Water Cooled Lights vs. Air Conditioning

By. The Guru

It’s starting to get warmer here in Southern Cali and your indoor garden is getting hotter by the day. You most likely had one of your best harvests of the year recently due to the cooler season of winter, but the cooler temps won’t last long. Soon you’re going to be battling the summer heat again, just as we growers do every year. Plants don’t grow very well in bad environments and that includes hot temperatures. If it is 85 degrees outside and you’re using an open loop system with outside air to cool your grow room, then it is physically impossible to cool your room below 85 degrees. If you want a successful grow room in the summer, you will need to cool your environment.

There are only two ways to cool an environment in an indoor grow room. One is to use an air conditioner and the other is to use water cooled devices. Both methods have their positives and negatives. Let’s take a look at the pros and cons of each to help you make an educated decision on the best way to cool your room. Remember, your lights and ballasts are also increasing the heat to high levels, and CO2 generators are the biggest sources of heat in an indoor grow room other than the lights themselves. Often times, temperatures are high enough to kill the plants or simply make it almost impossible to have a good harvest and yield.

First, let’s look at what we’re trying to cool and how much heat we need to combat. Each 1000 watt light produces about 3500 BTU’s of heat and a single 1000 watt digital ballast produces around 2500 BTU’s of heat. Let’s just take care of the heat from the ballasts first by putting the ballasts outside of the grow room. Now we’re only dealing with 3500 BTU’s of heat. So basically you need 4000 BTU’s of cooling to offset and cool each 1000 watt light. A 6 light grow room will require a minimum of 24,000 BTU’s to keep the room cool from the heat of only the lights. Then you need to calculate in the other pieces of equipment that might be creating heat and make sure you have enough BTU’s to cool everything. Considering that, about 4500 BTU’s of cooling per 1000 watt light is required to cool the lights and the CO2 generator.

Now let’s look at what’s involved in setting up a water cooled system and what equipment is needed to do this. In a 6 1000 watt light grow room you would need a 2 HP chiller at 25 amps @ 240 volts, 8 Ice Boxes, tubing, a large reservoir, a large pump, and a water manifold delivery system on the ceiling above your 1000 watt lights. A quality commercial chiller capable of doing the job costs $6000 to $7000, and the rest of the equipment could cost another $2000 or more. Total costs could easily be $9000 for a 6 light grow room. We can get a 2 ton 24,000 BTU AC for around $4000, and the power draw is only 12 amps, less than half of the water chiller and pump. A water chiller might run a little less, thus saving some power, but in my experience, it doesn’t run that much less and it is definitely much more complicated to set up and operate.

So which is better or more efficient? A water cooled system or an air             conditioning system? Which system is right for you? Well, according to the leading manufacturer of water cooled devices for indoor grow rooms, Hydro Innovations, water cooled systems are more efficient than air cooled systems. The reason for this is that water thermal conductivity is 23 times greater than that of air. What this means is that a chiller using water will absorb and take away more heat in a quicker amount of time, making it more efficient and run for less time, in theory of course!

Here is my problem. A chiller is running almost all of the time that the lights are on, and so is an AC unit. If an AC unit uses 12 amps @ 240 volts to produce 24,000 BTU’s and is running most of the time, and a chiller uses 25 amps and produces 24,000 BTU’s at twice the amps, then is it really that much more efficient? While it is true that many industrial and commercial buildings use water cooled chillers, nearly every building in Las Vegas is cooled with air conditioners and not water cooled chillers. All I know is that in life, if you look at what the big boys are doing, you usually find the best and most efficient way to do that too.

Yet another drawback is that water and electricity don’t mix well together. Bad things can happen when they do, especially with 1000 watts of electricity right below your water lines. If a leak or break occurs in the water lines, and they do, then disaster is sure to happen if water leaks into the bulb. Besides that, the chiller still needs to go outside or in the window hanging outside so that the heat is not going into the grow room. And the chiller needs large amounts of fresh air to keep working properly.

I’m not saying that the manufacturer of the water cooled device is wrong, but I am saying that you need to closely consider what is involved in setting each one up. If you want something simple, then an AC unit is definitely the choice. A water chiller requires a lot more work to setup and install than an AC unit. Commercial, residential, and split AC units are all much more energy efficient than the small 4500 portable units, which are very inefficient. The upfront costs of running a water cooled system are much higher than that of setting up an AC unit. Also, an AC unit runs about half the amps.

All of these items are tools, and some tools are just easier and more efficient to use for most of us. Look at all the details involved before choosing the best cooling system for your grow room.


Author: Steve

Built Like That!

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Very good post. I’d like to use some of this information on my blog if you don’t mind, and I’ll provide a link back to your site.

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