rtm

I've just picked up one of these too. I think the point of the high and low alarm is to warn if anything has gone wrong with the heater thermostat. Your heater should be able to keep your water pretty close to your desired temperature. So in the case of the low temperature warning I think if you have it set at a couple of degrees below your desired temperature it will warn you something has gone wrong with the heater (our cold snaps in New Zealand aren't usually so extreme the heater can't keep up). The high alarm is slightly different because as Caryl points out the ambient temperature of the surroundings can raise the tank temperature considerably, not just the heater jamming on. I'd set it two or three degrees higher than your desired temperature and then when it beeps you can check whether it's a heater problem or if just the surrounding air temperature has raised the water temperature. Rod