Installing Aqara Presence Sensors: Mounting Height and Placement

Answer up front — Aqara's recommended mounting height for its Spatial Multi-Sensor FP400 is 3 to 4 metres, and at 3 metres it covers up to 5 × 6 m for motion and 4 × 5 m for presence directly below the sensor, across a 120° field of view. It supports side, corner and ceiling mounting. That geometry is the whole design constraint. In a high-ceiling landed-house living room it works cleanly; on a 2.7 metre condominium ceiling it does not, because you are below the height the coverage figures were measured at and you must not quote the 3 m numbers. Rating is IPX5 — a water-jet ingress rating, not a permanent-outdoor rating — so a car porch in monsoon season needs a sheltered position or a different sensor.

This is the trade guide to installing Aqara's Spatial Multi-Sensor FP400 and its immediate predecessors, and it is mostly about one number: mounting height. Aqara publishes clean coverage geometry, and it only holds at the height it was measured at. Most Malaysian installations do not happen at that height, so most of this post is about recognising when to say no to a layout.

The coverage geometry

Two things about that table deserve emphasis before you design anything.

Motion coverage is larger than presence coverage. At 3 m you get up to 5 × 6 m for motion and up to 4 × 5 m for presence. That gap is the sensor telling you the truth: detecting that something moved is an easier problem than detecting that a person is still there. If your automation depends on presence, design to the 4 × 5 m figure, not the 5 × 6 m one. Quoting the motion number for a presence-driven scene is the most common way these installations disappoint.

Presence detection is what makes a room worth automating. Tracking up to 10 people at once, distinguishing standing, sitting and lying, with no camera in the room, is the capability that lets a scene react to a person rather than to a door. The camera-free argument matters to homeowners, but as an installer you should also know it matters for building operators, where camera coverage of a bedroom or a meeting room is often simply not permitted.

Hardware and environment

The power line is the one that costs you time on site. This is a USB-C device. Mounting it on a ceiling in a landed house means getting 5 V at that point — which usually means a new cable run, a supply in a fitting, or a decision to mount it on a side wall near an existing point instead. Decide that at survey stage, not on installation day. Corner and side mounting exist precisely because ceiling mounting is not always practical.

The dual protocol matters for how you commission it. Over Thread, the sensor exposes only one overall presence sensor and one illuminance sensor — you lose the per-person and zone data that justify buying it. That is covered in Aqara hub compatibility, and it is the reason to check your client's platform before you design zones.

The monsoon caveat: IPX5 is not an outdoor rating

IPX5 is an ingress-protection rating. It means the unit resists water jets from any direction. It does not mean the unit is rated for permanent outdoor installation, and Aqara publishes no UV rating, no corrosion rating and no prolonged-immersion rating alongside it.

So take a Malaysian car porch as the test case. It is sheltered by a roof but it is not sheltered in the way the datasheet assumes:

• Heat. The upper operating limit is 50 °C. A car porch with a metal roof and no cross-ventilation will exceed that on a clear afternoon. Treat 50 °C as a hard ceiling and check the site in the afternoon, not at 9 am on an overcast survey visit.
• Condensation. The humidity rating is 0–95% RH, non-condensing. A surface-mounted sensor on a porch ceiling collects moisture by day and sees condensation as the surface cools overnight. The datasheet assumes the air is non-condensing; it does not assume a nightly dew cycle on the housing.
• Direct rain. Even under an eave, wind-driven rain reaches a ceiling-mounted unit on a porch in a proper monsoon.

Our existing guidance on monsoon and outdoor sensor placement covers the general approach. For this sensor specifically: if the only available position is an exposed porch ceiling, do not specify it there. Move it under the eave line, inside the house looking at the opening, or specify a device rated for the job.

The ceiling height problem

Here is the trade conversation, and it is the reason this post exists.

A high-ceiling landed-house living room. Double-height, or a 4 m plus ceiling. The FP400's recommended window is 3–4 m. A ceiling mount at 3.4 m sits comfortably inside it, and the 5 × 6 m motion and 4 × 5 m presence figures apply to the floor below. Zone planning against a 4.5 m room works: eight zones is plenty. This is where the sensor is genuinely strong, and it is the room where presence-driven lighting earns its cost.

A 2.7 m condominium ceiling. You are 300 mm below the lowest mounting height Aqara specifies. The coverage figures were published at 3 m. Mounting lower shrinks the footprint — that direction is certain — but the magnitude is not published, and anyone who quotes 5 × 6 m for a sensor at 2.7 m is extrapolating past the manufacturer's own test condition.

Say that plainly to the client rather than quietly hoping. Then work through the options:

A client who hears "the coverage will be smaller and the published figures no longer apply" accepts a design decision. A client who discovers it after the sensor is on the ceiling does not.

Commissioning checklist

1. Measure the ceiling at the proposed position, not at the room centre. Popcorn trays, dropped bulkheads and aircon ducts all change the number.
2. Confirm the mounting style — ceiling, side or corner — and check the field of view points where the scenes need it.
3. Solve power at the mounting point, at survey stage. USB-C, 5 V, and a cable run you have costed.
4. Confirm the platform before you design zones. Over Thread the sensor exposes one presence entity and one illuminance entity; the zone and per-person data needs the right hub. Check hub compatibility first.
5. Check radio reach from the hub, especially in a double-height room where the hub and the sensor are in different volumes of space. See Zigbee mesh repeaters and dead zones.
6. Design scenes against the presence coverage figure, not the motion figure.
7. Record the mounting height in the handover pack. It is the single value that determines whether the installation still behaves correctly after someone adjusts the curtain or the sofa.

More general site mistakes are covered in eight installation failures to avoid.

What this page does not claim

• It does not claim a Malaysian price for the FP400. Availability in Malaysia — confirm with us. Do not assume it is on the shelf at a local store.
• It does not claim the FP400 or FP400 Pro is confirmed Malaysian stock.
• It does not state warranty durations or after-sales terms.
• It does not extend the published coverage figures below the 3 m mounting height they were measured at.