What Steinel documents
For article number 079734, Steinel provides both a data sheet and an instruction manual, and both are unusually complete. Documented are 942 lumens at 9.4 watts power consumption, which corresponds to an efficacy of 100 lumens per watt. The colour temperature is 3000 kelvin, the colour rendering index Ra 82, and the colour consistency SDCM 3 as an initial value. The housing measures 280 millimetres in diameter and 110 millimetres in height and, according to the Steinel product page, weighs 0.437 kilograms; the cover is made of PMMA. Steinel gives IP rating IP44, impact resistance IK03 and Class II. The sensor works with high-frequency technology at 5.8 gigahertz and detects over 360 degrees, according to the instruction manual with an opening angle of 160 degrees. The detection range is adjustable from 1 to 8 metres and covers 50 square metres at full setting; the possible mounting height ranges from 2.00 to 4.00 metres. The overrun time can be set continuously from 5 seconds to 15 minutes, and the dusk threshold from 2 to 2000 lux. In addition there are a basic light at 10 per cent of the light output for 10 minutes, 30 minutes or the whole night, a soft-light start and a switchable permanent light for 4 hours. All settings are made with rotary dials in the housing; there is no remote control. It is connected to 220 to 240 volts at 50 to 60 hertz, the mains current is 45 milliamps and the power factor 0.91. Up to ten lights can be networked by cable in master/master operation. The light source and control gear are explicitly not replaceable, and the energy efficiency class of the included light source is E.
Why radial and tangential are the same here, for once
This is the real difference from the familiar Steinel floodlights with an infrared sensor. With a passive infrared sensor such as in the XLED ONE S, the radial and tangential ranges are far apart, because the sensor registers heat sources crossing its detection segments. Someone walking straight towards the light is detected much later than someone walking across. The RS 20 S is different. The data sheet lists radial and tangential range as two separate lines and gives the same value for both, namely a diameter of 8 metres and an area of 50 square metres. The detection diagram accordingly draws only a single area and labels it as applying to radial and tangential. The reason is in the manual: the high-frequency sensor emits electromagnetic waves and evaluates the change in the returning echo. This works regardless of direction and, as Steinel expressly writes, regardless of temperature. This advantage is real; the trap lies elsewhere. The manual defines the term range as follows: it means the roughly circular diameter on the floor that results as the detection area when mounted at a height of 2.5 metres. The 8 metres are therefore the diameter, not the range in every direction. From the mounting point it is about four metres, and the stated 50 square metres confirm exactly this calculation. The listing text describes it as a reaction to movement at a range of 1 to 8 metres, which reads as twice as far as intended. Two details from the manual are added: the sensor suppresses very fast movements to minimise interference, and after every switch-off, detection pauses for about one second.
Where the data sheet and instruction manual differ
Four values are stated differently in the two documents. For its own consumption, the data sheet gives 0.38 watts, while the instruction manual gives 0.50 watts standby power for the sensor. That sounds small, but it concerns a device that hangs on the mains around the clock: over a year that is about 3.3 against about 4.4 kilowatt hours, a difference of roughly a third. For the temperature range the deviation is even clearer. The data sheet and product page give 10 to 40 degrees Celsius, the instruction manual minus 10 to plus 40 degrees Celsius. A twenty-kelvin difference decides whether an unheated cellar corridor, a garage or an open stairwell is still within the specified range in winter at all. For lifetime, the data sheet advertises 30 years at an average of 4.5 operating hours a day, which works out arithmetically at about 49,000 hours. The instruction manual, by contrast, gives a mean rated lifetime of 60,000 hours to L70B50 at 25 degrees Celsius. The sensor's transmission power is also stated once as less than 1 milliwatt and once as about 1 milliwatt. There are also two gaps rather than contradictions: you will find the colour rendering index Ra 82 only in the manual, while the data sheet gives only the colour consistency. Conversely, the advertised soft-light start and the networking of up to ten lights do not appear at all in the German part of the manual, neither as a description nor as a connection instruction. How long the soft-light start takes to reach full brightness is not stated in either document. For setting up the device, the rule is therefore: rely on the paper that is in the box.
