A Chilling Experiment

[Shilo]

Spent the last week browsing for any information on cooling aquariums for the NZ biotope I'm slowly setting up. When running normally the tank averages 2 deg C above ambient room temperature. I put this difference down to the lights (5x 18 watt energy saver bulbs) and the 2 pumps.

Most native fish start to stress at 24 deg (18C or below preferred) so even at this time of year they can be effected since the room temp averages 20 to 22C. In summer it can get as high as 28 so before fully stocking the tank I need to have some sort of chiller operating. Preferably one that can lower the temperature by at least 5 deg of ambient. Of course I can always spend a grand and get a commercial one, but existing aquarium system is almost entirely DIY and only cost $300 fully stocked as a tropical so why spoil a good thing! By the way the tank is 160ltr with another 25ltrs in the sump.

Cooling will be a 3 pronged attack:

1. Get the temp down to room temperature.

Removing the heater of course helped. Also plan to add a computer fan in the hood to draw air over the bulbs and expel it away from the tank. There is already an existing and opposing gap in the hood on one side where I access the overflow. The hood is fairly low and there is a layer of glass between the bulbs and water. This is acting like a mini greenhouse. Hopefully I can find some plastic egg crate material to replace the glass with. If the lights are left off for a day the temperatures are almost equal so cooling the bulbs should work.

2. Lower the temp by another 5 deg C.

This ones a bit harder. For the last week I have had a fan hitched up to the lights timer and blowing directly into the sump. This managed to lower the temp by 2 deg. Not enough.

So a chiller is needed. Researched on using Peltizers, Fridges, Air Conditioners, Dehumidifiers etc. Wanted to keep the project under $200 so peltizers were out because of the number that would be required. Everything I read on fridges said that they just weren't powerful enough for the continued operation required. They are also too bulky. A cheap 2nd hand portable air conditioner would have worked but even on Trademe they are above budget. So that left a dehumidifier.

When grocery shopping today I literally stumbled into one at Woolworths (why do they always put these things in the way of the trolleys!) $169 for a 10ltr/day dehumidifier was a bit more then buying 2nd hand but I knew it was in good order. Warranty will soon not apply though

Poor thing, doesn't know what its in for!

1st test was to see if it was powerful enough to cool the water. Since I didn't want to destroy it before knowing if it would work (could do with one in the house anyway), I rigged up a system that trickles the water over the cold bits. Excuse the technical language.

It’s hard to see in the photo but there is a piece of clear pvc tube that is running over the top. This has holes drilled into it and the end blocked off. The water is supplied by tapping into one of the main pump pipes with a 6mm tube. It returns back to the sump via another 6mm tube from the dehumidifiers external drain.

The water flow is not great but even with this trickle of chilled water entering the system it has cooled the aquarium by 3 deg below room temperature after 3hrs of operation. This is with the lights on so in reality it has dropped the temp by 5 deg's. It is not the permanent solution since it is energy inefficient and because it is still acting as a dehumidifier its adding more water to the sump then it is being supplied with.

Next step will be to work out a method of building a tank around the coils which water from the sump can be pumped into. Complete immersion would avoid any extra water appearing from thin air. The unit is small enough that I can fit it under the stand if I make a different shaped sump.

3. Temperature control

Haven't thought of this one much. But do plan on insulating the stand and any exposed pipes to avoid the cool water heating up before entering the main tank. Also need some sort of thermostat that will come on when the temperature reaches a certain mark (unlike a heaters thermostat that comes on if the temp drops below a mark).

If anybody is interested I will keep you updated on how to destroy a perfectly good dehumidifier while electrocuting myself and flooding the house at the same time.

Cheers

Grant

[Ira]

Hmmm, that's an interesting idea. How is that section you have the water trickling over plumbed into the rest of the system? Maybe you can remove the cold side and drop that whole part into the sump with just some extra hardline back to the dehumidifier? Should make it cool better.

