Heater issues

[fernalfer]

I have 2 Finnex HMO-300 w/digital controller. http://www.bulkreefsupply.com/finnex-hmo-heater-w-digital-led-controller.html

Now one reads 2 degrees higher then the other. One reading 80F and the other 82F pretty close to each other in my sump. Now i have a glass thermometer reading 76 in the tank and 2 digital thermometers reading 76 as well. on in tank and 1 in sump.

#1 how can i tell the true degrees? (finnex heaters saying 80-82 and 3 thermometers saying 76)

#2 is their a way of calibrating the heaters? So they can both read 76 as well and go from there)

#3 Best advice on how i can get my Tank water to 78 with the readings so different from the heaters to the 3 thermometers?

 

[rockhead51]

Just my 2 cents, but a heater's job is to heat and a thermometer's job is to measure. If all three are at 76, my guess is it is 76...