How to Test and Calibrate Aquarium Heater

[Mark303]

I purchased two 150W Eheim Jager heaters for a 75 gallon tank. Before putting in my display tank I thought I would test the calibration in an empty tank to not risk harming my fish. However the only empty spare tank I have is a 10 gallon. Both heaters were wildly inaccurate. Testing individually I set at 75 degrees and tank reached 85degrees, which maxed out the calibration adjustment ring. Since it happened with both heaters I was wondering if this is due to the small size of the tank and overpowering of the heaters for that size. 

Any suggestion of how to accurately test and calibrate?

Edited April 4 by Mark303
typos

[nabokovfan87]

On 4/4/2023 at 1:39 PM, Mark303 said:

I purchased two 150W Eheim Jager heaters for a 75 gallon tank. Before putting in my display tank I thought I would test the calibration in an empty tank to not risk harming my fish. However the only empty spare tank I have is a 10 gallon. Both heaters were wildly inaccurate. Testing individually I set at 75 degrees and tank reached 85degrees, which maxed out the calibration adjustment ring. Since it happened with both heaters I was wondering if this is due to the small size of the tank and overpowering of the heaters for that size. 

Any suggestion of how to accurately test and calibrate?

Yes, I had a pretty similar experience.  Those things being +/- 2 degrees is pretty normal.  That being said, I had one peg on and I highly recommend using a controller if you can find one for that specific heater in question.

Alright, as far as what's going on, let me break things down for you.
1.  you need to have good circulation to keep them from overheating and damaging themselves.  Place it near flow and try to keep it as vertical as you can.  In my 75 I tend to run 2 HoBs and 2 heaters.  Heater goes right next to the input and right under the HoB itself.

2.  Calibrating a high wattage heater in a lower wattage volume won't work as well as you thing, but it's a good idea.  For the heater required on a 75G volume I would imagine you're in the 200W+ range and I wouldn't put that in something smaller than a 40B tank.

3.  Thankfully the heaters are a breeze to calibrate, but you do need to follow a few steps and keep an eye on it from cooking the tank.
A.  Turn the heater on to the desired temp in the tank you want to use it in.
B.  Place it so the flow works to the advantage of the heater
C.  Test the temperature of the water every 30 minutes with a thermometer, preferably 2 different ones.  This gives you a value to base your heater on.
D.  Once the heat has "settled" and is no longer trying to heat the tank, record that temperature.
E.  Set the offset on the heater so that you can adjust the internal thermistor up / down the degrees you need to.  This is a red sliding dial on the top of the heater itself.
 

 

[Pepere]

I would not set up a 75 gallon tank without an inkbird controller myself.

$30.99 is pretty cheap insurance considering the cost of the livestock in the tank.

 

https://www.amazon.com/gp/product/B01486LZ50/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

In addition to turning off power to the heaters when set temp is reached, I like the ability to set your own temp differential.  I run a 2 degree differential with a target temp of 76.  It energizes the heaters when tank drops to 74, and shuts them off when tank gets to 76.  Reduces the number of cycles the heaters go through.

I figure running a controller and 2 heaters gives you multiple safeties. If One heater fails to heat up, the other one will keep the tank from getting too cold.  And observing the Inkbird digital  readout gives me info I can interpret easily enough.. Ie if all of a sudden it is reading 72, I am going to suspect a dead heater.

If the thermostat on a heater fails in the always on position, the Inkbird will de energize it when my target temp is reached.

I believe There are more expensive wifi enabled inkbirds that will send you an alert if the temp gets too low or too high..  more than I need though…

Ising the inkbird I set the heaters a bit higher so they are still in the call for heat position in case the inkbird failed to denergized, but just barely above.  This way if the Inkbird failed in always on position, the heaters would hopefully shut off slightly above my set point.

[jwcarlson]

My experience with every brand of adjustable heater is that it might be kind of close for a bit, but as soon as you move it, all that's out the window and you can't get it back.  I have everything cranked to max and use InkBirds.  It's the way to go.  They can be had for $25 at the moment on EBay and occasionally they'll dip down under $20.

[Mark303]

I do have an inkbird that I haven't set up or really learned yet. I guess my thought process was to test the heaters for any issues and have them somewhat close to calibrated to the desired temp before putting in the display tank and using the inkbird as a failsafe rather than relying on as the temp controller. I expected the heaters to be off a couple degrees but was confused as to the 10 degree variance that is greater than the calibration ring allows to adjust that much. But sounds like the small tank is the issue. 

really appreciate everyone's input!

[nabokovfan87]

This one was recommended on the forums to me elsewhere. Just wanted to share it as well.  https://www.amazon.com/dp/B083Q7YRBM/ref=twister_B08YP92RF4?_encoding=UTF8&th=1

[Pepere]

I would always use the inkbird as a temp controller rather than as a failsafe.  Thermostats n heaters are notoriously unreliable and variable.  The calibration of all of my inkbirds as verified with floating thermometers have always been spot on.