Setting heaters?

[Reef.]

Daft question but is there a knack to setting the temp on a heater?

I normally use a controller but want to try running the heaters without the controller, 2 Eheim heaters, both set to 79f, a couple of hours later whilst at work I checked and was slightly shocked to see the temp of the tank was 83f! Checked the heater when back home and there are both set to 79f, are heater normally that far out?

 

[Greg P]

Jager heaters have a red ring on top used to 'calibrate' them to the blue temperature ring. Of 8 I've owned, only 1 would not match.
Put 1 heater in a bucket of water with a powerhead and floating glass thermometer. Run the heater overnight or all day and adjust the red ring to match the blue part of the heater with the reading on the thermometer.

 

[Reef.]

Jager heaters have a red ring on top used to 'calibrate' them to the blue temperature ring. Of 8 I've owned, only 1 would not match.
Put 1 heater in a bucket of water with a powerhead and floating glass thermometer. Run the heater overnight or all day and adjust the red ring to match the blue part of the heater with the reading on the thermometer.

thanks for that, I had a feeling it was something to do with the rings as I twisting not knowing which to turn.

 

[Reef.]

Just took a look today and the calibration ring was fully on, I had no idea that was what it was, I must have been using that to set the temp!!!!