Electronic control of a dual-stage water heater in a hot-beverage vending machine

An electronic control system for a dual-stage water heater in a hot-beverage vending machine;

• wherein the water heater comprises:
• a water boiler;
• and
• a water booster housed in, and fluidically series-connected to, the water boiler;
• wherein the water boiler comprises:
• an external water tank with a cold water inlet and a hot water outlet;
• and
• a first electric heater housed in the external water tank and activatable to heat the water contained in the external water tank up to, and maintain it at, a temperature comprised in a first temperature range;
• wherein the water booster comprises:
• an internal body housed in the external water tank and defining a water passage with a water inlet in fluidic communication with the internal volume of the external water tank to receive hot water contained therein, and a water outlet fluidically connected to the hot water outlet of the water heater;
• and
• a second electric heater associated to the internal body and selectively activatable to heat water flowing in the internal body up to a temperature comprised in a second temperature range higher than the first temperature range and depending upon selected beverage;
• the electronic control system comprising:
• a sensory system to measure water temperatures in the water boiler and in one or both of the water booster and the hot water outlet of the water heater, and to output electrical signals indicative of the measured water temperatures;
• and
• an electronic control unit electrically connected to the sensory system and to the first and second electric heaters and programmed to receive electrical signals from the sensory system and control the first and second electric heaters based on the received electrical signals;
• wherein the electronic control unit is programmed to output electrical control signals for the first and second electric heaters based on measured water temperatures and on associated reference water temperatures;
• wherein the electronic control unit is further programmed to implement:
• a water boiler control designed to output an electric power demand for the first electric heater based on a water temperature error between the measured and reference water temperatures in the water boiler;
• a water booster control designed to output an electric power demand for the second electric heater based on a water temperature error between the measured and reference water temperatures either in the water booster or at the hot water outlet of the water heater;
• and
• an energy manager designed to receive the electric power demands for the first and second electric heaters, and to control energization and de-energization thereof based on an energy-management logic;
• wherein the reference water temperatures in the water boiler and at the hot water outlet of the water heater are stored in the electronic control unit, at least the reference water temperature at the hot water outlet of the water heater as a function of selected beverage, together with heater parameters comprising physical response times of the water boiler and of the water booster, inertias of the first and second electric heater and masses involved;
• wherein the water booster control is further designed to implement:
• a planner designed to compute, in response to a beverage selection, the reference water temperature in the water booster based on the measured water temperature either in the water booster or at the hot water outlet of the water heater, the water reference temperature at the hot water outlet of the water heater, the physical response times of the water boiler and of the water booster, and inertia of the first and second electric heaters and the masses involved effective to anticipate possible adjustments of the reference water temperature in the water booster necessary to track sudden changes of the reference water temperature at the hot water outlet of the water heater.