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PIRs are everywhere, but they should not be thought of as basic, commodity items. Opting for the cheapest off-the-shelf PIR is never wise because replacing faulty devices is never easy just because of where they are likely to be mounted.

What, then, if you have invested in branded quality but the lights still aren’t working s expected? Here the problems are more likely to arise from having specified the wrong PIR for the job or getting the set up wrong.

The Tech Team at Timeguard are always happy to advise, and there’s no premium charge for calling them. There’s also plenty of information on the company website and product packaging and instruction leaflets. All the same, we asked them what you should be asking yourself before you choose a motion or presence detector.

What type of lights and what load?

Be sure to pick a PIR detector that is specifically tested with and rated for LED loads if that’s what you need to control.

You shouldn’t need to do the maths yourself: the specification on the box should already state what LED loading is acceptable – if not steer clear.  Timeguard thinks it’s always wise to add at least 10% for good measure.

There’s a huge difference between ratings for the same PIR detector for halogen and LED. For instance, while Timeguard’s mini linkable PIR foris rated for 1000W max. halogen, the LED rating is 250W max. LED. That’s because the LED rating allows for the strong inrush current on switching, not the subsequent low running current.  That said, 250W is usually enough for these PIRs with the option of up to five pre-wired RJ11 plug-in slave units per master, allowing for quick installation for corridor and multi-zone use.

Will there be lots of luminaries?

Take care if the total LED load is getting near the limit of the PIR’s specification, especially when controlling small luminaries.  Due to their physical size, lower wattage LED lamps (GU10 type lamps) commonly have very simple circuitry with surge protection and power factor correction omitted. That puts a massive strain on whatever is switching/controlling them.

So, for instance, the Timeguard SLW360^o ceiling-mounted and flush-mounted detectors have a maximum LED load of 150W but are rated for a maximum of 10 separate LED10W lamps (ie only 100W). Yet the firm rates – and guarantees – them for LED lamps above 10W, right up to the 150W limit.

Where’s it going?

Most good PIRs now offer more sensitive presence detection. Remember, PIRs are often installed so that lights or fans turn off when a space is empty, so more often than not they do need to be able to detect the difference between an empty room and people sitting quietly  at a desk.

You don’t have to spend £100s for a single detector that offers presence detection. Presence detection is standard on most Timeguard PIR detectors.

Will the detector be surface or flush mounted in a standard ceiling aperture? Most people prefer flush mounting if practicable, but Timeguard has proved that surface mount doesn’t have to mean clunky looking if the manufacturer has put the effort into design.

As a rule, a ceiling height of 2.5m will give optimum coverage but be sure to check the manufacturer’s instructions. You also need to be aware that highly reflective surfaces and heat sources like extractor fans nearby can interfere with sensitivity. Remember, too, that sensitivity is greatest for movement across the field, rather than directly towards it when choosing locations. It may be useful to mask part of the detector to avoid nuisance switching, and unnecessary call backs form disgruntled customers.

Choose products that make installation and setting up straightforward, because it’s usually done at the top of a ladder! Big wiring terminals and simple adjustment controls should be at the top of your wish list.

The bottom line, as ever, is branded quality assurance – good products, good information and good, free tech desk back up for installers.