Affect of room temp on water temp?

[limitup]

We're going to be building a new house, and I'm already starting to plan my new inwall tank. One thing I'm starting to think about now are the methods I'll use to keep the tank cool. Most likely it's going to be a 280g with a very small "room" behind it (plenty wide but only about 6 ft deep as that's all the room I have).

My current 140g is an inwall tank with a small closet behind it, and so I'm all too familiar with heat problems. After a lot of trial and error my current setup (various ducts, vents, fans and a chiller) works great, but I'd like to improve on it for the next setup. With my current set-up my chiller comes on once per day in the late afternoon (in the summer) and I'd like to eliminate that if at all possible.

One thing I don't have any experience with is the affect that a lower ambient room temp has on water temp - because my current tank "room" is always 80 degrees or hotter ...

All else being equal, what kind of effect would there be if the tank was say 80 degrees and the surrounding air was only 70 degrees? Would the rate at which the tank water heats up throughout the day be significantly slower?

At this point I'm just brainstorming on the "bigger" ideas and trying to figure out if I want a dedicated A/C thermostat for my tank room, or if I'm just going to rely on vents and a chiller, etc. For example, if I had a dedicated A/C system and kept the tank room at 65 degrees during the day would that seriously reduce the rate at which the tank water heats up, to the point where I probably won't need a chiller at all?

On a related note, does anyone in a warm climate NOT use a chiller, even as a backup? Even if it never came on I'm not sure I would feel safe without having a chiller as a backup in case anything went wrong with the A/C, or the tank heated up for some other reason. As much as I hate chillers it almost seems like I would still want one just for "insurance" ... but at the same time I'd love to have a setup where I didn't need a chiller at all.

[Tunguska]

If I didn't just give my thermodynamics and transport phenomenon books to a friend, I'd volunteer to do the math.

Just something to consider: water requires the same amount of heat loss to lower one degree no matter how you accomplish this. You would want to make your choice depending on the efficiency of your chiller compared to an air conditioner+insulation. I don't think that windowsill air conditioners are very efficient, if that's what you were considering.

[limitup]

Definitely not a window A/C ... it would be another separate zone on the central A/C system. If keeping the room really cool would make a big difference I would probably go that route because I really wouldn't want the chiller coming on. Mainly due to the location of the tank/room and the noise of the chiller.

There will be an exterior wall on one side of the tank room and I *could* put the chiller outside, but there will be problems with that too - not the least of which is the fact that when I need the chiller most it will be 100+ degrees outside.

[NHMarine]

limitup, I live up here in New Hampshire, but make no mistake it can get hot and humid up here too (June, July and August). Actually today was 93 degrees.

I built my house a few years ago, and installed my own central air unit...I love it!!

I have a 75 Gallon tank with 2 250W halides and 2 110W VHO's, so I'm generating some heat with my lights. I am running 4 Ice cap smart fans in the canopy (I only run two in the winter and four on the lowest setting in the summer) I have been watching the tank / room temp thing very closely lately as summer is upon us now. What I have noticed is the fans are able to cool the tank about 1-2 degrees below room temp, the heater kicks on at 79.5

Here is a thought for your fish room.....I would run a supply line only to the tank room (Don't want to smell stinky skimmate while you have guest over for dinner :eek:, make up the return line somewhere else. Run it off one of your big zones that runs alot.... like you living room, use a manual adjust butterfly vent and choke it down until you reach you desired temp. i.e. like my house....I have one zone for the house with 12 supplies & returns. I start out with all of the butterflies (vents) wide open. I wait until the living room (where the thermostat is) is cooled down to the set temp. I then go around to all the rooms and see which ones are colder and choke them down a bit...after a couple days of tweaking the hole house is the same temp. This is how the vents will stay all the time.

The great thing about the central air, is its usually very dry, so it should help combat the humidity.

[limitup]

This is going to be our "dream" house and my "dream tank", so I don't mind spending a little extra. I was actually thinking of having the tank room on it's own separate zone - that way I can adjust the temp a lot lower than the surrounding rooms if necessary. I could have the supply down low and then a big huge return up near the ceiling, which would give the rooms lots of needed air flow, plus I wouldn't have to worry about stinking up the house since it would be completely separate from everything else.

