Chiller - Undersized or oversized

[banzai75x]

I read somewhere that is better to get a little bit of an undersized chiller that runs more often than get an oversized chiller that barely runs.

Don't know where I read this but any thoughts on this?

[Mr.Lloyd]

I would rather have the extra capacity in a bigger one.This is not like it will never come on and the seals would dry out.

[pecan2phat]

I think your better off with a slightly oversized chiller with a good controller that can regulate your temps by 1 degree.

If you utilize your theory, the electrical draw would be inefficient if the compressor is always on and probably the life of the chiller itself would be decreased.

[grim]

Slightly over-sized is better than under-sized for a few reasons.. First, people tend to underestimate their heat load, thus their first choice is already under-sized (not right-sized), so further under-sizing gives you way too small of a chiller. Second, chillers are very noisy, most people would rather have a chiller run for 5 minutes every hour than for half of that hour to keep up.

I've never seen any numbers that say it's any less or more efficient to under or oversize a chiller. So, theoretically, if the chiller needs to run for 30min/hr versus 10min/hr, the total wattage used to cool the tank should be equal.

There is another problem with chillers, usually called cycling, and this usually happens when someone runs an oversized chiller *and* directs the chiller effluent to somewhere near the temperature controller. For example, the chiller feeds and returns to the sump, where the temperature controller is. The sump, due to reduced volume, chills quickly, so the chiller is only on for a few moments, but as new water is cycled through the display tank, it also quickly warms, and goes through this rapid cycling until the tank is cooled. This should definately be avoided. It's usually remedied by returning the chiller effluent to the display tank, or monitoring temperature in the display and running the chiller on a closed loop with the display.

And yet the final reason to oversize a chiller slightly.. Both future heat load (maybe you'll upgrade your lights), or a future tank upgrade (please hunny, it's just a few more gallons).. :)

jb

[banzai75x]

Good points!

I know the JBJ Artica chillers come with their own temperature controller. Would that be acceptable to use or would I need to purchase another one?

[pecan2phat]

Check to see the temperature differential before the compressor kicks in.
They're usually 2 degrees, controllers will give you a 1 degree control point.
2 degrees is good. Some older chillers were 4 degrees, so people went out to buy controllers.

Also see if you can adjust the temp reading on the unit so that you can calibrate it with a known accurate source.