Maintaining the optimum temperature of the water in a hydroponic system is extremely important. Not maintaining this temperature can cause a host of problems, including slow growth, mildew, and mold. You need the right tools for maintaining an optimum temperature and regulating fluctuations as well. Growers use heaters and chillers for this. This article will cover how to determine the ideal size of your heater/chiller. Before that, though, it’s important to know why water temperature is so important.

Water Temperature and Oxygen

The primary reason why water temperature is so important is that it affects the amount of oxygen that the water absorbs. When the temperature of any water body rises, its capacity to retain oxygen decreases.

In a hydroponic system, where the grow medium is only water, we can see how this directly affects plant growth and your plants’ ability to absorb nutrients. For every ten °C (18 °F) increase in temperature, the amount of oxygen in water decreases by 3 mg per liter. So, the warmer your water gets, the lesser oxygen it will carry.

Warmer water is also conducive to the growth of bacteria and fungi that can harm your plants. Water that is too cold brings problems. Plant growth slows down significantly, and nutrient intake decreases. The ideal water temperature range that you need to maintain is 18 °C - 20 °C (65 °F - 68 °F).

Chillers for Hydroponic Systems

Chillers have two important specifications. These are flow rate and horsepower (‘HP’). The flow rate is in gallons per hour (‘GPH’). Horsepower is a measure of how much refrigerant is needed. Growers have to select an ideal chiller for their system; it can’t be too large or too small.

How Large Should Your Chiller Be?

Firstly, decrease the temperature of your system till it reaches the optimum level. One of the methods of doing this is with bagged ice. There are other methods of doing this as well. Just make sure whatever method you use does not lead to adding water to your reservoir.

Let your system run for at least an hour once the water is at the right temperature. Make sure all heat sources and lights are on. Doing so will let you know the amount of energy that your chiller will have to reimburse.

Measure the temperature of your water when an hour has passed. Calculate the difference between this figure and the ideal temperature. This is known as the temperature differential. The formula for determining the size of your water chiller is:

No. of gallons of water x 8.33 x Temperature Differential = BTUs/hr.

Give yourself a safety margin and increase this figure by 25%.

How to Size Your Chiller

We can illustrate this with a hypothetical hydroponic system. Our system has 100 gallons of water. We need the temperature to be 65 °F.

We'll first cool our system down to this temperature using the methods we discussed above. We'll turn on our system, along with all the heat sources, such as humidifiers, grow lights, etc., and let it run for an hour. Let's assume that our temperature differential is 5 °F. Using the formula above, we get:

100 x 8.33 x 5 = 4,165 BTUs/hr.

Increasing this figure by 25% gives us 5,206.5 BTUs/hr.

Dividing this figure by 12,000 gives us the horsepower (‘HP’), which in this case is:

5206.5/12000 = 0.43 tons

So, we need a chiller with 0.43 HP for our hypothetical hydroponic system. Different chillers offer different cooling capacities and reservoir sizes. The surrounding temperature also affects the performance of a chiller.

For example, a chiller operating at an ambient temperature of 65 °F will perform better than an ambient temperature of 90 °F. Therefore, it's better to place your chiller outside your growing space, where the air is bound to be cooler. If you haven’t installed a chiller before, you can go through our guide on installing hydroponic water chillers.

Water Pumps

Some chillers require an external water pump to function. So make sure to size your water pump correctly! You’ll need to consult your chiller manual to determine the minimum throughput that would need to be supplied by your water pump.

There are two kinds of water pumps. One is an inline pump and the other is a sump pump.

Hydroponic Water Heaters

Water heater must be at the bottom of the reservoir in a hydroponic system. They function as a thermostat, i.e., they heat the water to the requisite temperature and switch it off till the temperature goes down. Ratings for water heaters are in watts. Place your water heater close to where the flow of water originates for maximum effect.

The following table illustrates different water volumes and the required wattage to heat them for differentials’ specified temperatures. This assumes a room temperature of 50 °F.

How to Size Your Heater

If you need to increase the temperature of 40 gallons of water by 18 °F, you will need a 150-watt heater. As per our practice, we strongly suggest adding a 25% safety margin to account for possible changes in the surrounding temperature. So, in this case, a 200-watt heater would serve your purposes (rounding off 187.5 to 200).

Final Thoughts

Maintaining the ideal water temperature in a hydroponic system is essential for the health of your plants. It affects the amount of oxygen available to them as well as their nutrient intake. You can face a host of problems, such as slow growth, mildew, and mold, if the temperature is not in the ideal range.

At GroIndoor.com, we have a wide range of water heaters and chillers for all possible water reservoir capacities. Contact us now!