Sizing a chiller can be a difficult decision.
Factors that affect chiller performance include:
- Volume of liquid
- Heat inputs = lighting, pumps, etc.
- Ambient Temperatures
- Desired goal temperature
- Some specialized applications have specific time requirements to cool from specific temp, or flow rates that also need to be considered.
The most common error is underestimating how much heat is being put into the water. A common answer to the question – “what is the heat load?” is “Not much”. Well that doesn’t help “much”. If a heat load is unknown one of the best ways to estimate it, is to get your system to goal temperature using ice or some other means. Pull all of the ice out and then time how rapid the heat gain is. If you know the volume of water, and the time it takes for it to go from one specific temperature to any other specific temperature an estimated heat load can be calculated. (See article on BTU) It’s still just an estimation, but it’s a lot better than a “not much” type of answer.
When it comes to chillers in general, it’s pretty much impossible to oversize a chiller. The general rule of thumb is when in doubt go with the next size up. This is because it never hurts to have extra cooling power. A common misconception is that a bigger chiller will use more electricity, and under that logic consumers try to squeeze into a chiller that may be too small. You should instead look at is as the work to be done on your setup (aka chilling) will not change if you use a smaller or larger chiller, the work load stays the same. It will take roughly the same amount of electricity to do that amount of work regardless of chiller size. A larger chiller will use more electricity when on, but it will run less often, so it all roughly balances out in the end. However if a chiller is undersized it may not be able reach your desired goal temperature, and it will run more often, which likely lead to a shorter lifespan.