Indoor light with IP44: what the IP rating provides and what it does not
Steinel lists the model as a sensor LED indoor light and expressly enters indoor area under place of use. Two lines further on, under room of use, however, next to hallway, stairwell, changing room, kitchenette, utility room and toilet and washroom, it also lists the outdoor area. The instruction manual resolves this in the section on intended use, and far more cautiously: in the outdoor area the light can be used only to a limited extent because of the sensitive detection. That is a restriction, not an approval. IP44 means protection against solid foreign objects from one millimetre and against splashing water from all directions. That is enough for a bathroom, a washroom or a covered entrance; it is not enough for jets of water, for cleaning with a pressure washer or for a position where driving rain hits the light directly. Where exactly a light may sit in a bathroom also depends on the installation zones of the applicable regulations and belongs in the assessment of a qualified electrician. The second reason for caution outdoors is the sensor itself. According to the data sheet, a high-frequency sensor may detect through glass, wood and lightweight partition walls; the manual additionally mentions doors and thin walls. The listing text sells exactly this as an advantage. In the troubleshooting table of the same manual it appears as a cause: if the light switches on seemingly for no reason, it is due, among other things, to movement behind a wall. In a stairwell this behaviour is practical; on a room wall shared with a neighbour or on a house wall directly beside the pavement it can become a permanent nuisance. If you need light outdoors without a fixed supply cable, a solar solution is closer to the task anyway.
Fixed mains connection, Class II and the limits of mounting
The light has neither cable nor plug; it is connected permanently to 230 volts. Steinel states unambiguously that this is work on the mains voltage, to be carried out properly in line with the installation regulations customary in the country, and names VDE 0100 for Germany, ÖVE and ÖNORM E8001 Part 1 for Austria and SEV 1000 for Switzerland. Before mounting, the supply cable must be isolated and checked with a voltage tester to confirm it is dead. If you are not permitted to do this yourself or are unsure, hire a qualified electrician. In practice that also means: this light is not a solution for a flat without an existing ceiling outlet and no substitute for a light with a plug. Class II means that the light itself needs no protective conductor. The manual nevertheless describes the supply cable as three-core, because at the terminal, besides live and neutral, there is also the switched live through which the networking runs. Swapping the connections leads to a short circuit according to the manufacturer. Two restrictions are easy to overlook: connecting to a dimmer damages the sensor light, and for ceiling mounting it is expressly not suitable with a surface-mounted supply cable. For the permanent light function over 4 hours you additionally need a mains switch in the supply cable, which you must switch off and on again twice within 0.2 to 1 second. After the first switch-on there is also a calibration phase in which the light switches itself off once after 10 seconds. And because neither the light source nor the control gear is replaceable, at the end of its life the complete light is due for replacement, along with the associated electrical work.
What the data does not answer
Despite the dense documentation, exactly the questions that matter in daily life remain open. Steinel gives not a single illuminance value. How many lux reach the floor when the light hangs at 2.5 or at 4 metres is stated nowhere, even though that decides whether 942 lumens are enough for your room. There is no statement on glare, no UGR value and no statement on flicker of the light. The soft-light start is advertised but not described anywhere, neither with a ramp-up time nor with a curve. There is no threshold at all for behaviour around pets, and with a high-frequency sensor that weighs more heavily than with an infrared sensor, because it reacts to movement and not to heat. Whether several of these lights in neighbouring rooms influence each other is not clarified in the German part of the manual. The networking also remains under-documented: that up to ten lights can be connected together is on the data sheet, and the two wiring diagrams are included there as drawings, but an explanatory passage in the text part is missing. It is also striking that the manual speaks in two places of an emergency light module and an emergency light, although the data sheet lists no emergency light function for this model. That points to a document covering several model series together, and is one more reason to follow the data sheet for product data and the enclosed booklet for setting values.
Our assessment
The RS 20 S is neatly built for its purpose and unusually well documented. A high-frequency sensor that detects equally far in all directions and does not depend on temperature differences solves exactly the problem on which infrared lights in hallways and stairwells regularly fail, namely the person walking straight towards the light. The disappointment arises elsewhere, namely with the area. If you read the 8 metres as a radius, you plan with about 200 square metres and get 50. For a hallway, a stair landing or a short cellar corridor that is ample; for a large garage or a long passage with side branches you need several lights, and that is exactly what the networking is for. As for the light itself, the basic light function at 10 per cent and the soft-light start are the more sensible arguments for a stairwell at night than the lumen figure, because both prevent the harsh jump from dark to bright. Before buying, check two things: whether there really is a fixed supply cable at the planned spot and whether it runs concealed, and how cold it gets there in winter. On the second point the manufacturer documents contradict each other, and when in doubt we would go by the more cautious figure. This light is not intended for living spaces in the narrower sense anyway; it belongs in utility rooms and circulation areas.
Further reading: Steinel XLED ONE S with infrared sensor for comparison, Steinel XLED home 2 XL for larger areas, a plug-in night light with sensor as a small solution, how many lumens a room needs, what standby and basic light cost in electricity per year and our source rules.