It may be a model that pre-heats the water. If so, and if the water entering the dishwasher is cool, the heater may take up to half an hour to heat the water. To avoid the wait, increase the incoming water temperature before turning on the dishwasher. Do that by running the kitchen sink faucet until the water runs hot. Or increase the temperature of the hot water to the entire house at the hot water heater. Warning! To lessen the risk of scalding, don't set the hot water heater temperature higher than 120 degrees Fahrenheit (48 Celsius).