing full torque. Some VFD manufacturers recommend oversizing to at least 125% of the motor's FLA for constant-torque applications.
Honestly, I'm not sure why the industry still leads with horsepower instead of amps. My best guess is that horsepower is simpler to put in a catalog, and the fine print about FLA and duty cycle just gets lost.
Electric Actuators and Controllers: Same Rules, Different Boxes
Electric actuators have been showing up in my orders more and more since 2022. Linear actuators in particular—they're all over modern automated equipment. And they do not get the same care as a motor purchase. That's a mistake.
The unit that runs a linear actuator is the linear actuator controller, and here's the thing: it's not always included with the actuator. Sometimes it's a separate line item. Sometimes it's optional. And sometimes you find out after the shipment arrives that the actuator and controller were never checked for compatibility. Ask me how I know.
Two things to verify on every electric actuator order: the voltage, and the limit switches. Most linear actuators run on 12V or 24V DC. Your control cabinet might be set up for 120V AC. I once ordered a 24V actuator for a cabinet wired for 120V control. The vendor happily offered a power converter as an "accessory." The accessory was $45. The real cost was two days of downtime and the look on our maintenance lead's face.
A lesson learned the hard way.
Also worth asking: does the controller have built-in limit switches, and does it support the full stroke length of the actuator? I've never fully understood why this information is so buried in datasheets. It's the first thing I need and the last thing I find.
The Checklist I Actually Use
If you're starting from zero, here's what I've landed on. It's basically common sense, but common sense gets skipped when machines are down.
- Get the exact model number off the existing motor's nameplate. A previous vendor's part number is not the same thing.
- Download the manufacturer's wiring diagram and compare it to the actual motor leads. Discrepancies happen. Check before you buy.
- Look up the motor's full-load amps from the nameplate, and size the VFD from that. Not from the horsepower number.
- Ask specifically whether an electric actuator includes a controller. Then ask what voltage the controller takes. Write both answers down.
- Confirm the return policy on electrical parts. I don't have hard data on how often people get burned by this, but anecdotally, it's way more often than it should be. Electrical items are frequently final sale.
Plus, one more: take the photo of the old nameplate before you even start shopping. Future you will be grateful.
When This Advice Doesn't Apply
Here's the honest part: everything above works for standard, catalog-order situations. There are plenty of cases where you should stop reading and call someone smarter.
If the motor is on a critical piece of equipment and downtime is measured in hours, same-day local sourcing beats any online ordering strategy. The motor price suddenly stops mattering. The cost of lost production does.
And oversizing a VFD isn't always the right call. In some applications, a bigger drive can cause motor ringing and nuisance faults. I've never fully understood the electrical mechanics of why—my best guess is it's related to reflected wave voltage on longer cable runs—but I know enough to tell people that bigger isn't automatically better.
If you're dealing with mixed voltages in the same panel, single-phase and three-phase side by side, get an electrician involved before you order anything. I'm comfortable writing motor POs now. I still don't wire them. There's a difference.
So take this for what it is: a purchaser's checklist, not engineering advice. If you're in over your head, that's exactly the right time to ask. I do it all the time. It's cheaper than the alternative.
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