Short answer: Most Somfy roller shutter jobs in North America run on the LT50 platform, which needs a tube with at least 1.85 in inside diameter. Pick the Oximo RTS 525A2 (1033402) or the Altus RTS 525A2 (1043423) for radio control at 25 Nm, or a wired 4-wire LT50 such as the 520R2 (1042055) or 540R2 (1049894) when a wall switch runs the shutter.
A rolling shutter puts more load on a motor than an interior shade does. The slats are aluminum or vinyl, the curtain rolls into a box above the opening, and the motor holds that weight whenever the shutter stops halfway. Somfy builds a full LT50 range for this work, and four of its motors list rolling shutters among their applications. The choice comes down to the tube, the torque, the control and the hardware around the motor head.
Start with the shutter you already have
On a replacement, the old motor tells you most of what you need. Pull the end cap on the shutter box and read the label on the motor head. A Somfy label carries a reference number and a model code such as 525A2 or 540R2, and our guide to reading a Somfy motor label walks through each field.
Note four things before you order. Record the tube profile and its inside dimension, the torque code on the label, the number of wires in the motor cable, and whether a hand crank sits on the box. The wire count separates a radio motor from a switch motor. A 3-wire cable (line, neutral, ground) usually means the receiver lives inside the motor. A 4-wire cable means a wall switch sends up and down on separate conductors.
A missing or faded label changes the order of work. Measure the tube first, then ask the shutter maker for its motor recommendation by width and height.
Measure the tube: octagonal profiles and the 1.85 in minimum
Somfy publishes a 1.85 in minimum tube inside diameter for its LT50 motors, against a motor body of 1.77 in outside. Rolling shutter tubes are octagonal in most boxes, so measure across the flats rather than corner to corner. Corner readings run high and lead to the wrong crown.
The crown centers the motor inside the tube and the drive turns the tube wall. Both parts belong to the tube profile. A 60 mm octagonal tube takes the Somfy Octagonal LT50 60MM Crown/Drive Set (9012233), and a 70 mm octagonal tube takes the Somfy Octagonal LT50 70mm Crown and Drive Set (9012234). Order the crown and drive as a matched set. A crown from one profile with a drive from another lets the motor slip inside the tube under load.
Large shutters can outgrow the LT50 platform. Somfy caps LT50 at 50 Nm and moves heavier loads to LT60, which needs a larger tube and its own crowns, drives and brackets. Our LT50 vs LT60 comparison covers that step up.
Torque: read the old code, then the shutter maker's chart
Somfy prints torque and speed in the model code. A 525A2 delivers 25 Nm at 20 rpm. A 520R2 delivers 20 Nm at 14 rpm, and a 540R2 delivers 40 Nm at 14 rpm. The digits after the leading 5 give the newton-meters.
Shutter torque depends on curtain weight and on how fat the roll gets as the slats wind up. A tall shutter with heavy slats needs more torque than its width suggests, because the roll diameter grows with every turn. The shutter fabricator publishes a motor recommendation for each size, and that figure outranks any rule of thumb. Match the old code on a like-for-like replacement, and step up one size if the shutter has gained weight from added slats or a new curtain.
Undersizing shows up fast. The motor trips its thermal protection or stalls near the top. Our guide to sizing a Somfy motor explains how torque, tube and speed interact.
Four LT50 motors Somfy lists for rolling shutters
Somfy names rolling shutters among the applications for each motor below. Figures come from Somfy's product records for each reference. Prices are live store prices on October 14, 2026.
| Motor | Torque and speed | Control | Limits | Price |
|---|---|---|---|---|
| Somfy Oximo RTS 525A2 (1033402) | 25 Nm (221 in-lb), 20 rpm | RTS, built-in receiver | Electronic, 200 turns | $448.59 |
| Somfy Altus RTS 525A2 (1043423) | 25 Nm (221 in-lb), 20 rpm | RTS, built-in receiver | Electronic, 250 turns | $448.59 |
| Somfy 520R2 120V 4-Wire Motor (1042055) | 20 Nm (177 in-lb), 14 rpm | Wired switch, 4-wire | Mechanical, 46 turns | $322.95 |
| Somfy 540R2 120V 4-Wire Motor (1049894) | 40 Nm (354 in-lb), 14 rpm | Wired switch, 4-wire | Mechanical, 46 turns | $407.45 |
All four run on 120V AC, 60 Hz, carry an IP 44 rating for exterior use, take a star head bracket and fit the same 1.85 in minimum tube. Somfy backs each with a 5 year warranty.
