Chiller sizing question

[M.E.Milz]

My new set-up has been up and runnig for a few months now. Through the use of fans and other ventilating devices, I have been able to maintain my water temp in the 82-84 degree range. I would prefer to keep the tank at a constant 82 degrees (I have always kept my reef tanks on the warm side). I am also concerned that the water temp will creep up if the room temp should rise (like if we are out of town and a heat wave hits). I therefore would like to add a chiller just to be safe.

The total volumn of water in my system is around 400 gallons, less whatever water is displaced by my sandbed and live rock (whcih is probably 50-70 gallons). According to the sizing charts provided by most chiller manufacturers, I should get a 1/2 hp chiller. A 1/2 hp will supposedly give me a 10 degree pull-down.

For various reasons such as electrical draw, cost, size of the chiller, and noise produced by the unit, I would prefer to to use a smaller chiller - say a 1/3 hp unit. I figure that a 1/3 hp unit will be more than enough since I only need to pull the temp down 1-2 degrees. Is my reasoning flawed? I have talked to dealers that have said a 1/3 hp unit will be enough. But I have also talked to other dealers/manufacturers that have told me I need the bigger chiller, and it doesn't matter that I only need to 1-2 degrees pull-down. This doesn't make any sense, but maybe I don't know enough about how chillers are designed to function. Any help on this would be greatly appreciated.

Mike

 

[M.E.Milz]

Anybody?

 

[danmhippo]

I am using a 1/2 HP CSL inline chiller. My pond water temp raises by 15 degree if not chilled during the day. Pond water volume is approx. 120Gallon. The 1/2 HP is barely adequate for this application.

But, since you do not often observe temp over 84 for your 400G. Then I think 1/2HP should be adequate. 1/3HP doesn't do crap for your tank volume IMHO. Noise is a definete concern, and you will want to place the chiller out in the yard. My chiller is noisy, it's like running an window aircon.......well, essentially, it is like an air con. If where you want your chiller to be placed is more then 4ft from your tank, you can only purchase the in-line model, not the coil model.

 

[Anonymous]

hi.
It is usually recommanded that you get the 1/2 hp chiller for your tank size although the pull down needed is only 2 degree. You don't want a 1/5 hp chiller to work 26 hours a day to keep you tank temperature because although rated for a X degree pull down, it is for continuous operation.

I suppose the 1/3 hp chiller is fine, but be forewarn that if you need to get it to run more than a few hours a day, the compressor may not live long. But for your "just in case" operation, it should be sufficient (IMHO).

 

[miken]

Like I was mentioning on an earler post at www.fritzpet.com I found out that there are a lot more variables to consider when choosing a chiller, like ambient temp, wattage of lights and pumps, amount of rock, type of tank, ventilation, flow rate, etc.

Go to Fritz's site, click products, then chillers, from there they have an article entitled "Choosing the right chiller". Of course they want you to buy a Teclima, but I think it's pretty much geared at Chillers in general.

I also called them and spoke to a tech there who helped me figure sizing out. You do not want to undersize!!

Good Luck!

 

[M.E.Milz]

danmhippo, I am on the 57th floor, so my "yard" is a long ways away. Obviously, I don't have a garage or a basement either. That is why I am concerned about a 1/2 hp unit - it will have to sit right next to the tank in my living room. The additional amps that a 1/2 hp unit draws (over a 1/3 hp unit) may also require me to add a separate circuit - something that I would like to avoid.

miken, I talked to someone at Firtz yesterday and they were very helpful. I also talked to a rep at Aqua logic and Custom Sea Life. They gave me different answers as to whether a 1/3 hp unit will work. That is why I started this thread.

I suppose the 1/3 hp chiller is fine, but be forewarn that if you need to get it to run more than a few hours a day, the compressor may not live long. But for your "just in case" operation, it should be sufficient (IMHO).

