Blind Solutions Academy · C21 · A4 Quick Reference

Motorisation & IBMS Integration Cheat Sheet

Torque sizing, protocol comparison, wiring & commissioning quick-ref and decision trees on four pages — the working numbers for the desk and the site.

Page 1 · Motor sizing

Torque & motor selection

F = m × g

Load force (N). m = fabric area × mass/m² + bottom bar (+ side-channel friction). g = 9.81.

T(tube) = F × r

r = effective lifting radius = radius to the OUTER fabric wrap, not the bare tube. Largest when rolled up.

T(motor) = T(tube) / η × margin

η = gearbox/assembly efficiency 0.6–0.85. Margin 1.2–1.5× (more for exterior / high-cycle).

Exterior: add windload

Wind force on fabric area (SANS 10160-3) often dwarfs gravity — the governing load for motor, brackets, fixings.

Worked: Sandton boardroom roller

Step	Value
Area 2.4 × 3.0	7.2 m²
Mass (0.35 + 1.8 kg bar)	4.32 kg
F = 4.32 × 9.81	42.4 N
r (45 mm tube + wrap)	0.030 m
T(tube)	1.27 Nm
/ 0.70 × 1.3	2.4 Nm req.
Select	6 Nm Sonesse 50

Duty cycle: shading motors are intermittent-rated (~4 min run, then thermal cut-out + cool-down). A motor near its torque limit trips sooner under sun-tracking.

Common Somfy interior Nm ladder	Typical use
6 / 10 / 15 Nm	Interior roller / screen blinds (Sonesse class, quiet)
20 / 30 Nm	Larger / heavier interior, light exterior (Altus/Orea)
40 / 50 Nm +	Heavy / exterior screens, projection, awnings

Page 2 · Protocol & bus comparison

Control bus & integration protocols

Control bus	Type	Feedback	Best for
Somfy RTS	433 MHz 1-way radio	None	Residential / simple retrofit
io-homecontrol	~868 MHz 2-way AES	Yes	Integrated retrofit, feedback
Zigbee	2.4 GHz mesh	Yes	3rd-party / IoT ecosystems
Dry contact	Volt-free relay	None	Safety / global overrides
RS485 / DC wired	Wired data bus	Full	Large new-build integration

Integration protocol	Model	Blind represented as	Doc to require
KNX	Decentralised, group addresses	DPT objects: move, stop, position %, status, slat %	DPT list / ETS project
BACnet	Object/property (IP & MS/TP)	Analog Value (position), Binary (cmd), Multistate (mode)	PICS
Modbus	Register-based master/slave	Holding regs (cmd/position), input regs (status)	Register map

Rule: don't pick a protocol in the abstract — match the gateway to what the building's BMS already speaks (BACnet/IP is common in large SA commercial work). Multi-protocol buildings are normal.

Page 3 · Wiring & commissioning quick-ref

Topology & commissioning

Power & cabling

Coincident start: integrated systems move many blinds at once (sun/wind/scene). Check coincident starting current, not just running — stagger group moves or split circuits.

LV DC: SELV + quiet + data-on-cable, but volt-drop over distance is real — size cable & locate PSUs per zone.

Buses: RS485 / KNX TP = daisy-chain + end termination, screened twisted pair, segregate from power.

SA frame: SANS 10142-1 + Certificate of Compliance by a registered person. Define the blind-installer vs electrician trade split.

Commissioning sequence

1. Set limits, verify direction, check travel/noise (every motor)

2. Assign addresses; configure zones/groups

3. Bind gateway objects (ETS / BACnet / Modbus); verify read + write

4. Calibrate sensors; witnessed wind-retraction test (local logic)

5. Tune sun-tracking & daylight; avoid hunting (hysteresis)

6. Program scenes; verify priority hierarchy

7. Integrated test with BMS + lighting; as-builts + training

Page 4 · Decision trees & standards

Choosing the architecture

Control-bus decision tree

BMS position feedback / closed-loop sun-tracking needed?

No, simple/retrofit → RTS (or io if 2-way wanted)

Yes → need feedback

Cabling practical? (new-build, large, RF-hostile) → RS485 / DC wired

Existing building / minimal cabling → io-homecontrol (or Zigbee for IoT)

Intelligence-location rule

Where does the logic live?

Wind / life-safety → LOCAL controller (never BMS-only)

Comfort / energy / scenes → may live in BMS over gateway

Priority hierarchy (top = wins)

1. High-wind / life-safety retraction — LOCAL, pre-empts all

2. Manual override (with timeout to auto)

3. Scheduled scenes

4. Automatic sun / daylight logic

SA / IEC standards quick map

Standard	Use
IEC 60335-2-97	Drive safety (rolling shutters, awnings, blinds)
IEC 60335-1	General appliance safety (used with -2-97)
SANS 10142-1	Wiring of premises + CoC
SANS 10160-3	Wind actions → exterior load & retract setpoint