Exterior work asks more of a motor than interior work does. A rolling shutter carries its own weight in slats, an awning fights spring tension through the whole extension, and both live outdoors. The Somfy Altus RTS 525A2 (1043423) is the LT50 motor Somfy builds for that band of work: 25 Nm, a star head, an IP44 rating, and an RTS receiver already inside the tube.
Somfy lists it for awnings, exterior solar screens, rolling shutters, projection screens, retractable insect screens, and interior blinds. One motor covers most of a dealer's exterior line sheet.
Minimum tube inside diameter is 1.85 inches
Somfy publishes 1.85 in as the minimum internal diameter, with a motor body of 1.77 in outside. That gap is small, and it decides the job before anything else does.
Rolling shutter tubes are usually octagonal rather than round. An octagonal tube gets measured across the flats, corner to corner reads high. A 60 mm profile and a 70 mm profile both accept an LT50 motor and take different crown and drive sets, so the profile has to be confirmed before hardware ships.
Measure the tube you have. A shutter box built twenty years ago may hold a profile no longer in the current range, and a photograph of the end of the tube with a rule across it settles the order faster than a part number from an old invoice.
Verified specifications
| Torque | 25 Nm (221 in-lb) |
| Speed | 20 rpm |
| Control | RTS, built-in receiver, 433.420 MHz |
| Channels | 12 |
| Radio range | 656.2 ft open field, rolling code |
| Power supply | 120V AC, 60 Hz, range 108V to 132V |
| Rated current | 1.6 A |
| Consumption | 180 W running, 0 W standby |
| Noise | 56 dB |
| Minimum tube inside diameter | 1.85 in |
| Motor outside diameter | 1.77 in |
| Head type | Star |
| Limits | Electronic, 250 turn capacity |
| Ingress rating | IP44 |
| Insulation class | Class I |
| Operating temperature | -4 F to 158 F |
| Warranty | 5 years |
Figures come from Somfy's published product record for 1043423. Somfy also publishes a 40.4 kg CO2 lifecycle footprint for this motor, which turns up on LEED and WELL documentation packages.
Zero standby draw on an exterior circuit
The motor draws 180 W while it runs and nothing at rest. A shutter that cycles twice a day spends a few seconds under load and the rest of the day at zero.
That matters on a facade with a bank of shutters sharing a circuit. A designer sizes the breaker from the worst case, which is every shutter moving on the same schedule command, and 1.6 A per motor at 120V is the number to multiply. Somfy's electronic limits hold through a power cut, so an outage does not send an installer back up the ladder to reset the closed position.
IP44 covers rain and splashing from any direction. Mount the head so water drains away from the cable entry and leave a drip loop below it.
Star head, and the brackets that accept it
The star head is the LT50 standard, and it seats in a bracket cut for that shape. Two options cover most installs.
The Somfy LT50 Star Head Motor Bracket (9410651) is the plate built for this head, which suits a shutter box with a flat mounting face. On a retrofit where the old bracket position has to change, the Somfy LT50 Universal Bracket with Spring Clip (9420631) lets the motor drop into place and clip home, which saves a fight in a tight box.
Order the bracket with the motor. A star head sitting in a bracket meant for a round head is the single most common reason a shutter install stalls at the opening.
Crown and drive for an octagonal tube
The crown centers the motor inside the tube and the drive hands rotation to the tube wall. Both parts belong to the tube profile rather than to the motor.
A 70 mm octagonal shutter tube takes the Somfy Octagonal LT50 70mm Crown and Drive Set (9012234). A deep-section 78 mm profile takes the Somfy LT50 DS78MM Crown and Drive Set (9012239).
Mixing a crown from one profile with a drive from another produces a motor that spins inside the tube under load. It survives the commissioning cycle and fails a season later, which is the worst kind of failure to diagnose from a phone call.
Setting limits from the ground
Limits are electronic and get set from an RTS transmitter, with 250 turns of capacity between the open and closed stops. An installer stands below the opening, drives the shutter to each end, and records the position.
That is a real difference from a mechanical-limit motor on exterior work. A shutter box eight feet up over a sealed patio is a ladder job every time a limit drifts, and this motor removes the ladder from the adjustment.
Programming needs a transmitter on hand at commissioning. The Somfy Telis 4 RTS Multi-Channel Patio Remote (1810645) handles four channels and doubles as the owner's handheld afterward, and the motor accepts several transmitters, so a wall switch can join the same shutter later.
Wind protection on anything that extends
An awning left out through a gust loses fabric, arms, or the whole frame. Somfy's Eolis 3D WireFree RTS Wind Sensor (1816081) mounts on the front bar, reads movement rather than air speed at a fixed point, and retracts the awning when the bar starts to shake.
Pair the sensor to the motor the same way a handheld pairs, since both run on the RTS radio at 433.420 MHz. Price it into the quote from the start on any exposed elevation. Owners rarely ask for wind protection before their first storm. They ask after it.
Ordering
Confirm the tube profile and its inside diameter against the 1.85 in minimum, then order the Altus RTS 525A2 (1043423) with a crown and drive set matched to that profile, a bracket cut for a star head, and one RTS transmitter for commissioning. Add a wind sensor on any awning. Somfy covers the motor for 5 years.
Questions we get on this motor
How much shade will 25 Nm lift?
Torque covers load, not square footage. The answer changes with slat weight on a shutter and with arm tension on an awning. Somfy's 525A2 designation reads as 25 Nm at 20 rpm, which covers most residential rolling shutters and mid-size lateral arm awnings. The fabricator publishes a motor recommendation per frame, and that figure outranks any general guidance.
Does the Altus RTS 525A2 need a separate receiver?
No. The RTS receiver sits inside the motor, so the only run to the tube is 120V power. Limits get set from a handheld transmitter and the motor accepts several of them, which lets a remote, a wall switch, and a wind sensor share one shutter.
What tube does the Altus 525A2 fit?
Somfy publishes a minimum internal diameter of 1.85 in against a motor body of 1.77 in. On a rolling shutter the tube is usually octagonal and gets measured across the flats, with 60 mm, 70 mm, and 78 mm profiles all taking their own crown and drive set. Confirm the profile before ordering hardware.
Can this motor run on the TaHoma app?
Yes. The motor speaks RTS at 433.420 MHz, and a Somfy TaHoma hub brings the app, sun and time schedules, and voice assistants to RTS motors already installed. The shutter hardware stays as it is and the existing handheld keeps working alongside the app.
Shade Motors Direct is an authorized source for genuine Somfy motorized window shade, blind, and drapery parts.
