Inkbird or Heaters as Primary Control?

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Dstelter27

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Hey everyone!

I am about to switch my heating system up for my 25 gallon tank before adding my first two clowns from QT. I have an Inkbird and two 75 watt heaters.

Question: for those of you who use dual heaters and a controller, do you use the heater thermostats to control tank temp with controller as backup, or do you use the controller as primary temp control with heaters as backup?

While I’m sure the Inkbird is more accurate, I also think it may be best to place greater stress on the cheap heater thermostats than on the Inkbird that controls both heaters. What do you think?

Thanks for the insight!
 
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blaxsun

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If you're using the Inkbird, you want to use the Inkbird temperature probes to regulate the heaters and set the temperature on the heaters to ±1°F higher/lower as a backup (that way the Inkbird shuts them off). The reason for this is that the Inkbird can only run for so many hours without setting off an alarm, and if you run it in reverse the Inkbird ends up never turning off.
 

JonahDeMarco

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If you're using the Inkbird, you want to use the Inkbird temperature probes to regulate the heaters and set the temperature on the heaters to ±1°F higher/lower as a backup (that way the Inkbird shuts them off). The reason for this is that the Inkbird can only run for so many hours without setting off an alarm, and if you run it in reverse the Inkbird ends up never

I'm a bit confused by this. Say I have my inkbird range from 77-78, if I was to set one heater to 76 and one to 79 how would that act as a back up? If I need 200w of heater and I'm running 2 100w heaters and one of them is set to turn off at 76 then the other one would get almost all the use since the tank rarely would drop below 76. Or did I misunderstand?
 

Sleeping Giant

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I turn the temp on my heater up about 3 degrees higher than what I set my inkbird controller just incase the controller doesn't work and the extra 3 degrees setting on the heater allows for the controller to maintain the heat I set on my tank.
 

JonahDeMarco

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I turn the temp on my heater up about 3 degrees higher than what I set my inkbird controller just incase the controller doesn't work and the extra 3 degrees setting on the heater allows for the controller to maintain the heat I set on my tank.
You run 1 or 2 heaters? Would you set both of the heaters this way, or one above/one below like the above post says?
 
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JonahDeMarco

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I have my controller turn on at 77 and off at 79.
I have the heaters set to 78.
This allows the heaters to control themselves while providing a second safety off with the controller.
That's what would make sense to me, I was a bit confused by the 1°above/ below thing. Only reason I could see to do that would be the one set 1° above would be the primary heater and the other would be there incase the primary was to fail in the off position.
 
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Sean Clark

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That's what would make sense to me, I was a bit confused by the 1°above/ below thing. Only reason I could see to do that would be the one set 1° above would be the primary heater and the other would be there incase the primary was to fail in the off position.
Some people like a really tight range. I prefer some swing because I think that it it more natural. Setting the controller this way also ensures that the heater is never on when the controller relay switches. This will extend the life of the relay as there is never a current demand state during a relay switch due to the heater calling for heat.
 

92Miata

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That's what would make sense to me, I was a bit confused by the 1°above/ below thing. Only reason I could see to do that would be the one set 1° above would be the primary heater and the other would be there incase the primary was to fail in the off position.
People think that by setting the heater thermostat above the range that they're not "using" it, and stressing it, and it will be able to reliably open if the Ranco/Inkbird ever fails.

The problem is that most heaters are bimetal switches/simple relays/etc, which means that every time the controller turns the heater outlet back on, the switch inside the heater has to close again - which means that by the time the controller fails, the heater switch probably has fused closed.

Set the heater to 78. Set the controller to send an alarm and turn off the heater at 79. Guard against heaters sticking ON. Don't worry about heaters failing off - just send an alarm - it does way less damage and takes way longer to do damage.
 

Biglew11

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The problem is that most heaters are bimetal switches/simple relays/etc, which means that every time the controller turns the heater outlet back on, the switch inside the heater has to close again - which means that by the time the controller fails, the heater switch probably has fused closed.

this isn't accurate, the power goin to the heater doesn't affect the state the bimetal switch is in. a bimetal switch is made of two different metals which causes it expand and contract from temperature changes not the power going to it. the bi metal switch is closed at all times the temperature is below the set point, and will be open if the temperature is above the set point. so set the heater 1 degree higher than the controller will cause the heater thermostat to be in the on state at all times regardless of power going to it, however the heater it self won't heat up until there is power supplied to it.
 

92Miata

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this isn't accurate, the power goin to the heater doesn't affect the state the bimetal switch is in. a bimetal switch is made of two different metals which causes it expand and contract from temperature changes not the power going to it. the bi metal switch is closed at all times the temperature is below the set point, and will be open if the temperature is above the set point. so set the heater 1 degree higher than the controller will cause the heater thermostat to be in the on state at all times regardless of power going to it, however the heater it self won't heat up until there is power supplied to it.
Glass is poorly conductive, and glass heaters have built in hysteresis. Bimetal switches in heaters are frequently opening and closing - and moving the control externally worsens this.

In addition - bimetal switches rarely make perfect contact - which means you get arcing every time they get re-powered. Arcing is what causes them to eventually weld together.

The controller as the failsafe is a much safer situation than the heater thermostat as the failsafe.
 
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