Temperature

[Hentie]

Hi All, I am really having issues with keeping my tank temp stable.

240 L Red Sea tank
Running for 6 months
Temp fluctuates between 23 and 27 degrees Celsius during day night cycle
Winter over here
2 heaters in sump sobo 300 W and eheim 200 W
Some advice please?

 

[TX_REEF]

what's the temp in your home? where do you have the heaters located in the sump and where are the temperature probes?

 

[Hentie]

Temp in home varies during day night

Heaters located in first compartment of sump with reef mat. Probes in last compartment with pump

 

[GARRIGA]

No experience with SOBO but Eheims are very stable. Are you however using an external controller?

Just noticed you do have a probe. Perhaps faulty probe.

 

[BeanAnimal]

Temp in home varies during day night

Heaters located in first compartment of sump with reef mat. Probes in last compartment with pump

What are the temperature in the home?

What is controlling the heaters?

How many gallons total in the system?

 

[TX_REEF]

Temp in home varies during day night

Heaters located in first compartment of sump with reef mat. Probes in last compartment with pump

I'd recommend you move the probes to the overflow chamber in the display. You want the heaters to control the display temp ultimately, in your current setup your heaters are thinking heat is good enough because you have the probe right after the heaters.

 

[BeanAnimal]

I'd recommend you move the probes to the overflow chamber in the display. You want the heaters to control the display temp ultimately, in your current setup your heaters are thinking heat is good enough because you have the probe right after the heaters.

That is not the issue, that would just cause them to cycle on and off....

In any case, the probes should (always) be just upstream of, but in the same compartment as the heaters.

 

[GARRIGA]

Possibly not enough wattage to raise the temps at night although I had a 200w Eheim in a 75g in a room constantly around 70 and raised that temperature to 88 to treat FW ich otherwise hummed at 78 and at both it held steady.

 

[TX_REEF]

That is not the issue, that would just cause them to cycle on and off....

In any case, the probes should (always) be just upstream of, but in the same compartment as the heaters.

i see, my point was having the probes immediately downstream of the heaters is not a great call generally, I assume this would cause deficient water temperatures

 

[GARRIGA]

i see, my point was having the probes immediately downstream of the heaters is not a great call generally, I assume this would cause deficient water temperatures

I can see how that's possible but then one just raises or lowers the desired target since the entire system should stabilize to a temperature and unless the pump fluctuates then it should be receiving and sending water at the same rate which would affect the main display. Probably not razor precise but I can't see it fluctuating by more than a degree which is far from the OP experience. Celsius and calculus hurts my brain so no clue what that variance actually is.

 

[TX_REEF]

I can see how that's possible but then one just raises or lowers the desired target since the entire system should stabilize to a temperature and unless the pump fluctuates then it should be receiving and sending water at the same rate which would affect the main display. Probably not razor precise but I can't see it fluctuating by more than a degree which is far from the OP experience. Celsius and calculus hurts my brain so no clue what that variance actually is.

I'll admit I'm far from an expert on the matter, but I have a red sea reefer 350 with my probe in the overflow and heaters in the sump under the drain. I have the controller set to 80 and the thermometer in my display always reads between 78-80, so this approach works for me. In my frag system, I have the probe under the drain and the heater in the fuge/center chamber. Same result.

 

[BeanAnimal]

i see, my point was having the probes immediately downstream of the heaters is not a great call generally, I assume this would cause deficient water temperatures

Given the volume of water, modest flow and size of the heater, the system will remain pretty much in equilibrium.

The reason that we want the probes in the same compartment is that when the pump is off, the heaters and the probes will operate as expected. If they are separated the call for heat will heat the chamber they are in and the probes will never read that temp and tell them to turn off, quite literally boiling the water in the heater chamber. Not good...

Upstream (in the same compartment) because if they are right in front of the heaters then you may get weird short cycling. The tank will heat but the heater may very will turn on and off in very short cycles as it read the heat coming right off the heater surface. This is hard on heating elements and relays, electronics.

 

[TX_REEF]

Given the volume of water, modest flow and size of the heater, the system will remain pretty much in equilibrium.

The reason that we want the probes in the same compartment is that when the pump is off, the heaters and the probes will operate as expected. If they are separated the call for heat will heat the chamber they are in and the probes will never read that temp and tell them to turn off, quite literally boiling the water in the heater chamber. Not good...

Upstream in the same compartment because if they are right in front of the heaters then you may get weird short cycling. The tank will heat but the heater may very will turn on and off in very short cycles as it read the heat coming right off the heater surface. This is hard on heating elements and relays, electronics.

Your second point is a very good one, thanks for the reminder

 

[BeanAnimal]

Possibly not enough wattage to raise the temps at night although I had a 200w Eheim in a 75g in a room constantly around 70 and raised that temperature to 88 to treat FW ich otherwise hummed at 78 and at both it held steady.

It takes 1 BTU to raise 1 Pound of water 1 Degree Fahrenheit.

1 Watt for 1 Hour produces 3.41 BTUs of heat.

There are ~8.4 pounds in a gallon of seawater.

So it takes 8.4 BTUs to raise 1 gallon of seawater 1 degree Fahrenheit.


