Dual Heater Setup Question

[Oxboy]

Say I have a 55 gal and a single 150W heater does a consistent job, but I'd like a dual heating solution for peace of mind/backup. Best practice may say get two 100W heaters. However, if one of them goes out, a single 100W may have trouble keeping a constant temp until the problem is discovered.

In this scenario, wouldn't I be better off having two 150Ws in the first place in case? That way, if one completely dies, the working one could pick up and keep things constant without missing a beat?

Is there any danger or issues with redundant "over-wattage" in a tank besides a higher electric bill? Thanks for thoughts.

[14Discus]

Two 150s is exactly right. Remember that if two are working in tandem, actually the cost difference is not an issue as each will work less/for shorter ‘on times’. Your thinking on this is spot on regarding one unit failing etc. My 60g has two 150s and my 75g has two 200s. I might also suggest you use a controller like a Blueline to run the heaters off of so that a malfunctioning heater overheating is prevented. My controllers are set to 3 degrees above my desired tank temp so that the heaters cannot overheat and boil the fish bc the controller will shut off the power to the heaters hooked up to it should the tank temp rise above that 3 degree mark. Some people use controllers to actually operate the heaters at desired tank temp. I prefer to use the controller as an insurance plan.

[dspeers]

On the one hand having the redundancy of two heaters, each of which is fully capable of maintaining temp in case one quits does ensure that there will be no "cooling" even if one fails. But, that also means that regardless of whatever temp control you have (even with redundancy) that if the failure mode is for one of the heaters to be always on there is greater threat of overheating. A reasonable compromise is to use two with just enough wattage to be a couple of degrees below your target if one fails in off mode. Of course knowing what that wattage should be depends on heater type, tank size, surface area (evaporation) and temperature of room. One guide is here https://www.themandaringarden.com/aq...ize-guide.html

Also I agree that the "backup" controller should be a backup aka insurance. If used as primary control then the tank will either overheat or over-cool if the controller fails in either direction.

[Willie]

I'd go with 2 X 100 W heaters. The idea is that if one gets stuck on, it's not powerful enough to boil the fish. If one heater croaks, the temperature may drop 5 - 10 degrees, but slowly, so there's no harm to the fish. Having 2 X 150 W heaters would serve the same purpose as having only one.

Willie

[Johnny95132]

Also, check out this calculator for finding the right wattage heater for your tank. http://www.kernsanalysis.com/HeaterCalculator.cgi

[dspeers]

Very cool, thanks.

[Oxboy]

Two 150s is exactly right. Remember that if two are working in tandem, actually the cost difference is not an issue as each will work less/for shorter ‘on times’. Your thinking on this is spot on regarding one unit failing etc. My 60g has two 150s and my 75g has two 200s. I might also suggest you use a controller like a Blueline to run the heaters off of so that a malfunctioning heater overheating is prevented. My controllers are set to 3 degrees above my desired tank temp so that the heaters cannot overheat and boil the fish bc the controller will shut off the power to the heaters hooked up to it should the tank temp rise above that 3 degree mark. Some people use controllers to actually operate the heaters at desired tank temp. I prefer to use the controller as an insurance plan.

Explain this to me. What keeps the controller from trying to constantly raise the temps up to the +3 mark?

Say you want your 60g to be a constant 85 degrees. What do you set/calibrate the two 150s at? What temp do you set the controller at?

[14Discus]

If I set my tank temp to 85 (using your numbers), I’d set my heaters to 85 and the controller to 88. It works like this.....
One plugs in the heaters to the powered controller outlet. If the controller is set to 88, it will provide power to the heaters to heat to the heater setting (to 85). The controller does no more than prevent the heaters from heating above 88. So...if the heaters were to screw up and start overheating and heated the tank to 88, the controller would shut power off to the heaters until the temp was below 88. The heaters work independently with mere power from the controller and the controller is not doing anything except providing power until such time that the temp reaches 88 with a heater malfunction (which is your set emergency upper limit for tank temp). If your heaters work correctly, the controller will do no more than provide power to the heaters bc the heaters themselves turn off at 85.....thus never reaching the 88. This is how I use the controller.
Others who use controllers to regulate heater on/off tank temp might, with your numbers for example, set their heaters to 90 so they’d always be on, but then set the controller to 85. Then, when the tank temp got to 85, the controller would power off the heaters until the temp was 84. This is not my preferred use of a controller though.

