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Calibrating a Marineland Precision Heater

Discussion in 'Freshwater Equipment, Products, & DIY' started by apastuszak, Jan 6, 2019.

  1. apastuszak

    apastuszak AC Members

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    Jun 2, 2015
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    Bensalem, PA
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    I was an idiot and burned out the heater in my basement aquarium. I had a 300W heater in there, because the basement can get as cold as 66°F. Well, I ran out to Petco and bought a 200W Aqueon heater, because that was the most powerful heater they had. I went home and ordered an Marineland Precision 300W heater, mostly because it has a lifetime warranty.

    In my setup, I have a Home Automation tool called Home Assistant setup, and I have my heaters connected to a Sonoff TH16 temperature controller.

    The way things are setup:

    1. Home Assistant turn on the heater when temperature goes below 77.0°F and turns off when the temperature is above 77.9°F
    2. The TH16 itself has rules on it that turns on the heater if the temperature drops below 76°F and turns the heater off if the temperature goes above 78.9°F.
    3. The thermostat on the heater is set to 80°F

    So, if Home Assistant crashes and can't shut the heater off, then the TH16 itself will shut the heater off a degree hotter, and if the switch glitches out, then the heater's thermostat itself will turn off the heater off at 80°F.

    In order to make this whole thing work, I needed to calibrate my heater so I know what the actual temperature is when the setting is 80°F.

    I took a glass, filled it with ice and then added water. Waited 3 minutes and stuck my thermometer in the water. The temperature should read 32°F. My thermometer was at 32.5°F. I then boiled some water, which should be 212°F (at my elevation and barometric pressure, it's actually 211.4°F). I check the thermometer and it shows 211.9°F. So I know my thermometer is only off my 0.5°F.

    I then get a Home Depot bucket, throw the heater in, fill it with water, toss in a power head and the thermometer. I turn the pump on and wait 15 minutes. Then I plug in the heater and walk away for an hour.

    An hour later I come back, and check the temperature. The heater is set to 80°F and the actual water temperature is 88.7°F. Corrected for the thermometer shift, the temperature is actually 88.2°F! That means my thermostat is off my 8.2°F!

    And that seems to be pretty consistent. If I dump the water out and replace with cold water and then set the thermostat on the heater to 78°F, after an hour, the bucket is 86.7°F.

    i think that having a thermostat discrepancy of 8.2°F is just WAY TOO MUCH of a discrepancy. The discrepancy is consistent, but it's still huge. I hate to think that I would set this to 80°F and drop it in a tank and end up with a tank that is 88.2°F instead.

    Am I crazy in thinking I should return this thing immediately? Anyone else seen these kind of wild calibration inconsistencies in Marineland heaters?

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