SO:
75 Gallons of water = 630 pounds
200W heater * 1 hours produces 682 BTUs

So that 200W heater can raise the temperature of your 75 gallon tank ~1.1 degrees F per hour.

The question then becomes simple. If you unplug the heater, how quickly does the water temperature drop? If faster than 1 degree per hour, we need a bigger heater. We can work backward to figure out how big). If slower then 1 degree per hours, then the heater is large enough and you have something else wrong

 

[GARRIGA]

Your second point is a very good one, thanks for the reminder

By default. I turn heater(s) off when return pump is off. Something I'll be programming into the controller as a safety valve. Also turn off UV and skimmer or any other items sitting inside a sump. Sort of like a kill switch.

 

[GARRIGA]

It takes 1 BTU to raise 1 Pound of water 1 Degree Fahrenheit.

1 Watt for 1 Hour produces 3.41 BTUs of heat.

There are ~8.4 pounds in a gallon of seawater.

So it takes 8.4 BTUs to raise 1 gallon of seawater 1 degree Fahrenheit.


SO:
75 Gallons of water = 630 pounds
200W heater * 1 hours produces 682 BTUs

So that 200W heater can raise the temperature of your 75 gallon tank ~1.1 degrees F per hour.

The question then becomes simple. If you unplug the heater, how quickly does the water temperature drop? If faster than 1 degree per hour, we need a bigger heater. We can work backward to figure out how big). If slower then 1 degree per hours, then the heater is large enough and you have something else wrong

Makes sense but wouldn't you also confirm that if house temps fluctuate between 69-72 daily and it's still holds 78 or 88 as in my case, then the heater was more than sufficient? Noticed 150w Eheim wasn't getting me to 88 but did hold 78 in the tank next to it. Ran two experimental 75s and that's what I noticed.

Also would titanium be more efficient or less efficient than glass? I ask because I tested the wattage per gallon and my 150 wasn't able to heat as high per watt in those 75 as did the 200 which I think went to 94 tricked by adjusting the slider for calibration. Granted all temps were checked with a infer red heat gun which was calibrated to the room and the 75 without heater before I started. Goal was what heater would be stable at need yet couldn't fry fish if it failed. 150 outside of ich treatment won.

If I have to do math I'm pulling my hair out and I started life as an accountant

 

[BeanAnimal]

Makes sense but wouldn't you also confirm that if house temps fluctuate between 69-72 daily

You would do your "test" during the coldest period in the room... ideally the coldest period expected during the year.

Also would titanium be more efficient or less efficient than glass?

No - all electric heaters are 3.41 BTUs per watt and because they are fully submerged, all of that heat goes into the water.

Yes, if the head of a heater out of the water will conduct a tiny amount of heat away to the air, but not worth measuring.

The difference between brands however is the actual wattage of the heating element. 200W likely means anything within 20-30 watts in either side of 200 and may even vary between individual pieces of the same model and production run. These are not precision heating elements, just cheap resistive coils.

 

[GARRIGA]

You would do your "test" during the coldest period in the room... ideally the coldest period expected during the year.



No - all electric heaters are 3.41 BTUs per watt and because they are fully submerged, all of that heat goes into the water.

Yes, if the head of a heater out of the water will conduct a tiny amount of heat away to the air, but not worth measuring.

The difference between brands however is the actual wattage of the heating element. 200W likely means anything within 20-30 watts in either side of 200 and may even vary between individual pieces of the same model and production run. These are not precision heating elements, just cheap resistive coils.

What I forgot to do was test those heaters for actual wattage and perhaps why the 150 wasn't as efficient.

I get your point on the coldest part but that's my point as well and perhaps didn't articulate correctly. Temps were checked several times a day where it cycled from 69-72 and yet both tanks held 78 with the treatment tank holding 88. Neither fluctuated one degree. Heaters are sold in larger increments of about 25w and to your point they may not be the exact wattage as labeled then one could just confirm it's holding at both ends and conclude they have enough wattage. Obviously, focus being the cold end but before adding life one might want to consider testing the upper limit as they might have too much wattage. I'm more concerned with cooking vs chilling. Thermostats fail and usually heater doesn't turn off vs apposite.

Seems multiple titanium plus probe the way to go. Although those Eheims do last. My 50w just manually turned off as tank was broken down and ran 2.5 years plus had ran another year several years ago. I'm expecting it will fire up and keep going next round of experiments. Not sure of longevity on titanium. Have heard of Eheims lasting 15 years.

Excuse my disdain for the details but as I migrated to strategy being holistic more applicable and why you'll rarely see me doing detailed math. Plus as you stated with the wattage being off perhaps best to actually test as you stated and my approach.

 

[BeanAnimal]

I'm more concerned with cooking vs chilling. Thermostats fail and usually heater doesn't turn off vs apposite.

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.

Seems multiple titanium plus probe the way to go.

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.

 

[BeanAnimal]

More simple heater rules

1 - never submerge the head of the heater. Expansion and contraction will eventually allow it to leak.
2 - heaters need to be in a part of the sump with a fixed water level where they will not get submerged during power/off and will not expose part of the envelope due to evaporation or other issues.

I prefer to run them through a bulkhead style fitting in the side wall. I know this does not work for everyone.