Short answer: Somfy rates 24V DC motor power runs at 240 ft on 14 AWG, 150 ft on 16 AWG and 100 ft on 18 AWG. Size the gauge from the longest measured run. Size the power from the motor count: 1870196 for up to 5 motors, 1870192 for 10, 1870197 for 15 and 1870198 for 20. These kits stay off SDN jobs.
Low-voltage shades fail in the field for two boring reasons. The run was too long for the wire, or the supply was too small for the motors. Both show up after the drywall closes, and both turn into a callback with a ladder and a ceiling patch. Get the gauge and the amps right on paper and the commissioning day stays short.
Free spec package
24V DC Shade Power and Wiring Drawing Set
- SMD-01 general notes and a system-limits schedule with a source for every number
- SMD-02 enclosure elevations with Somfy-published dimensions and a kit selection schedule
- SMD-03 riser and home-run wiring detail with a gauge and length schedule
- SMD-04 three-part guide spec, bill of materials and a submittal checklist
The four numbers that decide every 24V DC shade circuit
Somfy publishes the limits in the Low-voltage Databook. Pin these to the electrical drawings before rough-in.
Somfy 24V DC power limits
- 14 AWG: 240 ft maximum motor power cable length
- 16 AWG: 150 ft maximum
- 18 AWG: 100 ft maximum
- Sonesse 30 current: 0.8 A nominal load, 1.8 A starting for up to 300 ms
- Sonesse ULTRA 50 DC: 1.5 A rated current
- Supply sizing: 10 A supply for 5 motors, 20 A supply for 10 motors
Somfy prints the gauge table "to guarantee characteristics." Inside the table the motor delivers its rated torque and speed. Past it, Somfy makes no promise, and neither should your submittal.
Wire gauge vs run length: read the table from the longest run
Measure the real cable path from the supply to the motor head, including the drop down the wall and the service loop at the bracket. Plan distance on a floor plan runs short every time. Then read across the table and pick the first gauge that covers the run.
Our rule: pull one gauge for the whole floor, set by the longest run. One spool, one pull, no mix-ups at termination. A crew that carries 18 AWG for the short runs will use it on the long one by Friday.
Somfy lists its SDN low-voltage cable as an accessory for the Sonesse 30 RTS 24V DC. The non-plenum 9020126 and the plenum-rated 9020127 carry one 14 AWG power pair, one 22 AWG shielded data triad and a 24 AWG drain in a single jacket, rated for installation lengths up to 240 ft. On an RTS job the power pair does the work. Our rule: pull it on any RTS floor the owner may take wired later, since the data triad is already in the wall.
Size the power: count motors, then climb the kit ladder
Somfy pairs each supply with a motor count. The databook lists a 10 A, 24V DC DIN rail supply for 5 motors and a 20 A supply for 10 motors. That works out to 2 A of supply per motor, above the 1.8 A Sonesse 30 starting current. Somfy specifies only its own supplies to keep the UL listing and the motor performance.
The kit ladder follows the same math:
- 1 motor next to a receptacle: the 24V DC plug-in transformer 1822209.
- Up to 5 motors: Power Distribution Enclosure Kit, 5 Motor 1870196.
- Up to 10 motors: Power Distribution Enclosure Kit, 10 Motor 1870192.
- Up to 15 motors: Power Distribution Enclosure Kit, 15 Motor 1870197.
- Up to 20 motors: Power Distribution Enclosure Kit, 20 Motor 1870198.
Our rule: place one kit per riser or per floor, centered on its motors, so the longest home run stays inside the gauge you picked. Two smaller kits close to the shades beat one big kit in a far closet when the runs pass 150 ft.
Inside a Somfy power distribution enclosure kit
Each kit ships assembled in a UL listed enclosure with one dedicated 120V/60 Hz input and a fused output for every motor. An LED on each output shows power at a glance, and plug-in connectors speed termination. The enclosure is rated IP 20, so it belongs indoors in a dry electrical space.
The databook breaks the kits down:
- 1870196: one 5-motor panel and one 10 A supply in a 12 in x 12 in x 6.25 in enclosure.
- 1870192: one 10-motor panel and one 20 A supply in an 18 in x 18 in x 6.25 in enclosure.
- 1870197: one 5-motor and one 10-motor panel, with a 10 A and a 20 A supply, 18 in x 18 in x 6.25 in.
- 1870198: two 10-motor panels and two 20 A supplies, 18 in x 18 in x 6.25 in.
Fused ports save your service day. A shorted motor lead takes out one port and one LED goes dark. The other nine shades keep running and the tech walks straight to the fault.
Motors that belong on a kit, and why SDN stays off
Somfy built these kits for radio and dry contact 24V DC motors. Its compatibility list names the Sonesse 30 RTS 1241142, the Sonesse 30 DCT 1241146, the Sonesse 30 Zigbee 1241970 and the Sonesse ULTRA 50 RTS 1134023. Somfy also publishes wire details for Sonesse 30 DCT, Sonesse 30 RTS and Irismo to the kit.
The Low-voltage Databook marks the kits "Not to be used with SDN installations." An SDN job needs power and the RS485 bus on the same home run, with termination and bias handled at the panel. That is the job of the SDN PowerConnect Surface-Mount Panel 1871026. Put a kit on an RTS or DCT floor. Put PowerConnect on an SDN floor. Keep the two apart on the riser drawing.
Write it into the spec so the electrician bids it right
The shade spec and the electrical drawings have to say the same thing. Put these items on both:
- Dedicated 120V/60 Hz circuit at each kit location, installed per NEC and local code.
- Home-run conductor gauge per run length, from the Somfy table.
- Kit part number and location on the riser, with the motor schedule mapped to ports.
- Plenum-rated cable wherever the run passes through a return-air plenum.
The download carries a three-part guide spec with bracketed items you can edit, a bill of materials and a submittal checklist. Drop it into the project manual and mark it up.
Take the spec package to your submittal
24V DC Shade Power and Wiring Drawing Set
- SMD-01 general notes and a system-limits schedule with a source for every number
- SMD-02 enclosure elevations with Somfy-published dimensions and a kit selection schedule
- SMD-04 three-part guide spec, bill of materials and a submittal checklist
FAQ
What wire gauge do Somfy 24V DC shade motors need?
Somfy's Low-voltage Databook limits the motor power cable to 240 ft on 14 AWG, 150 ft on 16 AWG and 100 ft on 18 AWG. Pick the first gauge that covers your longest measured run.
Can I use a Somfy power distribution enclosure kit on an SDN project?
No. Somfy marks the kits as not for SDN installations. SDN motors take power and RS485 data from an SDN PowerConnect panel such as 1871026.
How many Sonesse 30 motors can one power supply run?
Somfy pairs a 10 A, 24V DC supply with 5 motors and a 20 A supply with 10 motors. The Sonesse 30 draws 0.8 A at nominal load and 1.8 A for up to 300 ms at start.
Which power distribution kit fits 12 motors?
The 15-motor kit 1870197 covers 11 to 15 motors. It holds a 5-motor and a 10-motor panel with a 10 A and a 20 A supply.
Sources: Somfy Low-voltage Databook (gauge and length table, motor current, power supplies, power distribution enclosure kits); somfysystems.com product pages 1870196, 1870192, 1870197, 1870198, 1241142 and 9020126; Somfy PDEK-WIRING-01 to 04 wire detail titles.
Ryan Towns writes the Somfy Integrator Guides for ShadeMotorsDirect, an authorized Somfy distributor. Questions on a spec or a retrofit: 859-414-6872 or colin@shademotorsdirect.com, 8:00 AM - 7:30 PM ET.
