What size chiller should I get?

[Spar]

I have a friend selling me a nice and nearly new 1/2HP chiller for my 450g. I was running LED's, but am switching to MH's, probably 2 400w and 2 250w, with 4 29W T5's for accenting.

The tank has no canopy, and is open top in a decent sized room (8x12). I also run a strong exhaust fan (like the ones in bathrooms) 24/7 in the room to suck out heat and humidity. I only plan to drop my temp to ~79, so estimating a 5-6 degree drop.

The chiller will be stationed directly underneath the exhaust fan (albeit 10 feet under it).

So other than the running MH's, everything else is on my side of a smaller chiller working out ok... but wanting others thoughts on if a 1/2HP may be a mistake? Don't want to completely over work the thing or drain too much electricity unnecessarily.

Thoughts? Other facts needed?

 

[sirreal63]

It's undersized, as you already know, but I have to ask, why 79 degrees? An undersized chiller will run more, which of course equates to a higher electric bill.

 

[grigsy]

I agree.

A 1/2 HP chiller is too small for a 450 gallon tank.

My experience with chillers has taught me it is always a good idea to be a size above what you really need.

That way, the chiller isnt on all the time. Plus, it cools the water quicker using less electricity and it uses less freon meaning you dont have to get it charged as soon.

 

[tkeracer619]

I got a 1/4hp for my 360 but my tank never needed a chiller. I just got it in case something happened and the tank started to overheat while I was out of town due to an ac break.

It won't cool the tank when the house is 90deg and everything is on but it will keep it from climbing. I have it in the crawl space and set to 83deg. Only came on when I was testing it. I am willing to bet it will only come on a few times a year so I am not too worried about it being very undersized.

I would think a 1/2hp would be enough to keep the tank stable should something go wrong but if you are going to actively use it on a daily basis to keep the tank cool I would consider a 1hp unit.

 

[Spar]

Thanks all. I went with a 1HP chiller to play it safe.