An MDR conveyor divides the line into zones, each driven by its own brushless, gearless 24V DC motor, with a photo-eye and zone controller deciding when each zone runs. The mechanical side of powered conveyor is well understood. What trips up most projects is the electrical side: how many motors a power supply actually carries, where supplies have to sit, and how zone length limits accumulation. Those three answers set the layout.

Power Supply Sizing Is About Simultaneity, Not Motor Count

A typical 24V DC power unit is rated 40 A and supports up to 40 motors, with 100 W standard motors and 125, 160, or 200 W options on a PowerCube control card.

Those two numbers look contradictory until you run them. A 100 W motor at 24 V draws about 4.2 A at full load, so a 40 A supply carries fewer than ten motors running at once. The 40-motor figure assumes the zones are not all running at once, which is exactly how a zone-controlled line behaves.

The practical consequence: a transport line where product runs continuously has high simultaneity and needs far more supply capacity per foot than an accumulation lane where most zones sit asleep. Specify the supply against your worst-case running state, not the motor count on the drawing.

Higher-wattage motors make this tighter. Moving from 100 W to 200 W roughly halves how many motors one supply can run at once.

Voltage Drop Drives Where Supplies Sit

On 24V DC, a 1 volt drop across the cable run is a 4.2 percent loss. The same 1 volt drop on a 480 V feed is about 0.2 percent. Low-voltage distribution has very little margin, which is why MDR lines use power supplies distributed along the conveyor rather than one central cabinet feeding the whole run.

Undersized or overlong DC runs show up as zones that start sluggishly, motors that fault under load, and intermittent faults that move around the line. It is an electrical design problem, not a motor problem, and it gets solved at layout rather than at commissioning.

Zone Length Sets Accumulation Capacity

Standard EZLogic zones are 24 inches, and a single power unit's controller handles up to 50 zones. That works out to roughly 100 feet of zero-pressure accumulation per power unit at standard zone length.

Zone length also has to match your product. Zone length should exceed the longest item so a carton does not straddle two zones, because a straddling item confuses the release logic the whole system depends on. Long product means longer zones, fewer zones in the same footprint, and less granular accumulation.

Energy Follows Product, Not the Clock

Zones wake when product arrives and sleep when empty, so the conveyor draws power only where product is moving.

The arithmetic is straightforward. A 100 W motor running continuously for a year consumes about 876 kWh. At 25 percent duty it consumes about 219 kWh. On a line shaft system, the single drive motor turns the entire shaft whenever the line is energized, whether product is present or not, so the load does not scale down when volume does.

Guarding and Service Advantages

MDR systems run without drive chains, belts, or line shafts, so lines run quieter and motors are safe to service.

That has a compliance dimension. OSHA requires sprocket wheels and chains to be enclosed unless they are more than seven feet above the floor or platform. MDR removes most of that exposure from the conveyor bed. General machine guarding still applies at transfers, diverts, and any remaining rotating parts.

Clearing a jam inside a guard remains servicing under the lockout standard, and new or modified equipment must have energy isolating devices designed to accept a lockout device.

NFPA 79 governs the electrical equipment of industrial machinery, including material handling machinery, and the National Electrical Code references it through Article 670. The 24V DC side sits downstream of an AC supply of 120 or 230 V single phase, so the machine's electrical design is in scope even though the motors are low voltage.

Failure Modes and Spares

Because every zone is a self-contained module, sections plug together, individual zones reverse or run at their own speed, and a failed motor swaps out without stopping the line for a chain or shaft repair.

That changes what you stock. On a line shaft system, the spares list centers on one drive, its reducer, and shaft components. On MDR, the spares that matter are motorized rollers, control cards, power supplies, and photo-eyes, held in the specific wattages and zone configurations your line actually uses. Buy them by zone type, not by count.

Diagnostics matter as much as parts. Well-built conveyor controls surface zone faults and jams for fast troubleshooting rather than forcing maintenance to trace I/O.

Migrating a Line Shaft Section to MDR

Line shaft systems remain in service in older buildings, and a planned migration to MDR usually happens section by section.

Section-by-section works because each MDR zone is independent, but the electrical scope is the part people underestimate. Each converted run needs DC power distribution, supply locations, and control integration with whatever still runs the rest of the line. Sequence the conversion so the power infrastructure goes in ahead of the belt, not after.

Getting MDR Into Your Line With HOJ

Whether you are converting one accumulation lane or building a new line around MDR, HOJ handles mechanical, electrical, controls, and install with one team. One point of contact, one company accountable for whether the line holds rate.

We size the electrical before we quote the steel. HOJ's PLC and controls integration team engineers controls in-house, so supply sizing, zone layout, and cable runs are part of the design rather than a field problem.

Panels are built and tested in our shop. UL 508A panels with full schematics, BOM, and component traceability, proven in factory acceptance testing before anything ships.

Your team gets the documentation. Commented code, I/O lists, as-built drawings, and known-good backups, so maintenance owns the system instead of calling the integrator.

Our own crews install and service it. Installation carries a one-year warranty, equipment carries manufacturer warranties, and a 70-plus vehicle service fleet keeps parts and technicians close.

Send us your product profile, throughput target, and accumulation requirement, and an HOJ engineer will lay out the zones and size the power.