It must be made of something that won't corrode much, and it's a FW tank so I don't think you need to worry too much about it being in the sump...It wouldn't be any worse that way than collecting the water that's trickled over it anyway.

[Shilo]

I was toying with the idea of dropping the evaporator into the sum. Its made of aluminium so one of the loops could be carefully straightened out enough until the other loops are at ground level. See http://www.guarriello.net/chiller.htm for an example. For you marine guys, the above link also shows how to prevent corrosion of the coils.

To drop it into the sump I will need to make a new one. Did some measurements last night and worked out that to contain the same amount of water (to cope with power cuts etc) the Wet/Dry filter will only be a wet one. The sides of the sump will be high enough to make maintenance a pain as well. Instead I might build a "bolt on" cabinet to the side of the stand to contain the dehumidifier and divert some water from the main pump pipe to a chiller tank.

[RnB]

this has been documented elsewhere as working well, and the dehumidifer is rated to take high work loads, i run one constanly on the yacht over winter to get rid of the mositure inside.

Peter

[SteveA]

What temperature is the ground outside your house, say 10cm below the surface?

Do you have a water tank outside. What temperature does that sit at?

Both these provide opportunity for a basic heat exchange system requiring nothing more than a pump and a lot of tubing.

I breifly used something like this on a marine tank but instead of taking a pipe outside I had 25-30m or tubing coiled in a drum through which town supply water slowly trickled. A plumbers nightmare, but it worked well and had I not discovered I could get the same end result by blowing air across between the water and the lights, I would still probably be using it.

Steve

[Shilo]

Hi Steve,

By looking at the house you might think its ideal. 10000ltr water tank (no mains on Waiheke) 1/2 set in the ground, shady position etc. But any pump will need to lift the water by about 20m and operate for longer periods then house pump and these pumps are bigger $$$ then I want to spend. Also the house is a rental so can't drill holes in the floor etc.

Because I rent the chiller really needs to be stand alone. Keep eyeing up the water tank though - Perspex window, few fish thrown in, guests will never know their drinking aquarium water

The dehumidifier is starting to look promising. Have managed to get enough courage to bend the coil down. Just need to make a chiller tank for it to fit into and a cabinet to go over the whole contraption. Only worry is how long the aluminum coils will last before they start to corrode in the fresh water.

[SteveA]

Hi Steve,

..... But any pump will need to lift the water by about 20m

No it wont.

A continuous run of hose from your tank down to the tank then running round inside the tank for a bit then back up to your tank will take only a moderate pump to operate as it will have almost zero head, only internal resistance - in fact the head will be only the difference in height between the two ENDS of the hose. The hose itself though, will need to be able to take the pressure of a 20m head.

If you developed a leek in the hose near the bottom it would then act like TWO 20m high siphons and so you would need to ensure it did not pick up or discharge water anywhere near the bottom of your tank, in case this happened.

Steve

[Control]

I've been thinking of modifying my dead delonghi to do that, it gets pretty hot in the summer in Christchurh.

Aaron

[Shilo]

Steve,

Yes you are right, I forgot it would be a semi-enclosed system and the downward pressure will be equal to the upward pressure (less friction as you pointed out). A smaller pump then I was thinking off could be based at the aquarium itself either pulling the water up or pushing it down, rather then at the water tank.

Still not feasible in my position (renting) but definitly a workable idea for other people on tank water. By taking the idea a step further for those with a tank below the house, a bypass on the upward pipe could be plumbed into the house supply pipe just above the house pump (with a tap attached) and a bypass with tap connected to the aquariums down pipe. Will make water changes a breeze, just turn the 2 taps on - 1 to drain the aquarium and one to full it up

Control,

If the delonghi's compressor goes and theres still gas in the coil then it shouldn't be any different to what I'm doing with the no name woolies brand. Hardest part seems to be bending the evaporator coils and thats not hard just scary. If the gas leaks its stuffed! When planning it out I thought of quite a few configurations and ways of using the dehumidifier. Only thing to watch out for is that the radiator is not covered up too much and airflow is restricted. What I'm doing is just what I think best suits my individual system. But stay tuned, it could all end in up in flames

[Control]

It's cheap to get them regassed.