My actual controllers are set to 90. My actual desired tank temp is 86. So....my heaters do their thing heating to 87, then turning off and on as needed to maintain the 86 degrees. The controller is doing nothing but being a power source for the heaters. That is.....until such time that my heaters somehow malfunction and start heating the tank above the 87 until the temp reaches 90. At that time, my controller would cut power to the heaters until the tank temp was below 90. At that time my controller would power up the heaters never allowing the tank temp above 90. When I got home and saw the temp to be 90, I’d know that my heaters needed attention or replacement bc my desired temp was 87, yet the actual temp was 90. My controller acted like insurance preventing the water from boiling the fish.

I know this seems confusing.....hope I helped.

[Oxboy]

If I set my tank temp to 85 (using your numbers), I’d set my heaters to 85 and the controller to 88. It works like this.....
One plugs in the heaters to the powered controller outlet. If the controller is set to 88, it will provide power to the heaters to heat to the heater setting (to 85). The controller does no more than prevent the heaters from heating above 88. So...if the heaters were to screw up and start overheating and heated the tank to 88, the controller would shut power off to the heaters until the temp was below 88. The heaters work independently with mere power from the controller and the controller is not doing anything except providing power until such time that the temp reaches 88 with a heater malfunction (which is your set emergency upper limit for tank temp). If your heaters work correctly, the controller will do no more than provide power to the heaters bc the heaters themselves turn off at 85.....thus never reaching the 88. This is how I use the controller.
Others who use controllers to regulate heater on/off tank temp might, with your numbers for example, set their heaters to 90 so they’d always be on, but then set the controller to 85. Then, when the tank temp got to 85, the controller would power off the heaters until the temp was 84. This is not my preferred use of a controller though.

My actual controllers are set to 90. My actual desired tank temp is 86. So....my heaters do their thing heating to 87, then turning off and on as needed to maintain the 86 degrees. The controller is doing nothing but being a power source for the heaters. That is.....until such time that my heaters somehow malfunction and start heating the tank above the 87 until the temp reaches 90. At that time, my controller would cut power to the heaters until the tank temp was below 90. At that time my controller would power up the heaters never allowing the tank temp above 90. When I got home and saw the temp to be 90, I’d know that my heaters needed attention or replacement bc my desired temp was 87, yet the actual temp was 90. My controller acted like insurance preventing the water from boiling the fish.

I know this seems confusing.....hope I helped.

I will need to study and digest this. Check out the below from jehmco -- I think they are supporting what you are saying?


