tank temp with out a heater

[wolf_bluejay]

I run a similar tank to the one mentioned earlier -- same thing as well -- no heater no chiller.

Im a 220, with about 50 gal sump. My house is about 74F all day long, and I have an HRV as well. I had the same thing where the heater just never kicked it.

A fair amount of heat comes from the pumps, and I think this is what is happening:

Some heat comes from the pumps, and extra is from the lights -- during the day the extra heat is controlled through evaporation (fan blowing across the lights) and low humidity where I live allows a lot of evaporative cooling. As everything is well closed up, the whole tank holds a LOT of heat, so it is a slow rise (1-2 degrees) over the day, and a slow cool down just because of the tank volume. Hence, no heat or cooling needed.

Once upon a time I left for a weekend and my A/C didn't run. Came back to the tank at about 85 -- and it took 4 days after the A/C was running for the tank to cool down.

Originally Posted by sphelps

What temp is your house kept at, still find it somewhat unbelievable that the tank temp doesn't drop more at nght. 21C is 70F so I'm guessing the lighting adds most of the heat to bring it up to 77F so I still curious how the temp doesn't drop with the lights off? The house temp prevents the tank from overheating but how does it prevent it from cooling off?