Somfy 540R2 LT50 Wired Motor Torque and Tube Fit Guide

Torque sets the ceiling on this motor. The Somfy 540R2 produces 40 Nm at 14 rpm from a 120V AC supply, which places it above the 30 Nm 530R2 and under the 50 Nm 550R2 in the same LT50 wired range. Installers reach for 40 Nm on wide retractable awnings and on rolling shutters built from heavy slats, where a 30 Nm motor works at the edge of its rating. Size the torque from the weight of the curtain or shutter plus the finished roll diameter, never from the width on its own. A 14 rpm head turns slower than the 20 rpm units in the same family, and that slower rotation is what carries the extra load.

Somfy publishes two applications for reference 1049894, awnings and rolling shutters. Both live outdoors, and the motor carries the rating to match: IP 44, with an operating range from -13 F to 158 F and storage down to -4 F. A shutter box on a south wall sees every part of that range across a year.

The motor runs at 55 dB, a figure that reads fine behind an exterior shutter box or inside an awning roller. Interior shade work belongs to the Sonesse line, where Somfy builds the motors around quiet running. For an exterior tube, the 540R2 gives you the torque and the weather rating in one 120V unit.

Verified specifications

Figures above come from Somfy's own published data for reference 1049894 on somfypro.com and from the Somfy 500 Series Databook.

The tube and crown that fit it

Somfy sets the minimum tube inner diameter at 1.85 in. Measure the inside of your tube before you order anything else, because a tube under that figure will not take the motor body. The motor itself measures 1.97 in across, and the drive end sits at 1.77 in.

Inside the tube, a crown rides on the motor head end and a drive wheel keys into the tube profile at the other. Two sets cover most LT50 exterior work on this store. The Somfy LT50 2.5" Round Crown and Drive Set (9012231) seats a 2.5 in round tube, the common choice on larger awning rollers. For an octagonal shutter tube, the Somfy Octagonal LT50 70mm Crown and Drive Set (9012234) keys into a 70 mm octagonal profile. Match the set to the tube you own rather than to the motor, since the motor end of every LT50 set is identical.

Brackets for a star head

Somfy publishes this reference with a STAR head, and the head shape decides the bracket. A star plate carries the four-lobed head and locks it against rotation, so the tube turns and the motor body stays still.

The Somfy LT50 Star Head Motor Bracket (9410651) is the direct match. On a retrofit where the existing mounting holes do not line up, the Somfy LT50 Universal Motor Bracket (9410665) gives you more hole positions on the same star pattern. Check the clearance between the bracket face and the tube end before you cut the tube, because the head and bracket together eat into the finished roller length.

Wiring and control from a switch or relay

The 540R2 arrives with a 9.84 ft SJTW 4-wire pigtail in white, stripped at the ends, and Somfy lists that cable as removable at the head. Four conductors give you line, neutral, and the two directions. A maintained rocker or key switch drives it, and a third-party relay or dry-contact output from a building control system drives it the same way.

No radio receiver sits inside this motor, so an RTS remote has nothing to pair with. Somfy covers that path with the Altus RTS 540R2 under reference 1240556, which carries the same 40 Nm rating with a built-in RTS receiver. Pick the wired 540R2 when the wall has a switch leg in it or when a relay panel runs the elevation, and pick the radio version when the walls are closed.

Current draw reaches 1.8 A at 210 W in motion, and the motor settles at 0 W once it stops. Size the branch circuit and any relay contacts around that 1.8 A figure, and count every motor on a shared circuit at full draw, since shutters on one facade tend to run together.

Setting the mechanical limits

This reference uses mechanical limit switches with a capacity of 46 turns, which covers a tall shutter on a small-diameter tube. Set both ends at the motor head with the adjustment screws, run the tube to each stop, and recheck after the first few cycles while the fabric or slat curtain settles. Somfy publishes repeatability at plus or minus 5, tight enough to keep a shutter bottom bar square to the sill across a season.

Thermal protection gives 5 minutes of continuous run time before the motor rests, with the thermal cutout set at 284 F. Rolling shutters and awnings rarely approach that limit in service. Commissioning a facade does, so stagger your test runs across several motors instead of cycling one unit over and over.

Ordering the 540R2 and the parts around it

The Somfy 540R2 120V 4-Wire Motor (1049894) ships as the bare motor with its pigtail. Build the order around the tube you have: the crown and drive set for your profile, plus the star head bracket. Installers who stock LT50 parts often keep both the round 2.5 in and the 70 mm octagonal sets on the van, since retrofit work turns up both profiles.

For loads past what 40 Nm will carry, Somfy's 550R2 in the same wired LT50 body steps up to 50 Nm at 14 rpm with the same star head and the same 1.85 in tube requirement, so the rest of your parts list carries over without change.

Frequently asked questions

What tube does the Somfy 540R2 fit?

Somfy sets a minimum tube inner diameter of 1.85 in for reference 1049894. The motor body measures 1.97 in across and the external diameter at the drive end is 1.77 in. Pair it with an LT50 crown and drive set that matches your tube profile, either a 2.5 in round tube or a 70 mm octagonal shutter tube.

Does the 540R2 work with a Somfy RTS remote?

This reference is a wired 4-wire motor with no radio receiver inside, so an RTS remote has nothing to pair with. Control comes from a maintained switch or a relay output. For remote control at the same 40 Nm rating, Somfy offers the Altus RTS 540R2 under reference 1240556 with the receiver built into the head.

How many limit turns does the 540R2 have?

Somfy publishes a mechanical limit switch with a capacity of 46 turns and repeatability of plus or minus 5. Set both limits at the motor head with the adjustment screws, then run the tube to each stop and confirm the positions after a few cycles once the curtain or slat stack has settled.

What cable comes on the 540R2?

The motor ships with a 9.84 ft SJTW cable in white, four conductors, stripped at the ends, and Somfy lists it as removable at the motor head. That removability helps on a retrofit where the run length changes. Rated current reaches 1.8 A at 210 W in operation, with 0 W draw in standby.

Shade Motors Direct is an authorized source for genuine Somfy motorized window shade, blind, and drapery parts.