Mean Well LRS-100-5

Mean Well LRS-100-5 — 5V 18A (90W) enclosed switching supply

This is the small, low-voltage member of Mean Well's LRS enclosed metal-case family — the same fanless, screw-terminal switcher line as the LRS-350-24 that powers Voron beds, but configured for 5V at 18A instead of 24V. In a 3D-printer build this is the supply you reach for when you need a clean, dedicated 5V rail: a Raspberry Pi (or CB1/CM4) running Klipper, an MCU/control board's logic supply, LED strips, fans, or other 5V accessories. It is not a bed-heater supply — for the heated bed and 24V electronics on a Voron/RatRig you want a 24V LRS unit. Use this alongside one.

The real spec (read the part number carefully)

Despite the "100" in the name, the 5V model is rated 90W, not 100W: 5V x 18A = 90W. Mean Well derates the low-voltage members of the LRS-100 series, so you get 18A at 5V, not 20A. Plan your load budget around 90W / 18A. A Pi 4 under load plus a few 5V fans and an LED strip sits comfortably inside that; this supply has plenty of headroom for typical printer 5V duties.

• Output: 5V DC, 18A, 90W
• Input: 85-264 VAC full range (no voltage-select jumper) or 120-370 VDC
• Efficiency: ~86%
• Cooling: free-air convection — fanless and silent, no fan to fail or add noise to the enclosure
• Dimensions: 129 x 97 x 30 mm — the 30 mm low-profile case, easy to tuck into an electronics bay
• Protections: short circuit, overload, over-voltage
• Output trim: on-board SVR pot for fine 5V adjustment if you need to compensate for wire drop
• Safety/EMC: UL/CUL, TUV, CB, CE

Wiring and safety — this is a bare-terminal mains unit

Be clear-eyed about what you're buying: the LRS is an open-frame-style enclosed supply with exposed screw terminals, not a sealed wall-wart. The input side carries live mains voltage on a screw terminal block. You are responsible for:

• Mains wiring to the AC terminals (L, N, earth/⏚). Earth/ground must be connected to the metal case — this is non-negotiable for safety.
• Upstream fusing and a means of disconnect. The LRS has internal short-circuit protection on its output, but it does not replace a properly rated mains fuse or breaker on the input. Fuse it.
• Strain relief and a terminal cover. A clear plastic terminal guard is included; fit it. Don't leave live screw terminals exposed inside a printer enclosure.

If you're not comfortable terminating mains-voltage screw terminals and fusing an AC input, have someone who is do the install. This is standard practice for every LRS/HDR-class supply — it's the trade-off for the compact, cheap, field-serviceable form factor.

Why this form factor

The enclosed LRS case is the workhorse choice for printer builds: a vented steel shell, convection cooling (no fan noise), screw terminals you can actually service, and a price that's hard to argue with. The slim 30 mm height makes it easy to mount flat in an electronics compartment. If you instead want a clean DIN-rail control-cabinet install, look at the HDR (ultra-slim DIN) or UHP (slim, PFC, kit-grade) families; for a fully encapsulated PCB-mount module there's the IRM series. For a 3D printer's 5V accessory rail, the LRS-100-5 is the straightforward, proven pick.

On the price

This unit is on clearance. For reference, hobby/maker resellers list the LRS-100-5 around $27 (ProtoSupplies $26.95); component distributors like Digi-Key are lower at ~$18.60 in single quantity because they don't carry it as a niche printer part. Our clearance price sits between the two — a fair maker-channel price on the way out the door.