hello everyone new person here..

i just sold my 75 setup and got a 150.
3 250 watt metal halide 20k's
1/3hp prime chiller
skimmer

my question is my chiller is a 1/3 hp curent usa chiller
it is cooling my tank from 80 to 78 and it is taking almost 3 hours to
turn off.. any idea why? i have an external pump so the only heat is
the lights and even at night when the lights are off the chiller runs a
long time...#