NOTES on electrically heating larger aquariums or central systems:
Large aquariums or Central Filtration systems with Sumps can benefit from using heaters with a separate controller. Considering an average of 4 watts per gallon minimum requirement, one 300 watt heater would not be adequate to keep a 90 gallon aquarium at 80 degree F. In fact any aquarium 48 or longer can benefit from having 2 smaller heaters on opposite ends.
Perfectly synchronizing both heaters’ thermostats can be problematic at best, if not impossible. Conventional aquarium heaters are made primarily for low cost sales appeal. The integrated thermostats are not very accurate nor reliable, but the primary problem occurs with regards to the setpoint and the differential built into all thermostats. The differential is the difference between the turn on setting and the turn off setting. This prevents the heaters from turning on and off rapidly (cycling), in response to small changes in temperature. This setting can be between 1/2 and 2 degrees and when installing multiple heaters within the same body of water it becomes impossible for both these thermostats to operate identically.
As an example of problems related to setpoint variance: An 100 gallon aquarium with (2) 200 watt heaters on opposite ends of the tank. One heater senses the temperature drop to 77 F and turns on, beginning to heat the water. Meanwhile the other heater has not yet turned on and may not since the turn on temperature setting may not be exactly the same. Or the water could be very slightly warmer where this heater is, preventing this heater from ‘seeing’ its turn on temperature. As the first heater begins to heat the water, the second is much less likely to turn on now, since the turn on temp setting is slowly being exceeded. This leaves the first heater doing most of the work to bring up the tank’s temperature and reach its turn off setting. It most likely will have difficulty just maintaining the tank’s temp., since one 200 watt heater may not be adequate for an 100 gallon aquarium. The second heater may eventually turn on, but not before the first heater has been on for an extended period.
An example of thermostat differential problems: Consider a situation where 2 heaters manage to be on at the same time, then one heater reaches its turn off setting first either due to slightly different differentials, inaccuracies in the thermostats, or slight water temp fluctuations. The remaining heater is now doing all the work trying to reach its turn off setting. It is struggling to maintain temperature in the tank. The second heater does not turn on yet since the required differential has not been reached. (turn on setting is below what the second heater, by being on is allowing the tank’s temp. to fall to) it may stay on for hours in this mode before the desired temp. is reached or the other heater switches on!
The larger the aquarium, the more heaters required, the more problems with synchronizing occur. Many larger aquariums with multiple heaters will have at least one heater operating at long intervals, sometimes always on. This puts a lot of wear on the heater, increasing the likelihood that it will fail at some point. With all heaters properly synchronized, the service life of aquarium heaters will be much longer. This is only possible by using a separate controller. All of the heaters are adjusted to their highest setting, (permanently on) and all plugged into a power strip type adapter. This is then connected to the output of the controller, thereby effectively bypassing the heaters’ thermostats.
The problems with synchronization can be exacerbated when multiple heaters are placed in a sump, as is common on larger aquariums with Wet-Dry filtration systems. Consider the high wattage requirements of a 180 gallon aquarium with a sump size of maybe 30 gallons. Even with a flow rate of 1200 GPH through the filter the proximity of the heaters to each other is so very close that the likelihood they all operate concurrently is even more remote than if they were placed directly in the aquarium. The need for a separate controller is strongly indicated in this configuration.
With properly synchronized heaters, the actual on time for heating the aquarium is much less, thereby providing less wear on individual heaters. The cost savings in electricity usage alone may pay for the price of the controller in a short time.
The use of a Temperature Control device with a remotely mounted sensor, provides much better aquarium temperature maintenance. The sensor can be mounted unobtrusively anywhere needed in the aquarium. Near the filter intake or even within the overflow box, however we recommend always keeping the sensor in the same body of water as where the heaters are located to avoid a situation where water is not moving due to a water pump stoppage or leak in plumbing. Sensor would be calling for heat yet the heaters are boiling away in the separate sump!

Adjustments to the tank’s water temperature is done much easier than without a controller. (Imagine trying to raise the settings equally on 4 or 5 individual heaters) By using this controller in conjunction with higher quality Aquarium heaters such as Ebo-Jager or our large Titanium Heaters will provide the aquarium with a reliable system for maintaining proper temperature control at a fraction of the cost of other set-ups such as Industrial type Immersion Heaters and high wattage inline heater modules. This controller can alternatively operate a chiller or be wired in series with the chiller’s control to prevent both from operating at the same time

[Oxboy]

