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 for your project. The general rule of thumb is when in doubt, go with the next size up! It never hurts to have extra cooling power. A common misconception is that a bigger chiller will use more electricity. Under that logic, consumers often try to squeeze into a chiller that may be too small for their project which then causes the unit to run way more often than may be needed had they simply gone up a size in chiller. Think of it this way, your chilling work load will not change regardless of using a small or large chiller. It will take roughly the same amount of electricity to do the amount of work. Its true, a larger chiller will use more electricity when running, however, it will need to run much less often. Also, if your chiller is undersized, it may not be able to reach your desired goal temperature which will cause it to run more often. Keep in mind the larger chiller running less often will be more likely to have a longer life span than the smaller chiller which is running more often. In the end, after considering all of the variables and looking at the bigger chilling picture, it seems to be a safer bet to upsize and select the larger Chiller.