I have considered putting a dryer in the line from a car to make it more efficiant.

The sensor went in the Delonghi and the Delonghi service agent after I had read the instruction manuel to them couldn't fix it.

Noel leemings who I purchaced it from wouldn't take any responcability for the piece of junk so I don't deal with either of them anymore.

I must be able to get something out of it for what I paid for it.

Aaron

[Shilo]

Chillers now completed, well.... until the all bugs show up. Crunch time is tomorrow when I plumb it up to the sump.

Tank

The tank is made out of 3mm ply coated and glued together with epoxy. The base is extended so I had somewhere to bolt it down to the base of the dehumidifier. Covered it with thin polystyrene, not sure if it was necessary but it was laying around the work shed.

Fittings

Couldn't find anything to use as bulkheads at the local hardware store so raided the irrigation section and used 19mm / 13mm reducers. The small ends are forced through the holes in the tank and glued in with silicon on the inside. The top one has most of the 19mm end cut off so its almost flush on the inside to allow the coil to fit in the tank. The outside of the fittings are also siliconed.

A short section of hose is crimped on the end to stop the fittings from being able to be pushed inwards. The joiner on the top fitting and the elbow on the bottom one will allow me to connect or disconnect the hose without putting to much pressure on the bulkhead fittings. Confident it will hold as I couldn't move them only a few hours after applying the silicon.

Water will enter via the bottom fitting, past the coils and flow out of the top one to siphon back into the pump. Although 13mm tube has been used for both the inlet and outlet, a tap is attached to the inlet so I can reduce the pressure to avoid the tank overflowing.

Some other things

Before attaching the tank I remembered (just!) to jam the water container cut off switch in the on position. Another job was to cut off the drip tray since this would interfere with the air circulation.

Also bent up some of the cold end of the coil since leaving it as it was would have exposed some copper pipe to the water (bye bye shrimp and crays!) A lid will follow at a later stage.

Do you think the warranty will still apply?

I didn't need to put the sides back together since the whole contraption will be covered with a cabinet that matches the stand, but the sides allowed me to firmly mount the top which contains the controls. Had to cut out an area for the copper pipe (it moved out of position when I bent the coil) and holes in the sides to allow air to enter for the radiator.

Started it up and it still went. The evaporator coil frosts up almost straight away so it should cool the water fairly fast.

[Shilo]

All plumbed up and working. One minor change was to replace the flush fitting on the top outlet of the chiller tank with an elbow bend. Found that a flush fitting drags in a lot of air were as an elbow has the inlet below water level and very little air enters the system. The water level in the chiller tank is controlled by a tap on the inlet. Not very obvious in this pic but the tap is 1/2 way up the black pipeing.

The temperture dropped much faster with a full chiller tank then in the trickle experiment. Within 3/4hr there was a 4 deg C difference between the aquarium and room tempature.

Left = Room, Right = Aquarium

I didn't want to stress the fish too much so turned it off and closed off the water flow to the chiller soon after. The fan was set on high for this try out so a low setting should bring down the temperture more gradually.

Very pleased with the result. It's not as loud as a fan heater and cheap. $169 for the dehumidifier + $23 for hoses and fittings, everything else I had laying around the house.

Still haven't solved the temperture control problem. In the mean time I will just use a timer so it comes on for 1/4hr every 2hrs. Ideally it will be good to just unplug the humidstat probe and plug in a thermostat probe as this will allow the use of the existing dehumidifier controls. A probe could easily be wired up with a thermo resistor but not sure if the power requirements of the existing humidstat probe and the resistor will be the same. Any ideas?

