Oversized Heaters

[Jdubyo]

Hello fellow reefers!

I realized today that I accidentally purchased 2 heaters that are rated for 53-79 gallons when I will only have about 30 gallons of water. I was planning on using 2 heaters with a controller, 1 set a degree or 2 lower, for redundancy. I am wondering how much of a stress it would put on the heaters and the system for them to be oversized. I imagine they would be turning on and off more frequently and possibly more temperature swings? The heaters are the Eheim Jager TruTemp line.

Thank you for any input!

 

[Ippyroy]

They would possibly overheat your tank. It might take longer for them to cool off or they might heat up too fast.

 

[Thor1911]

idk maybe I'm an idiot but I just use a spare 300gal heater on my 5gal qt lol, controller does all the work I just make sure the thermostat probe is on the heater.

 

[Jdubyo]

They would possibly overheat your tank. It might take longer for them to cool off or they might heat up too fast.

it shouldn’t overheat if using a controller with a temperature probe though right? And I didn’t think to take into consideration a heating up and cooling down phase...

 

[Jdubyo]

idk maybe I'm an idiot but I just use a spare 300gal heater on my 5gal qt lol, controller does all the work I just make sure the thermostat probe is on the heater.

oh wow, that is beyond oversized! Haha

Do you mind me asking how long you have had this going without issue?

 

[Ippyroy]

it shouldn’t overheat if using a controller with a temperature probe though right? And I didn’t think to take into consideration a heating up and cooling down phase...

I use oversized because I live in an extreme winter environment. 40 plus below for a few months most years. I have large temp swings in the summer, a couple of degrees. I had to get creative and change the calibration a few times to negate it.

I've had it overheat several times in the beginning. I also use a 300w to heat my 5 gallon buckets for water changes. It heats up to over 80 in 20 minutes. I take it out and use it in the second bucket for 15 minutes and then both are at 78. All of my heaters are titanium and on controllers. Just be sure to watch it closely. You will be able to figure it out with trial and error.

 

[nashvillian]

Not as much as actual operation, but if it fails with the thermo stuck on, will go south a lot faster. Not sure if turning off/on quantity matters as much as age does.

 

[GaryE]

Better to be oversized than undersized.

 

[Thor1911]

oh wow, that is beyond oversized! Haha

Do you mind me asking how long you have had this going without issue?

I did a 80 day qt with no problem, but that was a 20gal tank with my 300gal heater. Right now I have two baby clowns in a 5gal w/ the 300gal heater and no problems. Just a 1degree temp change. I secured the probe right next to the heater itself so it turns on/off quickly. Does a short burst to keep it at temp

 

[Thor1911]

Better to be oversized than undersized.

Thats what she said

 

[NeonRabbit221B]

Kinda throwing out my experience with oversized heaters. I always aim for a rating for 1.25x what they rated and a second heater about on par for the rating. BRS has a good video on heater mistakes. Over sizing heaters will lead to temperature fluctuations and wearing out of the heating element from turning on/off frequently. Ideally your heater would stay on all the time and the controller is used to cut it off if it is stuck on.

 

[Pistondog]

it shouldn’t overheat if using a controller with a temperature probe though right? And I didn’t think to take into consideration a heating up and cooling down phase...

The heaters will obviously heat up faster, but won't overshoot.
The only downside is they will cycle, turn on and off more frequently.
The Jaegers use bi metal thermostats, about as idiot proof as it gets.
You could put an inkbird above them and let that do the switching, and add some safety.

 

[vetteguy53081]

generally a higher wattage works less to heat tank therby having a longer useful life.

 

[living_tribunal]

Ya

 

[ca1ore]

Seems to me it’s the on/off cycles that get these kinds of things. That would suggest that an oversized heater would not last as long. I have always targeted multiple levels of redundancy, thus my preference for multiple, lower wattage heaters.

 

[Jdubyo]

generally a higher wattage works less to heat tank therby having a longer useful life.

I like this answer but there seems to be some opposing opinions. I understand the logic but am wondering if all heater should be judged equally with this. I literally have only used Eheim Jager and cobalt Neo-Therm heaters. While I don’t know anything about the cobalt heaters (or other brands) I do know the Eheim heaters use a metal the bends at different temperatures to start and stop the heater. I wonder if this happening more frequently would end up increasing the chances for failure?

 

[Jdubyo]

The heaters will obviously heat up faster, but won't overshoot.
The only downside is they will cycle, turn on and off more frequently.
The Jaegers use bi metal thermostats, about as idiot proof as it gets.
You could put an inkbird above them and let that do the switching, and add some safety.

Do you know if added a controller such as the inkbird if it would keep the thermostat on the heater at the “on” position? It seems to me this would be the area most prone for failure.

 

[Jdubyo]

Kinda throwing out my experience with oversized heaters. I always aim for a rating for 1.25x what they rated and a second heater about on par for the rating. BRS has a good video on heater mistakes. Over sizing heaters will lead to temperature fluctuations and wearing out of the heating element from turning on/off frequently. Ideally your heater would stay on all the time and the controller is used to cut it off if it is stuck on.

If we should aim to have the heater stay on more often than not, wouldn’t we want to undersize them?

 

[NeonRabbit221B]

If we should aim to have the heater stay on more often than not, wouldn’t we want to undersize them?

Essentially, yes but that’s assuming the ratings and temperature ranges are accurate. Oversizing has its benefits but in a longevity standpoint having that heating element click on and off more than a few times per day will lead to failure.

 

[ca1ore]

Stick heaters are cheap. I think the biggest worry is cooking the tank. My rule of thumb has always been to figure out the peak heat wattage requirement for your tank, divide that number by two and buy three heaters of that wattage. That way, no single heater stuck on or failed off can crash the tank. of course, putting multiple heaters on a single controller negates at least some of the benefit of redundancy.