Welcome to Lux's review of underwater luminaires. When we say underwater, we're not talking about puddles but deep pools of water where the equipment will function safely at a depth of three metres or more. I am using the word ‘pool’ to mean any underwater application such as dockyards, deep water features, aquariums, caves and industrial cooling. For applications like this, you're probably looking for an ingress protection rating of IP68.
You have to be careful when you read IP68 claims because the supplier must state the depth for which the luminaire is suitable. The test then sets out a procedure (increased pressure, on/off cycle, temperature difference) to confirm conformance. In principle, the IP68 test is meant to be more onerous than IP67, which uses a pressurised jet of water that is equivalent to submersion to a depth of a metre. However, it is possible to claim IP68 conformance at a shallower depth, so you should always ask to see the test certificate and have a good look at the procedure. Also, make sure the test was for a luminaire – I've seen test certificates for underwater spotlights (not any of those reviewed here, I should add) that referenced the procedure for IP68 enclosures.
The first thing to consider is whether it is a marine or freshwater environment. Bronze luminaires have excellent thermal properties with much better conductivity than stainless steel. However, bronze can be attacked by the chlorine used in freshwater pools. Conversely, freshwater pools don’t always contain chlorine and some of the other purification chemicals used will attack certain grades of stainless steel. There’s no easy answer; you just have to check compatibility very thoroughly.
If you are using recessed luminaires, you should find out if they are ‘wet niche’ or ‘dry niche’. Wet niche means the luminaire is surrounded by cooling water. It must be fitted with a thermal cutout to stop it operating if the water level drops or the pool is drained.
Dry niche luminaires are often larger so the heat from the lamp can be safely conducted away.
Several manufacturers emphasised that the quality of the installation is critical to success. You don’t want a pool to leak through the luminaire recess or cable entries. Get references from your contractor so you know they can do the work competently.
Finally, don’t forget fibre-optic luminaires. Their big advantage is that the luminaire itself doesn’t have to be relamped or otherwise maintained. The projector containing the light source can be put in an easily accessible, dry location.
Every product we've tested here was exceptionally well made. I suppose if a product is suitable for use at least three metres underwater, it has to be made well.
The Hydrel M9700 is a recessed luminaire that accepts a range of lamps rated from 35 to 150W in metal halide and 70W high-pressure sodium. There are various lens and reflector options and I managed to count eight different beam types.
It can be used to a depth of three metres and also in ‘dry-land’ applications. The visible part of this recessed luminaire, what you would generally call the bezel, can be supplied in stainless steel, bronze or aluminium.
To accept a 150W lamp, the body has to be quite large to dissipate the heat – this is the biggest and most powerful of the luminaires in this review.
The surface temperature of the front glass can be a problem in public areas. Holophane has got around this by offering a double front lens system – the lens nearest the lamp absorbs most of the heat and there is a layer of air that ensures the front face remains much cooler.
Roblon FL500 Aquarius
This product, available in the UK from Light Projects, uses fibre optics. The big advantage of using fibre optics to light your pool is that you don’t have to drain it just to change a lamp or do maintenance. The light engine or projector, that produces the light and directs it into the fibres, can be fitted in a dry, easily accessible space. This particular model from Roblon is rated IP65 so it makes finding a location even easier.
The other advantage of fibre optics is that there is no electricity at the luminaire. And they don’t heat up. It’s as safe as can be. Neither do the seals have any need to ‘breathe’. As such, it is much easier to make the luminaire leak-proof. The Aquarius unit will operate at depths of 10 metres.
Obviously, the amount of light emitted depends on the lamp used and the size of cable. Some people think fibre optics are only good for sparkle and not for functional lighting. That’s true for poor quality suppliers but Roblon has software you can download to calculate the output from the luminaires and the illumination that can be achieved.
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Wibre 4.0282 swimming pool light
Wibre (represented in the UK by Architectural FX) is a specialist in underwater lighting – its lighting factory was founded in 1953. The company also makes underwater speakers and windows. It has a huge range from surface-mount to recessed and everything is made of 316 (V4A) grade stainless steel.
One of the newer units is the 4.0282 (Wibre doesn’t go for memorable product names). This particular unit is suitable down to depths of five metres in saltwater applications.
It can run at 35 or 62W in several different white CCTs and the RGB sample we had is rated at 110W.
One feature that sets this apart from other units is that the lens has a combination of LED lenses. One group is 120 degrees so the beam will illuminate the bottom of the pool and swimmers. The other group is 30 degrees so it can illuminate right across the pool to the far side. There are plenty of other beam options.
We-Ef has been making outdoor luminaires in Germany for over 50 years.
The model we tested was the ULC230 medium-beam spotlight with a 20W metal halide lamp and integral electronic gear. The complete underwater range includes 2W LED and 35W metal halide luminaires. In the same underwater family are 65W halogen models.
This is a surface-mount unit – it rests on the bottom of the pool rather than being mounted in a recess. It’s solid construction means it operates happily up to 10m below the surface. The thick front lens resists impacts of IK10.
This is a robust, compact product. It is only 170mm in diameter and 175mm deep, but it weighs over 6.5kg.
What is really nice about this unit is the beam. The intensity of the 16-degree beam reduces uniformly from the centre and it has a nice, clean edge. Coloured filters, baffles and linear spreader lenses are also available.