# Is it Normal for heater to turn on/off while under its set temperature? Taking breaks



## SpaceLord (Feb 29, 2016)

Hello. 

I was worried that my oversized heater which is so long , that it almost reaches out of the tank and possible a danger if the water level goes down too far during travel or if the thermometer breaks, will fry the fish since its 300 watts. 

I got a smaller 100 watt heater for my 75 gallon tank with the idea that if the thermometer breaks, it will not be powerful enough to fry the fish as well as staying towards the bottom of the tank. 

The heater I think is preset at 78 degrees however the tank is at 75.4 and I notice that the red light turns on for a few minutes then turns green(Red means its heating, green means its has power but is not heating) 

The aquarium in the room without a heater is 71.2 ( Goldfish) So, its 4.2 degrees above the no heater tank. 

Are heaters programed to basically take breaks when they have been on too long even if they have not reached their set temperature? 

Thanks.


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## thedood (May 30, 2015)

I dont think 100 watts will ever get that tank up to temp its just going to burn up. Do you know if your 300 has to be vertical? What brand heater is it? I run 2 250 watt heaters (my house gets cold) on a controller in my 75g and they are both horizontal at the bottom of tank hidden.


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## Clear Water (Sep 20, 2014)

Your way under size for 75 gallon. I would think the 300 watt would work good for the 75. Like thedood wrote a controller is great addition because you never have to get your hands wet, messing with the temp.


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## jeffkrol (Jun 5, 2013)

SpaceLord said:


> Are heaters programed to basically take breaks when they have been on too long even if they have not reached their set temperature?
> 
> Thanks.


Depends on the design.....There are good reasons to behave as the above behaves. That said most heaters don't .Well at least not on purpose.

For those w snap switches via bi-metal, localized heating could cause a snap on/off effect.

Heaters that "pulse" by design are trying to control overshoot from the last bit of discharge on the heating coil..say the water has reached 75 degree set point but your "glow coils" are still at 200F. As heat is transferred from that to the water the tank temp can overshoot..causing a see saw temp swing..
This is a type of process control and quite complicated really..
Any heater using this would most likely be thermistor and micro-controller regulated.


Of course there are probably hybrids. i.e simple timer circuit.. on for x off for y till temp is reached..That type could have a difficult time heating water from a very low to high point.


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## thedood (May 30, 2015)

What brand and model is the 300 watt heater. I still think the answer is horizontal or diagonal placement of the 300 watter.


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## Kubla (Jan 5, 2014)

Probably a faulty heater. In my opinion heater sizes are under rated by the manufacturers as much as filters are over rated. The recommended sizes always turn out too large for my tanks. I think my 92g has a 150 watt. You are a lot less likely to grossly overshoot the set temperature with a smaller heater. Also, as you said, you're a lot less likely to cook your livestock. A smaller heater will cycle on and off less often so it should last longer. You will not 'burn out' a heater by running it too much. It's the on and off that's an issue. 
There's a lot of folks recommending sizes here. Not sure how that can be done without knowing the ambient conditions around the tank. Since you gave us a clue and said the other tank stays above 70 it doesn't seem like you need much of a heater. 
If it was me, I'd contact the manufacturer and ask them about the on and off and go from there.


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## thedood (May 30, 2015)

Kubla said:


> Probably a faulty heater. In my opinion heater sizes are under rated by the manufacturers as much as filters are over rated. The recommended sizes always turn out too large for my tanks. I think my 92g has a 150 watt. You are a lot less likely to grossly overshoot the set temperature with a smaller heater. Also, as you said, you're a lot less likely to cook your livestock. A smaller heater will cycle on and off less often so it should last longer. You will not 'burn out' a heater by running it too much. It's the on and off that's an issue.
> There's a lot of folks recommending sizes here. Not sure how that can be done without knowing the ambient conditions around the tank. Since you gave us a clue and said the other tank stays above 70 it doesn't seem like you need much of a heater.
> If it was me, I'd contact the manufacturer and ask them about the on and off and go from there.


When you go to warranty the 100 watt heater and they find out you are heating a 75g with it then good luck. They rate them the way they do for a reason. I also think if the op has a tank with no heater and that tank is 71ish then it is a fair assumption that the ambient temp on average is in the low seventies, is it not? The op is then trying to raise the temp about 7 degrees or so above ambient. I think 200 watts or more is what is recommended to raise a 75g 5 - 10 degrees above ambient.


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## Oso Polar (Apr 22, 2015)

thedood said:


> I dont think 100 watts will ever get that tank up to temp


I agree. If other tank is staying at 71 without any heater (with lights, filters, pumps etc. - all generating heat) then room temperature is probably 70 or even less. 100 watt heater alone will not be able to raise temperature to 78 (by 8-10 degrees). You need at least two of these for your tank.


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## SpaceLord (Feb 29, 2016)

thedood said:


> I dont think 100 watts will ever get that tank up to temp its just going to burn up. Do you know if your 300 has to be vertical? What brand heater is it? I run 2 250 watt heaters (my house gets cold) on a controller in my 75g and they are both horizontal at the bottom of tank hidden.



