How to maximise chiller efficiency

[BarraCuda™]

Sizing of chiller

First of all, size yr chiller according to the heat load and tank capacity. A oversized chiller will consume more power even when the operation time is shorter. A undersized chiller will overwork resulting in higher wear&tear and high operation time. More info here


Flowrate

I heard many said that the chiller need a slower flowrate in order to chill but I would say, the higher the flowrate, the better it is. Here's why.

The slow flowrate only works when the water only passes through the chiller once. That is because water need more contact time to try to equalize with the cooling coil. If the flowrate is too fast, the water coming out would not be chilled. However our aquarium chiller and tank is in a continous loop and the same water will pass through the chiller many times until its chilled.

Temperature difference
Heat loss/gain is greater when there is a higher temperature difference between 2 matter. E.g If 30C water going into the chiller, the output maybe 27C which is a difference of 3C. Now if 25C water goes into the chiller, the output maybe only 24C with a difference of 1C.

The higher the water temperature going into the chiller, the greater the temperature difference between the input and output. I personally set the chiller at 26-28C.

Now the process is reversed when we talk abt lighting. The lower the water temperature, the higher the heat gain! Thus if you set the water temperature low, the water will be slower to chill and yet faster to heat!

Temperature equalization
I suggest high flow is because of the above theory. If the flowrate is slow, the water will be chilled rapidly within the heat exchanger thus reducing the temperature difference between the water and the heat exchanger. The idea is to make sure that the water temperature within the heat exchanger is as close to the main tank as possible.

Compressor workcycle
If the flowrate is slow, you risk the temperature probe registering a false reading. This will cause the chiller to start/stop regularly, sometimes 4-5 times/hr. E.g if the water do not leave the heat exchanger fast enough before the reaching the preset temperature, the chiller will sense that the water is chilled thus shutting down the compressor. When warm water from the tank gradually replaced the chilled water, the chiller will again start the compressor because now the water is warmer than the preset temperature!

Power consumption
The compressor will consume much more power during initial start up and it will take a few minutes for the chiller to start cooling. So if yr chiller have a frequent start/stop cycle, you are using more electrical power (higher power during start up) at lower chilling power (few minutes for the heat exchanger to start cooling). All these will add up to yr monthly bills!

Wear & tear
The compressor suffers the most wear & tear during start up. The higher the start/stop frequency, the faster the wear & tear.

Temperature differential

Most set the temperature differential between 0.5C to 3C. The lower the differential, the higher frequency of the start/stop cycle but if its too high its stressful to the fishes/corals due to temperature fluctuation. IMO, 2C is a good balance.


Heat exchanger coil

The heat exchanger coil is the only place where chilling occurs so its important to ensure that the coils are clean and have maximum contact with the water. Connect the input of the chiller to a high powered pump to flush out the dirt accumulated inside. You can also run vinegar to dissolve calcium deposits.

Condensor coil

This is the coil where the chiller loses heat to the environment. The more heat the chiller lose to the environment, the more heat the chiller gain from the aquarium water (faster chilling effect, thats why the chiller run less on cooler days). A dirty condensor coil will increase the electrical consumption by 10-20% and increase the chiller operation time. Its very important to keep the condensor coil clean to ensure max air flow thus max heat loss.

Vacuum the condensor coil at least once a month and perform a chemical wash every 6months. More info here

Summary

As you can see, the most neglected parameter like the flowrate have a larger chain effect on the overall efficiency of the chiller. Size it correctly, apply the max flowrate and do yr monthly cleaning that will ensure that yr chiller is working at its peak efficiency.