Question on heater functionality

[marnel]

So I've had my 55gal tank set up for about 3 weeks now and have maintained a steady temp of 77 degrees 'F since the 3rd day, the first night i practically boiled my tank at 86+ degrees F, so i cranked my 200w submersable All Glass branded heater down to 71 which resulted in my steady tank temp of 77 'F.

My question is this. Is there some sort of calculation that you need to do to determain at which temp to set the heater at. I would have assumed you set it to the temp you'd like the tank water to be, and the heater would maintain that, or is it just trial and error. My Heater placement is to under the waterfall of my HOB filter.

 

[dskidmore]

There could be two things going on here:

1) Your heater is not calibrated correctly.

2) You have a heat source other than your heater.

You can check the calibration of your heater with an accurate thermometer in a bucket of water. If the calibration is off, you can find out what setting is appropriate for the desired temp. You may want to check the details of your warranty if this is your problem.

If you have another heat source (bright lighting, inefficient pump...) then any setting between 71 and 77 should give you the same results. If your lights are the culprit, you should see colder temps at night. If a pump is the culprit, then the water should be warmer at the output side of the pump.

For my first 15 years in the aquarium hobby, I ran the old-fashioned heaters that didn't have numbers printed on them. The general rule for setting those up is to make a tiny adjustment every 2 hours until an independent thermometer reads your target temp.

 

[blumley]

For my first 15 years in the aquarium hobby, I ran the old-fashioned heaters that didn't have numbers printed on them. The general rule for setting those up is to make a tiny adjustment every 2 hours until an independent thermometer reads your target temp.

Some of us still do this when we accidentally order that heater that we thought had a thermometer built in... 8O

 

[Lonewolfblue]

Recommendation:

DO NOT TRUST SETTINGS ON HEATER.

They are very inaccurate. None of my heaters other than my HYDOR ETH inline heaters were even close, and my inlines are within a degree of being perfect. Use a good thermometer as your guage, and turn the heater up or down til you get it to where you want it.

 

[Guest]

general rule for setting those up is to make a tiny adjustment every 2 hours until an independent thermometer reads your target temp.

That is how I still do it even with good expensive heaters