The 100 watt heater is a Tetra 
Amazon.com : Tetra 26446 Submersible Aquarium Heater, 100-Watt : Aquarium Heaters : Pet Supplies

The 300 watt heater is an Aqueon. 

Amazon.com : Aqueon 06104 Submersible Aquarium Heaters, 300 Watt : Pet Supplies

I will try the horizontal. I have AC in my house but I do live in a warm area of the country. The 100 watt heater seem to be stalling out at about 76 Degrees(has taken several days to get to this point) which I think is good enough for my fish however if its preset for 78 degrees you are saying that constantly turning on and never reaching the temperature may "burn it out"? 

The reason I tried this was because I have heard horror stories about heaters sensor messing up and stop working causing the heater to be always on and cooking the fish. So I was trying to error on something small enough that was not capable to cooking the fish. 

I think I may end up going trying a 200 watt ( set temperature) heater next. Hopefully 200 watts on 75 gallons is not enough to bake the fish if something goes wrong. 

Thanks


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## PlantedRich (Jul 21, 2010)

It takes some work to find what will do just enough to keep the tank right. There are so many variables involved that there can't be a firm answer for all cases. I currently heat my 125 gallon with just 200 watts and it can go well past 80 if needed. But then the tank also has a full canopy with lights inside the canopy, two canister filers underneath the fully enclosed stand so that all the heat goes up and the room temperature rarely drops below 68. Also a larger tank will be more stable than smaller tanks as they don't heat and cool quickly. In my 50 gallon reserve water barrel I use a 100 watt heater and it may run continuously for 12 hours to get a fresh fill of 65 degree water up to 78. I'm sure the heater coil reaches max temperature in minutes but that is okay with me as the control contacts are not burning out once contact is made.


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## Kubla (Jan 5, 2014)

PlantedRich said:


> It takes some work to find what will do just enough to keep the tank right. There are so many variables involved that there can't be a firm answer for all cases. I currently heat my 125 gallon with just 200 watts and it can go well past 80 if needed. But then the tank also has a full canopy with lights inside the canopy, two canister filers underneath the fully enclosed stand so that all the heat goes up and the room temperature rarely drops below 68. Also a larger tank will be more stable than smaller tanks as they don't heat and cool quickly. In my 50 gallon reserve water barrel I use a 100 watt heater and it may run continuously for 12 hours to get a fresh fill of 65 degree water up to 78. I'm sure the heater coil reaches max temperature in minutes but that is okay with me as the control contacts are not burning out once contact is made.


Some good info there as your giving advice based on real world experience!

Originally posted by *thedood*


> When you go to warranty the 100 watt heater and they find out you are heating a 75g with it then good luck. They rate them the way they do for a reason.


I doubt there will be much of an investigation when returning a heater that turns off before it reaches temperature. I think the reason the manufacturers rate heaters like they do is so you'll buy a more expensive larger one then you need that will be replaced sooner. The manufacturers rate uv lights, filters and circulating pumps. An Eheim 2215 is rated for 92 gallons! All the other ratings are way off, why would the heaters be right?


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## Kubla (Jan 5, 2014)

SpaceLord said:


> The 100 watt heater is a Tetra
> Amazon.com : Tetra 26446 Submersible Aquarium Heater, 100-Watt : Aquarium Heaters : Pet Supplies
> 
> The 300 watt heater is an Aqueon.
> ...


The way to get the longest life out of a resistance heater is to not let it get too hot (surrounding it with 78 deg water will take care of that) and never turn it off. The number one reason for contacts to stick and the heater stay on is from arcing from the heater turning on and off. An oversized heater will turn on and off more often, give you larger temp swings, cost more to purchase, take more space in the tank, not last as long. Of course it will give you the ability to heat the water quickly and cook your fish.:wink2: It's the same thing I've been fighting in the AC & heating business for the last 35 years. Everyone wants to go bigger and it's a bad choice.

IMHO Your heater is not functioning properly, I would not put an electrical appliance in my tank that is not functioning properly.


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## thedood (May 30, 2015)

SpaceLord said:


> The 100 watt heater is a Tetra
> Amazon.com : Tetra 26446 Submersible Aquarium Heater, 100-Watt : Aquarium Heaters : Pet Supplies
> 
> The 300 watt heater is an Aqueon.
> ...


The best way to keep from frying your fish is dual protection. The thermostat in the heater and an external controller. If the external controller should fail then the heater thermostat kicks off and if the heater sticks on because of failure the controller kicks it off. Save the money on the heater and get yourself a good controller and slap the 300 in there horizontally connected to the controller and call it good. You will drastically reduce the chance of cooking your pets and keep the water at a reasonable temperature. 

I have the 50 watt version of that heater you have and I dont like it nor do I trust it. Before next winter it will be replaced. I also use a controller on that heater as I do all of my tanks.