This is what I am thinking. But I would love to hear from someone in a similar situation that can confirm I will be ok. Of course, it would be nice if the retailer from which I decide to buy the unit would let me exchange it for a bigger unit if I try it out for a few days and discover that the chiller runs around the clock.

 

[miken]

I'm curious what each company said? Did they contradict one another?

 

[Anonymous]

I'm curious what each company said? Did they contradict one another?

hi.
I won't call it contradiction, but it is like "Well, the manufacturer say this X hp chiller should do it, but I feel you will need something at least Y hp instead..."

I doubt that any legit business will let you return an used chiller, unless you are willing to be slapped with a 20% restocking fee or something like that. How about ask anyone local with a similar chiller to lend you one for a few hours?

All and all, chiller selection is a well defined engineering problem, but somehow, we are getting a trial and error solution out of it.

 

[miken]

I think in the long run, just from energy costs, if would be cheaper to get the larger model that would not be running constantly. Does that make sense?

 

[miken]

How about ask anyone local with a similar chiller to lend you one for a few hours?

I know that it takes a while for the temp to actually get to where it needs to be, maybe even a day or two. So it would be difficult to determine if it was working well on a certain size tank (especially a large tank).

I would ask for a guarantee that a certain size chiller would work in your situation. I'm curious if anyone would do that?

While speaking with Fritz they told me that they had let customers return a chiller for a larger model if they were mislead or given bad advice by the reseller. Of couse the chiller was only run a short time and was still in good condition.

 

[M.E.Milz]

I'm curious what each company said? Did they contradict one another?

Whoever I talked to at Aqua Logic just stuck to their chiller sizing chart, stating that it didn't make any difference that I only neede to draw down the temp 2-3 degrees. He really didn't want to talk about my specific application.

The person I talked to at Fritz said that they couldn't recommend using the smaller sized chiller (their 6800 is similar to a 1/4 hp), but acknowledged that the smaller unit might be enough since I was only trying to drop the temp a degree or two.

The people at Custom Sea Life were very helpful, sending me chiller sizing charts and formulas, as well as talking to me on the phone several times. They felt that those charts that suggested that there was a linear relationship between volumn of water and temperature draw down were incorrect (eg, if a 1/4 hp unit can drop the temp of a 100g tank 10 degrees, then it can drop the temp of a 200g tank 5 degrees). This is because the mechanism by which chillers remove heat from a tank are dependent on too many variables. In any event, they did think that I might be ok with a 1/3 hp unit since all I was trying to do was remove the excess heat added by my lights, which was not very much since I am only seeing a 1-2 degree temp rise from the lights. But again, they were not absolutely positive. They did ask me to let them know how a 1/3 hp unit works so that they can pass the info on to others with similar situations.

The most relevant info came from someone at AETech, whom sells the Custom Sea Life chillers. Whoever I talked to there told me that they had 1/3 hp unit on a similarly sized tank in the shop, and it had no problem dropping the temp a few degrees.

 

[M.E.Milz]

Anybody out there with a large tank and an "undersized" chiller??

 

[MrPuma]

I have a 750 gallon fish only tank built into the wall with a closet access which gets very hot. the tank was getting to about 94 degrees. I bought a chiller for it. of course according to their calculations I needed a 1hp or so. too expensive. I bought the 1/2 hp and it is mounted in the garage. I run the hoses through the wall in the garage and return it. the tank is maintained at about 80-82 even in the hottest part of summer at 95 degrees out side. my lighting is only flour. but I have 10 of them over the tank and the room is enclosed which is still hot on an outside wall. I also have a 90gallon reef with 2x175w 10K metal halide with 2 fans. I have a 1/4 hp on that and it maintains it at 78 degrees. that chiller is in the basement with the hoses running there. you really cant have the chiller next to the tank or below. it produces a lot of heat plus it is noisy. hope this helps.

 

[M.E.Milz]

Thanks MrPuma. That helps.