Somfy Altus RTS 550R2 LT50 Motor Fit and Torque Guide

Somfy builds the Altus RTS 550R2 for the heavy end of the 500 Series lineup. The motor carries a star head, an RTS receiver inside the housing, and 50 Nm of torque at 14 rpm. Buyers order it for large rolling shutters and wide retractable awnings, then hit one question at the bench: will the tube on hand take this motor. Somfy answers that with a published minimum internal tube diameter of 1.85 inches and a motor diameter of 1.97 inches.

Torque, speed, and where the 550R2 sits in the 500 Series

Somfy publishes 50 Nm at 14 rpm for reference 1038170. That converts to about 442 in-lb. The official Somfy name reads "550R2 ALTUS RTS 50/14SJTW 10FT", and the string carries the torque, the speed, and the 10 foot SJTW pigtail Somfy ships on this reference.

The 550R2 tops the LT50 Altus RTS ladder. Below it sit the 525A2 at 25 Nm and the 535A2 at 35 Nm, both on the same tube platform and the same RTS radio. Torque doubles from the 525A2 to the 550R2 while speed drops to 14 rpm. Installers trade travel time for lifting power. A wide shutter curtain or a heavy acrylic awning fabric on a 2.5 inch tube asks for the 50 Nm motor, and dropping to a smaller motor to save money shows up later as a stalled shutter on a cold morning.

Size the motor from roll weight and finished roll diameter, not from fabric width alone. The 500 Series Databook carries the torque tables Somfy publishes for that calculation, and Somfy Pro lists reference 1038170 on its own e-catalog page with the figures in the table below.

Applications Somfy names for reference 1038170

Somfy lists six applications on this reference: awnings, exterior solar screens, interior window coverings, projection screens, retractable insect screens, and rolling shutters. The breadth comes from the IP 44 rating and the 55 dB sound level. Exterior work suits this motor. A 55 dB motor inside a quiet bedroom will announce itself, so specify the Sonesse family for interior rooms where sound matters and keep the 550R2 on the exterior openings and the large projection screens where its torque earns its place.

The Shade Motors Direct listing names three of those six applications. Somfy publishes all six, and a buyer sizing a large projection screen or a retractable insect screen can order this reference with confidence.

Verified specifications for the Altus RTS 550R2

Figures come from the Somfy Pro e-catalog page for reference 1038170 and the Somfy Systems product page for the same reference. The store listing for the Somfy Altus RTS 550R2 (1038170) carries a seven row table. The rows above fill the gaps a bench installer needs: current draw for the circuit, the 1.85 inch minimum tube bore, the 26.89 inch motor length that has to clear the end bracket, and the 5.6 lb weight the bracket carries.

Tube, crown, drive, and bracket fitment

Three pieces of hardware turn this motor into a working assembly. The crown seats in the tube and holds the motor body from spinning. The drive wheel keys the motor output to the tube. The bracket carries the head end at the wall or the shutter box. Somfy sizes each piece to the tube profile, so the tube decides the part number.

For a 70mm octagonal shutter tube, the Somfy Octagonal LT50 70mm Crown and Drive Set (9012234) matches the profile and comes as a pair, which removes the mismatch risk of ordering a crown and a drive from separate lines. Round 2.5 inch tube work uses the LT50 2.5 inch crown and hard clip drive instead. Check the tube bore against the 1.85 inch published minimum before ordering either set, because a tube that measures under 1.85 inches will not accept the motor no matter which crown you buy.

The head end has two bracket paths. The Somfy LT50 Star Head Motor Bracket (9410651) takes the star head on this motor and locks it against rotation. The Somfy LT50 Universal Bracket with Spring Clip (9420631) gives a faster drop-in with a spring clip that holds the head while you set the fasteners. Measure the pocket depth before choosing. A 26.89 inch motor plus the bracket and the idler end sets the minimum tube length for the opening.

Control path and programming

The RTS receiver lives inside this motor, so no control wiring runs back to the head. Somfy publishes 433.420 MHz, 12 channels, and a 656.2 ft range for the radio. That range covers a house and a detached patio structure from one handheld.

The Somfy Situo 1 Channel RTS Pure Remote (1870571) pairs to a single motor and gives an installer the handheld needed to set limits at the opening. Multi-channel Situo and Telis remotes run several motors from one handheld, and the Telis Soliris versions add sun and wind response for awning work. DecoFlex RTS wall switches mount without a wire chase, since they talk to the motor over the same radio. Somfy TaHoma brings the motor into app and voice control and pulls it into scenes with the rest of the RTS equipment in the building.

Connect power before pairing. The motor accepts a remote in its programming window, and the Somfy RTS Pocket Programming Guide covers the button sequence for pairing, limit setting, and adding a second remote.

Install notes and the limit system

Somfy publishes electronic limit switches on reference 1038170, with a 250 turn capacity. An installer sets those limits from a paired RTS remote, which means the head end stays accessible during setup but needs no screwdriver at the limit ports. The Shade Motors Direct listing describes mechanical limits with rapid-adjustment push buttons, and Somfy's own data for this reference says electronic. Trust the Somfy figure and expect remote-set limits on the motor you receive.

Two more notes matter at the bench. The motor draws 2.1 A and consumes 250 W while running, so a shared circuit with several of these motors needs a load check. Thermal protection cuts in after 5 minutes of continuous run, which suits shutter and awning duty cycles and rules out continuous-motion display work. Standby draw reads 0 W, a figure that helps on projects with plug load budgets.

Somfy ships this reference with a 9.84 ft SJTW cable. Class I insulation means the ground conductor carries a job, so terminate all three conductors. The listing title omits the 10 foot pigtail Somfy names in the official product name, and a buyer comparing references should read the cable length as part of the spec rather than an option.

Frequently asked questions

What tube diameter does the Altus RTS 550R2 need?

Somfy publishes a minimum internal tube diameter of 1.85 inches for reference 1038170, with a motor diameter of 1.97 inches. Measure the inside bore of the tube, not the outside. A 70mm octagonal shutter tube or a 2.5 inch round tube clears that figure with the matching Somfy crown and drive set.

Does this motor need a separate RTS receiver?

No. Somfy builds the RTS receiver into the 550R2, so a Situo or Telis remote pairs to the motor with no extra hardware. The published radio specification reads 433.420 MHz across 12 channels with a 656.2 ft range. Power and a paired remote are all the motor needs to run.

How loud is the Altus RTS 550R2?

Somfy publishes 55 dB for this reference. That figure suits exterior shutters, awnings, and screens along with large projection screens. For a bedroom or a conference room where quiet matters, Somfy's Sonesse line publishes lower sound levels and serves those interior rooms.

Which bracket fits the star head on this motor?

The Somfy LT50 Star Head Motor Bracket (9410651) takes the star head and holds it against rotation. The Somfy LT50 Universal Bracket with Spring Clip (9420631) also accepts it and speeds the drop-in. Pocket depth and the 26.89 inch motor length decide which bracket suits the opening.

The Somfy Altus RTS 550R2 (1038170) covers the heavy LT50 work a 25 Nm or 35 Nm motor cannot carry, and its 5 year Somfy warranty backs the install. Add the crown and drive set that matches your tube profile, the bracket that fits your pocket, and an RTS handheld to set the limits. That short list gets a shutter or an awning running the day the parts land.

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