At this point though I'm just trying to figure out how much of a difference it will make if the tank room is at say 70 degrees vs. 80 degrees, etc. If it will make a huge difference I would probably do it, but if not than obviously it wouldn't be worth the extra expense.

[tgrunewald]

It will always help to have a supply and return in the room, your supply can also be up high since cold air drops warm air rises. How much it will help tank temp has a lot to do with sump/refuge etc. you will get more heat transfer from the moving water contact with cold air then thru the glass/acrylic tank where you will get very little. You will probably still need a chiller I would focus on a high quality, quiet, chiller money well spent, you could even insulate around the chiller to silence it. Point being unless you are building a very large home where you need zoning I would install a normal hvac system with a fairly large supply and return to fish room and spend the money on a higher quality chiller and design an insulated cabinet to house it.
TOM

[limitup]

Oh yeah, the house is going to have multiple zones for HVAC already, so I figured it's no big thing to just add one more tiny zone for the tank room. I have a huge sump that I will be re-using, and I'm sure I'll copy my current set-up where I have multiple fans blowing across the top of both the tank and sump.

[NewMariner]

I had a 180g tank with 2 400w MHs, and a 175w MH....I kept the house thermo on about 76(wife wouldnt allow anything lower). I never got a chiller, I did put some fans in the canopy to blow out the hot air. Tank temp without the fans on was about 84 degrees, with the fans brought the tank down to about 81 degrees.... And this with the 100 degree Texas Heat outside....

If I were able to be in your shoes, I would run your AC to your fish room as you will want to cool your lights and pumps... If I had my way I would have separate units for your house/fishroom, as it would be cheaper and more effective then your chiller. Have the return up high as that will pull the heat out of the room, as heat does rise...

[kbmdale]

Ever thought about building the room like a cooler. Insulate the room really well with styrofoam sheets or something like that. Then your room will better hold the cool air you give it. Just a thought, may be overboard. lol

[NewMariner]

Originally posted by kbmdale
Ever thought about building the room like a cooler. Insulate the room really well with styrofoam sheets or something like that. Then your room will better hold the cool air you give it. Just a thought, may be overboard. lol

I think that would be a bad idea....during the winter when he wont be using the AC, the fish room would still require AC as it would then be holding heat in.....

[limitup]

All good ideas, keep 'em coming. It helps with the brainstorming...

One thing that works well in my current set-up are several fans hooked up to a temp controller. I have 2 fans over the tank and 3 fans over the sump, and they make a huge difference as many of you know. They hold the water temp down almost all day until the chiller finally kicks on at around 4-5pm.

What I'm really trying to figure out is the difference I might expect to see if the room was much cooler. I really have no idea where to begin looking. If anyone has any experience in thermodynamics and can point me in the right direction it would be much appreciated. I'm sure there's a page on the web somewhere that explains how to calculate this type of thing, I just haven't found it yet ...

[NewMariner]

If you keep your room at an ambient temperature of 60 degrees then your tank will be 60 degrees(this is without any lights or heaters). Your tank will drop or raise dependant upon the air temp around it.

Its just like a lake. You dont go swimming in a lake in the dead of winter because the water is to cold due to the air around the lake being cold. When the air warms up, it warms the lake up.

So yes, cooling your room will effect the temp of your tank. how much is dependant upon how much heat is in the room, and the size of the a/c cooling the room.

[limitup]

Yes I understand the general concept, but there's a little more to it than that for this type of an application. Most importantly, the length of time it takes for the water to change temperature. Sure if the room was 60 degrees the water would eventually go to 60 degrees ... but can the cool air be used as a "chiller" or does it take too long for it to be effective in that sense?

For example, if the room is 75 and the tank is 82 can I drop the air in the room to 68 and hope to see the tank temp drop in 1 hour, 5 hours, 10 hours, etc? If changing the ambient air temp doesn't affect the tank temp for 10 hours, that won't be much good. On the other hand if changing the ambient temp has a pretty quick effect on the tank temp then that could be an integral part of the cooling system.

