JPH05149552A - Hot-water space heater - Google Patents

Abstract

PURPOSE:To improve thermal efficiency by a method wherein the flow rate of a heat medium is choked automatically to reduce a returning temperature when the returning temperature from a boiler is increased. CONSTITUTION:The outputs of thermistors 6, 7, which detect heat medium temperature in a sending pipeline 2 and a returning pipeline 3, are sent to a controller 8 and are compared with a reference voltage corresponding to respective set temperatures whereby the fuel supplying proportional valve 9 and the number of rotation of a pump are controlled so as to be constant. Accordingly, when a space heating load is reduced and a returning temperature is begun to increase, for example, the voltage of the thermistor 7 is increased and the number of rotation of the pump 4 is reduced whereby the flow rate of heat medium is reduced and the returning temperature is maintained in constant. As a result, the thermal output of a condensing boiler 1 is reduced and a temperature in a heat exchanger 12 is increased, however, the thermistor 6 detects it and the fuel supplying amount of a gas burner 11 is kept in constant whereby the thermal efficiency of the boiler 1 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot water heater using a condensing boiler.

[0002]

2. Description of the Related Art Recently, in order to improve the thermal efficiency of a boiler,
A condensing boiler is being developed. A condensing boiler is a boiler that also recovers the latent heat of condensation when the steam in the exhaust gas changes to water, and the temperature setting of the heating medium is lower than that of a normal boiler (about 80 ° C). 6
(0 ° C) so that the return temperature becomes equal to or lower than the dew point of exhaust gas (usually, about 42 ° C when the excess air ratio is 1.5), and the exhaust gas is exhausted in the upper part of the heat exchanger (condensation latent heat recovery part). It is designed to condense the water content. Figure 3
A schematic structure of a condensing boiler is shown below.
1 is a gas burner, 12 is a heat exchanger, the lower part of the heat exchanger 12 is a normal heat transfer part 12a, and the upper part is a latent heat recovery part 12b for condensation.
The water condensed in the latent latent heat recovery section 12b flows along the lower side of the diagonally cut fins and is collected by the gutter-shaped condensed water receiver 13.

[0003]

In the hot water heater using the condensing boiler as described above, the temperature control of the heat medium is controlled so that the outlet temperature of the boiler, that is, the feed temperature is constant. The return temperature naturally changes according to the fluctuation of the load. Therefore, in the case of normal load, the return temperature becomes lower than the dew point temperature of the exhaust gas, and thermal efficiency of 90% or higher is obtained. However, when the heating load becomes small and the return temperature becomes high during the relatively warm daytime, the exhaust gas Moisture does not condense and thermal efficiency drops sharply (75-80%). As described above, the condensing boiler has a problem that its effect is halved with respect to a load having large fluctuations.
The present invention aims to solve the above problems.

[0004]

As shown in FIG. 1, in the present invention, in a hot water heater using a condensing boiler 1, the fuel supply amount of the gas burner 11 is adjusted so that the feed temperature of the boiler 1 becomes constant. It is characterized in that the flow rate of the heat medium in the circulation pipe is controlled so that the return temperature of the boiler 1 becomes a constant value that is set lower than the dew point temperature of the exhaust gas of the gas burner 11 while being controlled. is there.

[0005]

According to the above construction, the return temperature can be maintained below the dew point temperature of the exhaust gas even if the load fluctuates, so that the hot water heater can always be operated with high thermal efficiency of 90% or more.

[0006]

1 shows an embodiment of a hot water heater according to the present invention, and the structure of a condensing boiler 1 is shown in FIG.
Is the same as the conventional example. About 60 ° C in heat exchanger 12
The hot water, that is, the heating medium, is sent out from the feed pipe 2 and circulates in the radiator 6 such as an indoor heater or a floor heater,
Return to the return pipe 3. Reference numeral 4 is a pump for circulating the heat medium, and 5 is an expansion tank for replenishing the heat medium and releasing pressure. 6 and 7 are thermistors for detecting the temperature of the heat medium in the feed pipe 2 and the return pipe 3, respectively, and the output of each thermistor is sent to the controller 8 to reach the set temperature (for example, 60 ° C and 40 ° C), respectively. It is compared with a corresponding reference voltage, and the rotational speeds of the fuel supply proportional valve 9 of the gas burner 1 and the pump 4 are controlled to be constant by the comparison output. Therefore, for example, when the heating load decreases and the return temperature starts to rise, the voltage of the thermistor 7 rises and the rotation speed of the pump 4 decreases, and as a result, the flow rate of the heat medium decreases and the return temperature becomes constant. maintain. Therefore, the heat output of the condensing boiler 1 decreases and the temperature inside the heat exchanger 12 rises. The thermistor 6 detects this and throttles the fuel supply amount of the gas burner 11 to keep the feed temperature constant. Keep it.

FIG. 2 shows another embodiment of the present invention. As shown in the drawing, the flow rate variable valve 10 controls the flow rate of the heat medium with the rotational speed of the centrifugal pump 4 kept constant. However, the same effect can be obtained.

[0008]

As described above, according to the present invention, when the return temperature becomes high due to a change in load, the flow rate of the heating medium is automatically reduced to reduce the return temperature. Since the temperature of the condensation latent heat recovery unit is always maintained below the dew point temperature of the exhaust gas, there is an advantage that the thermal efficiency can always be maintained at 90% or more even when the load changes.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment according to the present invention.

FIG. 2 is a system diagram of another embodiment of the present invention.

FIG. 3 is a schematic explanatory view of a conventional condensing boiler.

[Explanation of symbols]

 1 Condensing boiler 2 Feed pipe 3 Return pipe 4 Pump 5 Expansion tank 6 Thermistor 7 Thermistor 8 Controller 9 Proportional valve 10 Flow rate variable valve

Claims (1)

[Claims] 1. In a hot water heater using a condensing boiler, the fuel supply amount of the gas burner is controlled so that the boiler feed temperature is constant, and the boiler return temperature is higher than the dew point temperature of the exhaust gas of the gas burner. A hot water heater that controls the flow rate of the heat medium in the circulation pipe so that it will be a low, constant value.