Free Cooling

[gabew]

I am in the process of building my 55gallon cold water aquarium so I am still working out the details. One problem I have been wrestling with is the temperature the tank would need to get down to in the coldest of the winter months. The temperature needs to get down to at least 40 degrees Fahrenheit but preferably it should get all the way down to 36 degrees in February. This is very cold and I would need a very powerful (and VERY expensive) chiller. One way I have thought to solve this problem is using the cold outside to cool the tank. First off obviously if the water is that cold the air is cold too, and yes it is. In February the average outside tamp is around 30degrees here, but in the winter it can get much colder, down to 10 bellow! So anyway my plan would work like this, the tank would be set up near a wall between the tank and outside. Water out of the sump would be pumped outside through a hose that goes outside, which would be coiled several times for maximum cold air contact, then back into the sump. This would run constantly in the winter as well as a chiller. This would hopefully take much strain off the chiller letting my get away with a less powerful and cheaper one.

So that is my plan but I want to make sure it works so have a few questions.
Would this work?
Could the water freeze in the hose?
Could it cool the tank TOO much?
Should I add an emergency heater just in case?
How powerful a pump should I use?

thank you for any helpful information

 

[nemosworld]

good read:
http://www.ehow.com/how_7435159_prevent-pvc-pipes-freezing.html

 

[Acronic]

I thought of something simmilar about a year ago. The difference was that, instead of being outdoors, the coil would be in a large chest freezer. That way it operates during all four seasons. It would be a seperate system, that constantly cycles and keeps the water moving to prevent freezing. you could "tap" into the "colder water tank system" via an overflow system that is acctuated by a controler turning on a pump from the display system leading to the "cold water system" when temp gets too high. There could even be a heater in the cold water system that would help keep the water from freezing if need be.

Another good Idea would be to do a similar thing from your hot water tank. Im pretty sure I saw someone do that in their build thread a while back.

 

[gabew]

Cool i was hoping i would get some advice from someone who had done it before
so did your system work?
what temperature was the freezer?
the thing is that this system would have to run all the time or the water would freeze so i agree that i think a back up heater would be helpful in case the system works too well
however i can't find a heater with a 36 degree thermostat, any advice on a cold model

 

[James77]

A ranco dedicated controller has a setpoint in that range. the dual stage could control a cooler and heater....FAR more reliable as well.

 

[Paco]

I think you would need a proper heat exchanger (like a radiator) and a fan blowing over it to get most effect. Just running PVC doesn't sound too efficient for thermal transfer.

You might want to look at something besides standard chillers -- you need something industrial. I've seen some outfits using A/C compressors with their own dedicated heat exchangers (titanium, etc. made for salt water) that might help.

Good luck.

 

[Humu Humu]

Just a thought. If the power goes out for a few hours in the dead of winter, and your line freezes outside, it may burst. Then when the power comes back on, you may lose your tank water. I know the salt water will tend to keep it from freezing, but it could if given enough time.

Remember Mr. Murphy.

 

[mscarpena]

It gets to 10 below it will freeze fast. I dont think the cooling effect you will get is worth the hassle at all. If you have the money to spend on a chiller that size you are looking at saving peanuts per month running the line outdoors. The water flowing through the tube will have very little effect. I would put the time and money into better insulated glass. Good luck. Sounds like a nightmare keeping your tank that cold.

 

[droberts]

it might be a silly question but why would you want your tank that cold? what kind of fish needs to be that cold?

 

[norskfisk]

I have quite some experience with coldwater tanks. Let me give you some advice:

1. You are right about the 40 degrees temperature. You should follow realistic temperatures all year. It is important for the organisms. But you don't need to go lower than 40. The water is warmer at depth.

2. Buy a chiller. I spent years researching the issue. It is the cheapest and the only thing that works. Period.

3.If you are going to grow macro algae the chiller must be rather powerful. The reason is that in spring the water is cold, but the light input is high. If you only have non photsynthetic organisms the chiller can be small. No problem to reach 40 when the lights are off. Lights are the main source of energy if the tank is insulated. Pumps are second.

4. Insulate the tank. Place the sump in an insulated cabinet.

5. Use double glass. You can make that yourself for any tank.

You may want to check out my site:
http://www.jonolavsakvarium.com/

 

[BeanAnimal]

I thought of something simmilar about a year ago. The difference was that, instead of being outdoors, the coil would be in a large chest freezer.

It would depend on the size of the tank, but in most cases, even a LARGE chest freezer will not work.

Freezers are not designed for that kind of duty cycle. They are designed to remove a relatively small amount of heat over a long period of time with the aid of a well insulated box. The compressors are, in fact, rather small and not suited for constant heat removal from something like an aquarium.