[KDodds]

I don't believe the cooling effect of ambient room temperature would be AS effective as using a chiller. You are, after all, cooling a much larger volume which, in turn, you hope will cool the original volume. Ambient temperature usually has an effect on running temp, but it's not as great as one might think. For instance, in the case of external pumps and MH lighting, etc. that add a lot of heat, dropping the room temp 10ºF will not, from my practical experience, result in a 10ºF drop in tank temp. Possibly this is because of the effects of evaporation and evaporative cooling at higher ambient temps, or because of the resistance of the heat source to change is greater than the more passive ambient cooling. I don't pretend to understand it, I just know that chillers are more effective and reliable than room cooling. Whether or not they're more financially efficient is another matter. Personally, I use a combination of both. My home is climate controlled to 70ºF throughout. From experience, a drop from room temps of 85ºF in the summer (before we installed central A/C) to 70ºF resulted in a change in running temp, with chiller off, from 88ºF to 84ºF, with occasional jumps to 86º if the sun hit the tank for a few hours. So, that 15ºF drop netted 4ºF running temp, again, without a chiller running.

[kbmdale]

Originally posted by NewMariner
If you keep your room at an ambient temperature of 60 degrees then your tank will be 60 degrees(this is without any lights or heaters). Your tank will drop or raise dependant upon the air temp around it.



Not to the extremeity you desribe it. Water holds heat better than air. So if your room goes from a temp of 70 to 60 lets say over a 12 hour period. I bet your tank will be between 65-68 at the same time your room hits 60. Water tempatures of a lake are effected by the air but not controlled. The water temp of feeding streams and the sun also play an effect. The sun heats water as well but not to the tempature of the air. Water is a mass, air is not. The room temp is going to be related to water temp but you can't set your thermostat to 60 and expect your tank to be 60. Equipment(pumps, PWHeads, ETC.) in the water also come into play.

[limitup]

So, that 15ºF drop netted 4ºF running temp, again, without a chiller running.

This is exactly the type of experiences I was hoping to hear about. That would be perfect if I saw the same type of thing. With my current setup my tank room is usually 83-85 degrees. If it had a dedicated A/C system I'm sure I could drop it to 70. If that resulted in even an overall 2 degree drop in water temp then my chiller would never need to come on at all. The fans wouldn't even run for that matter, except on the hottest of days.

[KDodds]

YVW, just keep in mind that, with different equipment, your net result may be different.

[limitup]

Yeah, most definitely. My new setup will be similar to my current setup ... so I'm just basing my "guesses" on that for now. The new tank will be twice as big, with twice as much light. So that should pretty much be a wash there. The new tank room will be slightly bigger than my current room. From what I'm gathering, being able to keep the room temp in the low 70s will make enough of a difference to achieve what I want. I could also move from internal to external pumps if necessary too.

[KDodds]

I would highly recommend having a "return" installed in the room as well if you're planning on using central A/C zones to do this. It may be necessary if it's a totally separate zone, anyway, but it will help with heat removal as well as humidity removal. Humidity removal (or lowering, really) will also help enhance evaporative cooling.

[glaudds]

Here's my experience with ambient temperature with my tank. During the summer here in so. cal, our AC is set around 78 degrees for the whole house. With that, my tank will hit 82-83 in the late afternoon (125 gallon tank with sump). The light canopy is vented to the outside with with a 4" icecap fan. No chiller.

In the evening when it is cool enough, I open the window in the tank room. When the room drops to 70 degrees, it takes about an hour or two for the tank temp to drop about a degree. This is also with the halide lights running. If it is a really cool evening, it will drop even further, where I have to shut the window.

Hope that helps.

[limitup]

Every little bit of info helps, so thanks to all.

One thing that makes a huge difference is that my tank is inwall with a pretty small tank room behind it. It's not even really a tank "room" in that my current space is only about 13 feet by 4 feet. In the new house it will be about 18 feet by 5.5 feet. So think of it more like a big closet. This creates unique challenges in regards to airflow, heat, humidity, etc. On the other hand, the small space should be a "benefit" in that a dedicated A/C system should be able to keep the room really cold if necessary ...

