Somfy Altus RTS 506S2 Motor Sizing and LT50 Parts Guide

By Linda Barber, Shade Motors Direct

The Somfy Altus RTS 506S2 120V 3-Wire Motor (1033399) sits in the middle of the LT50 range, and it is the motor most exterior solar screen jobs land on. Somfy pairs 6 Nm of torque with 38 rpm, which reads as a fast motor that still has enough muscle for a large screen. The reason it shows up on so many quotes has less to do with the torque number and more to do with the radio: RTS means the installer runs power to the motor and stops there. No control wire, no low-voltage run back to a switch, no second trip through the soffit.

The 506S2 name decodes to the spec

Somfy names LT50 motors by torque and speed. The 506S2 delivers 6 Nm at a nominal speed in the S2 band, which Somfy publishes as 38 rpm for this SKU. Step down to a 503 and you get 3 Nm for small interior tubes. Step up to a 520 or a 525 and you reach 20 and 25 Nm for heavy rolling shutters. The 506S2 covers the middle: exterior solar screens on a residential elevation, retractable insect screens, retractable awnings, and projection screens.

Somfy lists the motor for exterior solar screens, interior shades, projection screens, and retractable insect screens. The IP44 rating and the operating range of -4 to 158 degrees F back that exterior listing, which is the line most interior-only motors cannot cross.

Verified specifications

Class I insulation matters at the panel. The 3-wire SJTW cable carries line, neutral, and ground, and the ground has to land. An electrician who has only wired Class II low-voltage shade motors will sometimes cap the green conductor. Do not let that happen.

Five parts, and the motor is only one of them

Ordering an LT50 motor by itself buys one fifth of a working shade. The bracket carries the star head. The crown locks the motor body so it cannot spin inside the tube. The drive wheel hands torque to the tube wall. An RTS transmitter sets the limits and runs the shade for the next decade. Miss any one of those and the box sits on the truck.

Crown and drive selection follows the tube, not the motor

Installers get this backwards often enough that it deserves its own paragraph. The motor determines which family of crown and drive sets you can use. The tube profile determines which set inside that family is correct.

Round tubes at 2.5 in take the Somfy LT50 2.5 in Round Crown and Drive Set (9012231). Octagonal tubes at 70 mm, the profile most rolling shutter and exterior screen assemblies use, take the Somfy Octagonal LT50 70mm Crown and Drive Set (9012234). Measure the tube, then order.

Bracket choice depends on the pocket

The Somfy LT50 Star Head Motor Bracket (9410651) is the direct match for the 506S2 head, and it drops the motor into a fixed position. On pockets where the geometry fights you, the Somfy LT50 Universal Motor Bracket (9410665) gives more mounting options at the cost of a deeper footprint. Both carry the same motor.

Setting limits from the remote

Electronic limits are the feature that earns RTS its reputation on exterior work. You set the upper and lower stops from the transmitter, standing on the ground, instead of climbing to a limit-setting cap on the motor head. The motor holds 250 turns of limit capacity, which covers tall screens without a secondary gear.

A Somfy Situo 1 Channel RTS Pure Remote (1870571) does the programming and then becomes the client's handheld. For a client who wants a wall control that looks permanent, the Somfy Maintained Rocker Switch Kit with Standard Plate in White (1800342) fits a standard plate and pairs to the same motor. Both can live on the same shade, since the motor accepts multiple RTS transmitters.

Exterior install notes

IP44 protects against splashing water from any direction. It does not make the motor submersible, and it does not license a mounting position where the head sits in a puddle. Drip loop the SJTW cable below the entry point. Keep the head out of direct standing water at the sill. On a coastal elevation, spec stainless fasteners for the bracket even though Somfy ships the motor ready for the environment.

The 656 ft open field radio range collapses fast through masonry and stucco. On a house with a thick exterior wall between the client's usual standing position and the motor, add a repeater or move to a TaHoma hub rather than assuming the published number holds.

Ordering

Build the order as motor, crown and drive matched to the tube, bracket, and transmitter. The Altus RTS 506S2 (1033399) ships with the 9.84 ft SJTW pigtail already on it, so the only wiring decision left is where the junction box lands.

Questions we get on this motor

Can the Altus RTS 506S2 run an exterior solar screen?

Yes. Somfy lists exterior solar screens as a primary application and rates the motor IP44 with an operating range of -4 to 158 degrees F. Mount the head so it drains, add a drip loop on the SJTW cable, and the motor is rated for the position.

What crown and drive does the 506S2 need?

The set follows your tube profile. A 2.5 in round tube takes the LT50 2.5 in Round Crown and Drive Set (9012231). A 70 mm octagonal tube takes the Octagonal LT50 70mm Crown and Drive Set (9012234). Measure the tube before ordering.

Does the Altus RTS 506S2 need a control wire?

No. RTS carries the commands over 433.42 MHz radio, so the only run to the motor is 120V power on the 3-wire SJTW pigtail. Limits get set from the RTS transmitter, and the motor accepts more than one transmitter.

How much shade will 6 Nm lift?

Torque capacity depends on tube diameter and fabric weight together, since the tube acts as a lever arm. Somfy publishes sizing tables in the 500 Series Databook for each combination. A 6 Nm motor covers most residential exterior solar screens, and heavier rolling shutters move up to a 20 or 25 Nm LT50.

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