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Thread: Setting Finnex 300w high to get up to the Apex set temperature

  1. #1
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    Setting Finnex 300w high to get up to the Apex set temperature

    Just got my new Apex Fusion installed in a 66 gal DT and 20 gal sump. I have a Finnex 300w heater in the sump. My temp probe from the Apex is in my DT right now near the return overflow box. The Apex says the temp is 75.7 and in order for me to keep it going up to the 79F I want, I'm finding I'm having to set the thermostat on the Finnex to the high 80's so far to keep the heater on. My intent is to what everyone suggests which is to use the heater's thermostat as an emergency backup in case the Apex fails, but at 85F+ on the heater, my worry is I'd cook the tank!

    Is it unusual to have to set the heater thermostat high in the sump to get the DT to a reasonable temperature or do I have something wrong? Or is my heater thermostat defective? I used a instant read digital thermometer in the DT which read 75F and the sump in the heater compartment which said 75.5F. So I know the heater is reading high.

    Thanks for any advice! My first attempt at a saltwater tank so taking it slow to try to do it right!

    Jim

  2. #2
    Frequent Contributor zombie's Avatar
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    Find a reliable thermometer (NIST traceable preferred) and verify what the temp actually is in the tank. The apex could be right (likely), the finned could be right (less likely), or it could be somewhere in the middle (most likely). Calibrate the apex temp probe to match the thermometer and then adjust the finnex temp to 2 degrees above what it reads at your target temperature after calibrating the apex probe and getting temp up to where you want it.

    Sent from my SM-G965U using Tapatalk

  3. #3
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    Perfect! Great answer and thank you! I assumed the truth was going to be somewhere in between.

  4. #4
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    Follow up: Looks like it just took some time for the heater to work through its cycle on/off while adjusting the temperature up. I was able to set a more reasonable temperature on it and now things are fine.

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