A higher wattage aquarium heater?

[Fresh Brewed]

My FOAF is having trouble keeping his FC in the low 70's. The FC is a converted Igloo cooler. It's well insulated, above and beyond the coolers inherent insulation, and is heated with a open topped heat bomb with a airstone bubbling in the bottom(thought that that would serve to transfer heat out of the water into the environment). The FC though is located, by neccesity in an unheated garage where the ambient night time temps will routinely be in the 20's. My question is, would a higher wattage aquarium heater do better at heating this space, or would it just be quicker at reaching the too low temps? If a higher wattage heater is not the answer, what is?

[bugs]

Probably the higher wattage heater would help. Is the one FOAF has now set to max. temperature? The setting is just the temperature that it keeps the water. The chamber will generally run cooler than the temp setting if it's in a cold environment.

[Fresh Brewed]

Yes, it's set to the maximum setting...This exact set up has worked for him in the past, so he's puzzeled about whats wrong now. It is a new heater, I wonder if it's not working properly. I'm going to go measure the temp of the actual water.

[~Hippie3]

extra watts won't help,
but a bigger water reserve would.
those heaters can do at least 10 gallons,
so the problem is just too much heat loss,
20*F just is beyond the ability of any heatbomb.
either go up to an oil-filled radiator to heat the garage
or possibly use an electric blanket.

[CoyoteMesc]

Yeah, what Bugs said.
If you dont have it turned up then do that first.
If it is turned up you may need a heater that reaches higher temps not just watts.

This igloo has a lid Im guessing by your post?

[CoyoteMesc]

Oh yeah man, that heat blanket would do the trick for sure.

[bugs]

Electric blanket's a good idea, or just a nice cozy blanket for more insulation. More insulation is always a better idea than more fuel.

Like the man said, the heater might not get as warm, at the max. setting, as the one he used to use. Measuring the water temperature is a really good idea.

Hip, I gotta disagree. If more watts are being dissipated from the box than the heater can put in, you need more wattage to make up the difference. Or (see above) add more insulation.

[~Hippie3]

a gallon of water can only hold so many calories of heat.
a heater rated at 10 gallon aquariums has plenty of power
i.e. wattage to heat a small jug of water.
problem is that
a small jug of water just cannot give off enough calories
to heat a 20*F garage.
if it could the furnace people would be out of business.
you could heat the water to boiling steam
and it STILL wouldn't heat up a 20*F garage.

[Fresh Brewed]

Water temp is 80 degrees...don't remember what the package advertized, but that sounds about right don't you think? What about creating a second external heatbomb out of a gallon milk jug, and coiling the excess air tubing inside to heat the air going into the FC heatbomb?

[~Hippie3]

not going to be enough buddy.
to heat a garage you're needing a device
that can crank out several thousand BTUs an hour.
no heatbomb is going to manage,
just not designed for such large spaces.
hell, an oil-filled radiator won't cost much more
and will do the job nicely.

[Fresh Brewed]

Just checked the manufactures website, and they claim that it's max temp should be 89.6, and I'm only getting 80. 89.6 should be enough to maintain 72-74 in a very well insulated cooler(3-4 square feet) I would think. I think I got a dud. Going to try a different submersible heater tomorrow before taking more drastic measures.

Glass is better than plastic at transmitting heat isn't it?

[~Hippie3]

it'll never hit max when in such a cold environment
as it losing heat faster than it's being replaced.
nothing wrong with the heater,
aquariums just aren't meant to be run outdoor in the winter.

[CoyoteMesc]

12-Volt Heated Travel Blanket with Safety Timer: CozyWinters

electric blankets are sometimes found cheap...I found this one in 5 sec from google. Those heaters for aquariums aren't much cheaper IME. So my advice is this. Since you already have a good heater, insulate the FC with the blanket.

[Fresh Brewed]

Seems like everytime it's checked though the little light that indicates that the heater is actively heating is off(it does come on, he's checked). It seems that if it were working perfectly and were just not able to keep up, it would be always on, but the heaters internal themostat is turning the device off when the water temp reaches 80 not 89.6 as the manufacturer states that it should. This design has worked in the winter before, and the cooler is very well insulated(it's in a large plastic container sitting on a 2 inch sheet of foam, the excess space between the outside wall of the cooler and the inside wall of the plastic container is filled with loosley wadded newspaper, and the lid had holes drilled into it and insulating foam was injected into the empty spaces(wouldn't have thought there would be empty spaces in the lid, but I guess it's designed to keep cold in rather than heat)). I feel like he has created essintially a very small house out of the cooler.

