Purpletrain said:



1. As accurately as possible, calculate how much water is in your hydroponic system.
2. During the hottest part of the day, turn everything in your garden that produces heat on. The goal is to let the room get to max temperature.
3. Now, chill your system down to your desired temp (often 60-70F). Do this with sealed bags of ice or frozen two liter bottles so you won’t be adding extra water to your system.
4. Once you reach your desired water temperature, remove the ice from the system and circulate the water.
5. Start a timer and write down the starting temperature.
6. One hour later, write down the current temperature.
7. Subtract your starting temp from your 1 hour temp and write it down - this is your temperature differential.
8. Now, use the following formula to calculate the BTUs you need:

Gallons of Water X 8.34 (weight of a gallon of water) X Temperature Differential

Now you know how many BTUs you need to adequately chill your system.















Example Reservoir Calculation
If you have a 75 gallon system, your max temperature is 80F, your desired temperature is 65F, and after an hour the water temperature is 70F…

75 X 8.34 X 5 = 3,127.5

Here are your conversions to the standard sizes that water chillers are sold in:

Tons

BTUs

1/10 ton

1,200 BTU

1/4 ton

3,000 BTU

1/2 ton

6,000 BTU

1 ton

12,000 BTU


It’s recommended to give yourself a bit of a cushion, especially when buying a low-end chiller. Typically, they won’t put out their actual power rating, so I would recommend adding about 25% to your total BTUs when deciding.

That means in the example above, you would want to boost up to the ½ ton chiller just to be safe.

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Midwestjay said:

Bro that's bad ass, I always wondered how to figure that. You explained it perfect

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