Furthermore even if the compressor was large enough, a freezer is a phase change cooler, just like an aquarium chiller. The difference is the number of boundries that the heat has to cross to get pulled from your tank to the outside environment. Due to the losses associated with the system as a whole (chilling a box that chills the water instead of just directly chilling the water), it would be MUCH cheaper to just run a dedicated chiller.

You can't cheat basic physics folks

 

[JHemdal]

+1 on what BeanAnimal says.

I *have* heard of a freezer being used to maintain Arctic marine species - but they set the tanks up INSIDE the walk-in freezer (grin). IIRC, they held the temp at 30 degrees F.

One additional note - I don't fully understand the details, but if you want a chiller to drop down down to 40 degrees, you need to specifiy that when you order it - a proper expansion valve needs to be installed. My understanding is that "reef tank" chillers do not have this installed because their designed operating water temp is higher and the differential is less.....

Jay

 

[herostar]

Don't forget that if your tank needs to be ~36*, then the fluid in the heat exchanger needs to be colder. Water won't be a good working fluid because it will freeze, but saltwater or anti-freeze (from a car) will work.


I would get two radiators/heat exchangers, a pump, tubing, and fluid. Put one exchanger outside and the other in contact with the water. Use the pump to circulate fluid through the tubing/exchangers. Make sure whatever you use is reef-safe. As stated before, a fan will increase efficiency of a heat exchange by a large amount.

 

[JHemdal]

Propylene glycol is better to use than car anti-freeze I think...much less toxic in case there is a leak in the system.

Jay

 

[norskfisk]

JHemdal: What is the function of that expansion valve?

I did cool down my 1000 liters tank to 42F with a TECO SeaChill TR20 1/3 HP chiller that is made for ordinary reef tanks. That was only possible during the darkest period though. During spring it went up to about 48F even with the chiller running 24/7. I also did the same on a smaller tank with an Aqua Medic 1/4 HP chiller. I measured the watt uptake of the TR20 and it went from the rated 480W down to about 380W at the lowest temperature. So I'm imagining that the compressor met less resistance.

A 1/4 HP ordinary chiller won't have any problems keeping a 55 gal tank at any desireable temperature if even the slightest consideration to insulation and light levels are taken.

 

[JHemdal]

norskfisk,

I'm not sure for all chillers, but expansion valves are required on Tecumseh compressors (used on a lot of chillers in the US) if you want to efficiently cool the water below 65 degrees F. Your chillers may have one built-in, but manufacturers often leave them out to save costs - if they think that the chiller is only going to be used on tanks in the operating range of 65 to 80 degrees.

I just ordered a 1/3hp Aqualogic chiller from Champion Lighting not five minutes ago - and since I plan to use it to hold a tank at 50F, I paid $150 extra for that option (they were still a lot cheaper than anyone else).


Jay

 

[gabew]

wow lots of great information
i was thinking of using THIS chiller for my tank but i wasn't sure if it was powerful enough

@norskfisk: if you managed to cool 1000litres with only a 1/3 chiller i think this may work in which case the back up out door setup wont be necessary which would be awesome. Also i will certainely try to absolutely insulate all i possibly can (by the way you wouldn't happen to be the writer of THIS blog which i find amazing)

@James77: i believe the seller that sells the above chiller also sells that kind of temperature controller. i know you need to buy the single stage one to correctly operate the chiller alone but if "dual stage" means that it can both heat and cool at the SAME time then i would diffidently want to spend the extra $50 for it

@droberts: i agree it is nuts but you really want to replicate the environment as good as possible, though i still think 36 degrees is REALLY COLD

 

[norskfisk]

(by the way you wouldn't happen to be the writer of THIS blog which i find amazing)

Yep, thats me ;-)

1/2 HP for a 55 gallon tank that is monstrously overpowered, so no need to worry about that. The optimal cooling power is 1750 Watts. Say at very low temperatures the performance goes down to 1300 Watts. So in a well insulated system you must have less than 1200 Watts of average lights and pumps (I had around 500 Watts in my 1000 liters). This allows for 100 Watts environment loss. These are not entirely theoretical numbers, I have to a certain degree tested them in my tanks. It works.

 

[gabew]

great! if that chiller will be enough i am very happy
the biggest source of heat will diffidently be the lights so i have been thinking about ways to reduce this effect. so far i think i will use LOTS of cooling fans (either 8 or 12) and on top of that i had the ingenious idea to add double glass between the lights and the fish tank (well it won't be glass, it will be clear plastic but it will still work in the same way) i am hoping this will help reduce the effect of the lights
and if you are the writer of that blog i will most certainly be coming to you for more advice later on

 

[norskfisk]

Just ask ;-). The cooling fans probably aren't a good idea. The air flow will just generate cold loss from the tank. Just let the hot air go straight up and keep the air just above the water still. It will form an insulating lid because the water is cold and cold air sinks down.