Temperature

[GARRIGA]

The only thing that the on-board thermostat should be used for is as a fail-safe set manually (and confirmed to be) just above the controller's set point.




Yes several small heaters offer more redundancy in the event of failure. If you can't (you should) use a commercial/industrial quality controller, then a stuck small heater has far less chance of causing a catastrophic overheating event.

We’re on the same page but my point about the heater thermostat being not all use controllers. I won’t usually on a 20g but everything else will and mostly because I’ve tested the max that 50 does in a 20 and it’s 81. No need there to get fancy and for some if they have the correct wattage likely won’t need a controller, either. Just test its max to confirm. Some have limited funds and/or space and this offers them an option.

 

[BeanAnimal]

We’re on the same page but my point about the heater thermostat being not all use controllers.

They should, but if they don't, using the math and deltaT will help determine how much heat is needed. From there one can decide on a plan for redundancy and/or safety by splitting the heating duties to multiple smaller heaters. I wrote an article (not sure if it is still published) some decades ago breaking this all down.

This is all beyond the scope of helping the OP.

I won’t usually on a 20g but everything else will and mostly because I’ve tested the max that 50 does in a 20 and it’s 81.

Size (to an extent is not relevant). It is (as much as I hate the metric) the watts per gallon that matter. (ignoring the difference in how different size tanks shed heat or the mass of the rock, glass, etc.).

A 20 gallon tank holds maybe 16 gallons of water. Let's call it 135 pounds of water. The 50W heater can do 170 BTU/h. So roughly 1.3 degrees per hour of temp rise.

No need there to get fancy and for some if they have the correct wattage likely won’t need a controller

We use the controller because it is more reliable than the internal thermostat (by magnitudes). The most common failure mode of an aquarium heater (solid state or mechanical thermostat) is to fail ON (heating).

The most common failure state of a commercial quality controller or power relay is to fail OFF (not heating).

In most cases, the failure to heat is far safer than the failure to stop heating.

In any case, let's not get too far down a path here, as we wait for the OP to provide an update so that we can offer a solution.

 

[GARRIGA]

They should, but if they don't, using the math and deltaT will help determine how much heat is needed. From there one can decide on a plan for redundancy and/or safety by splitting the heating duties to multiple smaller heaters. I wrote an article (not sure if it is still published) some decades ago breaking this all down.

This is all beyond the scope of helping the OP.


Size (to an extent is not relevant). It is (as much as I hate the metric) the watts per gallon that matter. (ignoring the difference in how different size tanks shed heat or the mass of the rock, glass, etc.).

A 20 gallon tank holds maybe 16 gallons of water. Let's call it 135 pounds of water. The 50W heater can do 170 BTU/h. So roughly 1.3 degrees per hour of temp rise.


We use the controller because it is more reliable than the internal thermostat (by magnitudes). The most common failure mode of an aquarium heater (solid state or mechanical thermostat) is to fail ON (heating).

The most common failure state of a commercial quality controller or power relay is to fail OFF (not heating).

In most cases, the failure to heat is far safer than the failure to stop heating.

In any case, let's not get too far down a path here, as we wait for the OP to provide an update so that we can offer a solution.

I know all this

I'm just pointing out the reality that not all will use a controller and size does matter because a 20 anything often implies lack of space and/or funds and for those best they not just consider minimum to cool but also max before all are cooked beyond done. Most also not going to math the science out of this as if lost on Mars. Not all heaters show same efficiency, either. Eheims well known for performing as advertised yet others I wouldn't dare run and those Eheims have pretty good thermostats and still I'm going test what I have for both minimum to heat and max should failure come which should also be the case with controllers since anything mechanical is a point of failure.

OP obviously got more than expected but perhaps another learned or not. Knowledge is never too far down the weeds. Best obtain, retain and decipher then apply as best fits their particular chapter.

 

[BeanAnimal]

I honestly have no idea where you are going with these responses. If you don't like math and prefer trial and error, and/or don't like controllers in certain situations, etc. then by all means test or apply whatever logic makes you comfortable.

I just dropped in to help the OP, which nobody can actually do until they provide a few more details.

 

[GARRIGA]

I honestly have no idea where you are going with these responses. If you don't like math and prefer trial and error, and/or don't like controllers in certain situations, etc. then by all means test or apply whatever logic makes you comfortable.

I just dropped in to help the OP, which nobody can actually do until they provide a few more details.

We all don't think alike and I'm just replying to your direct comments to me. Why I always suggest each obtain the knowledge and go from there. I specifically mentioned that and now not sure where you're going with this response that I fail to see how it's helping anyone and forces me to respond to ensure I'm better understood although not sure something I need to do. Can't we all just help as we best see fit or must there be the same path? Your experience not mine and vice versa yet we both have something to contribute and perhaps leave it at that.

 

[Hentie]

Thank you for the replies.

Sorry for only replying now, been away.

I have certainly learned a thing or two!

For starters, the total heater was submerged, will change that.

I have now removed the sobo heater and replaced it with another eheim heater and set the temp per heater lower hoping that temp will then be stable.

Hope that you guys agree with my method. I know it is not very scientific and that currently I am doing this trial and error.

Just for info, the day temp vs night temp changes with 10 degrees celcius (think thats approx 50 fahrenheit). Big difference

Thanks once again