Not Exactly the "Usual" Chiller Question...

[naterealbig]

Hi there,

1) Problem statement - I will have 2 x 20g QT tanks in my garage in Orlando Florida that will need to be cooled 24x7.

2) Questions:
i) I currently have a 1/3 (JBJ Arctica - standard - NOT a drop-in-coil) HP chiller - given the temperature difference of say ~ 25 degrees F that will need to be maintained, is this chiller right-sized for 1 x 20g aquarium?

ii) If the chiller is oversized, could I theoretically run a closed loop on this chiller (say poly tubing with 2 x DIY stainless coils) and cool both aquariums? I don't know the technical HVAC terms here so please see diagram of what I am proposing below.

iii) If I could run the theoretical setup below, what liquid would I want to run inside the closed loop?

 

[Jay Hemdal]

The issue that I see is that you can only have a single thermostat control point, but two tanks. The cooling coil will lose cooling capacity as it travels from tank one to tank two. If you put the thermostat in tank two, tank one will get too cold and vice versa. Even putting the thermostat on the return line won't work - tank one will still over cool. If both tanks are exactly the same in terms of water volume, evaporation and heat load, and if you put the thermostat in the line between the two tanks, you MIGHT be able to finagle things and balance it out, but I doubt it.

Oh - and another issue: you will be using a chilled water loop I think. I don't see any provision for water make up in the loop. I used to manage a system that uses glycol to chill many tanks. I needed a loop temperature many degrees colder than the tank target temperature in order to get the drop down needed for each tank, and that is with using titanium heat exchangers. I set my chilled loop at 43 F.

Connecting both tanks so they share water (and avoid using SS heat exchangers) would be one solution, the other would be to buy two chillers.


Jay

 

[SPS2020]

One other note, the JBJ chiller has a built-in thermostat.

 

[naterealbig]

The issue that I see is that you can only have a single thermostat control point, but two tanks. The cooling coil will lose cooling capacity as it travels from tank one to tank two. If you put the thermostat in tank two, tank one will get too cold and vice versa. Even putting the thermostat on the return line won't work - tank one will still over cool. If both tanks are exactly the same in terms of water volume, evaporation and heat load, and if you put the thermostat in the line between the two tanks, you MIGHT be able to finagle things and balance it out, but I doubt it.

Agh! I actually thought of this, and I started writing without thinking. Agreed on all fronts here... Another option I thought of was just running the (chill water) loops in parallel. I anticipate the tanks will have very similar heat loads, and I know that I would need some sort of flow meter as the head losses will be different.

Oh - and another issue: you will be using a chilled water loop I think.

I think so.... Not sure if there is any other chemicals I could play around with, that I won't kill myself with somehow, that also have a higher specific heat capacity... Is glycol something I should/could use (as a hobbyist)?

I don't see any provision for water make up in the loop.

Didn't get that far, but I imagine a relatively easy evolution with the simple set up. Any idea what the frequency might be for makeup? Are we talking like once/wk or every day?

Connecting both tanks so they share water (and avoid using SS heat exchangers) would be one solution

Heh - did I mention that 1 (prophylactic) quarantine is for fish, and the other (passive) for coral?

the other would be to buy two chillers.

Yes, thought about this.... I have 1 chiller now, hence the feeble work-around attempt... Will eat the cost of a second chiller if I need to, in order to make the 2 x QT's work (not having one is not an option... I think you may have replied to a thread I started earlier re: QT in-line w/ display ... QT in the house is not an option, so the garage it is... And too much risk running the QT in line with display without having clear guidance UVC dosing requirements for AEFW and the like).

Thank you for your help and discussion!

 

[naterealbig]

One other note, the JBJ chiller has a built-in thermostat.

Very true - may make chill water temp control easier... don't know off the top of my head what the lowest temp setting is. Will take a look. Thank you!

 

[naterealbig]

Another concern I thought of was the 1/3 HP chiller potentially being over-sized for the 20g (maybe not, just because it will be so hot in the garage, but....)

Should I be concerned with the chiller switching on and off a hundred times a day?

 

[Jay Hemdal]

Another concern I thought of was the 1/3 HP chiller potentially being over-sized for the 20g (maybe not, just because it will be so hot in the garage, but....)

Should I be concerned with the chiller switching on and off a hundred times a day?