Radio or wired: Oximo, Altus RTS or a 4-wire LT50
The Oximo RTS 525A2 is Somfy's dedicated rolling shutter motor. Somfy lists one application for it, rolling shutters, and describes it as compatible with all types of rolling shutters. Somfy's launch notes for the Oximo 50 RTS line describe obstacle detection on the way down and frost protection that stops upward travel when ice holds the slats. It draws 180 W running and 0.37 W in standby, and the power run to the box carries three conductors with no control wire.
The Altus RTS 525A2 shares the torque, speed and head. Somfy lists it across awnings, exterior screens, rolling shutters and interior blinds, rates it at 56 dB, and publishes 250 turns of limit capacity with 0 W standby draw.
The wired 520R2 and 540R2 suit a shutter already wired to a switch. Somfy rates the 520R2 at 48 dB and the 540R2 at 55 dB, and both list awnings and rolling shutters as applications. Limits are mechanical, set at the motor head, and a 4-wire cable brings separate up and down conductors from the switch. These motors have no radio inside, so a handheld remote will not pair with them. If you want a remote, choose one of the RTS motors and run power only.
A shutter with a hand crank on the box needs a CMO (crank manual override) motor. Somfy builds LT50 CMO motors for awnings and rolling shutters, and they take a different head from the star-head motors above, so order a bracket made for the CMO head.
Brackets, a remote and what to order with the motor
Each motor in the table uses the LT50 star head. The Somfy LT50 Star Head Motor Bracket (9410651) is the plate cut for that shape.
An RTS motor needs a transmitter on site to set its limits. The Somfy Situo 1 Channel RTS Pure Remote (1870571) programs one shutter and stays with the homeowner afterward. Several transmitters can share one motor, so a wall switch or a TaHoma hub can join later without opening the box.
A complete order for one shutter looks like this. Pick the motor by torque and control, add the crown and drive set for the tube profile, add a star head bracket, and add a transmitter for an RTS motor. Browse the full range in our Somfy LT50 motors collection, and keep the install guide for your motor from our Somfy spec sheet library with the job paperwork.
Somfy roller shutter motor FAQ
What size Somfy motor does a roller shutter need?
Torque depends on curtain weight and roll diameter, so the shutter maker's motor chart decides it. On a replacement, match the torque code on the old label: 525A2 means 25 Nm, 540R2 means 40 Nm. Somfy's LT50 range for shutters runs up to 50 Nm, and heavier shutters move to the LT60 platform and a larger tube.
Can I add a remote to a wired 4-wire shutter motor?
A 4-wire LT50 such as the 520R2 has no radio receiver, so a Somfy remote cannot pair with the motor itself. The 4-wire motor runs from a wall switch. For handheld or app control, replace it with an RTS motor such as the Oximo RTS 525A2 or Altus RTS 525A2, which carry the receiver inside and need power only.
What is the difference between Oximo and Altus RTS?
Both deliver 25 Nm at 20 rpm on the LT50 platform with a star head and a built-in RTS receiver. Somfy lists the Oximo RTS 525A2 for rolling shutters alone and describes obstacle and frost protection on the Oximo line. The Altus RTS 525A2 covers awnings, screens and shutters, with 250 turns of limit capacity against 200 for Oximo.
Will my old crown and drive fit a new Somfy motor?
Crowns and drives belong to the tube profile and the motor platform. Somfy LT50 crowns and drives fit Somfy LT50 motors, so a Somfy LT50 swap can reuse a set in good condition. If the old motor came from another maker, measure the octagonal tube across the flats and order the matching Somfy LT50 set, such as 60 mm or 70 mm.
Sources: Somfy product records on somfysystems.com and somfypro.com for references 1033402, 1043423, 1042055 and 1049894; Somfy Systems press release on the Oximo 50 RTS exterior rolling shutter motor (September 2014).
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