Water Cooling
Water cooling is a relatively new technology in the grow room. Essentially the idea is that by chilling water to low temperatures (45-60 degrees F) you are then able to pass this water through the equipment in your grow room which generates heat. The water will then absorb the heat by passing the hot air through a coil system inside of the equipment or on a separate piece of equipment which is mounted on the air exhaust for that machine. Therefore the air being blown out by that piece of equipment will no longer be hot. Water is a very efficient, all natural, heat absorber. Water has the ability to absorb heat with very little change to its own temperature. Water is also able to retain heat better than most substances. These factors are commonly called a substances heat capacity. On the contrary, air has a very low heat capacity. Think of it this way. Let’s say it’s 40 degrees F outside. How long could you walk around with no clothes on before your body started to suffer hypothermia or other debilitating effects? Now jump in a lake that is 40 degrees and see how much quicker you start to suffer. That is why using a chiller is always more efficient (both in energy consumption and cooling output) than using air conditioners. Plus with chillers you never have to worry about Freon and they also are much easier to use in multiple room setups whereas with an A/C you would either have to buy 2 separate units or have dual climates and dampers installed into a condenser unit.
All of that being said it should be pointed out that water cooling is not the most cost effective route for MANY growers. If you are a small scale grow or a beginner then the initial costs of an effective water cooled system may not be worth it. If you are growing in a climate where it is relatively cool or cold for most of the year then it may not be necessary to invest in a water cooled system. The ideal candidate for a water cooled system is a 100% closed environment grower who has multiple heating issues within your space; whether it is your ambient temperature, nutrient reservoir, etc… This is not to say that these systems do not have benefits for all growers. Water cooled systems can alleviate the need for A/C units, inline fans, ducting, reservoir chillers, etc…
Chillers
Chillers are the essential elements of any water cooled grow room setup. The chiller is used to cool the water that is passing through the equipment in your grow room; be it your lights, a Co2 burner, air handlers, dehumidifier, etc… Chillers come in a range of sizes and functionalities. They range in size from .1hp (1,200btu) all the way up to 20hp (240,000btu). Chillers are rated the same way that air conditions are; in btu’s with 12,000btu being 1 ton. Some of the popular chiller brands are Ecoplus, Chillking, and Active Aqua. The smaller chillers (2hp and less) usually require you to purchase a pump(s) and reservoir separately. The pump is then fed water from the bottom of the reservoir and pushes this water to the chiller which it in turn chills the water and discharges it back into the reservoir. Depending on the quality of pump you have you may then use the same pump (if it has a high enough rating and multiple ports) or another pump to push water from the reservoir to the equipment you are cooling in your room. The larger chiller systems (3hp +) will usually have built in pumps and reservoirs.
There are a bunch of useful formulas to calculate how to size the chiller for your garden. In my experience none of them work because there are just too many factors involved. You have to factor in the ambient temperature outside, number of lights; how you will be cooling the lights; what other equipment you are using that is being water cooled and equipment not being water cooled; etc… The ideal situation would be for you to water cool all equipment which emits heat that is inside of your room. A lot of growers (myself included) who are looking into water cooling for the first time do not take the full plunge. My first experience with it was a small 2hp chiller which I used to cool 4 1000w hoods and a Co2 generator. Since then I have moved onward and upward to larger scale operations with 10hp chillers in which all our equipment is water cooled. There are some general calculations you can make though. Starting with your room; assuming that you just wanted to cool a space that had no equipment in it and that your ceiling were 8-9’, that the outside temp never got over 100 degrees and that the room was well insulated. Assuming all of this you would use approximately 4,000btu to cool every 100sq.ft. of space. Basically the same way you would size an A/C. So a space of 300sq.ft would need a 1 ton (12,000btu) chiller in order to cool the air (I will talk later about how you do this). Now for the equipment; you can generally use these calculations for some of the common things you will find in a grow room. Remember; these are just general calculations designed to get you started in the right direction.