Most chillers have an offset that can be adjusted, a differential in X degrees, to keep the chiller from cycling too often.

jay

 

[Jay Hemdal]

Agh! I actually thought of this, and I started writing without thinking. Agreed on all fronts here... Another option I thought of was just running the (chill water) loops in parallel. I anticipate the tanks will have very similar heat loads, and I know that I would need some sort of flow meter as the head losses will be different.

I think so.... Not sure if there is any other chemicals I could play around with, that I won't kill myself with somehow, that also have a higher specific heat capacity... Is glycol something I should/could use (as a hobbyist)?



Didn't get that far, but I imagine a relatively easy evolution with the simple set up. Any idea what the frequency might be for makeup? Are we talking like once/wk or every day?



Heh - did I mention that 1 (prophylactic) quarantine is for fish, and the other (passive) for coral?


Yes, thought about this.... I have 1 chiller now, hence the feeble work-around attempt... Will eat the cost of a second chiller if I need to, in order to make the 2 x QT's work (not having one is not an option... I think you may have replied to a thread I started earlier re: QT in-line w/ display ... QT in the house is not an option, so the garage it is... And too much risk running the QT in line with display without having clear guidance UVC dosing requirements for AEFW and the like).

Thank you for your help and discussion!

I've never tried to run a closed chilled water loop. I just know that our glycol system has a sump that we have to add glycol to, for uptake into our system as needed. Very similar to the overflow tank in a car's radiator system.

Jay

 

[DCR]

You would need a break tank or head tank on the return of the chilled water to deal with the expansion and contraction of the closed system with temperature. That would be where you would add water. I think you may be surprised how large of a coil you may need to transfer heat to chilled water and then to refrigerant. Consequently you will need to run the chilled water system at lower temperatures. Also 316 SS is not great for saltwater and may add some heavy metals to your tank. I think you would better off combining the two tanks into one system with a common sump or buying two smaller chillers

 

[naterealbig]

Most chillers have an offset that can be adjusted, a differential in X degrees, to keep the chiller from cycling too often.

jay

Will research with JBJ - thanks for the idea.

 

[naterealbig]

I've never tried to run a closed chilled water loop. I just know that our glycol system has a sump that we have to add glycol to, for uptake into our system as needed. Very similar to the overflow tank in a car's radiator system.

Jay

Understood, and thank you. May break out the heat transfer and fluid flow texts and review the physical properties vs water, and try to get a gage on the work necessary to keep the tank cool. Normally wouldn't be antsy, but by happenstance there is a used 1/3 HP chiller for sale in my area, and I want to make a move quickly if I will need it... Thanks for all of your help.

 

[naterealbig]

You would need a break tank or head tank on the return of the chilled water to deal with the expansion and contraction of the closed system with temperature. That would be where you would add water.

- All familiar theory, but it's been too long since I've studies to develop an independent thought - makes complete sense. Didn't even think about a break tank (sump) as you and Jay mention... Thank you for this - certainly much easier than bleed/fill that I was thinking initially...

I think you may be surprised how large of a coil you may need to transfer heat to chilled water and then to refrigerant. Consequently you will need to run the chilled water system at lower temperatures.

Also considered the amount of surface area and volumetric flow rate to transfer the heat out of the QT's... At a glance, the drop-in chiller coils didn't seem that large/long, but I imagine it's part of the primary R134A loop, so much more efficient/effective?

Also 316 SS is not great for saltwater and may add some heavy metals to your tank. I think you would better off combining the two tanks into one system with a common sump or buying two smaller chillers

All makes sense - will consider carefully. Thank you.

 

[Pistondog]

Share the water, either with a common sump or connect the 2 tanks low, in1 and out the other, just watch the flows and connection tube sizes.

 

[naterealbig]

Share the water, either with a common sump or connect the 2 tanks low, in1 and out the other, just watch the flows and connection tube sizes.

These are quarantine tanks, so can't mix.

 

[waqas_01]

Another concern I thought of was the 1/3 HP chiller potentially being over-sized for the 20g (maybe not, just because it will be so hot in the garage, but....)

Should I be concerned with the chiller switching on and off a hundred times a day?

If you dont have a sizeable expansion tank for the chilled water, the constant on/off will be an issue. You would be cooling the volume of water in the pipes rapidly and while the tanks will take time to cool down and transfer the heat to the chilled water. Unless if your heat exchanger is really large and is able to transfer heat quickly to the water. This would typically be one of the heavy metal heat exchangers we try to keep out of our tanks. Your tanks would also have a massive eye sore to look at.