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Sideways heater and water temp


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Due to a recent re-arrangement of my LR, my submersible 50W heater is at least temporarily angled at about a 30 degs with the top being towards the water. I have heard a heater is only supposed to be put in straight upright but I can't see why this is the gospel. Since heat rises, wouldn't the heater's own internally gererated heat keep the thermostat from sensing and responding to water temp changes? i mean, the last time I checked, heat still usually heads upwards. It seems this would be a better way to have it as long as the heater is not inverted all the way.


Anyhow, it could just be my imagination and it could be my latest attempts to cool the tank with a fan to counter the Texas heat, but has anyone had a problem with unstable temps after using a heater at an angle like this? For a thermometer I use one which I bought at Radio Shack, an RV thermometer (why it's for RV's they don't say) that has a sensor probe on the end of a plastic-coated cord. It looks, functions and costs half the price of very nearly similar items I have seen for aquariums. Of course I'll have to go through all this again after my new power compact retrofits arrive soon.


I have a seven bow aga.



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i prefer positioning heaters in the horizontal position with your same logic. the temerature mechanism in most heaters uses properties of the expansion coeficients of different metals to create a temperature dependent "switch" which completes the circuit and fires the coils up. unless you put some good flow aimed at the coils (ie powerhead, HOB, etc), the heat will rise up (in stagnant water) and screw with your temp stability. this may also be why heaters "fail" and in some cases "stick" in the "on" position. the rising heat causes the internal thermometer to think "wow it's hot in here" and resultingly the heater "never turns on." the tank temperature reads lower than what is set on the heater and so, the aquarist turns it up a notch (a notch too high). something happens in a thank - flow patterns change, new powerhead, re-scaping of rock, and BAM. hot-cha-cha.


i say run your heaters parallel to the water surface/sandbed or at least angled (not vertical). just my opinion.

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I think its pretty unlikely that the water flow around a heater in a reef tank would be so bad that you'd see that kind of differential between the position of the bimetallic strip and the coil of the heater.


Vertical alignment actually improves water circulation through convection as the warmer less dense water moves upwards from the area of the coil near the sand to be replaced by cooler denser water in the process. That effect is lost to a certain extent when the heater is horizontal and close to the surface. In that configuration, active circulation by means of the powerheads must be relied upon entirely to minimize termperature stratification and if, like many, the powerheads are aimed at the surface, you might get a few cold spots near the bottom of the tank. Just a thought - I might be wrong.

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the majority of vertically positioned heaters i see on either of the back corners. circulation through convection makes sense, and is why i put my heaters horizontal, low, in the back, with coils centered to the back panel. but, vertical in a corner position just seems risky to me


vertical in the corner (as i see it):


the good -

1. coils low: better heat distribution as warm water rises from top to bottom

2. lower risk of being smashed by rocks

3. easier to make adjustments or remove if necessary


the bad -

1. low circulation in corners

2. temperature sensor is near the water surface where faulty/fluctuating/conflicting readings are more likely to take place

a. evaporation at water surface

b. heat from lights from above

c. heat rising from coils


as for heat differential at the poles of a heater, ever run a heater in a tank with just water? if there is not sufficient circulation to disperse the hot water you can definitely see the whisps of warm/less-dense water radiating from the coils


let's see where this goes. if i'm wrong, i sure as heck would like to know :)

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I never put my heaters in the corner. They are always out a little and partly in front of the corner powerhead for better energy distribution. Most of the cons you mentioned go away by pulling it out of the corner. With quality heaters, temperatures anywhere in my tanks are always within one to two degrees of the setting on the heaters.


You make a good point though regarding the evaporation issue. Mine are all submersed completely but I do notice an increase in temperate if I miss a day topping off the small tanks. I don't think that has anything to do with the heaters though. I think that is more an issue of heat energy from the light acting on a smaller volume of water thereby raising the temp by up to 1 degree.

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Maybe I should have have mentioned this, but the temp in my tank was rock solid at 78.1 (right where I set it at) when I had the heater completely vertical.

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