If I set my tank temp to 85 (using your numbers), I’d set my heaters to 85 and the controller to 88. It works like this.....
One plugs in the heaters to the powered controller outlet. If the controller is set to 88, it will provide power to the heaters to heat to the heater setting (to 85). The controller does no more than prevent the heaters from heating above 88. So...if the heaters were to screw up and start overheating and heated the tank to 88, the controller would shut power off to the heaters until the temp was below 88. The heaters work independently with mere power from the controller and the controller is not doing anything except providing power until such time that the temp reaches 88 with a heater malfunction (which is your set emergency upper limit for tank temp). If your heaters work correctly, the controller will do no more than provide power to the heaters bc the heaters themselves turn off at 85.....thus never reaching the 88. This is how I use the controller.
Others who use controllers to regulate heater on/off tank temp might, with your numbers for example, set their heaters to 90 so they’d always be on, but then set the controller to 85. Then, when the tank temp got to 85, the controller would power off the heaters until the temp was 84. This is not my preferred use of a controller though.

My actual controllers are set to 90. My actual desired tank temp is 86. So....my heaters do their thing heating to 87, then turning off and on as needed to maintain the 86 degrees. The controller is doing nothing but being a power source for the heaters. That is.....until such time that my heaters somehow malfunction and start heating the tank above the 87 until the temp reaches 90. At that time, my controller would cut power to the heaters until the tank temp was below 90. At that time my controller would power up the heaters never allowing the tank temp above 90. When I got home and saw the temp to be 90, I’d know that my heaters needed attention or replacement bc my desired temp was 87, yet the actual temp was 90. My controller acted like insurance preventing the water from boiling the fish.

I know this seems confusing.....hope I helped.

Wait I think I get it -- so you are not inputting a desired temp into the controller? You leave that setting deactivated and the heaters handle all temp control.

[14Discus]

I see the points w this. My two heaters each go on and off frequently at opposite ends and one is not doing all the work. When the temp drops at one end, that heater goes on...and the same for the other.

If you’d like to use the method you cited, then use two controllers.....one to turn on the heaters bypassing the heaters own thermostat bc the heaters were set to on all the time and one to prevent that first controller from malfunctioning. In other words, you’d power the first heater controller with the second controller. If the first controller operating your heaters at 85 failed, the second would be there (set to 88) to prevent overheating if the temp got higher than 88 from the first one.

Ex. A. Single controller powers heaters not allowing them to surpass 88.

Ex. B. Controller 2 at 88......powers controller 1 at 85 which is powering two heaters set to max.

IMHO.....the main goal of a controller is to prevent an overheating catastrophe. So, if you use one controller, it merely shuts off your heaters if they overheat. If you use two controllers, the second controller turns off the first controller (which actually takes the place of the heater thermostats) if it overheats.

[14Discus]

Wait I think I get it -- so you are not inputting a desired temp into the controller? You leave that setting deactivated and the heaters handle all temp control.

Yes. The desired temp is done through heaters and emergency max temp is done w controller as I do it. This is contrary to what you referred to by Jehmco. They do use the controller for desired temp as I read it. If you go w their approach, that’s ok....if you have a second controller with the goal of overheating insurance by not allowing the first controller which actually replaces the heater thermostats to go beyond your 88.

[Oxboy]

Yes. The desired temp is done through heaters and emergency max temp is done w controller as I do it. This is contrary to what you referred to by Jehmco. They do use the controller for desired temp as I read it. If you go w their approach, that’s ok....if you have a second controller with the goal of overheating insurance by not allowing the first controller which actually replaces the heater thermostats to go beyond your 88.

I like your approach better. Thank you for all the responses.

[14Discus]

Happy to help. I do this approach having bought very good quality Finnex HMO and HMX Heaters with the reliable Blueline Controllers. Other Brands of controllers have failed me.....not Blueline.

[Oxboy]

Happy to help. I do this approach having bought very good quality Finnex HMO and HMX Heaters with the reliable Blueline Controllers. Other Brands of controllers have failed me.....not Blueline.

I guess I still don't understand why the controller doesn't override the heater thermostats when they hit 87 and try to take them up to 90 degrees, which is the set point of the controller.