[Ira]

Hmmm, I don't know if you'd be able to replace it with a temperature proble, but that's an interesting idea. Ideal would be a temperature controller, of course. But, that kinda defeats the cool cheap ghettoness.

[Shilo]

Back to the Drawing Board

Just got back from a weeks holiday to find some fine bubbles coming up from the evaporator coil. The chiller had been switched off since its not needed but the tank was still full of water. So I switched it only to created with geysers that would make Rottenrua look on with envy.

The aluminium coil had corroded through. It was a fear of mine but considered that since the coil is constantly wet as a dehumidifier it must be reasonably corrosion resistant - Wrong!

I think the concept is still workable, the coil would have to be kept in a non corrosive fluid (anti-freeze?) and the aquarium water piped through either a stainless (freshwater) or titanium coil sitting in the coolant fluid.

Either way this dehumidifier is now defunct. Once I get over swearing and cursing (the joys of DIY!) I might look up a local refridgeration guy to see if he could cut the coil off and join on a stainless one then regas the contraption.

Got a few months to go before temps become a problem, and its to late to give up on a native tank now - part of my holiday involved hunting for native plants and catching more fish for the tank which are currently swimming around in a fish bin (with filter) waiting to be introduced into the aquarium after I renovate it tomorrow.

If you don't try you never win.......

[neopole]

last year, and gave simple instructions on how to make it.

it works great. and cost less than $100

i had a 5ft cold marine tank, sitting in a sunroom. the temp in the sun room hit 40deg in summer but the tank never went over 22 23 deg.

find the thread....bathtub chiller in the marine section.

[Shilo]

Thanks Neopole,

Saw your threads when seaching for chiller ideas. But in my case I'm restricted to what I can do. Rental property thus no holes drilled in house (have a wicked workshop under the house that would be ideal - but can't pipe to it!) and a lack of room in the stand for anymore contraptions. Also have to watch the humidity levels if anything is put inside the house.

But I AM NOT BEATEN!!!. Have sourced some free S/S pipe that is to wide but can devise a system around. Just means I will need to grab yet another dehumidifier.

Plan on filling the chiller tank with the sort of antifreeze you get in chilly bin ice packs (not toxic) and pump the water through the S/S pipe set into the chiller tank.

Despite writting off one dehumidifier ($169) and having to get another it will still work out much cheaper then a commercial model. Confident it will work OK this time around

[Wok]

why buy a dehumidifier when you can go to either Foodtown, woolworths or Countdown and buy one of those larger airconditioning units for $399.00

[Control]

Wok

That's great in theory but you will find it hard to find an installer that would be game enough to guaranty the installation on such a cheap unit let alone agree to install it in the first place.

If you were a certified electrician and were able to gas it yourself it wouldn't be a problem, but if not the intallation would cost more than the unit and considering the life span that such a cheap heat pump would have it just wouldn't be worth it.

[Shilo]

From what I've heard the Air Conditioners aren't very effective unless they are vented outside. Venting will ofcourse mean cutting holes in a wall which I can't do. Without venting the a/c will be adding just as much heat into the room as it is removing.

The advantage of using the dehumidifier is that it will be cooling only the water while the heat it produces is released into the air. This heat can be removed by open windows (where as a a/c unit will be trying to cool the outside air as well if the windows are open).

Of course a A/C could be used to cool the water directly, but at $169 from Woolies or $153 at The Warehouse a dehumidifier wins hands down.

If I owned my own home then yes a permenant aircon would be best, but mainly for me - the fish wouldn't notice

[Control]

From what I've heard the Air Conditioners aren't very effective unless they are vented outside

No you don't vent outside those units are cheap all in one things, that like saying a fridge is more efficiant if you leave the door open.

The ones you are talking about use both outside are or the cooling if need be to save power.

where as a a/c unit will be trying to cool the outside air as well if the windows are open

You don't leave your windows open if you are trying to cool down a room.

but mainly for me - the fish wouldn't notice

If a heat pump keep a room at 20 degrees you will have no need to cool the tank.

