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Anybody have trouble with these before? I have a 300w model, able to heat tanks up to 1000 ltrs, running on a 500 ltr aquarium. It was set on 28c and barely heated the tank to 24c, now its set on 32c and the tank is sitting at 26c! Its also running constantly which can't be good for my energy bill. The heater is in a sump.
Shaun

Shaun wrote: The heater is in a sump.

Apparently, you loose a lot of heat between the sump and the tank - or in the sump

When you put your heater to a higher temp, the tank temp raises. So the thing basically is OK.

All energy the heater takes up is turned into heat (the second Law of Thermodynamics can be read as stating that all energy ultimately turns into heat, while energy does not get lost), so you will not pay for energy which is not turned into heat

I'd say - insulate your sump against heat loss - and your tank will get warmer, while the Jager will, also, not take this kind op energy

A 300 watt heater (that's a very powerful heater) unable to heat a 500 liter tank is probably not running at all. Stick down your hand and (carefully!) touch the heater, it's not hot, right?

I agree with all of the above: There's either something wrong with your heater, or your sump is loosing a lot of heat [I don't believe you can loose a huge amount between the sump and the main tank].

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Mats

I use these heaters in my tanks. Find them great!!

I use 1 300w heater voor my 550L discustank and warms it up to 30 degrees no problem. Also use 3 300w heaters in my breeding setup for catfish. This setup contains of 9 tanks and a large bio filter. The filter is 300L on it's own and the heaters lay here. The tanks combined are 1500L of water. All tanks are very well insolated. No problems here either with the heating.

Thanks guys.
The sump is in a cabinet and any lost heat seems to be trapped. The house is around 18c, all the other tanks are in the same room with no problems.
Jac, is the heater set on 30c and the tank is on 30c?
So, I guess I'll have to get a new one

I have recently started used Jager heaters since I got pissed off at stealth heaters. I find the temperature calibration of Jagers to be everywhere. They will keep a steady temp but the dial doesn't do a good job of going to the temp you set it at. You basically have to just keep playing with it. I have one set to 88 and it keeps the tank right at 82. of the six jagers I've tried. 2 doa's, 2 work perfect, 2 the temperature calibration is off from what the dial says. I'm not really all that happy with Jager either.

I would cover your sump if you don't have a cover. I have noticed that when I leave a lid open on a tank the heater will run a lot more often constantly. Also, do you have the plastic strip on the back of the lid cut out good around the devices. The plastic strip on the tank make a world of difference on trapping heat inside the tank.

I have to agree with @plecoCrazy. The heaters will not deliver the temperature you set it on, you will have to play around a bit with it.
It also depends on the room temperature and insolation. My discustank in the livingroom is set on 28 degrees but heats up to 30. My breeding setup is in the shed and in summer this will get so hot that I don't use any heaters at all In winter I insolate my tanks and filter to the max and then the heaters (3) warm no problem to 30 degrees. This is also what the are set on.

I learnt a hard lesson about relying on a single heater when an eheim stopped and i lost 3 of my 4 green spot puffers in that tank

Strangely the best run i have had is with a budget brand available in Australaisa called Aqua One. Have had 2 running in each of my rack sumps some as long as 4 years with no problems at all (running a dozen of them in fish room in total) I check them every couple of monthes and so far not a single failure.

Not sure if your problem has been solved or not, but you can recalibrate the heater if you need to.

You just put the heater in a bucket or a smaller tank, and wait for the temp probe light to go off. Make sure the water is evenly heated and has water flow, or you'll get thermal layering. Then take a real reading of the water temp with a proper thermometer and if the reading on the thermometer differs from the meter reading on the heater - pull up the little blue thingy-ma-giggidy thing that looks like a button and then turn the temp dial to the correct temp reading as is on the thermometer.

That might help, but on a 1000L tank I'd be running 2x300W jagers, despite what the box says.

I have a 300W jager on my 225L tank, and in the cold of winter, the tank drops by 3-4 degrees overnight. I can only assume Eheim rates the 300W heater for a 1000L tank with an ambient temperature of 24+ degrees Celsius.

As a side not to all this: The CORRECT way to determine the heater needed, we'd actually have to calculate the thermal transfer rate and delta temperature for each surface of the water - if the water is in contact with a concrete floor that is cool, for example, it will be different from a same size tank situated on a wooden floor which is "warm". Remember, heat only transfers from the surfaces on the sides of the tank [including the top]. To get cool in the middle, you'd have to stick a tube of ice into the middle of the tank.

And even if we simply give all surfaces "some arbitrary thermal transfer rate" and average the contact temperature to match the room temperature, for example, we still find that a bigger tank looses less heat. Say we have a tank that is 60 x 30 x 35cm - that's 63 liter (or about 17 US gallons). That tank has a volume to surface area of about 0.16. My RIO400 tank is 150 x 50 x 55cm - it holds just over 400 liters of water, and the surface to volume ratio is 0.09. If I make up a large tank of 400 x 100 x 100 cm (about 13 ft x 3ft x 3ft), it has a volume to surface ratio of 0.045. So per volume of water, you need a smaller heater the bigger the tank is. And the more like a cube it is, the smaller the surface are, for the same volume of water.

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Mats

A rather old book I got speaks of 6 watt per square meter per degree celcius for the temp difference

Obvioulsly, this is an estimation, as 6 mm glass does insulate less then 12 mm glass, but still it is usable

a square meter equals to 9 square feet + 21 % and a degree C to 1,8 degree F

therefore 6 watt per (9 square feet +21%) per (1,8 F) = 6/1,8/1,21/9 watt per square feet per F
= 0,30 watt per square foot per F

A value one should be able to remember too

I take it that is per square <insert unit> of all six surfaces of the tank [assuming normal block shape].

Glass is not a GOOD conductor of heat, but not a poor one either. But it's better than water, and a lot better than air. Aluminium (as used in heatsinks for computers, etc) conducts 250 W/mK, copper is 400 W/mK. On the other end of the scale, air conducts 0.022 W/mK. Water is 0.58 W/mK, glass around 1 W/mK (varies a bit depending on the type of glass - window glass is just under, Pyrex type glass is higher).

Ice, by the way, is 2.18 W/mK.

I don't think it makes THAT much difference at the low temperature differences we're talking of to have 6mm glass or 12mm glass.

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Mats

Hi,

adding a different point of view to it:
I´d say we only have to consider the "rate-limiting step". And that would be heat conductivity and heat capacity of air, all others get into equilibrium fast enough, and hence it is only the air accessible surface that matters in the equation. That changes, of course, if you use material with comparable heat conductivities (capacities) as insulation (like polystyrene or whatever its trivial name is in your respective country).

Cheers, Sandor

Good point, Sandor. The heat transfer is limited by the air/insulation conductivity - the rest of it will not matter much.

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Mats