This is our first pool and we've only had it a few months. Every time we go to use the heater, we have issues. Twice I have set it at night before bed so it would be warm by morning. In the morning, the heater is off and the water is 1-2 degrees warmer than when I went to bed. I turn it back on and it heats to temperature and then shuts off and doesn't come back on. My question is: Is it warming the pool and then shutting off in the middle of the night and so the pool is cooling back off? Is it running all night and not working so my gas bill is going to be outrageous? I've never had one so I don't know how they work. But it seems to shut off by itself unless it's during the day. During the day it will heat to temp. Is it a safety thing and won't run at night? I'm so confused.