Quick water heater

Abstract

A quick water heater includes a housing, a water tank, a heating device having an inlet and an outlet, a water pump, a water outlet, a NTC thermistor, and a control circuit board. The water pump is connected between the water tank and the inlet by two water pipes. The water outlet is connected with the outlet. The control circuit board is electrically connected with the heating device and the water pump. The control circuit board includes a first SCR cooperating with the NTC thermistor to control the water pump on or off and a second SCR cooperating with the NTC thermistor to control power of the heating device. When the water temperature of the water outlet reaches to a predetermined temperature, the NTC thermistor sends out a feedback signal to the control circuit board, and then the control circuit board cuts off a power supply of the heating device.

What is claimed is: 
     
         1 . A quick water heater comprising:
 a housing;   a water tank disposed in the housing;   a heating device disposed in the housing, the heating device having a cold water inlet and a hot water outlet;   a water pump disposed in the housing, the water pump being connected between the water tank and the cold water inlet of the heating device by two water pipes;   a water outlet disposed in the housing, the water outlet being connected with the hot water outlet of the heating device;   a NTC (based on Negative Temperature Coefficient) thermistor disposed at the water outlet for controlling the water temperature of the water outlet; and   a control circuit board disposed in the housing, the control circuit board being electrically connected with the heating device and the water pump, the control circuit board comprising a first SCR (Silicon Controlled Rectifier) which cooperates with the NTC thermistor to control the water pump on or off and a second SCR which cooperates with the NTC thermistor to control a power of the heating device, when the water temperature of the water outlet reaches to a predetermined temperature, the NTC thermistor sends out a feedback signal to the control circuit board , and then the control circuit board cuts off a power supply of the heating device.   
     
     
         2 . The quick water heater as claimed in  claim 1  further comprising an additional NTC thermistor disposed on the heating device for preheating and protecting due to over temperature, wherein the additional NTC thermistor detects the temperature of the heating device and sends out a feedback signal to the control circuit board, and the control circuit board controls the power of the heating device via the second SCR. 
     
     
         3 . The quick water heater as claimed in  claim 1  further comprising a water flow meter disposed on the water pipe between the water pump and the heating device to detect the water flow in the water pipe. 
     
     
         4 . The quick water heater as claimed in  claim 2  further comprising a water flow meter disposed on the water pipe between the water pump and the heating device to detect the water flow in the water pipe. 
     
     
         5 . The quick water heater as claimed in  claim 1  further comprising a button disposed at the water outlet for controlling the hot water on or off.