Water heating system and determination method of tank capacity in water heating system

Abstract

A water heating system includes a tank that retains water, a heat pump that heats the water in the tank, and a water heater that heats supplied water by combustion heat of fuel gas. In the water heating system, a tank use mode in which the water in the tank is mixed with tap water and supplied to a plurality of using locations including a bathtub, and a hot water supply use mode in which water supplied from the tank or tap water is heated by the water heater and then supplied to the plurality of using locations are executable. The tank use mode is executable at least in a predetermined second time slot, and a capacity of the tank is set to be equal to or more than a first reference capacity and equal to or less than a second reference capacity.

1 . A water heating system comprising:
 a tank that retains water;   a heat pump that heats the water in the tank; and   a water heater that heats supplied water by combustion heat of fuel gas, wherein   in the water heating system,
 a tank use mode in which the water in the tank is mixed with tap water and supplied to a plurality of using locations including a bathtub, and 
 a hot water supply use mode in which water supplied from the tank or tap water is heated by the water heater and then supplied to the plurality of using locations are executable, wherein 
   the tank use mode is executable at least in a predetermined second time slot, excluding a predetermined first time slot in which bath water filling to the bathtub is assumed, and   an amount of hot water in a time slot during which hot water is used most is used as a target water amount, the time slot is among a plurality of time slots into which the second time slot is further subdivided, the plurality of subdivided time slots are assumed to have no water use for almost one hour or more before and after the time slots based on a daily usage condition of water in a general household considered as typical,   an amount of water that allows producing mixed water with the target water amount of 40° C. is used as a first reference capacity, assuming that water between 65° C. and 75° C. is mixed with tap water supplied in winter,   an amount of tap water whose temperature rises to a target temperature of 65° C. to 75° C. in one hour is used as a second reference capacity, assuming that the tap water is retained in the tank and heated with an output of the heat pump of 1.5 kw to 2.0 kw, and
 a capacity of the tank is set to be equal to or more than the first reference capacity and equal to or less than the second reference capacity. 
   
     
     
         2 . The water heating system according to  claim 1 , wherein
 the first reference capacity is 17.73 L, and the second reference capacity is 29.96 L.   
     
     
         3 . The water heating system according to  claim 2 , wherein
 the first reference capacity is 19.28 L, and the second reference capacity is 25.52 L.   
     
     
         4 . The water heating system according to  claim 1 , wherein
 the first reference capacity is a required hot water amount derived based on a relationship between an inflow water temperature of tap water and a temperature of the water in the tank in order to output the target water amount at 40° C., and the target water amount is 34.16 L, and   the second reference capacity is a capacity that allows heating tap water in the tank up to a predetermined temperature by the heat pump within a predetermined non-use period during which water is not used in the second time slot, and the capacity is derived based on a relationship between the inflow water temperature of tap water and an output of the heat pump.   
     
     
         5 . A method of determining a tank capacity in a water heating system, the water heating system comprising:
 a tank that retains water;   a heat pump that heats the water in the tank; and   a water heater that heats supplied water by combustion heat of fuel gas, wherein   the method determines a capacity of the tank in the water heating system,   in the water heating system,
 a tank use mode in which the water in the tank is mixed with tap water and supplied to a plurality of using locations including a bathtub, and 
 a hot water supply use mode in which water supplied from the tank or tap water is heated by the water heater and then supplied to the plurality of using locations 
   are executable, wherein
 the tank use mode is executable at least in a predetermined second time slot, excluding a predetermined first time slot in which bath water filling to the bathtub is assumed, wherein 
   the method comprises:
 using an amount of hot water in a time slot during which hot water is used most as a target water amount, the time slot being among a plurality of time slots into which the second time slot is further subdivided, the plurality of subdivided time slots being assumed to have no water use for almost one hour or more before and after the time slots based on a daily usage condition of water in a general household considered as typical; 
 using an amount of water that allows producing mixed water with the target water amount of 40° C. in as a first reference capacity, assuming that water between 65° C. and 75° C. is mixed with tap water supplied in winter; 
 using an amount of tap water whose temperature rises to a target temperature of 65° C. to 75° C. in one hour as a second reference capacity, assuming that the tap water is retained in the tank and heated with an output of the heat pump of 1.5 kw to 2.0 kw; and 
 setting a capacity of the tank to be equal to or more than the first reference capacity and equal to or less than the second reference capacity. 
   
     
     
         6 . The determination method of a tank capacity in a water heating system according to  claim 5 , wherein
 the first reference capacity is 17.73 L, and the second reference capacity is 29.96 L.   
     
     
         7 . The determination method of a tank capacity in a water heating system according to  claim 6 , wherein
 the first reference capacity is 19.28 L, and the second reference capacity is 25.52 L.   
     
     
         8 . The determination method of a tank capacity in a water heating system according to  claim 5 , wherein
 the first reference capacity is a required hot water amount derived based on a relationship between an inflow water temperature of tap water and a temperature of the water in the tank in order to output the target water amount at 40° C., and the target water amount is 34.16 L, and   the second reference capacity is a capacity that allows heating tap water in the tank up to a predetermined temperature by the heat pump within a predetermined non-use period during which water is not used in the second time slot, and the capacity is derived based on a relationship between the inflow water temperature of tap water and an output of the heat pump.