[Agu]

Temp is only part of the equation, you also have to consider humidity. As you cool the air you'll have more condensation because cooler air can't hold as much humidity. Sure some of it will be removed by the ductwork. But what's it going to do in the ductwork besides cause rust and mold ?

I have nanos in Florida and I can tell room temp by looking at the tank thermometer, it's two degrees warmer in the tank than room air. In Mn summers my 180 in the basement was pretty much the same two degree difference.

I'd recommend using the house air con as backup only and installing a window unit as your main cooling source. Actually if you could get one of those units like they use in motels that heat/cool that would be ideal. It may not be the most efficient but it beats the efficiency of running a whole house unit because one small room has temperature extremes. Also it'll dehumidify that room and dump the moisture outside. A small window unit wouldn't cost that much money to buy, run, or replace when it rusts out.

jmo,

[mhurley]

Here is my experience with my fish room and my 330 gallon tank (plus 100 gallons of sump, refugium water).
My tank and fish room are in my basement, which is by default is cooler. I have I have 1600 watts of halides that I built a light box for that is mounted on rails and rolls over my tank. This box vents the heat from those lights directly out of the house via a few fans. However, as the day wears on, there is still heat radiating from that box. So it is still a heat source in the room.

If unchecked and I close the door to my fish room it will easily get over 90 degrees in there and in turn, warm up the tank pretty darn quick. So I have to constantly leave that door open. Even then, my undersized chiller (1/3 HP) will still kick on in the summer time (like today). I've tried a heat/air exchangers dedicated to that room but that does not help in the summer.

I am now probably moving on to an oversized chiller (1 HP) and an exhaust fan in the room tied to a thermostat (i.e. if Temp of room >80 degrees, turn on fan).

My experience is that a fish room will heat up significantly faster than a living room/whole house will, obviously because of the amount of air you have to deal with.

[limitup]

A window unit is not an option due to the location and construction of the proposed room. I don't see why the central A/C system will have a problem removing humidity - they are meant to do that and in my experience they do a good job of it. With my current setup, due to the fact that the tank/room is in a central location, most of the heat/humidity is dumped into a surrounding room via ducts. There is/was no noticable increase in humidity in this room.

[PeteUK]

What have you got against chillers?

If the tank is producing the heat that is making it too hot and you're not using a chiller but using Air Con instead, the room will have to be significantly cooler to cool the tank. You might end up having to wrap up warm just to go look at your fish, no?

[limitup]

My experience is that a fish room will heat up significantly faster than a living room/whole house will, obviously because of the amount of air you have to deal with.

Exactly. Unless you have an inwall tank with a small room behind it, it's hard to imagine the different challenges it poses. I have a total of 5 fans that vent my current tank room. 2 run 24/7. 2 turn on only when the MHs are on. The 5th fan is installed inline the ducting that vents the exhaust from the chiller, so this fan only turns on when the chiller is on and helps to pull the hot air through the ducting and push it out of the room. I basically rigged up a custom shroud around the exhaust side of the chiller which a big duct that runs up to a vent near the ceiling...

[limitup]

What have you got against chillers?

In my application, the primary problems are noise and heat.

If the tank is producing the heat that is making it too hot and you're not using a chiller but using Air Con instead, the room will have to be significantly cooler to cool the tank. You might end up having to wrap up warm just to go look at your fish, no?

No, this is an inwall tank. The tank and all the equipment is in a tiny room all by itself. This is the room that would be cooled down. You view the tank from outside of the "tank room". When I refer to tank room I mean the tiny room that the tank and all the equipment are in.

[NHMarine]

Could you put the chiller outside in a shed of sorts? I saw someone here with all the equipment in one of those Rubbermaid storage units.

Again, just adding to the "brainstorming"

[limitup]

Yeah I've given that some thought. Only problem is that the other side of the wall will be right in the middle of some outside decking that will be heavily trafficked. I mean literally right in the middle of the backside of the house where we'll be hanging out, having BBQs, etc. If it was off to the side or something that might be an idea, but I don't see it working well.

The other thing is that when the chiller would be needed most it will be 100+ degrees outside and with a high ambient temp like that I assume the chiller wouldn't work very well anyway?