Water heater and control method therefor

1. A water heater comprising:

combustion means that combusts fuel and generates exhaust;

heat exchange means that exchanges heat of the exhaust for supplied water;

bypassing means that makes the supplied water flow to an outlet of the heat exchange means;

exchanged heat temperature detection means that detects temperature of the supplied water after heat exchange;

flow rate adjustment means that adjusts a volume of the supplied water flowing into the bypassing means and the heat exchange means; and

a control unit that controls the flow rate adjustment means so as to make a predetermined volume of the supplied water or over flow to the heat exchange means.

2. The water heater of claim 1 , wherein

the flow rate adjustment means includes a switching valve that determines a flow rate of the supplied water to the bypassing means or the heat exchange means according to an opening thereof.

3. The water heater of claim 1 , further comprising timekeeping means that times elapsed time since combustion execution by the combustion means,

wherein the control unit makes the flow rate adjustment means execute adjustment of a flow rate of the supplied water to the heat exchange means when the elapsed time is a predetermined time or over.

4. The water heater of claim 1 , wherein

the control unit makes the flow rate adjustment means execute adjustment of a flow rate to the heat exchange means when water heating setting temperature is a predetermined value or over, or when the water heating setting temperature is below the predetermined value and temperature detected by the exchanged heat temperature detection means is below the water heating setting temperature.

5. The water heater of claim 1 , wherein

the control unit adjusts the flow rate adjustment means so that the supplied water is not allowed to flow to the heat exchange means when water heating setting temperature is below a predetermined value and temperature detected by the exchanged heat temperature detection means is the water heating setting temperature or over.

6. The water heater of claim 1 , further comprising:

water supply temperature detection means that detects temperature of the supplied water before heating; and

flow rate detection means that detects a volume of the supplied water,

wherein the control unit sets a minimum flow rate of the supplied water, which is allowed to flow to the heat exchange means, and adjusts the flow rate adjustment means based on at least the minimum flow rate, water heating setting temperature, the volume of the supplied water, temperature of the supplied water before heating and temperature of the supplied water after heat exchange.

7. The water heater of claim 6 , wherein the control unit calculates combustion for the combustion means so as to meet the water heating setting temperature based on the minimum flow rate of the supplied water, that is set, and outputs combustion control.

8. A water heating control method, comprising:

exchanging in heat exchange means heat of exhaust generated by combusting fuel for supplied water;

making through bypassing means the supplied water flow to an outlet of the heat exchange means;

detecting temperature of the supplied water after heat exchange;

adjusting by flow rate adjustment means a volume of the supplied water flowing into the bypassing means and the heat exchange means; and

controlling the flow rate adjustment means so as to make a predetermined volume of the supplied water or over flow to the heat exchange means.

9. The water heating control method of claim 8 , further comprising:

timing elapsed time since combustion execution by combustion means; and

making the flow rate adjustment means execute adjustment of a flow rate to the heat exchange means when the elapsed time is a predetermined time or over.

10. The water heating control method of claim 8 , further comprising:

making the flow rate adjustment means execute adjustment of a flow rate to the heat exchange means when water heating setting temperature is a predetermined value or over, or when the water heating setting temperature is below the predetermined value and the temperature of the supplied water after the heat exchange is below the water heating setting temperature.

11. The water heating control method of claim 8 , further comprising:

adjusting the flow rate adjustment means so that the supplied water is not allowed to flow to the heat exchange means when water heating setting temperature is below a predetermined value and temperature of the supplied water after heat exchange is the water heating setting temperature or over.

12. The water heating control method of claim 8 , further comprising:

detecting temperature of the supplied water before heating;

detecting a volume of the supplied water;

setting a minimum flow rate of the supplied water, which is allowed to flow to the heat exchange means; and

adjusting the flow rate adjustment means based on at least the minimum flow rate, water heating setting temperature, the volume of the supplied water, water supply temperature and temperature of the supplied water after heat exchange.

13. The water heating control method of claim 12 , further comprising:

calculating combustion for the combustion means so as to meet the water heating setting temperature based on the minimum flow rate of the supplied water that is set; and

outputting combustion control information based on the calculated combustion.