- Per 100sq.ft. of Space 4,000btu
- 1000w HID Bulb 4,000btu
- 1000w Magnetic Ballast 3,500btu
- 1000w Digital Ballast 2,500btu
- 600w HID Bulb 2,400btu
- 600w Magnetic Ballast 2,100btu
- 600w Digital Ballast 1,500btu
- Co2 Generator 2.5btu Per Cubic Foot
- Dehumidifier 30btu Per Daily Pint Rating
Using these calculations will get you started in the right direction when sizing your chiller. My recommendation is always to oversize your chiller should you decide to expand your operation or just to err on the side of caution should your room be warmer than expected.
Equipment
You can us a chiller to cool almost anything in your garden that produces heat; and even some things that don’t. Here I will talk about all of the options on the market now.
- Ambient Cooling – There are several different ways to cool the ambient temperature of your room using a chiller system.
- Air handlers can be paired with a chiller to cool your room just like you would use one with a compressor. Air handlers are normally for larger rooms and range in size from 2ton to 5ton.
- Heat exchangers can be used as spot A/C units (normally they are uses to cool the exhaust of a hood) and if paired with the right chiller and reservoir temp can provide up to 8,500btu of cooling. They come in both 6” & 8”. A heat exchanger has to be paired with an inline fan. They are essentially mini condensers in which cold water is passed through one side of the heat exchanger an fed into a disbursement coil system through which the air from the fan is pushed. Then the water is pushed out of the other side of the heat exchanger by the incoming water. You can also purchase air diffusers for these units which spread the air throughout the canopy or base of the plants.
- Hoods & Lighting – Water cooling has several different designs and methods of cooling the heat created by you HID bulbs and hoods.
- Water cooled light fixtures are essentially tubes of glass which are hollow in the middle. Your bulb is placed inside the hollow section and cold water is pumped through the surrounding tube. They are designed to remove the heat generated by your bulb before it goes into your garden. Two of the popular designs on the market are the Fresca Sol and Liquid Lumens.
- Heat exchangers can be used to cool the air as it is exiting your hood. They are placed over the exhaust port on your hood and using an inline fan the hot air inside of your hood is then pulled through the heat exchanger which in turn cools this air before exhausting it. From my own experience they are very effective. I have been able to place my face on the glass of a hood using a heat exchanger with a 1000w MH or HPS bulb. They are rated to cool the exhaust heat of a 1000w bulb to ambient room temperature. Two of the popular brands are the Hydro Innovations Ice Box and the generic Ice Flow.
- Air handlers can also be used to exhaust the hot air from your hoods. Recently we have been ducting our hoods to the return manifold of our air handler. This is by far the most efficient way to use an air handler in a grow room. It also alleviates the need for purchasing numerous inline fans.
- Dehumidifiers – There are now water cooled dehumidifiers on the market. Essentially a coil has been placed through the dehumidifier which cools the hot air the unit exhausts. When paired with the right chiller and reservoir temperature I have actually seen a 50 pint dehumidifier turned into a 1,200btu air conditioner.
- Co2 Generators – There are a few water cooled Co2 generators available on the market. Of the ones that I have seen all have been liquid propane or natural gas burning. The water is pumped through a coil inside of the generator and used to cool the exhaust air to ambient room temperature.
- Ballasts – There are ballast tubes available which allow you to place you ballast inside of a round enclosure. Cold air is them pumped through the enclosure from one end and exhausted out the other end. They come in both 6” & 8”. These are only really necessary if you have to keep your ballast in the grow room. All electronics function more efficiently and will last longer if allowed to operate at cooler temperatures.
- Nutrient Reservoir – By pumping cold water through a coil you can control the temperature of your nutrient reservoir. If you either purchase a resistat and gate valve or just control the pressure of cold water coming in with a simple t-ball valve. You’ll have to play with it a little to get it dialed in.
I decided to share this information as using water cooled technology has made my growing extremely automated and alleviated all of my cooling problems in a climate where it is 90+ degrees every day.
Feel free to share comments or ask questions.
I used to get a little condensation on my older system too; it's nothing to worry about. Now we have a system with 2 different reservoirs running at different temps. We keep the water for the air handlers at 45 degrees and the water for the feeder manifolds at 60 degrees. The air handler lines are fed tight into the back of them trough the wall so i get no condensation from them in my room.