[~Hippie3]

if it never shut off
it'd be a fire hazard.
it has to cycle so the wires can cool.
that's built-in safety switching off.
return it but the real problem will remain.
what's the temp running now ?

[Dr_T]

How about more insulation outside the Igloo cooler? Like Hippie says, you're losing heat too quickly. Maybe wrap a couple of blankets around the whole thing?

It happens in my apartment, but my 'heatbomb' takes up about a third of the cooler, and it has enough thermal storage to carry through until I come home and turn the heater on.

Another idea- a space heater, but just on Low. Don't try to keep the garage warm, just keep it from being so dang cold. Oh, and if there's empty space inside the cooler, that's a problem. Fill it with water bottles or boxes if need be.

[Fresh Brewed]

Heat bomb water 80...temp at the perlite level inside the cooler 68.7

[~Hippie3]

so close...
well, i hope a new heater can give you a few more degrees

[Fresh Brewed]

Thanks Hip...

[MrMerlin]

For a heat mat you can rip out a seat warmer from a scrap car seat, hook it up to a 12v transformer and your set mate...

[bugs]

Just got back to this.... The heat bomb isn't trying to heat the whole garage, just the inside of the cooler. The heat capacity of a volume of water is isn't a big issue. The water's purpose is to keep the heater from burning up and for to even out temperature fluctuations. A larger thermal mass takes longer to heat and cool, i.e. to absorb or to give up calories.

The main factors are the temperature differential between the inside and the outside of the enclosure, the amount of insulation, and the wattage of the heater.
A 100 watt heater can provide about 86000 calories per hour. If the box loses 86000 calories per hour, the temperature will remain constant and the thermostat will keep the heater turned on all the time. It's an exact balance between heat in and heat out.

If the environment outside the box gets warmer, or more insulation is added, then the box will lose fewer calories to the outside air. The 100W heater is then more power than needed, so the thermostat removes power when the inside of the box (or the water bath) reaches the setpoint. The power to the heater has to shut off now and then to keep the temperature from going too high.

If the environment gets colder or insulation is removed, the heater can't replace the heat flowing out of the box. More than 86000 calories per hour is flowing out of the box, and the heater can't keep up even though it's on all the time. The internal temperature will equilibrate at some temperature below the desired setpoint.

There are, basically, two ways to keep the temperature up in this situation. Either increase the insulation, or increase the wattage of the heater(s).

As an analogy, think of a bucket with a hole in it being filled by a garden hose. The object is to keep the bucket half full. If the hole is big (poor insulation or a big temperature difference) the hose needs to provide a lot of water (wattage or power). If the hole is made smaller (smaller temperature differential or better insulation) the flow from the hose can be turned down. Or, as is the case with a simple thermostat, the flow can be turned off and on to maintain water level at around the desired fill level.

This is a bit simplified; you also have the rate of thermal transfer from the water to the air in the box, the relative thermal capacities of air and water, etc. The underlying principle is, however, the same.

If more heat (watts or calorie hours) is being lost to the environment, then either more heat needs to be put in (bigger heater) to make up for it or the rate of heat loss has to be reduced (more insulation).

As a last comment; of course the thermostat can fuck things up if you can't turn it up high enough.

I'm usually pretty humble, but I'll brag a bit here. I'm a fair to middling thermal system designer. I've done it as part of my job for many years. Anybody's welcome to check my statements in the literature.

[Fresh Brewed]

My FOAF has corrected the heating situation, but multiple changes were made so he's not sure where the biggest gains were made. He first purchased a better aquarium heater...higher wattage and correctly functioning(he's convinced that the previous one though new was not working properly). He also added a second external heatbomb through which he ran about 8 coiled feet of his bubbler tubing...to warm the air before it entered his FC. He also found some good opportunities to better insulate the FC, both inside the lid and externally. And lastly, he purchased and attatched to the lower outside wall of the cooler a reptile heatmat. These changes improved the situation to the degree that he has turned off the heat mat and lowered the temp on the aquarium heater about 4 degrees from the max setting of 89 degrees. He happily reports that his FC is cruising along at 73.4 and that pins have made an appearance.

[Fresh Brewed]

Thanks all of you for taking the time to give me your advice.

[Dr_T]

Hooray for pins! Good job!

[~Hippie3]

[bugs]