Bump:


Kubla said:


> The way to get the longest life out of a resistance heater is to not let it get too hot (surrounding it with 78 deg water will take care of that) and never turn it off. The number one reason for contacts to stick and the heater stay on is from arcing from the heater turning on and off. An oversized heater will turn on and off more often, give you larger temp swings, cost more to purchase, take more space in the tank, not last as long. Of course it will give you the ability to heat the water quickly and cook your fish.:wink2: It's the same thing I've been fighting in the AC & heating business for the last 35 years. Everyone wants to go bigger and it's a bad choice.
> 
> IMHO Your heater is not functioning properly, I would not put an electrical appliance in my tank that is not functioning properly.


So you are saying an undersized furnace that never shuts off is a good way to go?


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## SpaceLord (Feb 29, 2016)

thedood said:


> The best way to keep from frying your fish is dual protection. The thermostat in the heater and an external controller. If the external controller should fail then the heater thermostat kicks off and if the heater sticks on because of failure the controller kicks it off. Save the money on the heater and get yourself a good controller and slap the 300 in there horizontally connected to the controller and call it good. You will drastically reduce the chance of cooking your pets and keep the water at a reasonable temperature.
> 
> I have the 50 watt version of that heater you have and I dont like it nor do I trust it. Before next winter it will be replaced. I also use a controller on that heater as I do all of my tanks.



Can you recommend a good " controller" ? 
Also, I have read that particular heater has failed a lot. I actually had one that failed to work anymore because I simple took it out of my betta tank(after unplugging it). I have read on the review on amazon and one person said you have to wait 30 minutes after unplugging it before taking it out of the Aquarium. 

I am more concern about if it fails by getting stuck in the on position and will cook the fish. 

Please tell me more about this controller. Do you have a name, make model, link,etc... anything like that ? 

Thanks.


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## thedood (May 30, 2015)

SpaceLord said:


> Can you recommend a good " controller" ?
> Also, I have read that particular heater has failed a lot. I actually had one that failed to work anymore because I simple took it out of my betta tank(after unplugging it). I have read on the review on amazon and one person said you have to wait 30 minutes after unplugging it before taking it out of the Aquarium.
> 
> I am more concern about if it fails by getting stuck in the on position and will cook the fish.
> ...


How handy are you? You can build one which thats what I prefer. I also have 2 that I bought. I suggest for your needs if you are going to use the aqueon I would go with the Finnex HC-810. That controller will control about any heater you hook up to it and it has alarms for over and under temperature.
Finnex Digital Heater Temperature Controller +Memory: Aquarium Heater Controller

You can build your own that will also run cooling fans. For that I use inkbird ITC-1000. @PlantedRich has some info out there about those as he uses them as well. I have two of them and am building another in a few weeks.


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## PlantedRich (Jul 21, 2010)

Like most of the stuff we need, there are many levels and different ways to get where we want to go. I like DIY so I go with that but it does take some time and some smallish details work. But then that depends on how slick you want the result to be both in looks and how sturdy the result. 
For many of my controllers, I don't need looks as they are pure tools and set behind the tank or in greenhouses, etc. where if you are looking at the controller, your mind is in the wrong place to start! 
I start with the little cheap digital controllers I find on the auction and then mod them to suit. Some I just add the input AC cord and the output plug by cutting an extention cord in two pieces. They come with a small probe that needs attached to screws on the back. With just the pressure from the screw attachments holding the wires, this is not a thing of beauty nor something that you can wrestle around too much so the cords pull out. Works for me when I just set it in the fishroom where I'm pretty much the only one around and I will know how to fix it if I break it. 
Second option I've done is to add a standard receptacle and build it into a wooden box. More work, cutting fitting the wood and such but stronger and nicer looking. 
The first I can build for under $20. The second for under $25 using scrap wood but another $25 in labor! For a few dollars more for the controller, you can do a cooling fan as well as heating. 

A post with quite a bit of info: 

http://www.plantedtank.net/forums/9...ing-cheap-digital-temperature-controller.html

I use mine as a backup thermostat in case the heater thermostat fails on. Setting the heater to say 76 degrees and letting it run till it settles where I want, I then set the controller to cut power at like 78 with a slewing temperature of 2 degrees. Temperature can be calibrated, slewing changed and several others but this seems to fit me. 
When all is normal the heater keeps temp around 76 but if it fails or a warm day comes along and the tank drifts to 78, power is cut until it cools to below 76 (slewing?) 
One of the things I really like is the safety but it also lets me read the nice big temperature any time I pass without even stopping! I would come close to spending the $25 just for the ease of knowing what the temp is doing?


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## Kubla (Jan 5, 2014)

thedood said:


> I have the 50 watt version of that heater you have and I dont like it nor do I trust it. Before next winter it will be replaced. I also use a controller on that heater as I do all of my tanks.
> 
> Bump:
> 
> So you are saying an undersized furnace that never shuts off is a good way to go?


I would agree that the backup controller is a great way to go.

I'm saying a properly sized furnace that never shuts off would be a good way to go, if you didn't have a constantly changing load.


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