I know this because I have one.

[Faran]

For me it would be a matter of running costs over initial costs. While you're spending as little as $200 on the dehumidifier chiller, our dehumidifier costs about $75 a month to run. If you had used Peltizers you could have run the entire thing on a couple of volts and had perfect results. Would have cost maybe $5 a month to run. Oh, and try getting Peltizers off eBay if you don't have a source here in NZ. You'll save HEAPS.

[Shilo]

Hi Control,

No you don't vent outside those units are cheap all in one things, that like saying a fridge is more efficient if you leave the door open.

No I was meaning the cheap all in one portable units as well. Unfortunately a fridge, dehumidifier, air con unit, peltier or any similar cooling device also produces heat - energy has to go somewhere. If you feel the back of a fridge that is "going for it" you will feel the heat it produces. A fridge only cools the enclosed area behind the door but the heat it produces is expelled into the kitchen.

The problem with a portable all in one air conditioner is that it is not only cooling the air in the room, the heat it produces is also bowen into the room heating it up at the same time thus its inefficiency. By having the evaporator coil in contact with the water (or in an enclosed space where the water flows through) then it will work - but room temperature will rise thus the reason for leaving the windows open for this heat to escape. This is the same as the dehumidifier / chiller concept of course and insulating the sump and as much of the tank system as I can is important.

Hi BlueandKim,

I considered peltiers pretty hard before deciding on a dehumidifier. You may be correct about running costs but the startup costs (well untill I stuffed the 1st dehumidifier) put me off. Figured that to get approx the same cooling power I would need 4 x 270w Peltiers, 2x large heat sinks, 3x computer fans and a 12v adapter. At $106 each for the Peltier's (Trademe) I would be looking at around $450 - $500 for the chiller.

Guesstimate that the dehumidifier/chiller will only need to run for 3hrs (on and off) per day during summer to keep the temps 10 deg less then room so running costs will hopefully not be to much.

But the proof is in the pudding, so will see what happens to the power bill. I still want to play with Peltiers sometime though!

[Shilo]

Version 2

Main Changes:

Had to come up with another idea for the chiller tank since the previous one sprung a leak. This ones just a click clack container which has had the lid siliconed on and one end cut off. Cut up the old chiller tank to make a mount for it.

The green stuff is anti-freeze. Couldn't find the non-toxic stuff so just used car anti-freeze. There is nowhere in this system where the anti-freeze can leak or contact the aquarium water. All joins in the tubes are external. Have had the anti-freeze down to -8C before mushy ice started to form.

Internally the evaporator coil is wrapped with 8m of clear tubing. Additionally I flattened a piece of 5" stainless pipe, blocked off the ends and have the water circulating in there. Ideally a stack of 1/2" stainless pipe on both side of the evaporator should be used since the plastic tubing is a fairly good insulator but 5m of s/s pipe would have cost another $45.

Tapping off the main pump outlet didn't produce enough pressure to circulate the water through the system so a dedicated pump had to be installed. This is self defeating in a way since each additional pump in the sump (I now have 3) heats the water, but it means that I can have a strong flow through both the chiller and aquarium.

To disguise things I made a cabinet out of scrap ply to fit over it. Will replace the air grid in the back with something black sometime in the future. The cabinet is larger then the chillers since I want to move all the timers and power boards from the sump area into there.

Does it work? Yes. Not as efficient as it could be but it with the fan in the light hood I can now keep the aquarium 10C below room temperature. Total cost for version 2 is just under $200. Another $50 would make it much more effective.

[Control]

That's looking good, I think the Anti freeze is the best way to go.

Check for current and I mean very low current in the anti freeze, it will slowly eat away at the alloy if there is one pressent.

[Wok]

Mono Propolene Glycol is a good alternative. it is safe as well.

Used as a food ingredient in some products and works like an anti-freeze.

can be purchased through places like Swift International.

Not too expensive either.