Liquid-Cooled Systems

Creating the optimal liquid-cooled system will vary from customer to customer as everyone has different resources at their disposal. Below we will review a number of liquid-cooled applications, and ultimately we push our customers to be creative with their liquid-cooled systems by combining the concepts in any of these scenarios.

If your garden is in a rural area, and you're able to bury a large cistern (1500g+) outdoors this may be the most cost effective and energy efficient system. However, the installation of such a system may be too complex for gardens using less than 5 liquid-cooled lights.

If your garden contains 5 or more lights, and you're able to use a buried cistern for a reservoir you can substitute a radiator for an electric chiller. This method not only saves on energy costs but also takes advantage of the earth's inherent cooling capacity at no cost whatsoever.

As you can see in the photos below, all water lines are buried, and as the hot water comes out of the lights it passes through the radiator. The radiator is installed in an enclosure along with a fan, and it operates on the same principal as an automobile radiator. Once the water passes through the heat-exchanger (radiator) it returns to the reservoir to begin the cycle again.


The earth acts as a natural insulator for any sized reservoir, and a heat-exchanger may not be necessary depending on the size of your reservoir and the number of lights in your garden.

For smaller gardens, a variation on this concept could be to use a buried 55g drum for a reservoir. If your garden has less than 3 lights the natural cooling capacity of the earth may be enough to cool your water. Obviously this depends greatly on your local climate, but exploiting free, natural resources is a crucial element in any garden.


If you are unable to use an outdoors reservoir or would simply like to keep everything indoors, you may be limited in the number of lights you can use. The most common set up in gardens with less than 5 lights would be a 1/2hp chiller combined with a 55-150g reservoir.

With 1-3 lights you may be able to chain the lights together in-line with your chiller. This technique is not always recommended, and a larger (150g) reservoir would be helpful. Chaining your lights and chiller results in the water getting hotter and hotter with each light it passes through thusly increasing the load on your chiller.

A smarter approach, albeit more complex, is the "manifold" method. The basic concept of a manifold is to supply each light with cool water directly from the reservoir, and all warm water from the lights is returned directly to the reservoir. In addition, your chiller is not in-line with any light rather it is on a closed loop with the reservoir. This method requires at least two pumps - one to feed your manifold, and one to feed your chiller.

With a smaller number of lights (< 5) and a larger reservoir (150g+) you may be able to supply each light with a separate pump if PVC plumbing is not your specialty. Keep in mind that submersible pumps heat the water as they run continuously.

And finally, always try to keep your chiller out of your growing area as it produces a small amount of heat itself.
A key safety feature we recommend for any system is a "no flow / no go" switch. The power supply for your ballast is plugged into a relay controlled by an in-line water flow sensor. Basically, the flow sensor must register water pressure going to your lights in order to feed electricity to your light's ballast. In other words, if you're water pump fails and water flow ceases your ballast power supply will be cut. Remember, liquid-cooled lights are not designed for "dry" operation.
For large, commercial-scale applications an industrial chiller may be the preferred method for cooling your water. Industrial chillers are powerful and can dramatically effect the design of a liquid-cooled system. Industrial chillers should be considered for systems using 10+ lights, and the size of your reservoir can be decreased if necessary.