Temperature fluct

[kalani1126]

Okay. So I had installed a chiller that is rated up to a 75g on my 25g nano. My temp stays consistant at 78degrees. Now for the problem and im not sure how to tackle this. When my temp goes to up 80, my chiller kicks in and drops the temp down quickly to 77degrees even tho I have it set at 78. In a short period, in a span of 5minutes, my temp drops about 3degrees. This cant be good for my inhabitants can it? How can I keep this from happening? Any ideas?

[tbittner]

What chiller? Does it have a min-max setting you can configure on it? Mine keeps the temp between 77 and 79. I've never seen it out of that range.

Also, what water volume (gph) do you have pumping through the chiller? Is in within the recommended specs?

[BigAl07]

OUCH! Yes that's a lot of temp swing in a short period of time.


I don't know how you can adjust this but you need to get your temp MUCH more stable than that. I would assume the thermostat on the chiller has a setting that turns it off right at the set temp but everything is already chilling away and the temp slips lower than expected. Maybe setting your chiller to 79 would help? It's probably more of a trial & error type of thing.

I would highly suggest you get a "tank controller" that will control your chiller and heater to work as a team to keep things just right. I use a Neptune Aquacontroller on my tank and LOVE it.

Allen

[kalani1126]

Originally Posted by tbittner

What chiller? Does it have a min-max setting you can configure on it? Mine keeps the temp between 77 and 79. I've never seen it out of that range.

Also, what water volume (gph) do you have pumping through the chiller? Is in within the recommended specs?

I have a via aqua polar bear cc25. I have a mag drive 5 with a flow rate of 300gph. Im using a ball valve to control my flow so that it doesnt flow to much. The recommended specs are 150-450gph I believe.

Originally Posted by BigAl07

OUCH! Yes that's a lot of temp swing in a short period of time.


I don't know how you can adjust this but you need to get your temp MUCH more stable than that. I would assume the thermostat on the chiller has a setting that turns it off right at the set temp but everything is already chilling away and the temp slips lower than expected. Maybe setting your chiller to 79 would help? It's probably more of a trial & error type of thing.

I would highly suggest you get a "tank controller" that will control your chiller and heater to work as a team to keep things just right. I use a Neptune Aquacontroller on my tank and LOVE it.

Allen

I'll try setting it up. So a heater might help? I'll research more on that. Im kinda an amateur to controllers. Do they help and are they easy to use?

Thanks for the help guys

[Scouter Steve]

Maybe un throttle your pump, it may keep the temp more constant. Also a throttled Mag pump adds more heat I believe.

[AQTCJAK]

Sell that chiller & get one that is the proper size. throttling the pump back will make it worse

[BigAl07]

Originally Posted by AQTCJAK

Sell that chiller & get one that is the proper size. throttling the pump back will make it worse

I agree with Jack. The more you "tinker" with these things the less stable they are.

A controller is a thing of beauty. It CAN control your heater, chiller, lights, pumps and the list goes on and on. Very easy to use once you get used to it's "language".

Allen

[ScubaRW4]

I agree. The chiller you have is too powerful for a 25-gallon tank.

[Rcpilot]

I work in the HVAC business, so I can tell you exactly why it's not working right.

First thing--it's too big. WAY too big. Bigger isn't always better. There are actually engineers that design stuff for a spcific size house or tank--and some of those engineers know what they are doing.

When you oversize the central AC in your home, it comes on and runs for 3 minutes. It's SO big that it instantly satisfies the thermostat. When the thermostat reaches it's setpoint, it shuts off the power to the AC. It "flash cools" your house. The problem with that, is that your air handler (pump) never actually moves enough air across the cooling coils to circulate ALL of the air in the house. It circulates maybe 60% of the air in a very short time and then the T-stat shuts it all down. But, since all the air in the house wasn't mixed and blown across the coil, you will have stagnant pockets of air. Stale air. That air never got a chance to run through the return ducts and pass over the cooling coil.

2 minutes later, that stale air moves around the house and trips the T-stat to come back on. The central AC comes on and instantly flash cools the house and that triggers the T-stat to shut it all off again.

Vicious cycle.

It leads to a gazillion other problems that don't need to be explained here.

The pump you have should not be closed down to slow the water flow through the cooler. That just makes the water stay in the chiller even LONGER and it's probably bringing the water temp down to 65F. If anything-- speed the water up --- faster. Open the valve and let the water rush through the chiller so fast that it can't stay in contact with the chilling coils long enough to cool down very much.

Same thing with a car. Racing guys used to take the thermostat out of the engine, because they thought it would make the car run cooler. When in fact, that thermostat actually provided a lot of restriction in the cooling system. If the water rushes through the radiator (heat exchanger) too fast, it will never cool off enough. It just gets pumped back into the engine before it can ever cool off. The engine runs even hotter with the thermostat removed because that restriction the thermostat puts on the system actually slows the water down enough to cool in the radiator. Racers soon learned to just place a large flat plate with a 1" hole in the center where the thermostat used to be. The "washer" provided the restriction needed to cool the car beter than when it came from the factory. That was the original intent all along.

I think you goofed up by buying a chiller thats WAY oversized, but I don't think I'd call it a lost cause yet.

Open the valves and let that Mag 5 pump. Speed that water up so that it doesn't have enough contact time to cool off so quickly.

We deal with this in HVAC all the time. If you don't move enough air across the heat exchanger on the furnace, it overheats. There's a fire in there, and the air moving past the heat exchanger actually cools the heat exchanger enough to prevent it from overheating. When people don't change their furnace filters, it slows down the airflow across the heat exchanger and then safety switches start shhutting things off to prevent fires, explosions, cO poisoning and deaths.

If you don't run enough air across a cooling coil thats full of freon at -45F, it tends to freeze in the humid air. Once it starts to freeze--it's a snowball rolling down hill. Low airflow leads to freezing in the first place, and the frozen coil is able to pass even LESs air, so it freezes even more. And then it can pass even LESS air and it eventually ends up a frozen ice cube.

If you run too much air past a freon cooling coil, it looses efficiency on an exponential curve. The air and the coil actually have to go through a "contact time" in order for the air to absorb the cold from the heat exchanger in the freon coil. For X contact time (seconds) you need Y airflow (feet per minute) at Z pressure (inches of water column).

The point I'm making, is that you might just need to "balance" the flow through the system. By opening the valves on the Mag, you can slow the actual contact time between the chiller coils and your tank water. Reducing the contact time will also reduce the heat transfer and slow your cooling process.

It might work. But, if your chiller is to drastically oversized, you might be looking at another one.

OR, you could always just get a bigger tank.

[BigAl07]

Sounds like a good experiment to me. May even same some money on replacing the chiller.

Allen

[kalani1126]

Very inetersting. thanks for the input guys. I won the chiller at a LFS that had a grand opening. It was a cool prize though. Maybe I should get a bigger tank? That may help.

[goldenmean]

LOL
when all else fails Get a bigger tank!
That definately works!!