Method of controlling combustion apparatus

Abstract

A combustion apparatus having a burner, a combustion box, a combustion fan for supplying combustion air, and a regulator for regulating the amount of combustion fan, an inspection operation is performed in a state in which an operational quantity of the regulator (fan rotational speed) is kept at a maximum amount Nmax. When a deviation between a maximum set combustion amount YQmax corresponding to supply/exhaust resistances as detected in the inspection operation and an actually measured maximum combustion amount Qmax is outside an allowable range, a secondary inspection operation is performed by lowering the fan rotational speed down to a value Now which is lower than Nmax by a predetermined rate. Based on the rate of decrease of Qlow relative to Qmax as detected by the secondary inspection operation, computation is made of a fan rotational speed Nsat at which the burner combustion amount ceases to increase even if the fan rotational speed is increased. The upper limit value of fan rotational speed is then changed to Nsat.

What is claimed is: 
     
         1 . A method of controlling a combustion apparatus, the combustion apparatus comprising: a burner; a combustion box for disposing therein a to-be-heated object that is heated by combustion gas from the burner; a combustion fan for supplying combustion air to the burner; at least one of an air supply tube communicated with a suction side of the combustion fan, and an exhaust pipe communicated with an exhaust port of the combustion box; and a gas amount regulating means for regulating an amount of fuel gas supply to the burner, the method comprising:
 searching in advance for change characteristics of a maximum set combustion amount due to change in flow resistance through an auxiliary tube, where the maximum set combustion amount is defined to be such a burner combustion amount as will originally be obtainable when a primary pressure of the fuel gas is normal and when an operational quantity of the gas amount regulating means is at an upper limit value at which the fuel gas supply amount becomes maximum, and where the auxiliary tube is defined to be whichever of the air supply tube and the exhaust pipe the combustion apparatus is provided with;   performing an inspection operation while operating the combustion apparatus in a state in which the operational quantity of the gas amount regulating means is kept at the upper limit value, in order to detect the flow resistance through the auxiliary tube and the burner combustion amount;   obtaining, from the change characteristics, the maximum set combustion amount that corresponds to the flow resistance, as detected in the inspection operation, through the auxiliary tube;   when a deviation between the maximum set combustion amount and the actually measured maximum combustion amount that is the burner combustion amount as detected in the inspection operation is outside a predetermined allowable range, performing a secondary inspection operation to obtain a saturated value which is such a value of the operational quantity of the gas amount regulating means as the burner combustion amount will cease to increase even if the operational quantity of the gas amount regulating means is increased; and   changing the upper limit value of the operational quantity of the gas amount regulating means to the obtained saturated value.   
     
     
         2 . The method of controlling a combustion apparatus according to  claim 1 , wherein the inspection operation is performed at a time of trial operation after having placed in position the combustion apparatus, the method further comprising:
 when the flow resistance through the auxiliary tube as detected in the inspection operation is outside a predetermined reference range, displaying “auxiliary tube abnormal” which means that the auxiliary tube is abnormal; and   when a deviation between the maximum set combustion amount that corresponds to the flow resistance through the auxiliary tube as detected in the inspection operation and the actually measured maximum combustion amount is within the allowable range, displaying “primary pressure normal” which means that the primary pressure of the fuel gas is normal.   
     
     
         3 . The method of controlling a combustion apparatus according to  claim 1 , wherein the secondary inspection operation is performed by detecting the burner combustion amount while operating the combustion apparatus in a state in which the operational quantity of the gas amount regulating means is lowered by a predetermined rate from the upper limit value, the method further comprising computing the saturated value based on the rate of decrease of the burner combustion amount as detected in the secondary inspection operation relative to the actually measured maximum combustion amount. 
     
     
         4 . The method of controlling a combustion apparatus according to  claim 3 , wherein, when the rate of decrease of the burner combustion amount as detected in the secondary inspection operation relative to the actually measured maximum combustion amount is below a predetermined threshold value, displaying “primary pressure abnormal” is made showing that the primary pressure of the fuel gas is abnormal. 
     
     
         5 . The method of controlling a combustion apparatus according to  claim 1 , further comprising:
 when the upper limit value of the operational quantity of the gas amount regulating means is changed to the saturated value, displaying the upper limit value which shows the changed upper limit value.