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Cool Runnings: Current Culture Discusses Keeping Your Grow Room Cool

Don’t overheat the plants in your grow room. Stay cool! Don’t overheat the plants in your grow room. Stay cool!


Air conditioners cool your grow with brute force. But they can come with a brutal energy bill. Many indoor growers are exploring the benefits of water chillers as a way to keep their crop cool and their costs down.

To learn more, we spoke with experts to learn how these devices can keep temperatures in check, both in your grow room and in your hydroponic system itself.

Cool Runnings

Chillers can control the air temperature of your indoor grow op. But they can also improve the performance of your nutrient solution. Christian Long, Vice President of Current Culture (makers of the popular Under Current hydroponic system), explains why your crop prefers a nice cool nutrient cocktail.

Rosebud: So what is the idea of a chiller, and how is it used?

Christian Long: We’ve found over the years that to get the best results out of water culture, it is imperative that you use a water chiller to maintain the cooler water temps for two reasons. The first is that we get the highest levels of dissolved oxygen at water temperatures of about 65-68°F, and the second is that it creates an environment where it is difficult for bacteria and pathogens to thrive and reproduce.

I know I’ve read several times that water under 70°F maintains 30% more dissolved oxygen. That seems like quite a bit.

Yeah, it’s really an exponential number too. For every degree that the water goes up, its ability to hold onto the oxygen goes down exponentially.

I run my system in the lower 60s, like 64°F, because by the time it gets to bucket No. 16 it’s a little warmer, you know?

You’re getting a full turnover about every 10 minutes, so as water makes its way from one end to another it probably goes up a few degrees. So yeah, I think mid- to low-60s. Once you start getting down to the low 60s you could slow metabolism. But once you get up into the 70s you’re opening the door for the pathogens and bacteria.

Are there other benefits of keeping the chiller set like this?

When you’re chilling your entire system volume, which, depending on the size could be a pretty large volume of water, it acts like a giant heat sink in your room. So it even allows you to maybe run a little bit warmer room temperature because you’ve got this nice cool body of water that’s sitting in your room.

We often have growers that will use the little infrared thermometers and they’ll take a reading right off the leaf tent and it’s consistently three to five degrees lower than a plant in a container. As that plant is pulling up that cool water and transpiring it, it’s cooling the whole plant down as well as helping to cool the entire room. We don’t point that out very often, but it’s definitely something that’s interesting.

Outdoor plants in Santa Rosa, California, will hit 108°F during the summer. But their roots are embedded in 68°F soil, so they can handle it.


Should chillers be used in ebb-and-flow systems?

Anywhere where there’s a large volume of water that you’re aerating, you’re going to get the benefits of a water chiller.

We have some standalone DWC systems where it’s not as imperative because the water isn’t moving. But I think any hydroponic system where there’s a large body of water, you can see the benefit of the chiller.

And is there a chiller that you guys recommend over other ones?

I’m going to say Chillking, obviously, on the commercial side. And then I’ll probably give a shout out to the Eco Plus and the Active Aqua from Hydrofarm.

How do you install a chiller?

For us, you basically just need to pump water from the reservoir into the chiller and then from the chiller back to the reservoir. So for us, because our system circulates and there’s a circulation pump, it’s extremely easy to install a chiller.

One thing to note is that each chiller has a specific flow ratio that it’s looking for. You’re going to want to consult your manufacturer’s recommendation.

What are the downsides of running system water through the chiller as opposed to using a coil and keeping it entirely segregated?

Salt buildups are the reason why you would advise against pumping system water directly into your chiller. Most of the nutrients we recommend are mineral-salt-based.

It depends on the type of metal that’s inside the chiller — some of them are copper, some of them are stainless, some of them are titanium. All of those metals react differently to the mineral salt. We see that most of them on the market now are using stainless or titanium, which don’t really react to the minerals.

What would be the best product for breaking down these salts?

Any salt-leeching solutions or greenhouse disinfectants would probably do the job. Anything that’s going to break down scale or mineral buildups.

What about something like Final Phase or Clearex?

That’s kind of what I was thinking when I said “salt-leeching.”

Why wouldn’t you guys recommend using a coil? Is it because of the extra cost?

Yeah. Really the only time we do recommend coils is if somebody has more than one system they’re trying to chill with only one chiller.

How do you gauge the right amount of chiller?

The first thing I would do is look at your desired water temp. Say your desired water temp is 68°F and your room temp is 78°F. You’re going to have to chill the water about 10°F. They rate most of the chillers that way. It will say it does 100 gallons/10 degrees or 50 gallons/20 degrees. Make sure that the chiller is adequate to chill the total number of degrees for the room temp and the water temp for the total volume of their system.

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